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Abstract
Acknowledgement
First and foremost thanks are due to ALLAH, the most beneficial and merciful.
In a few grateful words I would like to express my greatest thanks to all my professors who helped this work to be carried out.
I wish particularly to express my deepest gratitude and appreciation
for the unfailing support, valuable advice, and generous help rendered me
by PROF. Dr. Adel Abdelkafy Professor of Orthopedic Surgery
Faculty Of Medicine.Suez Canal University. He sacrified a good deal of his precious time to guide me throughout the preparation of the essay.
I am indeed immensely indebted and deeply grateful to PROF. Dr. Mousa Abdelhamid Mousa Professor of Orthopedic Surgery. Faculty Of Medicine.Suez Canal University . Every step every detail in this essay has been kindly assisted by his untiring effort and his sincere care.
Also I am deeply grateful to Dr..Hesham Abdulsadek
Assistant Professor of Orthopedic Surgery .Faculty Of Medicine.
Suez Canal University. For his kind help and guidance during the preparation of this esay. His precious suggestions helped me a lot during this study.
Faculty of Medicine
Suez Canal University
List Of Contents
Introduction . 4
Aim of the work. . 6 List of figures . 7 Chapter 1: Anatomy of the knee joint. 8
Chapter 2: Biomechanics of the knee . 14
Chapter 3: Total knee arthroplasty . 26
Chapter 4: Complication of total knee Arthroplasty. 41
Chapter 5: Materials and Methods . 114 Chapter 6: Discussion . 115 Chapter 7: Summary . 125
Chapter 8: References . 126
Chapter 9: Arabic summary. 138
Introduction
The primary indication for total knee arthroplasty is to relieve pain caused by severe arthritis, with or without significant deformity. Other sources of knee and leg pain must be sought and systematically excluded.
Patients who do not have complete cartilage space loss before surgery tend to be less satisfied with their clinical result after total knee arthroplasty. Before surgery is considered, conservative treatment measures should be exhausted, including antiinflammatory medications, activity modifications, and the use of a cane for ambulation.Because knee replacement has a finite expected survival that is adversely effected by activity level, it is indicated in older patients with more sedentary life-styles. It also is clearly indicated in younger patients who have limited function because of systemic arthritis with multiple joint involvement.Severe pain from chondrocalcinosis and pseudogout in an elderly patient is an occasional indication for arthroplasty in the absence of complete cartilage space loss. Rarely, severe patellofemoral arthritis in an elderly patient may justify arthroplasty because the expected outcome of arthroplasty is better than that of patellectomy in these patients(Canale, 2003).
The success of total knee arthroplasty (TKA) in relieving pain and improving function has led to its widespread use worldwide. In addition, the increasing size of the aging population, especially in the United States, will only further test the longevity and durability of TKA. With the increasing demands placed on TKA in terms of longevity and function, the problem of failure has manifested itself as a substantial reconstructive challenge in the last decade( Chritranjan et al., 2000).
Deformity can become the principal indication for arthroplasty in patients with moderate arthritis and variable levels of pain when the progression of deformity begins to threaten the expected outcome of an anticipated arthroplasty. As flexion contracture progresses beyond 30 degrees, gait is significantly hampered and difficulty with regaining extension may warrant surgical intervention. Similarly, as varus or valgus laxity becomes severe, a constrained condylar type of prosthesis becomes necessary to prevent subsequent coronal plane instability. Intervening before this degree of laxity is present allows the use of a prosthesis that lacks coronal plane constraint and has a more favorable expected survival.Absolute contraindications to total knee arthroplasty include recent or current knee sepsis, a remote source of ongoing infection, extensor mechanism discontinuity or severe dysfunction, recurvatum deformity secondary to muscular weakness, and the presence of a painless, well-functioning knee arthrodesis. Relative contraindications are numerous and debatable. These include medical conditions that compromise the patient’s ability to withstand anesthesia, the metabolic demands of surgery and wound healing, as well as the significant rehabilitation necessary to ensure a favorable functional outcome. Other relative contraindications include monarticular disease in young patients, significant atherosclerotic disease of the operative leg, skin conditions such as psoriasis within the operative field, neuropathic arthropathy,HB<11mg%,varicose veins,history of DVT, morbid obesity, recurrent urinary tract infections, and a history of osteomyelitis in the proximity of the knee. This list is not all-inclusive, and any preoperative condition that can adversely affect the patient’s outcome can be considered a relative contraindication(Canale, 2003).
Aim of the work
(1)Evaluation of the T.K.R. and its complications.
(2)Planning for avoidance and treatment of these complications.
List of figures
Figure 1.1 page 8
Figure 1.2 Page10
Figure 1.3 page 12
Figure 1.4 page 13
Figure 2.1 page 15
Figure 2.2 page 16
Figure 2.3 page 18
Figure 2.4 page 19
Figure 2.5 page 20
Figure 2.6 page 21
Figure 2.7 page 22
Figure 2.8 page 25
Figure 3.1 page 31
Figure 3.2 page 35
Figure .3.3 page 36
Figure 3.4 page 37
Figure 3.5 page 38
Figure 4.1 page 52
Figure 4.2 page 60
Figure 4.3 page 62
Figure 4.4 page 65
Figure 4.5 page 78
Figure 4.6 page 79
Figure 4.7 page 80
Figure 4.8 page 81
Figure 4.9 page 81
Figure 4.10 page 87
Figure 4.11 page 101
Figure 4.12 page 101
Figure 4.13 page 103
Figure 4.14 page 104
Figure 4.15 page 106
Figure 4.16 page 107
Anatomy of the Knee Joint
The knee joint is the largest articulation in the body, for stability it depends on the capsule, collateral and cruciate ligaments, and the surrounding muscles. There are three categories for practical classification of the structures about the knee.
1-Osseous structures.
2-Extra –articular structures .
3-Intra – articular structures(Anson, 1984).
(Figure 1.1)
A. Anteroposterior radiograph of an adult knee (male aged 22 years). 1. Shadow
of patella superimposed on femur. 2. Adductor tubercle. 3. Medial femoral
condyle. 4. Radiotranslucent space occupied by medial meniscus and articular
cartilages. 5. Medial tibial condyle. 6. Intercondylar eminences. 7. Head of fibula.
B. Lateral radiograph of the partly flexed adult knee (same as in A). 1. Patellar
surface of femur. 2. Spiral profiles of femoral condyles. 3. Groove impinging on
anterior end of meniscus in full extension. 4. Note marked incongruity of femorotibial joint surfaces(Richard et al., 2001).
(1) Osseous Structures.
The osseous structures of the knee consist of three components:
The distal femoral condyles, the patella and the proximal tibial plateaus or condyles.The femoral condyles are two rounded prominences. Anteriorly the condyles are somewhat flattened which provides a greater surface for contact and weight transmission. The groove anteriorly between the condyles is the patello-femoral groove or trochlea, which accepts the patella. Posteriorly the intercondylar notch separates the condyles.The patella is a somewhat triangular in shape sesamoid bone that is wider at the proximal pole than at the distal pole. The articular surface of the patella is divided by a vertical ridge creating two facets, a smaller slight convex medial and a larger lateral articular facet. The patella is described as possessing seven facets. Both medial and lateral facets are divided vertically into approximately equal thirds, while the seventh or odd facet lies along the extreme medial border of the patella.The expanded proximal end of the tibia forms two flat surfaces, the larger medial tibial plateau which is nearly flat, whereas the lateral plateau is actually concave; both have posterior inclination of approximately 10 degree with respect of shaft of tibia.The spine of the tibia occupies the median portion of the tibia between the plateau. Anteriorly there is a depression, the anterior intercondyloid fossa, to which attached the anterior horn of the medial meniscus, the anterior cruciate ligament, and the anterior horn of lateral meniscus. Behind this region the medial and lateral tubercles. They are divided by the intertubercular sulcus. In the posterior intercondyloid fossa behind the tubercles are attached the medial and lateral menisci and behind them on the margin of the tibia between the condyles, the posterior cruciate ligament (Insall, 1993).
(2) Extra- Articular Structures.
The important extra-articular structures supporting and influencing the function of the joint are:
Synovium, capsule, collateral ligament, and the musculo-tendinous unit which are the quadriceps mechanism, the gastrocnemius, the medial and lateral hamstring groups, the popliteus and the iliotibial band (Sisk, 1987).
Figure (1.2)
Dissection of the right knee joint: lateral aspect(Gronblad et al ., 1985 ).
The musculo-tendinous structures:
The quadriceps muscle consists of four distinct parts that sheer a common tendon of insertion. These parts are the rectus femoris, The Vastus lateralis, The Vastus medialis, and The Vastus intermedius. The quadriceps tendon is trilaminar, the anterior layer being formed by the rectus femoris, the intermediate layer by the vastus medialis and lateralis, and the deep layer by the tendon of vastus intermedius. The tendon inserts into the patella with an expansion that passes longitudinally anterior to the patella. In addition, expansions from the medial and lateral vasti are inserted directly into the tibia via the patellar retinaculum (Insall, 1993).
The gastrocnemius, is the most powerful calf muscle.
Pes anserinus is the term for the conjoined insertion of the sartorius, grasilis and semitendinosus muscles. They are the primary flexors of the knee, these muscles help protect the knee against valgus stress. Their counterpart on the lateral side of the knee is the strong biceps femoris insertion into the fibular head, lateral tibia and posterolateral capsular structures. It is a strong flexor of the knee with simultaneous strong external rotation of the tibia.
The iliotibial tract, the posterior third of the iliotibial band, inserts proximally into the lateral epicondyle of the femur and distally into the lateral tibial tubercle. The popliteus muscle rotates the tibia medially during the initial stages of flexion and also acts to withdraw the lateral meniscus with flexion. In addition it stabilizes the femur on the tibia, and aids the posterior cruciate ligament in preventing forward dislocation of the femur on the tibia.
The semimembranosus muscle it is important as a stabilizing structure around the posterior and posteromedial aspect of the knee. its contraction tenses the posterior capsule and posteromedial capsular structures, providing stability. Functionally it acts as a flexor of the knee and internal rotator of the tibia (Sisk, 1987).
Extra– articular ligamentous structures:
Fibular collateral ligament, this cord-like ligament extends from the lateral epicondyle of they femur to the head of the fibula. Here it pierces the tendon of insertion of biceps femoris. It is separated from the fibrous capsule of the joint, and hence from the lateral meniscus, by fatty tissue in which the inferior lateral genicular vessels and nerve run. In its turn, the fibrous capsule is separated from the meniscus by the tendon of popliteus which is deep to the capsule.
Tibial collateral ligament, this broad, flat band arises from the medial epicondyle of the femur where it receives fibres from the tendon of adductor magnus. Inferiorly it splits into two layers. The deep layer passes to the articular margin of the medial condyle of the tibia and is fused with the medial meniscus. The superficial layer, is inserted into the medial surface of the tibia between the medial border and the insertions of sartorius, gracilis, and semitendinosus.
Oblique popliteal ligament, this is an extension of the semimembranosus tendon. It arises from the tendon close to its insertion, and runs upwards and laterally towards the lateral femoral condyle.
Patellar retinacula, these are fibrous expansions from vastus medialis and lateralis into the fibrous capsule on the corresponding side of the patellar ligament (Romanes, 1987).
Intra- Articular Structure:
The principal intraarticular structures of importance are:
1)The medial and lateral menisci.
2) The anterior and posterior crutiate ligaments.
Figure (1.3)
Posterior dissection of the right knee joint(Ghosh and Taylor , 1987 ). The medial meniscus is nearly semicircular in form and about 3.5 cm in length and is considerably wider posteriorly than anteriorly. It is firmly attached to the posterior inter-condylar fossa of the tibia. The anterior attachment is attached to the anterior intercondylar fossa, but this attachment can be quite flimsy within the realm of normal variation. There is a fibrous band that connects the anterior horn of the medial meniscus with the lateral meniscus (the transverse ligament). Postromedially, The meniscus receives a portion of insertion of the semimembranosus via the capsule.
The lateral meniscus is nearly circular and covers a larger portion of the articular surface than the medial meniscus. Its anterior horn is attached to the intercondylar fossa, lateral and posterior to the anterior cruciate ligament. The posterior horn is attached to the intercondylare fossa anterior to the posterior end of the medial meniscus. Variable fibrous bands connect the posterior arc of the lateral meniscus to the medial femoral condyle in the intercondylar fossa, embracing the posterior cruciate ligament. Posterolaterally, the meniscus is grooved by the tendon of the popliteus (Insall, 1993).
The cruciate ligaments
Figure (1.4)
Superior aspect of the left tibia, showing the menisci and the tibial attachments of
the cruciate ligaments(Richard et al., 2005).
The anterior cruciate ligament: is attached to the femur at the posterior part of the medial surface of the lateral condyle of the femur in the form of a segment of a circle. The anterior side is almost straight and the posterior side convex, the average length of the ligament is 38mm & the average width is 10mm. It proceeds distally to the tibial attachments, which is a wide depressed area in front of and lateral to the anterior tibial spine.
The posterior cruciate ligament: is attached to the posterior part of the lateral surface of the medial condyle of the femur and like the anterior cruciate, this attachment is in a form of a segment of circle. The average length of the ligament is 26mm & the average width is 13mm the fibers are attached to the tibia in lateromedial direction. The tibial attachment is to a depression behind the intra-articular upper surface of the tibia and extends for a few millimeters onto the adjoining posterior surface of the tibia. Shortly above its tibial attachment, the posterior cruciate ligament sends a slip to blend with the posterior horn of the lateral meniscus(Girgis et al., 1995).
BIOMECHANICS OF KNEE AFTER TOTAL KNEE
REPLACEMENT
The mechanics of joint loading in the limb with a total knee prosthesis do not differ substantially from those of the natural limb. As the joint surfaces are replaced by artificial components, the resulting forces will be much the same. The concept of the point of application of the joint compressive load needs closer examination. Condylar style prosthesis are available with a wide range of antroposterior tibial condyle curvatures. They vary from the relatively flat geometry, used most frequently in cruciate-retaining prosthesis, to the more curved geometry commonly associated with cruciate-sacrificing and curciate substituting prosthesis. In either case, the principles of mechanics do not change and if the joint reaction force is composed mainly of transmitted compressive load between the femur and the tibia, the load line must lie perpendicular to the surface of the joint at its point of contact. For the natural joint, with its remarkable low coefficient of friction, deviation from perpendicularity condition of approximately one part per thousand can not be exceeded if no cruciate force is applied. For total joint prosthesis with somewhat higher coefficient of friction, deviation from perpendicularity could be several parts of hundred (lnsall et al., 1993).
Antroposterior Stability:
Considering those prosthesis that require sacrificing of the cruciate ligaments. The loads usually borne by the surface of the natural joint, without cruciate force, can only vary about 8 degrees. Required angular deviations of the joint contact force greater than 8 degrees result in load application by the cruciate ligaments. The joint contact there still remain close to the 8 degrees deviation angle, but the cruciate ligaments are applying a transverse or shear load. What will be the required angle for a joint contact force if the joint did not contain a cruciate ligament? Considering, as a guideline, the ratio of normal to cruciate force occurring in the knee as reported by Morrison study, whereas, cruciate loads did not exceed 1/4 the normal loads. To obtain a ratio of axial load component to transverse component of 4: 1, the required angular deviation of the joint compressive load will be approximately 22 degrees. That is the combination of the normal force can be replaced by a single force inclined at angle of 22 degrees to the tibial axis.
i.e. normal axial force + cruciate force ==
inclined force at 22° to the tibial axis
The implication for total knee replacement is that if the curvature of the tibial component can have an angle of inclination of 22 degrees then it should be possible to replace cruciate function with the simple mechanical substitution of curving the articulating surface, For those prosthesis that do not have this an included angle, large joint displacements would be expected, requiring loading of the secondary anteroposterior constraints, namely, the collateral ligaments. If it is not desirable to have such large angle in the tibial plateau or if it is not suitable to allow the contact point shift to the extreme anterior position, the supplementary mechanisms can be used to provide the necessary cruciate equivalent force which is the posterior stabilized condylar prosthesis (Figure 2 . 1) (Whiteside , 1996).
(Figure 2-1) The included angle of the tibia in many prosthetic designs is rather large. This allows correspondingly large variations in the angular positions in the normal contact force. (Insall et al., 1993)
Although, the included angle of the tibial plateau is 42o, allowing approximately 22°- of inclination anteriorly and 20o posteriorly) at large flexion angles it is desirable to maintain contact in the posterior plateau (Morrison , 1970).
Varus Valgus Stability:
On examining the mechanisms for varus-valgus stability with total knee replacements, 3 mechanisms for joint stabilization are applicable for most prosthesis. They are (1) shifting of load, (2) muscle force, and (3) lateral ligament tension, (Figure 2.2A). Because the knee consists of 2 condyles, varus-valgus equilibrium can be obtained by shifting load from the lateral condyle to the medial condyle. Because the artificial material is stiffer than the natural cartilage, the amount of deformation of the surface, hence, the angulation required to relieve the load on the lateral surface is reduced. The second stabilizing mechanism is the muscle force which acts through production of valgus moment by the joint contact load in addition of agents and antagonist muscle activity. The Third mechanism is production of valgus moment by lateral ligament tension (Figure2.2B) (Insalll et al., 1993).
(Figure 2.2) (A) In the artificial knee as with the natural knee. varus-valgus equilibrium can be maintained by changing the distribution of the joint contact forces. In this case, a medial force at the foot of 150 N can be resisted in a manner similar to that of the natural knee. The lateral contact force is greatly reduced, while medial contact force increases. The patellar tendon force remains constant. (B) The mechanism of resisting excessive medial forces applied at the foot is similar in an artificial joint if the joint retains the characteristic behavior of being able to separate the contact surfaces on one condyle. In this case. the lateral condyle is separating and lateral ligament tension is induced. This ligament tension, even in the presence of constant patellar tendon force, increase the total force on the medial condyl (Insalll et al., 1993).
.
Although, these same equilibrium mechanisms are present in both natural and artifical knee joints, there are some important differences in the total knee replacement joint. In the natural knee joint, the stiffness of the cartilage is less than polyethyelene used in total knee replacements. Due to this difference in stiffness, less angulation will be required in the total knee replacement to produce load shift between medial and lateral condyles. There is increased affection in total knee replacement to changes in pressure distribution due to small angulation of the tibia. There is no obvious disadvantage to that increase in the affection to pressure changes , but should be noted that patient with total knee replacement when examined for varus-valgus stability in the presence of muscle contraction of the quadriceps,the clinical feeling of the knee is different from the natural knee, but the mechanisms and quality of both are identical (Berger et al., 2002).
Considering those prostheses with flat surface, varus angulation will result in decrease of the contact area at the extreme edge of the prosthesis. This is detrimental to the longevity of the polyethyelene tibial plateau, so prostheses having curved surfaces that maintain condylar region in constant contact on the plateau are more desirable(Bartel et al., 1991).
Tibial Component Stability:
The size and shape of tibial component has a great effect on the longevity of the total knee prosthesis. Due to knowledge’s gained during the last 3 decades, tibial component are well-fixed with long-lasting bone-prosthesis interfaces, early failure of a tibial component is more likely due to surface wear than component loosening. Surface wear clinically, related to the weight of the patient and the length of implantation (Hood et al., 1983).
Component wear:
Since the weight of the patient modulates the amplitude of contact stresses, and the length of implanlation determines the number of cycles of loading, wear failure mechanism is related to fatigue process. There are 2 types of wear depris; (1) fine wear”micrometer size range” results of surface abrasion, (2) coarse wear ”10 - 100 micrometers size range” results from fatigue cracking of polyethylene surface (Harry et al., 1993).
For examination of the effect of surface curvature on contact stress and surface fatigue. The model used to study that effect was a posterior stabilized type of total condylar prosthesis (Fig 2 . 3). The load used on one condyle was 150N, a joint compressive load ”Which represent about 2 times body weight”, contact patterns and contact stresses are shown in (Fig2 . 4)in flexion and full extension (Insall et al., 1998).
(Figure 2 .3) (A) Schematic view of a posterior stabilized tibial component, showing the location of the finite element model. Because of symmetry, it was only necessary to model one quarter of the contact region of the plateau. (B) Top view of the model in extension. (C) Top view of the model in flexion (Insall et al., 1998).
In full extension: contact area is larger and contact stress is smaller. Of major importance is the tensile stress that generated at the edge of the contact ”area of polyethylene whereas, only compressive stress within the boundary of the contact area, maximum compressive stress exists in the centre of the contact area, whereas maximum tensile stress at the leading and lateral edges of the contact surface. For load stress of 2 times body weight, the contact stress in the center of the area of contact are very high with respect to the elastic limit of polyethylene (Figure2 .5)(Scott et al., 1998).
(Figure 2 . 4) Values for the maximum principal stress (in units of megapascals) on the surface of the tibial component if Figure 2-4 (A)in extension and in(B) flexion. The lowest (most compressive) stress was at the center of contact and the highest (most tensile) stress was at the edge of contact(Insall et al., 1998).
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For example. 20% decrease in thickness results in 20% increase in contact stress below the critical threshold which is 10 mm thickness of polyethylene (Bartel , I986).
(Figure 2 . 5) The stress-strain behavior of ultrahigh molecular weight polyethylene in tension and compression. The yield stress is indicated (arrow) (Scott et al., 1998).
Femoral Components Stability:
The femoral component design, must replicate normal anatomy with a smooth contour. Some femoral components are designed with a sharp transitional area between the trochlear aspect of the femoral component and the condylar weight-bearing surface. These implants are fraught with problems of patellar maltracking and have a higher risk of patellar instability than those in which there is a smooth, rounded transitional phase through this area. The femoral component should require the removal of as little bone as feasible from the distal femur to maintain bone stock and mechanical strength of distal femoral bone. The majority of current condylar implant designs remove 8 mm or less of bone, from the distal femur are preferable. The trochlear aspect of femoral component design is becoming more critical to minimize forces across the patellofemoral joint. Some designs incorporate an extended trochlear surface of the femoral component that helps to maintain contact areas through 80 to 90 degrees of knee flexion. Elevation of the lateral aspect of the femoral component will help to minimize problems of patellar subluxation. Slight deepening of the patellofemoral groove helps to decrease patellofemoral stresses and improve patellar tracking (Bartel et al., 1991).
Load Distribution On The Tibial Plateau
For the total knee replacement, the interaction between joint motion and load transmission has another important effect; The stress distribution within the tibial plateau. It is thought that the more sever loading environment is beneath the tibial plateau. The clinical problem of tibial loosening has been associated with the mechanism of load transmission in that one probable cause of tibial loosening is thought to be either, (1) high stress in the interface region between the tibia and the prosthesis or, (2) high stress within the cancellous bone just below the interface region.
(Figure 2.6) As the thickness of a total condylar type tibial component decreases, the contact stress on the surface of the polyethylene increases (Rartel and Wright, 1991).
In order to understand the effect of tibial component design on load distribution, 3 questions must be asked:
(1) The first question about the use of a peg on the tibial tray, the aim of the peg is to provide a fixation mode if the plateau-tibia interface is degenerated, thus what is the load distribution existing between peg and plateau?
(2) The second question about the choice of material for the tibial plateau, wheather a plain polyethylene tibial plateau or a metal - backed polyethylene tibial plateau and their effect on distribution of forces at the plateau – bone interface?
(3) The third question is related to the effect of the position of the joint contact force on the stress distribution within the tibial plateau. In other wards, since asymmetric loads are quite feasible, what is the effect of such loads on the stress distribution at the plateau-bone interface?
• For answering these questions, we should use a finite element model. Figure (2 . 7) shows 3 models used to answer the previous questions:
(1) The upper model represents a polyethylene tibial
component without a peg.
(Figure 2 . 7) Finite clement models approximate the geometry of the real structures. In this case, a polyethylene tibial component without a peg is represented in the upper model. The middle model represents the same component with a polyethyelene peg. while the lower model represents a similar geometry, which contains a polyethylene articulating surface encased in a metal tray. which itself is attached to a metal peg (Bartel et al., 1982).
(2) The middle model represents a polyethylene tibial component with a polyethylene peg.
(3) The lower model represents a polyethylene tibial component encased in a metal tray on which there is a metal peg.
• Dimensionally, all models are similar except the omitted peg from the upper model.
• For determination of the effects of the pegs as well as the effects of the metal tray, a severe loading condition was examined. The load was placed entirely on one side of the joint in a position representing slight posterior subluxation (Figure 2.8 cases 4). Throughout its length, the peg does not transfer more than 8% the total load, and, more importantly, the load distribution reaching the cortical bone is virtually the same with or without peg. The metal tray and the metal peg may carry about 25% of the load in the most proximal section. This still leaves more than 70% of the load borne by the tibial plateau. Thus, a conclusion could be reached that the plastic peg plays a minimal structural role in transferring load, while the metal peg plays only a moderate role in the proximal region (Bartel et al., 1982).
• To examine the effect of load placement on the tibial plateau, 8 load cases were investigated by Bartel et al.,1982 In Figure 2-8, load placement in different situations.
(1) Cases 1 to 3 : represent the anterior, posterior, and centrally loaded conditions in which the load is placed symmetrically on the tibial plateau. In these cases, no varus - valgus moment would be produced.
(2) Cases 4 to 6: There is, again, anterior, posterior, and centrally placed load, but here the load is concentrated entirely on one plateau. These cases represent the maximum production of varus-valgus moments. The magnitude of load in cases 4 to 6 is the same as the sum of 2 magnitudes of the individual loads in cases 1 to.3: In other wards, this is a realistic condition in which the total equilibrium force is kept constant, but the load is shifted entirely to one plateau. The load in cases 4 to 6 is in the central region of the single plateau. This condition is consistent with the total condylar prosthesis, in which the load will remain essentially in the centre of the concavity.
(3) Case 7 : It is included to show the load condition comparable to case 2, in which a posterior stabilization, is added to the prosthesis. The aim of this case is to compare prosthesis containing posterior stabilizing features with those omitting it.
(4) Case 8: The load application point is shifted to the extreme of the edge of the prosthesis. This represents maximal varus-valgus moment which is supported by a prosthesis which may be flat in the antero-posterior view or a condylar - type prosthesis which is displaced to make contact at the extreme outer edge.
On examining (figure 2.8) the highest stresses are produced in those cases in which single load is applied to one condyle. In case 8, the load is applied most eccentrically, the magnitude of the stresses in the cancellous bone is greatest. It is noted in all cases, the metal tray and the metal peg produced slightly lower maximum cancellous bone stresses than other 2 models.
Metal trays provide modest reduction in the magnitude of the maximum compressive stress in the cancellous bone for all loading conditions. The more severe the loading condition, the greater the reducing effect on the metal tray. The tibial peg does not play a major role in the primary load transmission mechanism of the tibial plateau (Bartel et al., 1982).
Hint on Patello femoral Mechanics:
Clinical measurement parameters, such as the quadriceps (Q) angle are important in understanding the influence of anatomy on the components of the patellofemoral joint contact forces. Care must be taken to observe the three- dimensional nature of the forces on the patella which are (l) lateral facet force (2) medial facet force (3) vertical force ”quadriceps force and patellar tendon force”. When viewed in the anteroposterior direction, an extended knee displays a Q angle. The greater the Q angle, the larger the lateral facet contact force will be compared to the medial facet contact force. However, once the knee undergoes substantial flexion (greater than 20 degrees), the Q angle can no longer be considered as a measure of this load distribution because of the three-dimensional relationship between the force vector acting on the patella (Bartel et at., 1991).
(Figure 2 . 8) The maximum stresses that are induced in the cancellous bone underneath the tibial plateau is displayed for each loading case. The bars below the line represent compressive stresses, while those above the line represent tensile stresses. Results are shown for the three classes of the trays previously described. The magnitude of the single joint loads is equal to the sum of the symmetrical loads. This is consistent with the previous examples, which show the shifting of load from one condyle to the other in response to an application of a varus moment
(Bartel et al., 1982).
TOTAL KNEE ARTHROPLASTY
PROSTHESIS EVOLUTION AND DESIGN
EARLY DESIGNS:
As early as 1861, Fergusson reported performing a resection arthroplasty of the knee for arthritis. Verneuil generally is credited with performing the first interposition arthroplasty of the knee in(1863), when he inserted a flap of joint capsule between the two resected joint surfaces to prevent them from growing together. In the 1920s and 1930s, Campbell popularized the use of free fascial grafts as an interposition material. These grafts had limited success in ankylosed knees but not in arthritic joints. Following Smith-Petersen’s success with mold arthroplasty of the hip, mold hemiarthroplasty of the knee was attempted by Campbell and Boyd in 1940 and by Smith-Petersen in 1942. Both prostheses were metallic molds fitted to the femoral condyles, but neither produced significant pain relief. Later, a femoral stem was added to the Smith-Peterson device for improved prosthesis fixation, giving it some short-term success. Tibial hemiarthroplasty also was attempted in the McKeever and MacIntosh tibial plateau prostheses. These prostheses, like their femoral counter-parts, were subject to painful early loosening and failed to replace both surfaces of the arthritic knee joint, so the unaltered joint surface remained a source of persistent pain(Canale, 2003).
A Comparison of Models of Total Knee-Replacement Prosthesis:
In the last few years, interest in total knee arthroplasty has resulted in a proliferation of prosthetic designs, and many different types are now available in the United States and Europe.The prostheses can be categorized into two distinct types:
(1) Condylar Replacements: The joint surfaces alone are replaced. Ligaments then are needed to provide stability. This group can be further subdivided into designs which mimic the anatomical configuration of the normal knee, thus simulating normal motion (unicondylar, duocondylar, UCI, St. Georg, and Marmor), and prostheses of constant radius which do not copy the normal geometry. (Guston, polycentric, and geometric).
(2) Hinge-type Prostheses: In this type the ligaments are sacrificed and stability is provided by the design of the prosthesis itself. Hinges may have a fixed axis with a constant center of rotation (Walldius, Shiers, and Guepar) or be of more complex design allowing a variable axis of motion or rotation (stabilocondylar, Herbert, and Lyons rotational prosthesis). Thus, the selection of a suitable prosthesis has become confusing and difficult for surgeons who are not experienced in the field. The time has come to take stock and evaluate the quality of the results obtained using existing knee replacements(Insall et al., 2001).
The unicondylar prosthesis was used in the mildest cases and gave the least complications,but the quality of results was not superior to that achieved with the other prostheses.The duocondylar model was best suited for knees with rheumatoid arthritis and mild deformity.The geometric prosthesis was the best condylar prosthesis for osteoar-thritis with moderate to severe deformity, but gave the worst results in knees with rheumatoid arthritis.The Guepar prosthesis was used in the worst knees and gave the best results, but it had the highest infection rate and was the most difficult to salvage.A radiolucency was observed in about 60 per cent of the condylar replacements around the tibial component and in 45 per cent of the Guepar replacements around the femoral component. The significance of this cannot yet be determined but it suggests that the fixation may not be ideal(Canale, 2003).
PROSTHESIS SURVIVAL
Modern knee arthroplasty began in the early 1970s with the development of the condylar total knee prosthesis. The studies of prosthesis longevity with this prosthesis are the standard to which modern knee replacement is compared. Long-term series by Ranawat, Flynn, and Deshmukh, Scuderi et al., and Ranawat et al. have documented the longevity of the original total condylar prosthesis to be 91% to 96% at 14- to 15-year follow-up. The reported prevalences of early failure because of tibial loosening, polyethylene wear, and osteolysis has been higher in cementless TKA than in cemented designs. However, Buechel reported 95% clinical survivorship at 12 years for an assorted group of cementless low-contact-stress (LCS) knee prostheses that included unicondylar prostheses, meniscal-bearing prostheses, and a rotating platform version. Whiteside reported a 10-year survival rate of 96% with an earlier cementless design that included a tibial intramedullary stem and additional pegs but lacked tibial screw fixation. Subsequent modification of the tibial trays to include screw fixation has resulted in minimal short-term tibial loosening ( Rand and Ilstrup , 1991).
INDICATIONS AND CONTRAINDICATIONS FOR TOTAL KNEE ARTHROPLAST
TRICOMPARTMENTAL KNEE REPLACEMENT:
The primary indication for total knee arthroplasty is to relieve pain caused by severe arthritis, with or without significant deformity. Other sources of knee and leg pain must be sought and systematically excluded. These include radicular pain from spinal disease, referred pain from the ipsilateral hip, peripheral vascular disease, meniscal pathology, and bursitis of the knee.Roentgenographic findings must correlate with a clear clinical impression of knee arthritis. Patients who do not have complete cartilage space loss before surgery tend to be less satisfied with their clinical result after total knee arthroplasty. Before surgery is considered, conservative treatment measures should be exhausted, including antiinflammatory medications, activity modifications, and the use of a cane for ambulation (Adam and Noble , 1994)
Because knee replacement has a finite expected survival that is adversely effected by activity level, it generally is indicated in older patients with more sedentary life-styles. It also is clearly indicated in younger patients who have limited function because of systemic arthritis with multiple joint involvement. Severe pain from chondrocalcinosis and pseudogout in an elderly patient is an occasional indication for arthroplasty in the absence of complete cartilage space loss. Rarely, severe patellofemoral arthritis in an elderly patient may justify arthroplasty because the expected outcome of arthroplasty is better than that of patellectomy in these patients. Deformity can become the principal indication for arthroplasty in patients with moderate arthritis and variable levels of pain when the progression of deformity begins to threaten the expected outcome of an anticipated arthroplasty. As flexion contracture progresses beyond 30 degrees, gait is significantly hampered and difficulty with regaining extension may warrant surgical intervention. Similarly, as varus or valgus laxity becomes severe, a constrained condylar type of prosthesis becomes necessary to prevent subsequent coronal plane instability. Intervening before this degree of laxity is present allows the use of a prosthesis that lacks coronal plane constraint and has a more favorable expected survival( Hosick et al .,1994).
Absolute contraindications to total knee arthroplasty include recent or current knee sepsis, a remote source of ongoing infection, extensor mechanism discontinuity or severe dysfunction,recurvatum deformity secondary to muscular weakness, and the presence of a painless, well-functioning knee arthrodesis. Relative contraindications are numerous and debatable. These include medical conditions that compromise the patient’s ability to withstand anesthesia, the metabolic demands of surgery and wound healing, as well as the significant rehabilitation necessary to ensure a favorable functional outcome. Other relative contraindications include monarticular disease in young patients, significant atherosclerotic disease of the operative leg, skin conditions such as psoriasis within the operative field, neuropathic arthropathy, morbid obesity, recurrent urinary tract infections, and a history of osteomyelitis in the proximity of the knee. This list is not all-inclusive, and any preoperative condition that can adversely affect the patient’s outcome can be considered a relative contraindication( Canale, 2003).
INDICATIONS FOR PATELLAR RESURFACING
The role of universal patellar resurfacing in TKA is controversial. It has been advocated universal patellar resurfacing, with clinical series indicating that knee scores after patellar resurfacing are slightly better because of less residual peripatellar pain and improved quadriceps strength.Patellofemoral complications occurred in 4% of patients with patellar resurfacing compared with 12% of patients in whom the patella was unresurfaced. Significant residual anterior knee pain was the most common complication in the unresurfaced group(Berry and Rand , 1993).
The major argument in favor of selective resurfacing of the patella is that complications of resurfaced patellae account for most of the reoperations after TKA in many series. Also with selective resurfacing of the patella, using a femoral component that incorporates an anatomically shaped femoral trochlea, these authors reported essentially equal knee scores for resurfaced and unresurfaced groups. A prospective study by Keblish, Varma, and Greenwald included patients with bilateral arthroplasties in which one knee had a resurfaced patella and the other knee had its original unresurfaced patella. The patients had no subjective preference between the two knees, nor was there any difference in stair-climbing ability or the incidence of anterior knee pain(Bayley et al.,1988).
The desirability of resurfacing continues to be debated, and the results of selective patellar resurfacing appear to be design-dependent, favoring an anatomical femoral component trochlear design.Indications for leaving the patella unresurfaced are a primary diagnosis of osteoarthritis, satisfactory patellar cartilage with no eburnated bone, congruent patellofemoral tracking, a normal anatomical patellar shape, and no evidence of crystalline or inflammatory arthropathy. Patient weight also appears to be a factor, with lighter patients tending to do well with unresurfaced patellae ( Whiteside , 1995).
PREOPERATIVE EVALUATION
The most important part of preoperative evaluation is determining that total knee replacement is clearly indicated . Preoperative knee roentgenograms should include a standing anteroposterior view, a lateral view, and a skyline view of the patella. A long leg standing anteroposterior view is beneficial in determining the mechanical axis of the limb, specifically that of the femur (Figure 3-1) because the valgus angle of the distal femoral cut is determined by the angle between the mechanical and anatomical axes of the femur. The long leg film also is useful to determine if significant bowing of the tibia precludes the use of an intramedullary tibial alignment guide. Templates can be used to anticipate approximate component sizing and bone defects that will require bone grafting or the use of a metal block or wedge (Canale, 2003).
Figure 3-1Anatomical and mechanical axes of femur and tibia are determined independently on preoperative long leg roentgenograms, with goal of centering postoperative mechanical axis of limb within center of prosthetic knee. (1) Angle between anatomical (2) and mechanical (3) axes of femur (4) mechanical axis of tibia ( Canale, 2003).
Patients must have adequate cardiopulmonary reserve to withstand anesthesia, either general or epidural, and to withstand a blood loss of 1000 to 1500 ml over the perioperative period. A routine preoperative electrocardiogram should be performed, and those patients that have a history of coronary artery disease, mild congestive heart failure, chronic obstructive pulmonary disease (COPD), or restrictive pulmonary disease should be evaluated by appropriate medical consultants.In such patients, operative monitoring with a central venous pressure line or a Swan-Ganz pulmonary artery catheter may be indicated. Significant peripheral vascular disease in the operative leg also should be evaluated. If adequate vascularity is questionable, a vascular surgeon should be consulted. In patients with moderate peripheral vascular disease, knee arthroplasty can be performed without the use of a tourniquet and with attention to hemostasis .Routine preoperative laboratory evaluation should include CBC and urinalysis. Preferably, these tests are performed a few days before surgery to allow any medical intervention necessary to ensure optimal patient condition at the time of surgery. The routine use of a chest roentgenogram usually is not cost effective as a screening tool, but it is indicated in patients with a history of cardiopulmonary disease. Similarly, routine preoperative evaluation of coagulation studies is not necessary except in patients with a history of bleeding or coagulopathy ( Canale, 2003).
SURGICAL TECHNIQUE FOR PRIMARY TRICOMPARTMENTAL KNEE REPLACEMENT
A tourniquet is always used and the usual approach was medial parapatellar. Insertion of any of the three condylar replacements must be regarded as a difficult technical procedure; this is particularly true if there is severe preoperative deformity, instability, or flexion contracture.
Unicondylar
Flexion contracture is not correctable with this type of prosthesis, but any degree of varus or valgus instability can be corrected provided the knee can be passively aligned under anesthesia. It is usually easier to correct valgus than varus deformity, and release of the distal insertion of the medial ligament is sometimes done to aid correction of varus deformity. To maintain correction it is necessary to use the thickest tibial component that will fit. Positioning of the components is critical to ensure smooth motion and must be checked before cementing.
Duocondylar:
Instability is corrected by building up on the tibial side, but fixed deformity requires resection of bone. Because the duocondylar prosthesis has an anatomical shape, it does not fit well if too much bone is removed; this is particularly true of the femoral component. Flexion contracture must be corrected by adjusting the placement of the femoral component, because excessive bone resection from the tibia causes impingement of the tibial spine against the femur in extension. Asymmetrical bone resection for the correction of fixed malalignment creates laxity of one collateral ligament, a situation not well suited to the duocondylar model because of lack of constraint in the design.For practical purposes, these conditions limit the use of the duocondylar prosthesis to knees with more than 25 degrees of flexion contracture and 10 degrees of fixed malalignment. Severe rotatory deformities and lateral subluxation of the tibia are also contraindications. The principle of duocondylar replacement is the restoration of normal joint anatomy. Ideal positioning of the prosthesis results in placement of the femoral component in slight valgus and of the tibial components at right angles to the shaft of the tibia, with the ligaments under physiological tension. from the foregoing discussion, it is evident that this sometimes can be difficult.
Geometric:
Many of the comments relating to insertion of the duocondylar prosthesis also apply to the geometric design, but to a lesser degree. The prosthesis is non-anatomical and more constrained. Thus, bone resection from the femur is limited only by the ligament attachments and residual laxity of one collateral ligament is better tolerated. Up to 40 degrees of flexion contracture and 15 degrees of fixed malalignment can be corrected.
With both the duocondylar and geometric prostheses, there is a tendency to place the femoral component in excessive valgus and the tibial component in varus, resulting in an obliquity of the joint although the over-all alignment of the femur and tibia may be satisfactory.
It is also important with both prostheses to provide a smooth transition from the femoral groove to the prosthetic surface of the femoral component, otherwise the patella will impinge on any irregularity.
Guepar
The Guepar is the easiest prosthesis to use as it is largely self-aligning and insertion is not complicated by abnormalities in the knee. It can be used to correct almost any deformity provided the intramedullary cavities of the femur and tibia will receive the stems of the prosthesis. In one case, an obstruction of the femoral medullary canal necessitated cutting short the Guepar stem before insertion could be completed. A narrow intramedullary canal can create a similar problem.Care is also required to ensure that the flanges on the axle are adequately spread by the c-clamp. Failure to achieve this will result in axle loosening.The patellar mechanism tends to dislocate laterally in flexion and it is often necessary to perform a wide lateral release of the lateral retinaculum (Shoji et al ., 1993).
SURGICAL APPROACHES:
Multiple skin incisions have been described for primary total knee arthroplasty; the most commonly used is an anterior midline incision. Making the incision with the knee in flexion allows the subcutaneous tissue to fall medially and laterally, which improves exposure. Frequently, a preexisting anterior incision on the knee should be incorporated into the skin incision if it is in a usable position. If multiple previous incisions are present, the most lateral usable incision should be used because the blood supply to the skin of the anterior knee tends to come predominantly from the medial side. Generally, previous direct medial and lateral incisions, as well as transverse incisions, can be ignored. The skin incision should be long enough to avoid excessive skin tension during retraction, which can lead to areas of skin necrosis ( Canale, 2003).
Figure 3-2 Medial parapatellar retinacular approach ( Canale, 2003).
The standard retinacular incision in total knee arthroplasty is a medial parapatellar retinacular approach (Figure 3-2). The medial skin flap should be maintained as thick as possible by keeping the dissection just superficial to the extensor mechanism. The retinacular incision is extended proximally the length of the quadriceps tendon, leaving a 3- to 4-mm cuff of tendon on the vastus medialis for later closure. The incision is continued around the medial side of the patella, extending 3 to 4 cm onto the anteromedial surface of the tibia along the border of the patellar tendon.
The medial side of the knee is exposed by subperiosteally stripping the anteromedial capsule and deep medial collateral ligament off the tibia to the posteromedial corner of the knee (Figure 3.3). This dissection is carried farther distal in knees with varus deformities than in knees with valgus deformities and medial collateral ligament attenuation. The knee is extended and the patella is everted along with routine release of lateral patellofemoral plicae (Figure 3-4) and release of any lateral adhesions from previous surgeries. In obese patients, a formal lateral release may be necessary at this stage to allow eversion of the patella beneath the lateral subcutaneous flap. The knee is again flexed, and the remnants of the medial meniscus, the anterior cruciate ligament, and the lateral meniscus are removed along with any osteophytes that may lead to component malposition. If a PCL-substituting prosthesis is to be used, the PCL is resected at this time. With both PCL substitution and retention, the tibia can now be subluxated anteriorly and externally rotated. External rotation relaxes the extensor mechanism, decreases the chance of patellar tendon avulsion, and improves exposure. The lateral tibial plateau is exposed by a partial excision of the patellar fat pad and retraction of the everted extensor mechanism with a levering type retractor placed carefully adjacent to the lateral tibial plateau. During all maneuvers that place tension on the extensor mechanism, especially knee flexion and patellar retraction, attention should be paid to the patellar tendon attachment to the tibial tubercle. Avulsion of the patellar tendon is difficult to repair and compromises the result(Krackow , 1990).
Figure 3-3 Medial capsule and deep portion of MCL are elevated subperiosteally ( Krackow , 1990).
Figure 3-4 Lateral patellofemoral plicae are cut to allow mobilization of extensor mechanism ( Krackow 1990).
The subvastus (‘‘Southern’’) approach, as advocated by Hoffman, Plaster, and Murdock, differs from the above technique in the method of subluxating the extensor mechanism laterally for knee exposure (Figure 3-5). The same anterior midline knee incision is used, but the proximal retinacular incision is performed by incising the superficial fascia overlying the vastus medialis and bluntly mobilizing the distal medial border of the vastus medialis posteriorly to the medial intermuscular septum. The origin of the vastus medialis can be lifted off the medial intermuscular septum to approximately 10 cm proximal to the adductor tubercle, staying distal to the aperture for the femoral vessels. The synovium is incised and the entire extensor mechanism is dislocated laterally. The advocates of this approach claim that leaving the extensor mechanism intact allows a patient to perform a straight leg raise earlier after surgery, results in a more rapid return of quadriceps strength, and decreases the need for lateral release. The exposure is more limited than with the medial parapatellar approach and can be a problem in obese patients and those with previous knee procedures( Insall , 1993 ).
Figure 3-5 Subvastus approach involves lifting entire extensor mechanism off medial intermuscular septum and subluxating it laterally for exposure( Insall , 1993).
A lateral parapatellar retinacular incision has been advocated by Keblish in patients with valgus knees to improve visibility of the structures to be released at the time of ligamentous balancing. Others have found this approach problematic because limited exposure frequently requires a tibial tubercle osteotomy (Canale, 2003).
Cement Versus Cementless Fixation In Total Knee Arthroplasty:
Cementless fixation of total knee arthroplasty was developed because of concern about the long term durability of cemented component fixation.Cementless fixation would be more durable than cement. The future direction of knee reconstructive surgery would be toward cementless total knee arthroplasty which would be able to provide younger, more active patients a permanent and effective cure for disabling arthritis.Although loosening of cemented tibial components was the most frequent mode of failure of early designs,the long term durability of the cemented condylar prosthesis of certain designs has been excellent.Indications for cementless fixation were those that still advocated (younger age, good bone quality, ability to follow a limited weightbearing program. All the prostheses were of one design, eliminating differences in implant design features. The patients were matched for weight, gender, and diagnosis thus eliminating these factors as variables. The patients in the current review could not be matched completely for age.There was a high failure rate of the metal backed patellas .This complicates analysis as the failure of cementless metal backed patellas might have an effect on survival of the femoral and metallic tibial components. To minimize the influence of metal backed patellar failure on the survival analysis, the analysis was done without metal backed patellar failure as a revision. None of the knees with revised patellas in either the cement or cementless group subsequently had to have a revision of a femoral or metallic tibial component.The early clinical results of cemented and cementless total knee arthroplasty in younger patients were similar( Whiteside,1994).
Early studies comparing cement with cementless fixation did not find any significant differences in clinical results.In a report on 18 matched pairs of Porous Coated Anatomic prostheses at an average of 5 years followup. It has been found that the clinical and functional performance of each type of fixation were comparable and unrelated to the type of fixation method. Rosenberg et al., compared 123 cementless total knee prostheses to 116 cemented prostheses. The patients were followed up between 3 and 6 years. No cemented knee replacements failed because of loosening but three cementless knee replacements failed because of tibial loosening in two and pain of undetermined origin in one. There were no significant differences observed for pain, limp, or support scores(Rorabeck and Neill , 1997) .
The group of patients studied in this report has been reported on previously.18 At an average of 2.8 years after surgery there were no significant differences in knee scores between the two groups, leading to the conclusion that cemented or cementless fixation of this prosthesis provided equivalent early clinical results. This same group of patients was reviewed to see whether early equal results would be maintained with time. This has not been the case. There was a significant difference in the 10-year survival analysis of the two groups with a higher revision rate for aseptic loosening in the cementless group and also a higher rate of mechanical failure. The high incidence of radiolucent lines seen in the cementless tibial components is also noteworthy. For patients with surviving prostheses there were slightly poorer pain and function scores in the cementless group (but not statistically significant) ( Gavan et al., 1998).
POSTOPERATIVE MANAGEMENT:
Postoperative physical therapy and rehabilitation greatly influence the outcome of total knee arthroplasty. Initially, a compressive dressing and a knee immobilizer are worn to relieve pain and to decrease postoperative hemorrhage. Ice can be applied to the knee for the same reasons. The usefulness of commercially available cold knee dressings is controversial, although Levy and Marmar reported decreased blood loss, the use of less injectable narcotics, and faster achievement of knee range of motion in patients treated with the Cryocuff dressing compared to a control group. In patients treated with continuous passive motion (CPM) postoperatively, Healy et al. found contradictory results for these three parameters. No long-term benefit has been demonstrated with either of these devices (Canale,2003).
Range-of-motion exercises are performed postoperatively, with or without the assistance of a CPM machine. CPM has been shown in multiple studies to assist in obtaining knee flexion more quickly, which may decrease the length of stay in the hospital. Some authors have suggested that early aggressive CPM may compromise wound healing. Johnson demonstrated that knee flexion of more than 40 degrees in the first 3 postoperative days resulted in significantly lower oxygen tension in the skin flaps. However, multiple studies have not found CPM to have a deleterious effect on wound healing. McInnes et al. found that CPM increased active flexion, decreased swelling, and avoided knee manipulation postoperatively but did not significantly affect pain, active and passive extension, quadriceps strength, or length of hospital stay. CPM has not been proved to affect the prevalence of DVT, long-term knee range of motion, or knee functional scores. Passive knee extension is encouraged by placing the patient’s foot on a pillow while in bed. Dangling the legs over the side of the bed is used to promote flexion. Patients are instructed in a home exercise program. Many surgeons have their patients instructed by a physical therapist preoperatively, since postoperative pain and analgesics may hinder the patient’s understanding of the necessary rehabilitation.In addition to range-of-motion exercises, the postoperative rehabilitation protocol includes lower extremity muscle strengthening, concentrating on the quadriceps; gait training, with weight-bearing as allowed by the particular knee reconstruction; and instruction in performing basic activities of daily living( Diduch et al.,1997).
COMPLICATIONS OF TOTAL KNEE REPLACEMENT
1-Infection
Factors frequently associated with a higher rate of infection after TKA include rheumatoid arthritis (especially in seropositive males), skin breakdown, prolonged wound drainage (more than 6 days), previous knee surgery, use of a hinged knee prosthesis, obesity, concomitant urinary tract infection, steroid use, renal failure, diabetes mellitus, malignant disease, and psoriasis( Quanjun et al., 2007).
Infection should be considered in any patient with a consistently painful TKA and especially in a patient with a previously pain-free arthroplasty. A history of swelling, erythema, or prolonged wound drainage is suggestive of TKA sepsis, but these signs are not uniformly present. The erythrocyte sedimentation rate is elevated to more than 30 in approximately 60% of patients. Nuclear medicine scans can be helpful in the evaluation of a painful total knee. Comparing the differential periprosthetic uptake on a technetium scan with the uptake on a gallium- or indium-labeled white blood cell scan is a technique for differentiating infection from aseptic loosening, with a reported sensitivity of 80% to 90%. Aspiration remains the standard for diagnosing infection in TKA, although the sensitivity generally is reported to be only 65% to 70%. This sensitivity can be improved by repeated aspiration. Aspiration can be falsely negative in the presence of systemic antibiotics. The fluid cell count obtained at aspiration can be helpful, with a white cell count of more than 25,000 cells/mm3 indicative of probable infection. Roentgenographic changes of bone resorption at the bone-cement interface, cyst formation, and occasionally new bone formation are present only in advanced infections. While successful total knee replacement offers dramatic and lasting improvement in the quality of life, deep infection is the most feared complication of this procedure as it threatens the function of the joint, the preservation of the limb, and occasionally even the life of the patient (Lettin et al., 1990).
In the report by Peersman and his coworker (2001), 6489 TKR were done in 6120 patients of these knee replacements, 116 knees became infected and 113 were available for followup; 97 of these knees (86%) had deep periprosthetic infections and the remaining 16 knees had superficial wound infections; one third of the deep infections occurred within the first 3 months after surgery and the remaining 2/3 occurred after 3 months.Overall early deep infection rate for patients undergoing a primary knee replacement was 0.39%, whereas the rate for patients undergoing a revision knee replacement was 0.97%;predominant infectious organisms were gram-positive (staph aureus, staph epidermidis, and strept group B); 20% of the knees that were infected clinically had no organisms that could be identified in each case, the patient had been treated empirically at another institution with antibiotic before a culture of the joint was obtained( Peersman et al., 2001).
Predisposing factors
The rate of infection increased after implantation of cemented linked hinges, such as the Guepar prosthesis (Russel and James, 1994).
Various factors increase the risk of infection after total knee replacement; some are inherent to the host and cannot be altered while others may be reduced or eliminated by meticulous preoperative screening of the patient. Rheumatoid disease, patient on steroid medication, open skin lesions on the affected extremity, a previous operation about the knee, and a history of infection all have been associated with a significant increase in the rate of deep infection. While three of these factors cannot be altered by the surgeon, open skin lesion should be noted and treated before the elective operation is performed. Wilson et al., (1990) reported a rate of infection of 3.1 per cent in a study of 1857 osteoarthrotic knees that had had a revision total knee arthroplasty because of an infection around the previous implant.They also reported that recurrent urinary-tract infection ,diabetes mellitus, systemic use of steroids, immunosuppressive medication, advanced age, malnourishement, prolonged hospitalization before operation and obesity appeared to be associated with an increased rate of infection after total knee replacement.Routine dental cleaning and extraction produces bacteremia in nearly all patients. So the antibiotic prophylaxis is appropriate at the time
of dental manipulation (Ayers et al., 1997).
Early and aggressive attempts at debridement may lead to deep contamination that might otherwise have been avoidable. Very large area of necrosis, however, should be handled aggressively, utilizing appropriate skin grafts in consultation with a plastic surgeon(Russel and James, 1994).
Mode of infection
Infection in the early stage is most likely a result of bacterial contamination in the operating room although the possibility of hematogenous seeding from other sources cannot be ruled out ( Peersman et al., 2001).
Two additional mechanisms can lead to an early wound infection:
(1)-A leading hematoma that initially is sterile and subsequently becomes culture positive.
(2)-Defective skin healing that allows the contamination of the underlying soft tissues and prosthesis from the outside environment. Or remote sites of infection such as the oral cavity, the genito- urinary tract, the pulmonary system, and skin ulcers.
Three main portal of entry for infection after total joint replacement have been suggested:
- Intraoperative contamination.
- Postoperative inoculation of the joint.
- Haematogenous seading ( Peersman et al., 2001).
1- Intraoperative contamination
The main sources of infection are from the skin of the patient and air borne particles from the theater personal (Learmonth, 1999).
Operating room environment, frequency of air change per hour in the operating room, the contamination of some equipments commonly in use during arthroplasty, dress of the personal and the presence or absence of the laminar air flow, the positioning of the personal around the operating table is an important determinant of the rate of sepsis (Grogan et al., 1986).
Surgical technique must be meticulous to minimize soft tissue injury and necrosis. .Hemostasis decreases the availability of culture medium for any organisms introduced into the wound. Also prolonged operating time should be avoided (Rand and Fitzgerald ,1989).
2-Postoperative inoculation of the joint
Direct inoculation of the joint with bacteria may result from contamination through a puncture wound or dehiscence of the operative wound (Goregan et al., 1986).
3 Haematogenous seeding
Although the true prevalence of early and late haematogenous seeding of the site of total joint prosthesis is unknown, there is no question that this phenomenon occurs In the early postoperative period, the operative haematoma at the site of total joint arthroplasty is susceptible to haematogenous seeding; Therefore, when possible, conditions that may create an episode of bacteremia should be avoided during this period (Wilkins and Patzakis, 1990).
Diagnosis
Early diagnosis of an infected prosthesis requires a high index of suspicion.Infection may cause only knee pain, persistent effusion, or early painless loosening, or more obvious signs, including inflammation, drainage, and sepsis.
(1) Lab Studies
A- White blood cell count
The white blood cell count is usually elevated only in the fulminant infection, therefore a normal white cell count dose not exclude infection
( Rand and Fitzgerald, 1989 ).
B-Erythrocyte sedimentation rate
The erythrocyte sedimentation rate is frequently elevated but is difficult to interpret in patients with rheumatologic disease.
C- C- reactive protein
The elevated level of C- reactive protein should return to normal base line values within one month. Therefore the presence of an elevated C- reactive protein level can help in the differentiation of septic versus aseptic loosening of the implant (Shih and Yang, 1987).
D-cultures:
False-negative ;25% false negative results seen with aspiration rate means that positive cultures often will be isolated only after components are removed & tissue is cultured.False-positive ;cultures which show growth in broth only are generally not considered positive (probable lab error); when cultures are taken at the time of revision, the surgeon should be suspicious if only one sample (out of many) grows a pathogen (generally two positive culture samples are required to indicate a definite infection). Some surgeons require that a sample yield 5 colonies per plate inorder to indicate infection ( Peersman et al., 2001).
2-Radiological appearance
Plain radiographs are of limited value in establishing the diagnosis of infection. X- Rays are usually normal early in the course of infection or demonstrate non- specific soft tissue swelling or an effusion. As the infection becomes chronic destruction of the bone- cement interface may occur, resulting in wide ( > 2mm ), extensive, poorly marginated radiolucent zones (Schenk and Dalinka, 1999 ).
3- Bone scane
Technetium and gallium bone scans are of limited value scince persistant periprosthetic activity, particularly around the tibial component, can continue for several years following surgery in a symptomatic patient (Hoffman et al., 1988).
Likewise, indium- labeled white blood cells (In- 111- labeled leukocytes) a radionuclide commonly utilized for suspected infection in the appendicular skeleton, can focally accumulate around non infected prosthesis, resulting in false- positive examinations. This has been attributed to marrow redistribution in the periprosthetic region resulting in increased marrow and, hence, increased uptake around the prosthesis(Schenk and Dalinka, 1999).
4-Aspiration
Knee aspiration is the standard of care for conclusively determining whether there is deep wound infection. The fluid aspirated from the knee is sent to the bacteriologic laboratory for direct smear, and cultures with antibiotic sensitivities for aerobic and anaerobic bacteria, acid fast bacilli, and fungi (Windersor et al., 1990).
If fluid cannot easily obtained, a fluroscopically assisted aspiration should be considered. The aspiration should be performed under sterial
conditions and without the use of local anesthetics. The preservative used in the vials of lidocaine is bacteriocidal to many organisms and may lead to a false-negative aspiration. If enough fluid is aspirated from the knee, a complete blood cell count and a differential white blood cell count may also give valuable information. If the former (complete blood cell count) shows more than 10.000 polymorphonuclear leukocyte per cubic millimeter and the latter(differential white blood cell count) reveals a value greater than 75% , infection should be suspected. Fluid should also be sent for determination of glucose and protein levels. In normal synovial fluid, protein level are about a third of serum level, and glucose values are similar to those in plasma. In the presence of infection, synovial glucose values are decreased due to the presence of organisms that utilize sugar in their metabolism. Thus low glucose and high protein values are compatible with infection (Russel and James, 1994).
The overall accuracy rate of diagnosing on infection has been shown to be increased throughout the use of molecular biological technique called polymerase chain reaction (PCR) testing on the aspirated fluid. This testing is based upon the fact that almost of all the bacterial pathogens that cause infections after total knee replacement have a gene that encode the 16S RNA of a small ribosomal sub unite of the bacterium. A set of primers is used to target this gene to amplify the production of DNA from these bacteria, the bacterial DNA can then be identified(Schenk and Dalinka, 1999).
The PCR method has been found to be very sensitive for the detection of infection when a primer for a specific organism is used. In cases of polymicrobial infection or infection due to an unknown bacterial strain, the use of universal primers that amplify all bacterial species present is being developed. Identification of the amplified genetic material remains difficult (Song and Sloboda, 2000).
5 Biopsy
The most reliable technique for diagnosis is pathologic examination and culture of tissue obtained from the bone cement interface at the time of surgical procedure. Acute inflammatory changes of greater than five polymorph nuclear leucocytes per one high power field on frozen section is a reliable indicator of infection. Multiple cultures should be obtained and evaluated for aerobic and anaerobic as well as fungal and mycobacterial organisms (Rand and Fitzgerald, 1989).
6 - Arthroscopy :
Arthroscopic inspection and biopsy can be performed although the potentiel for scratching the femoral component is present(Song and Sloboda, 2000).
Clinical Presentation
The clinical presentation of an infected total knee arthroplasty has been well documented and generally does not present significant diagnostic problem. The time to diagnosis of infection following arthroplasty is highly variable (Morrey et al., 1998).
A- Early Infection (within three months of surgery)
The early postoperative infected patient will manifest elevated temperature; pain on motion of the knee .Inspection of the wound may show a full-blown acute abscess or a leaking haematoma. Alternatively, the incision may appear quite benign when infection is contained within the knee joint and its capsule. All patients gave a history that the knee had never been free from postoperative pain and all presented with painful swelling of the joint. Patients with superficial infections have dehiscence, cellulitis or suture-related abscess without extension into the joint .Those with deep infections have painful effusion with or without draining sinus (Russel and James, 1994).
B-Late Infection
Late infection is much more common than an early one. The delayed infection that appears after the initial three months but within the first year. Pain is a major presenting symptom. The pain pattern is generally dull and is usually present at night as well as in the day , typical descriptions may be throbbing , gnawing and aching . The pain has probably no connection with weight bearing or range of motion.There may also be increase in the temperature of the knee. Persistent unexplained pain, effusion .erythema, prolonged drainage from the wound, or a history of failure of primary wound healing should raise the suspicion of infection. This type of presentation may be best considered a delayed infection, since it is possible that the low virulence of the indolent organism or the bacteria- host response was such as to delay manifestations of the infection (Grogan et al., 1986).
Microbiology
The organism most frequently found in infected total knee replacements is staphylococcus aureus.
Differential diagnosis:
- Staph aureus 33%
-Staph epidermidis 24%
-Psuedomonas 9%
-H. influenza 9%
-E. coli 4% (Deacon et al., 1996).
Prevention of infection
Prevention of infection in TKA begins for the time of patient selection and in the operating room, which should be controlled with strict adherence to aseptic technique. Personnel within the operating room should be kept to the smallest number that can efficiently perform the procedure, and traffic in and out of the room should be held to a minimum. Operating room surveillance with adherence to such policies has been demonstrated to decrease the incidence of postoperative infection in total joint replacement. The use of ultra-clean air operating rooms has greatly affected postoperative infection rates in total joint arthroplasty. Filtered vertical laminar flow rooms with high rates of air exchange were widely used,this reduce the postoperative infection rate from around 10% to 1% to 2% by this measure alone. In a series of articles, Lettin etal,(1990) described the use of vertical laminar flow in operating rooms and the use of prophylactic antibiotics and reported similar effects in lowering the rates of postoperative deep infection in both hip and knee replacement. They stated that the combination of vertical laminar flow with prophylactic antibiotics has an additive effect in preventing deep infection. Statistically, this is difficult to prove because of the low incidence of infection with either prophylactic measure alone. In one clinical series, the use of horizontal laminar flow was demonstrated to actually increase the postoperative infection rate in TKA, probably because of positioning of operating room personnel upstream in the air flow from the operative field. Attention to better personnel positioning may improve results with horizontal laminar flow. Although not widely used, ultraviolet light is preferred by some centers to create an ultra-clean air environment, with infection rates similar to those with vertical laminar flow. The use of body exhaust systems has become wide spread in total joint arthroplasty and has resulted in low levels of bacterial shedding into the operative field. The effectiveness of these systems in preventing postoperative wound infection is again difficult to prove statistically because of the already low postoperative infection rate (Lettin , 1990) .
Treatment Options:
Treatment Options:
The treatment options for an infected total knee replacement include:
1- Antibiotic treatment based on organism.
2- Aggressive wound debridement, drainage, and antibiotic suppression therapy.
3- Staged revision with antibiotic spacer.
4- Knee arthrodesis.
5- Resection arthroplasty.
6- Amputation(James, 1996).
1-Antibiotic Suppression
The rheumatology literature has shown that treatment of knee sepsis may be accomplished adequately by serial aspirations and antibiotic treatment. However, treatment was successful in knees in which are total joint replacement was not implanted. The implant and acrylic cement act as foreign bodies that limit the ability of the immune system to adequately combat the infection. However, infection is not confined to cemented total knee replacements.Infection developed in 2.8% of uncemented total knee prostheses, 1.5% of 138 hybrid total knee replacements (with an uncemented femoral component), and 1.6% of total knee replacements with totally cemented components. These incidences were not statistically significantly different but show that infection is possible regardless of the method of implant fixation. The success of this treatment option is quite limited. However, although not generally recommended, antibiotic suppression alone may be the only option for a patient who is a poor surgical candidate and does not have other joint replacements that would be at risk of becoming infected by hematogenous spread of the original infection. Only organisms with extreme sensitivity to antibiotics, such as Streptococcus species and Staphylococcus epidermidis, can be treated in this way. The disadvantages of this treatment include the development of resistant bacterial strains, eventual painful loosening of the prosthesis, and the risk of antibiotic toxicity due to long-term use of the medication. This method does not definitively treat the infection. but rather suppresses it, and is useful only in the few patients who are so medically compromised that surgical methods would threatean their survival(Russel and James, 1994).
2-Debridement with Antibiotic Suppression Therapy
Vigorous wound debridement and antibiotic therapy with retention of the components has demonstrated limited success, even with the addition of an ipsilateral gastrocnemius muscle flap to provide adequate soft-tissue coverage and enhance vascularity(Johnson and Bannistor, 1986)
It has been found that the success is greater if infection is diagnosed within 3 weeks of implantation of the original device. The most successfull results were in seven knees in which the average time from the onset of infection to debridement was 21 days. However, the overall success rate was 23%, which reflects the fact that most of their patients had been infected for longer than 2 to 3 weeks.Organisms such as Streptococcus viridans and Staphylococcus epidermidis may be successfully treated by this method if they demonstrate exquisite sensitivity to parenteral or oral antibiotics. If this option is chosen, the patient must take antibiotics for the rest of his or her life. However, life-long antibiotic suppression poses the risk that resistant bacterial strains may develop and create breakthrough infections that are chemically difficult to treat.More radical options may become necessary if infection persists. If one thorough attempt at debridement proves unsuccessful, subsequent attempts are usually futile, and the prosthesis should be removed. Repeated attempts at debridement without removing the implants may compromise skin viability and may complicate definitive treatment by other surgical means. Debridement may be performed by arthroscopy or formal arthrotomy. Formal arthrotomy allows removal of most of the scar and devitalized tissue but may cause significant quadriceps weakness in the postoperative period due to the incision through the extensor mechanism. The surgeon should remove all synovium and scar tissue and
clear the medial and lateral gutters of debris. It may be necessary to fully
expose the knee replacement in order to properly debride the posterior joint capsule. Arthroscopic intervention may accomplish the same goals; however, multiple (up to six) portals may be required. The procedure is generally longer than arthrotomy because of the slower extraction of tissue by rotary suction blades. Infections that create significant scarring may render arthroscopy impossible as a treatment option ( Segawa et al .,1999).
Regardless of the surgical method used, a thorough debridement is
done, frozen tissue sections. gram stains, cultures of the tissue, and the
macroscopic appearance of the wound should provide diagnostic information.After debridement, the wound is closed over suction drains, which should remain in place for 36 to 48 hours. Using ingress and egress tubes with continuous irrigation is no longer recommended, as there is a significant risk of fluid extravasation as well as a risk of exogenous superinfection due to communication of the deep anatomic structures with
the skin. Under no circumstances should the wound be left open to close by secondary formation of granulation tissue.The wound is inspected after 2 weeks and is reaspirated under strict aseptic conditions. If the wound is begin and the cultures are negative, antibiotic therapy is continued for a further 4 weeks. When this is not the case. reoperation with removal of the
prosthetic components and all cement is performed. This decision should be made quickly before further compromise of the underlying tissues develops( Russel and James, 1994 ).
Figure 4-1Antibiotic-impregnated PMMA spacers are useful to maintain ligamentous relationships of knee during interval between debridement ( Canale,2003).
3-Staged Revision of The Infected Total Knee
Insertion of another prosthesis after thorough debridement and administration of appropriate antibiotics has become the treatment of choice for many patients with an infected knee replacement. The protocol populized by Insall et al .,1988 includes: soft tissue debridement and resection of the infected prosthesis and all cement followed by 6 weeks of parental antibiotic therapy maintaining a minimum bacterial titer of 1:8 and then implantation of new knee prosthesis.
Contra-indication and patient selection
Contra-indications for staged revision of the infected knee include:
(a) persistent infection, (b) medical illness precluding multiple reconstructive procedures, (c) extensor mechanism disruption, and (d) a marginally viable soft-tissue envelope.
Careful evaluation of the infected knee replacement includes documentation of range of motion, knee stability, neurovascular status, and status of the surrounding soft-tissue envelope with particular emphasis on extensor mechanism integrity, it is best to assess the necessity of soft-tissue coverage procedures at the initial evaluation and, when possible, use of these procedures is optimal at implant removal rather than at the time of reimplantation surgery( Markovich et al., 1995 ).
Arthrocentesis of joint fluid for culture and antibiotic sensetivity testing help to direct the initial antibiotic regimen in the postoperative period while waiting for final culture result from intraoperative tissue specimens( Markovich et al., 1995 ).
Surgical Techniques
Implant removal and debridement
The fundamental steps inherent in all of the various treatment approaches of staged revision surgery include adequate exposure and a thorough debridement. Careful placement of the skin incision is crucial. Sinus tracts that exit the wound should be ellipticallv excised as a part of the skin incision. Sinus tracts located away from the wound are also excised and closed after debridement of the sinus tract and any associated soft-tissue abscesses( Hanssen, 1999 ).
Formal arthrotomy is usually performed through a medial parapatellar capsulotomy. Another effective technique to increase exposure is the quadriceps snip. Use of a formal V-Y quadriceps turndown is avoided because of the potential for extensor mechanism necrosis.The prosthesis are carefully removed to preserve as much bone stock as possible, Patellar component removal is easily performed with the knee extended, which also minimizes tension on the patellar ligament insertion. The removal of the femoral component before the tibial component is done to avoid any fragments of cement or bone falling into the distal tibial canal. Screw tracts and serpiginous areas of osteolysis are debrided with a high-speed burr.The final step in debridement is meticulous synovectomy of the suprapatellar pouch, medial and lateral gutters. and the posterior capsular region, all synovium and scar tissue is sharply excised to expose viable bleeding tissue surfaces.Representative tissue samples should be obtained during the debridement for culture and sensitivity testing, specimens are obtained from the intercondylar notch, the prosthesis-bone interface of the femur and tibia three to five samples are usually adequate. Antibiotic then adminstered and the antibiotic choice is based on test result obtained from the preoperative aspiration. If there are no culture results available, a cephalosporin is usually used while awaiting final culture results( Hanssen, 1999 ).
Antibiotic Beads or Spacer Blocks
Most orthopedic surgeons use antibiotic-containing cement beads, spacer blocks, or a combination of the two in the resected knee joint between the two surgical stages. Tobramycin is the antibiotic most often placed in the cement. but various other antibiotics are also used. Booth and Lotke 1989 have preferred the spacer block technique because they believe it maintains soft tissue tension better, serve as an antibiotic delivery system that would also confer mechanical stability to the joint, facilitate patient ambulation, simplify surgical dissection at the time of reimplantation (Booth and Lotke, 1989).
The cement is placed into the tibiofemoral space during the final stages of polymerization and molded to the contour of the distal femur and proximal tibia. The formation of the short cement pegs which protrude into the bone defects and medullary canal enhances joint stability and helps prevent spacer subluxation in the postoperative period, extension of the cement from the tibiofemoral space over the anterior aspect of the femur into the suprapatellar pouch also enhances joint stability. Moreover, This portion of the spacer effectively maintain the length of the extensor mechanism by minimizing contructure and scarring against the anterior aspect of the femur. If the removed implant had stem or if the medullary canal were opened during debridement , an extra batch of antibiotic loaded cement is mixed to fabricate beads or dowel spacers that are placed into the canals prior to introduction of the tibiofemoral spacer.Beads and/or spacer blocks provide two potential advantages that make their use worthy of consideration. First, they deliver high levels of antibiotic locally. Second, a cavity is maintained in which the new prosthesis can be placed at the second stage of surgery(Hanssen, 1999).
Temporary Antibiotic-Loaded Prosthesis
This concept was initially developed in 1986 as a handmade facsimile of a knee prosthesis made entirely from acrylic cement to act as a drug delivery system and a mechanical device that imparted joint stability and also allowed partial weight-bearing and range of motion prior to the reimplantation. Further modifications allowed incorporation of small metallic femoral runners and a polyethylene tibial component to allow a smooth articulation. This modification was named the prosthesis of antibiotic-loaded acrylic cement (PROSTALAC) and was developed for use in hip and knee joints.The PROSTALAC system was modified further to address complex cases with severe bony deficiencies and soft-tissue defects. This system of molds includes a central libial cement post and corresponding femoral cam to compensate for posterior cruciate deficiency. These temporary antibiotic-loaded prostheses are placed into the joint in a manner similar to that of the block spacer so that the cement protuberances are interlocked but not interdigitated into bone.One significant advantage of articulated spacers when compared with block spacers is the advantage of range of motion while awaiting revision surgery. The typical range-of-motion are achieved with articulated spacers in the time period prior to reimplantation is approximately 70 degrees (Hanssen, 1999).
Reimplantation
It is often difficult to know if the infection has been eradicated prior to inserting another knee prosthesis. Many authors have advocated completion of antibiotics followed by a period of time to assess whether the infection may still be present by following parameters such as the erythrocyte sedimentation rate or C- reactive protein(Rand and Bryan, 1983).
Three different approaches to reimplantation have been utilized after completion of antibiotics: (i) arthrocentesis and culture testing of joint fluid, (ii) open debridement and surgical biopsy followed by wound closure and waiting for culture testing and (iii) empiric reimplantation at the completion of antibiotics.The open debridement and biopsy method was adopted because of concerns with the accuracy of aspiration results, however, this approach requires an additional surgical procedure.Reimplantation knee arthroplasty, is often associated with bone deficiencies and ligamentous insufficiency, which requires the use of more constrained prosthetic designs to achieve knee stability. Stemmed prosthetic components are typically used in this setting to augment prosthetic fixation (Hanssen et al., 1995).
When possible, cementation of the distal femur and proximal tibia with fluted press-fit stems can be used; and if reinfection should occur, these implants are easier to remove than cemented stems.Although the use of uncemented implants has been advocated for the use of reimplantation, the benefit of antibiotic-impregnated cement for prosthesis fixation should be considered during implant selection. Soaking of bone graft with antibiotic solution is an alternative mechanism of providing local antibiotic delivery when using uncemenled implants(Whiteside, 1994).
Unless one chooses to use an uncemented implant, the use of bone graft is rarely required for the reimplantation arthroplasty simply by utilizing other alternatives for the management of bone defects such as the use of modular augments or filling of bone defects with bone cement.
In the setting of minimal bone loss and an intact posterior cruciate ligament, it has not been demonstrated that cruciate-retaining or cruciate-substitution prostheses are preferable, currently, the majority of implant used for reimplantation are posterior- stabilized prosthesis fixed with antibiotic- imprignated cement(Hanssen et al., 1994).
Interval Between Surgical Stages
The length of time allowed to elapse between the first and second stages of reconstruction vary among different investigators and among different studies. A reasonable approach is to remove all foreign material and infected tissue from the operative site at the initial surgery, allow a sufficient interval for complete wound-healing to occur, and then allow enough time for antibiotic treatment to sterilize the resected knee joint. This process normally requires about 4 to 6 weeks, but may be slightly shorter or longer in selected cases(Hanssen, 1999).
Postoperative Management
Antibiotics are generally administered for 5 days until results are available from culture and sensitivity testing of intraoperative tissue samples obtained at reimplantation. If there are positive culture results with the same organism identified at the time of implant removal, an additional course of intravenous antibiotics is administered for 28 days, and then consideration of prolonged oral antibiotic suppression is individually assessed with the consultation of an infection disease specialist. If a positive culture result is determined to be a contaminant because of growth in broth only or identification of a different organism recovered on only one tissue sample, antibiotics are discontinued. Otherwise, all antibiotics are discontinued on the fifth postoperative day(Hanssen, 1999).
4-Arthrodesis of The Knee
Most failed prosthetic knee replacements can be revised to another functioning knee arthroplasty. However, in some patient populations and with certain types of failures, a revision arthroplasty is not a viable option and other treatment methods should be considered. Nelson and Evarts first described knee arthrodesis as a treatment for failed total knee arthroplasty in 1971and since that time, salvage of failed total knee arthroplasty has become one of the more common reasons for knee arthrodesis(Benson et al., 1998).
Indications for arthrodesis following a failed total knee replacement:
1- High functional demand,
2- Disease involving a single joint,
3- Relatively young age, which is not candidate for staged revision.
4- Deficient extensor mechanism,
5- Poor soft tissue coverage,
6- Immunocompromised condition, and
7- The presence of a highly virulent microorganism causing infection that requires highly toxic antimicrobial therapy.Destroyed bone or soft tissues may make implantation of prosthesis very difficult following the staged treatment of an infected total knee arthroplasty. In this setting, a successful arthrodesis of the knee can result in a stable, painless, functional extremity(Benson et al., 1998).
Relative contraindications to arthrodesis in failed totaLknee arthroplasty :
1-Bilateral knee disease.
2- Severe segmental bone loss.
3- Ipsilateral ankle or hip disease.
4- Contralateral leg amputation (Rand and Minnesota, 1993).
Preoperative Mangement
In order to enhance the probability of achieving asuccessful arthrodesis, the knee should ideally be in the same state that one would
require for reimplantation. This implies that if infected, the organism and appropriate antibiotic sensitivities should have been identified and the patient treated for an appropriate length of time. Good soft tissue coverage is essential, using muscle flaps or free flaps as necessary. For the infected total knee replacement, most authors favor a two-stage procedure to achieve arthrodesis.The prosthesis and all cement are removed at the initial stage, it is important to remove all the cement from the surface of the bone and the intramedullary cavities because cement retention is a source for residual sepsis. Meticulous debridement of fibrous membranes and granulation tissue is important. The patella is retained after debridement if it has a vascular supply to be used as a source of bone graft at the definitive arthrodesis. Antibiotics are administered postoperatively intravenously for 6 weeks during this time any soft tissue coverage procedures are performed. The limb is protected in a cylinder cast or molded brace and ambulation is attempted, although much weight-bearing is not feasible. The timing of the second-stage definitive arthrodcsis should not be at a fixed time but is determined by the general condition of the patient and the local condition of the knee. After completion of the antibiotic course, aspiration is attempted and the arthrodesis is delayed until the cultures are negative. Redebridement of any persistent draining sinuses is performed and the wound should lie completely dry with stable flaps(Malcolm, 1999).
Methods Of Fixation
Fixation possibilities include crossed pins or screws, external fixation devices, plates, and intramedullary devices. Crossed pins or screws provide inadequate fixation for a knee arthrodesls. particularly in the deficient bone remaining after prosthesis removal and have not been used in any reported series.
1- External Fixation
External Fixation has the advantage of not further damaging the vascular supply to the bone by intramedullary reaming or by the periosteal stripping needed for a plate, it leaves no longitudinal foreign body. The disadvantages of external Fixation are the possibilities of neurovascular damage during insertion and of pin-tract infection(Cunningham et al., 1989).
External fixation for arthrodesis involves four basic steps: (1) implant removal, (2) preparation of the osseous bad, (3) application of the
external fixator, and (4) bone grafting if necessary(Rand and Minnesota, 1993).
When bone cut is being performed, the femur usually is cut at 5 to 7 degrees of valgus to reconstitute the mechanical axis of the limb. The femoral cut should be at neutral to 5 degrees of flexion in relation to the sagittal plane. The tibial cut should be perpendicular to the long axis in all planes. It is best to use three transfixing pins in the distal femur and three in the proximal tibia. The pin sites are predrilled through a cannula to minimize thermal necrosis of the bone. The femoral pins are introduced through the medial side and the tibial pins from the lateral side to avoid impingement on the neurovascular structures. Fixation frame is then applied and enough compression is achieved to produce slight deformation of the pins. If good stability has not been achieved, consideration should be given to the addition anteriorly of two half-pins in the distal femur and two hall-pins in the proximal tibia. The rod connecting the anterior pins is then connected proximally and distally to the rods of the transfixing pins(fig.4-2).Once the frame is completed, consideration should be given to placing bone graft about the periphery of the anthrodesis. Do not attempt to fill large intramedullary defects because they will be in a largely avascular bed and will only incorporate very slowly.The patella can be the source of bone graft for small defects, but iliac crest cancellous bone or allograft may be necessary with the extensive bone loss.A bulky dressing is used for several days. and the patient is allowed to begin ambulalion with toe-touching weight-bearing when pain permits. The frame is removed after 2 to 3 months when there is some evidence of bone union. The patient is then maintained in a cylinder cast at a full weight-bearing status for an additional 2 to 4 months. Tomography may be of value in making the judgment as to whether bone union has occurred.Complications unique to external fixation are pin-tract infection, neurovascular injury, malalignmenl. and fracture through the pin tract, Fracture through the pin tracts can be minimized by a period of cast immobilization following removal of the fixator(Malcolm, 1999).
Figure 4-2 Knee arthrodesis with biplanar external fixation may be indicated for persistent infection ( Canale,2003).
2-Plate Fixation
Nichols el al., (1991) reported a series using dual plates to achieve knee arthrodcses in patients with failed knee arihroplasiy. They insert the plates medially and laterally. A two-stage procedure was done in the one patient with active infection with insertion of vancomycin-impregnated beads at the first stage, total knee cutting guides are used to achieve alignment of 7 degrees of valgus and 10 degrees of flexion. Broad staggered AO dynamic compression plates, appropriately contoured, were applied medially and laterally. These were appropriately twisted to conform to the anteromedial and anterolateral surface of the tibia (Fig 14). Usually, 12 hole plates were used. The patella was secured with screws to the construct and used as free bone graft. To fill large defects, iliac crest graft was used. The limb were splinted postoperatively, and an above-the-knee cast was applied. The cast was removed when radiographic union was achieved.
3- Intramedullary Fixation
The advantages of fixation using an intramedullary rod are that it is closer to the neutral axis of knee bending and it is a load sharing device which permits earlier weight-bearing, frequently without external protection, intramedullary rod may be most reliable technique for achieving union with total knee infection.Intramedullary fusion needs to be performed in a staged fasion with removal of components and control of infection before fusion is attempted(fig.4-3) (Malcolm, 1999).
Contra indications:
active infection, presence of active infection because of risk of infection spreading into medullary canals of the femur and tibia, deformity of the femoral or tibial shaft.
Preoperative Planning:
X-rays include a full-length AP radiograph of lower extremity and lateral radiographs of the femur and tibia, long intramedullary nail that extends from greater trochanter to distal part of the tibia is used for a knee arthrodesis, the diameter of nail depends on diameter of the medullary canal of tibia, which generally has a smaller diameter than the femur. When a large difference exists between the diameter of the femur and tibia, it will be difficult to achieve a tight interference fit, this may require application of cast postoperativey, nails of several diameters should be available at the operation (James et al., 1996 ).
TKR Implant Removal:
preparation of the bone ends should expose vascular bone, provide bone apposition, correct limb alignment, and preserve as much bone stock as possible. When bone cuts are being performed, extramedullary total knee replacement cutting jigs can be used to achieve alignment and bone apposition, bone resection should be limited to one to two mm of bone from the femur and tibia. Proximal part of tibia is be cut first to provide cut that is 90 deg to coronal plane and has the desired degree of posterior slope in the sagittal plane. Bone ends should be vascular, stable, apposed, and in correct flexion and valgus. Establish a tibiofemoral angle of 0 degrees to allow passage of intramedullary nail(James et al., 1996 ).
(Figure 4-3 Knee arthrodesis with intramedullary nail fixation after failed total knee Arthroplasty)( Canale,2003).
Nail Selection
Full length antegrade nails:
Refers to nails inserted antegrade from the piriformis fossa down across the knee and into the tibia, due to the disadvantages of this type of implant is less often used. Its advantages are that, these nails provide maximum stability, anteroposterior bow of the femur in the sagittal plane will allow three-point fixation of the nail in the femur. Disadvantages includes: entry through the piriformis fossa and intramedullary femoral reaming down to the knee joint causes significant bleeding which cannot be diminished by a tourniquet, implant removal is especially difficult if there is implant failure, reaming across localized infected tissue may cause extensive femoral and tibial osteomyelitis, tibial-femoral mismatch requires use of a smaller nail which decreases stability( Canale,2003).
Short nails inserted thru the knee joint:
Have become more popular due to ease of insertion and high union rate (over 90%).The nail is driven retrograde into the femoral canal, and then is backed out down into the tibial medullary canal. Its advantages includes: piriformis fossa remains intact and therefore blood loss can be minimized with a tourniquet, femoral - tibial mismatch is not a problem, implant failure is unlikely due to the smaller nail length(James et al., 1996 ).
Neff in (1989) reported the use of a modular titanium alloy intramedullary rod consisting of a curved femoral and straight tibial rod which arc joined together intraoperitively by a conical press-fit taper joint . Both components are available in 11, 13, and 15 mm diameters to accommodate the dissimilarity in size of the femoral and tibial intramedullary canals. The nails are supplied in 370-mm lengths for the tibia and 340-mm lengths for the femur and are cut to the appropriate length intraoperatively. The conical couple has a 4-degree press-fit taper. The tibial female component has provisions for three equilaterally spaced locking screws which are designed to seal the taper further and prevent distraction and rotation .
The knee is approached through the previous incision, using a two-stage procedure for infected knee, resects a minimal amount of tibial bone to achieve a broad surface which is perpendicular in all planes to the rod The tibial canal in then progressively reamed over a guide wire in 0.5 mm increment through its isthmus. A recommend reaming to 0.5 to 1.5 mm larger than the selected diameter of the planned rod to avoid fracture from hoop stresses in this usually compromised bone. The planned length is measured from the guide wire so that the rod will be beyond the isthmus by 5 to 6 cm without penetrating the ankle joint.The femoral canal is then progressively reamed over a guide wire through the isthmus to 0.5 to 1.5 mm larger than the planned diameter, the femoral rod should extend 4 to 6 cm past the isthmus, and the appropriate diameter femoral rod is cut to this length. The cut tibial nail is inserted first with the driver/extractor. Making sure that two of the set screw holes will be in the anterior tibia. Thc final seating of the nail is accomplished with the male impactor. The femoral nail is then inserted with the driver/extractor, with the curve corresponding to the femoral bow, and the nail is seated with the female impactor the tibial drill guide is used to drill the holes for the lucking set screws. The set screws should be partially inserted before coupling. The knee is extended, coupling and impacting the two nails is done. The final rotational relationship of the tibia to the femur should be checked and set before impaction.The patella can he used as bone graft about the periphery, and the wound can be closed in the usual manner, postoperatively. the patient is gradually ambulated with weight-bearing permitted , usually no external cast protection is needed.Because this device is completely buried in the bone, later removal, if necessary, can be problematic, particularly with a solid fusion (Malcolm,1999).
5-Resection arthroplasy of The Knee
Resection arthroplasty involves the complete removal of the entire knee prosthesis and all associated cement, in addition to complete synovectomy and excision of all associated scar tissue.Regardless of the type of infected prosthesis or the kind of infecting organism, the most common indication for resection arthroplasty of the knee is salvage of infected total knee prosthesis in a patient who is not an acceptable candidate for either reimplantation or fusion(fig4-4)(Falahee et al., 1987).
Patients who meet the requirements for resection arthroptasty generally have septic failure of a prosthetic total knee arthroplasty with a severe (a great deal of soft- and hard-tissue destruction) and chronic (duration of months or years) total knee infection, and infection caused by drug-resistant organisms, and/or impaired resistance to infection. This group may include patients with diabetes, rheumatoid arthritis, and immune deficiency, such as hypogammaglobulinemia or HIV, and those receiving therapeutic immune suppression, systemic steroid therapy, or both. Local factors that are relative indications for resection arthroplasty are multiple prior knee operations, extensive soft-tissue scarring, a large amount of bone destruction at the knee, and/or a large amount of bone resection necessary to control the infection at the time of the initial debridement procedure( Insall et al .,1983 ).
Figure 4-4 Resection arthroplasty of knee(Canale ,2003).
Technique Of Resection Arthroplasty
The resection arthroplasty operation is basically a thorough debridement of all infected tissue with complete removal of the prosthesis, the cement, and all tissue judged to be either nonviable or marginally viable. This judgment can be facilitated by intraoperative release of the tourniquet to visualize the blood supply to damaged tissue. After the debridement is complete, the distal end of the femur and the proximal end of the tibia should be reshaped a bit to obtain maximum bone contact and to achieve alignment of the femur and tibia on the mechanical axes of the limb in nearly full extension. After the operation, the limb should be maintained in functional position, with the femur and tibia on me weight-bearing (mechanical) axis and the knee flexed 10 to 20 degrees, for as long as possible, but certainly never for less than 3 to 4 months( Kaufer, 1999 ).
In most instances the desired alignment of the limb is best maintained with a long leg cast. After debridement, the limb may be very unstable, making it difficult to maintain the desired alignment while the cast is being applied. If this is the case, the femur and tibia may be held in the desired position relative to one another with one or more transarticular Steinman pins which can be removed few days or weeks after the cast has been applied. For some very obese patients, the necessary limb position may be difficult or impossible to maintain with a cast. In such eases, an external fixator with pins in two planes and a total of at least six pins in the femur and six pins-in the tibia will allow the limb to be maintained in the necessary position long enough to achieve stability .If, after complete debridement. the appearance of the wound is satisfactory, it may be loosely closed primarily, if the condition of the wound is questionable, it should be packed open and reinspecred at a later date for further debridement or closure as indicated .After completion of the debridement. if the condition of the wound is satisfactory, the operative wound should be loosely sutured over a drain( Kaufer, 1999 ).
Postoperative Care
Postoperatively, as, soon as the patients are physically capable
they are encouraged to participate in progressive ambulation activities and to bear weight as tolerated while the leg is in a cast or in an external fixator. The length of time before the cast or external fixator is removed
should be at least 3 to 6 months. After removal of the cast or external fixator, the patients were provided with a removable universal postoperative knee splint to be used for walking activities.
Amputation
Amputation may be the final salvage procedure for severe infections that are associated with large bone loss and compromised antibiotic treatment (Pring et al., 1988).
This procedure was required most frequently in infected knee replacements with cemented, stemmed hinges, which for the most part have become obsolete. The remaining shell of bone was frequently inadequate for subsequent arthrodesis or reimplantation, making the limb essentially flail. Amputation may be the only option in patients with mixed infection for whom antibiotic treatment has proved inadequate or in whom there is such massive tissue destruction that knee function is unsalvageable. This frequently occurs with mixed infections in which multiple abscesses and sinus tracts are present and significant destruction of the surrounding soft-tissue sleeve and muscle occurs. If successful treatment can not be accomplished in any other way, a succeful above knee amputation may provide the best functionless knee joint and distal extremity (Windsor and Rand, 1994 ).
2-THROMBOEMBOLISM
One of the most significant complications after total knee arthroplasty is the development of deep venous thrombosis (DVT), with subsequent life-threatening pulmonary embolism (PE). Factors that have been correlated with an increased risk of DVT include age over 40 years, female gender, obesity, varicose veins, smoking, hypertension, diabetes mellitus, and coronary artery disease. The overall incidence of DVT after TKA without any form of mechanical or pharmaceutical prophylaxis has been reported to range from 40% to 88%. The risk of asymptomatic PE may be as high as 10% to 20%, with symptomatic PE reported in 0.5% to 3% of patients and a mortality rate of up to 2%. Proximal thrombi, in the popliteal vein and above, occur in 3% to 20% of patients and have been thought to pose a greater risk of PE than thrombi in calf veins, which have been reported in 40% to 60% of patients. Thrombi in the calf veins do have a propensity to propagate proximally, as documented in 6% to 23% of patients. Routine duplex ultrasonic screening can detect asymptomatic thrombi, as well as proximal propagation of calf thrombi, and that full-scale anticoagulation should be used only in patients with proximal clots( Khaw et al., 1993).
The formation of deep venous thrombosis after such an operation is well documented, and therefore it is imperative that the appropriate prophylaxis regimen is provided for these patients at risk. Without prophylaxis, patients having total joint replacement have a greater than 1% incidence of having a fatal pulmonary embolism develop which results in 10,000 deaths every year. Commonly, a screening examination, such as a venogram or ultrasound imaging, is used to determine the existence and location of a deep venous thrombosis after a total joint replacement.Physical examination alone (Homan’s sign, edema) has proved less reliable, with a specificity and sensitivity below 50% (Westrich et al., 2000).
The use of a routine postoperative screening test is standard in most institutions; however, the type of examination and the accuracy of the testing vary considerably. The interpretation of the examination is technician and radiologist specific. It has been suggested that each institution perform its own internal validity study to assess the sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the screening test as used within each institution( Woolson , 2001).
Deep venous thrombosis can lead to a potentially fatal pulmonary embolism; therefore, administration of prophylaxis is necessary for these patients at risk. The use of postoperative screening to exclude deep venous thrombosis is a common practice in many institutions(Paiement et al .,1999).
Venography is the classic method of detection of DVT and may still be considered the gold standard, especially for research purposes. It does carry the risk of anaphylactic reaction to the contrast media and a small risk of actually inducing DVT. Duplex ultrasonography has excellent sensitivity in the detection of DVT after total joint arthroplasty.It has been documented that sensitivities of 89% or better with duplex ultrasound using venography for comparison ( Kraay et al., 1993).
Vascular ultrasonography for DVT after total knee arthroplasty
Screening vascular ultrasonography was performed postoperatively on 164 consecutive patients being treated with total knee arthroplasty (203 total knee prostheses). This consisted of examination of the femoral and popliteal veins of the operative extremity with color flow and duplex ultrasonography one week postoperatively. All patients received deep venous thrombosis (DVT) prophylaxis with sequential compressive pneumatic stockings, low-dose warfarin, continuous passive motion, and early mobilization. All patients were observed prospectively for thromboembolic sequelae for a minimum of six months postoperatively. The screening study was significantly limited in six (3%) of the 203 total knee prostheses. The overall incidence of sonographically detected proximal DVT or symptomatic calf vein thrombosis was 3% (6/203), and the incidence of symptomatic pulmonary embolism was 2% (4/203). Four of the ten thromboembolic complications occurred after hospital discharge. Results of this study suggest that duplex ultrasonography can be a useful screening method for identification of venous thrombosis after TKA. Patients with asymptomatic proximal DVT can be identified and appropriately treated before development of serious thromboembolic complications. Routine screening for DVT after TKA can avoid the considerable expense, inconvenience, and potential risk of complications associated with prolonged postoperative prophylactic anticoagulation. The combination of sequential compressive stockings, early mobilization, and low-dose warfarin appears to be a safe and effective prophylactic regimen against venous thromboembolic disease in these high-risk patients (Dhupar et al., 2006).
Prophylaxis
Many current methods of DVT prophylaxis are available, including mechanical compression stockings or foot pumps and pharmaceutical agents including low-dose warfarin, low-molecular-weight heparin, and aspirin. Interestingly, continuous passive motion has not been proven to significantly affect the incidence of DVT (Clagett et al.,1995).
(A)Prophylaxis with aspirin alone has not been shown to decrease the overall prevalence of DVT after TKA, according to Haas et al. and Maynard, Sculco, and Ghelman, but it may have some protective effect in the prevention of proximal thrombi. In another recent study, Westrich and Sculco found that aspirin combined with pulsatile pneumatic plantar compression decreased the overall DVT rate from 59% to 27% when compared with aspirin alone. Significantly, there were no proximal thrombi in the patients treated with pulsatile plantar compression combined with aspirin compared with a 14% incidence in the aspirin-only group( Westrich et al., 1996).
(B)Low-dose warfarin has been tested extensively for DVT prophylaxis in total hip arthroplasty and has been shown to lower the risk of DVT by approximately 60% to 70%. There are few studies of warfarin as a prophylactic agent in TKA patients, but these appears to be a small reduction in the frequency of asymptomatic DVT and a greater reduction in the frequency of symptomatic DVT and PE. Warfarin prophylaxis usually begun with a 10-mg dose on the evening before surgery or the evening after surgery and is adjusted according to the daily prothrombin time. The use of the international normalized ratio (INR) allows standardization of anticoagulant effect as measured by the prothrombin time. The current goal of warfarin therapy is to keep the INR between 1.8 and 2.5 for 4 to 6 weeks after surgery. The main disadvantages of warfarin therapy are frequent drug interactions, the need for continued monitoring, and bleeding complications in 1% to 5% of patients (Wilson et al., 1994).
(C)Low-molecular-weight heparin (LMWH) has been shown to be effective in DVT prophylaxis after TKA. In a randomized, double-blind study comparing enoxaparin (30 mg subcutaneous twice a day) to a placebo, Leclerc et al. found a venographically confirmed DVT rate of 65% with placebo compared with 19% with enoxaparin. Proximal clots occurred in 17% of the placebo group, compared with none in the enoxaparin group. In a study by the RD Heparin Arthroplasty Group, a regimen of twice-daily ardeparin was found to reduce the frequency of overall DVT to 26% compared with 43% using warfarin as the prophylactic agent. The proximal DVT rate was 6% with ardeparin compared with 10% with warfarin. The Prevention of Thromboembolism Task Force of the American College of Chest Physicians reported in 1995 that LMWH is more effective in preventing DVT after TKA than warfarin, aspirin, or heparin. The duration of treatment with LMWH is unclear at this time, with many of the current studies concluding after only 10 days. The benefits of LMWH include effectiveness, a standard dose regimen that needs to be changed only in unusual circumstances, and no need to monitor laboratory studies routinely. The disadvantages include greater medication cost compared with other agents, subcutaneous administration, which becomes problematic in the outpatient setting, and scattered reports of a slightly increased incidence of bleeding complications when compared with warfarin or aspirin (Comp et al., 2001).
In the report by Comp et al.,(2001) the authors evaluated the efficacy and safety of a prolonged post-hospital regimen of enoxaparin;following elective total hip or knee replacement, 968 patients received subcutaneous enoxaparin (30 mg twice daily) for seven to ten days, and 873 were then randomized to receive three weeks of double-blind outpatient treatment with either enoxaparin (40 mg once daily) or a placebo.
- of the 873 randomized patients, 435 underwent elective total hip replacement and 438 underwent elective total knee replacement, enoxaparin was superior to the placebo in reducing the prevalence of venous thromboembolism in patients treated with THR. 8.0% (eighteen) of the 224 patients treated with enoxaparin had venous thromboembolism compared with 23.2% (forty-nine) of the 211 patients treated with the placebo - enoxaparin had no significant benefit in the patients treated with knee replacement.Thirty eight (17.5%) of the 217 patients treated with enoxaparin had venous thromboembolism compared with 46 (20.8%) of the 221 patients treated with the placebo.symptomatic PE developed in three patients, one with a hip replacement and two with a knee replacement, all had received theplacebo.
(D)-pneumatic.compressive.devices
(E)-vena.cava.filter
Pharmacological prophylaxis of DVT in TKA definitely decreases the frequency of fatal pulmonary embolism and thus is strongly indicated( Zimlich et al., 1996).
3-NEUROVASCULAR COMPLICATIONS
A-Vascular complication
Arterial thrombosis after TKA is a rare but devastating complication, frequently resulting in amputation. Because extensive vascular calcification can make Doppler studies unreliable as preoperative indicators of postoperative arterial thrombosis, arteriogram and transcutaneous oxygen measurements may be more reliable preoperative tests. Several authors have recommended performing TKA without the use of a tourniquet in patients with significant vascular disease (Westrich et al.,1996).
Arterial Occlusion and Thrombus Aspiration After Total Knee Arthroplasty
Arterial complications after total knee arthroplasty are relatively uncommon. Various mechanisms of arterial injury have been described, of which intraoperative or early postoperative arterial thrombosis is the most frequently reported (Calligaro et al., 1994).
Less frequently, direct injury during posterior capsular surgery or during sawing the tibial plateau and indirect arterial occlusion after correction of substantial flexion deformities have been described. Although arterial thrombosis is a limb threatening complication, no consensus exists on the optimal management of this condition, and specifically, no consensus exists as to the place for isolated thrombectomy versus bypass surgery(Bellemans et al., 2000).
Associated risk factors for the development of arterial ischemic complications include a history of lower extremity arterial insufficiency, absent pedal pulses, calcification of the superficial femoral or popliteal artery, and correction of a substantial flexion deformity (Rand ,1997).
Most of the cases reported with vascular impairment after total knee arthroplasty have been attributed to arterial thrombosis secondary to use of a tourniquet. Some of the cases occurred intraoperatively, but others occurred in the early or later postoperative period (DeLaurentis et al., 1992).
It has been postulated that the mechanical pressure of the tourniquet can result in fracture and dislodgement of atheromatous plaques, completely or partially occluding distal blood flow, thus creating an environment for thrombus formation (Parfenchuck and Young , 1994).
In addition, direct partial or complete thrombosis on preexisting atheromatous plaques secondary to the cessation of blood flow with the use of a tourniquet has been suggested as a possible cause.( Hagan P and Kaufman E: 1990) According to published reports, most cases have been treated using isolated thrombectomy with variable success, ranging from full recovery to amputation, whereas others have strongly recommended a more aggressive approach with femorodistal bypass surgery. Parfenchuck and Young reported on a single case of arterial thrombosis diagnosed immediately after total knee arthroplasty that was treated successfully with isolated thrombectomy, whereas Hagan and Kaufman and Fortune reported on cases occurring later in the postoperative period (the first and ninth postoperative days) with a successful outcome after isolated thrombectomy.There is recommendation of femoral intrageniculate bypass surgery, instead of thrombectomy alone, in the treatment of arterial thrombosis after total knee arthroplasty. Their recommendation was based on favorable results seen with this technique in seven patients treated with a reversed contralateral saphenous vein bypass graft with limb salvage and on their observation that acute ischemia after total knee arthroplasty occurred only in patients with underlying chronic atherosclerotic disease. However, case reports have been published reporting a less satisfactory outcome even after bypass surgery, with persistent postoperative ischemic pain requiring additional arterial surgery or with a disabling neuropathic foot as an end result.Percutaneous thrombus aspiration is suggested as a possible technique in the treatment of popliteal artery thrombosis after total knee arthroplasty. The technique is simple and can be performed by the radiologist during angiography using the same approach. In addition, it requires little additional time and can be followed immediately by femorodistal bypass surgery when it is not successful in restoring reperfusion, such as when dislodgement of plaque is seen.Prompt diagnosis and treatment of this condition are mandatory because any delay increases the risk for irreversible ischemic necrosis(Bellemans et al., 2000).
B-Injury of the peroneal nerve
Peroneal nerve palsy is the only commonly reported nerve palsy after TKA. It occurs primarily with correction of combined fixed valgus and flexion deformities, and are common in patients with rheumatoid arthritis. The incidence of peroneal nerve palsy in the Swedish Knee Arthroplasty project was 1.8% in 2273 rheumatoid patients. The true incidence may be somewhat higher reported in 0,3% to 4% of all total knee operations because mild palsies may recover spontaneously and not be reported(Idusuyi 1996). The value of intraoperative exposure and possible decompression of the peroneal nerve is questionable. When a peroneal nerve palsy is discovered postoperatively, the dressing should be checked for peroneal nerve constriction and the knee should be flexed. Asp and Rand (1999) suggested that such conservative measures, though appropriate, are not very effective in restoring nerve function( Asp and Rand , 1999).
Peroneal nerve palsy following TKR usually presents acutely but in some cases there will be a delayed presentation(Furnes , 2002).
Risk factors of peroneal nerve palsy
Use of epidural anesthesia.
Previous spinal surgery (double crush).
Valgus knee deformity.
Flexion contracture more than 20 degree.
It may also be more common following previous high tibial osteotomy, and patients who also have peripheral neuropathy.
Prevention:
Postoperative dressings include Xeroform (vasiline gauze) and gauze padding over the fibular head region. Keep knee flexed the first postoperative night inorder to reduce tension on the nerve.With a valgus knee, intraoperative dissection & mobilization of nerve will not decrease incidence of peroneal palsy.The patient feels tingling and numbness in the foot, in cases of more serious damage the patient cannot stretch the foot. These symptoms are caused by the damage of the peroneal nerve (Furnes , 2002).
EMG
Useful to objectively document the conduction block.
If possible should be performed within one month of injury.
Management
Initial post operative management consists of removal of circumferential dressings and partial flexion of the knee.with persistent palsy, use DROPfoot brace and ROM exercises to prevent equinus deformity,if complete neurological deficit is present for more than 3 months then operative exploration and decompression is indicated.
even following decompression, there may be persistent weakness .
operative.treatment:
If there is no neurologic improvement after 3-4 months, then operative decompression is considered. Operative treatment invovles external neurolysis of peroneal nerve at the level of the fibular head,the nerve and its branches need to be freed from its adherence to the proximal fibula, particularly at its most proximal 4 cm as well as a second region of adherence which may lie between7and15 cm from the fibular head(Fabre , 1998).
4-Periprosthetic fracture
Fractures around the prosthesis are of three kinds:
(1)Intraoperative.
Can occur of either the tibial plateau or the femoral condyles.Most
Likely to occur when bone is brittle and when the prosthesis is
Driven hard onto the bone.
(2)Caused by stress or fatigue
Usually in the patella but also occur in the femur and tibia.These
have been seen after a stripping of the lateral femoral condyle
For the correction of fixed valgus deformity caused by
Avascularity of the bone.Stress fracture of the tibia have also been
seen in a rheumatoid patient.
Stress fractures involving femoral and tibial components usually
require revision.
(3)Caused by a fall or other injury.
Most injuries occur in the lower femur,supracondylar fractures are
often comminuted with displacement of the femoral component
posteriorly and laterally(Hernigou et al., 2006).
Supra Condyler Fracture Of Distal Femur:
Supracondylar fractures of the femur occur infrequently after TKA (0.2% to 1%) (Figure 4-5). Reported risk factors include anterior femoral notching, osteoporosis, rheumatoid arthritis, poor flexion, revision arthroplasty, and neurological disorders. The anterior femoral flange of condylar-type prostheses creates a stress riser at its proximal junction with the relatively weak supracondylar bone.Many patients with supracondylar fractures after TKA have prior anterior femoral notching, especially rheumatoid patients (DiGioia and Rubash , 1991).
The definition of a supra condyler femoral fracture following total knee arthroplasty should include any fracture occurring in the distal femur within 15 cm of the joint line. In addition, fracture should be included if they occur within 5 cm of the most proximal extent of an intermedullary femoral device, this can therefore include shaft fracture, stress fracture (Cecil and Taylor, 1999 ).
The predisposing risk factors for these fractures are rheumatoid arthritis, chronic steroid therapy, and other condition that results in osteopenia of the distal part of the femur. Other less contributing factors have included medication- induced osteopenia or an unsteady gait in patient who have a neurological disorder. Also, arthrofibrosis after a total knee replacement may predispose to fracture by increasing stress in the distal femoral metaphysic (Clup et al., 2001).
Anterior femoral cortical encroachment, including notching of 3 mm or greater during femoral preparation especially in the early postoperative period (the first six months). Additionally, revision of a total knee arhtroplasty with distal femoral bone loss was a risk factor(Cecil and Taylor, 1999).
Numerous systems of classifications of distal femoral fracture is used. The system found most valuable in management of these fractures was created by Lewis and Rorabeck, (1997). Their classification tacks into account both the status of prosthesis (whether it is intact or failing) and the displacement of the fracture.
Type (1) if the fracture is undisplaced and the prosthesis is intact.
Type (2) if the fracture is displaced and the prosthesis is intact.
Type (3) if the fracture is displaced or undisplaced and the prosthesis is loose or failing .
( Figure 4-5Supracondylar fracture of femur above total Arthroplasty) (Cecil and Taylor, 1999).
Figure 4-6 A and B, Supracondylar intramedullary nail used for fixation of fracture shown in Figure 4-5. C and D, Healed fracture ( Henry , 1995 ).
Periprosthetic Tibial Fractures
Tibial fracture following total knee arthroplasty is an infrequent
complication with a reported prevalence of 0.40 to 1.7 %(Felix et al., 2000).
Classification
Tibia fractures are divided into four major anatomic patterns (Fig.5A).
Type 1 fractures; extend from the tibial plateau and involve the prosthesis interface.
Type 2 fractures; occur adjacent to the tibial stem in the proximal metaphyseal-diaphyseal region.
Type 3 fractures; are distal to the tibial prosthesis.
Type 4 fractures; are limited to the tibial tubercle.
These four anatomic fracture patterns are then further categorized into three subtypes:
(A) Postoperative fracture with a radiographically well fixed prosthesis,
(B) Postoperative fracture with a radiographically loose prosthesis, and
(C) intraoperative fracture.
The anatomic fracture pattern and the associated subtype are combined to describe the specific classification (Stuart and Hanssen, 1999).
Tibial fractures below TKA are uncommon. Nondisplaced stress fractures are best treated by immobilization with restricted weight-bearing. Successful treatment of displaced fractures has been reported with the use of a long intramedullary stem in conjunction with revision of the tibial component. This technique also has been used in tibial nonunions and malunions treated concurrently with TKA.As outlined in a review by DiGioia and Rubash, treatment of periprosthetic fractures about TKA requires a variety of techniques dependent on the characteristics of the individual fracture. Ultimate function of the TKA after fracture healing depends on restoration of alignment, adequate patellofemoral function, maintenance of prosthesis fixation, and adequate residual motion (DiGioia and Rubash ,1991).
Management of Periprosthetic Fracture
1-Supra Condyler Fracture of Distal Femur:
The goal of treatment of a supracondyler fracture proximal to a total knee arthroplasty are union of the fracture and a return to the pre-fracture level of function while maintaining the range of motion of the knee(Fig.17). Non-operative treatment is recommended for non-displaced fractures as well as for minimally displaced fractures when alignment of the fracture and mechanical axis of the limb are easily achieved and maintained with closed reduction ( Rolston et al., 1995 ).
The patient wears an above- the-knee cast for three weeks and allowed to bear weight on the affected limb as tolerated during this period. Three weeks after the fracture a cast brace is applied and range-of-motion exercise are begun. The cast brace is worn until there is radiographic evidence of callus and the fracture has healed clinically.Operative treatment is indicated for a displaced fracture if satisfactory alignment cannot be achieved or maintained with closed reduction or if there is radiographic evidence of prosthetic loosening.Instruments and implant for both internal fixation of the fracture and revision with a long-stem total knee replacement should be available because revision may be necessary if stable internal fixation cannot be obtained or if previously unrecognized loosening of the implant is discovered intraoperatively and in severe comminution, extremely distal fractures ( Ayers et al., 1997).
Multiple options are available to provide secure internal fixation of supracodylar fractures of the distal part of the femur. The supracondylar blade-plate and the condylar compression screw and side-plate have been
used for many years to treat these fractures (Zehntne and Ganz, 1993).
These devices are most useful when there is little comminution of the distal fragment and for fixation of more proximal fractures.
The condylar buttress-plate is preferable when the distal fragment is comminuted because it allows multiple screws to be used for fixation of that fragment .Use of supracondyler interlocking rod is becoming the treatement of choice for the majority of displaced supracondyler fractures . It provides an attractive alternative to lateral plate fixation because of the simplicity of both the instrumentation system and the technique used, for insertion of the nail. In addition, intramedullary fixation is biomechanically stronger & provide good axial, angular, rotational stability with high union rates. Its contrindication include long preexisting total hip intramedullary stem, severe comminution and extremely distal fracure( Rolston et al., 1995 ).
Revision total knee replacement with use of long stem femoral component is recommended for all patients who have loosening of the femoral component in association with the supracondyler fracture. As stability of the femoral component may be difficult to determine in the basis of preoperative radiographs, it is recommended that instruments and prosthetic components necessary for revision total knee replacement be available at the time that internal fixation is undertaken(Kraay et al, 1992)
Evaluation of the overall clinical success should meat the following criteria:
1- The bone fracture should be united in less than six months.
2- The patient should not experience knee pain.
3- Range of motion should be from 0 to 90 degrees flexion (or motion no less than prefracture values)(Cecil and Taylor, 1999).
2- Periprosthetic Tibial Fractures:
(A) Postoperative fractures:
Type 1:
Fractures that involve the tibial plateau-implant interface (type 1) in the postoperative time period have invariably occurred in the setting of a loose prosthesis.A postoperative tibial plateau fracture in the presence of a loose prosthesis should be treated with revision arthroplasty. A combined cavitary and segmental defect of the medial tibial plateau characterizes the type 1B fracture. This type of bone defect is treated during revision surgery with cement fill, bone graft, modular metal augmentation wedges or blocks/ or a custom prosthesis. A cemented or press-fit stem on the tibial component bypasses the bone defect (Stuart and Hanssen, 1999).
Type 2
Fractures adjacent to the tibial implant stem may occur in association with well-fixed or loose prostheses, occur as a result of trauma. Treatment of the Type 2A fractures’ with rigid immobilization resulted in union in all cases without untoward effect on knee function. None of these knees required revision surgery.Type 2B fractures occur adjacent to loose stemmed tibial implants. The characteristic bone defect is a large cavitary defect of the proximal tibia combined with ectasia and segmental deficiencies in the metaphyseal-diaphyseal region. Management of these bone defects is quite challenging and often requires structural or morcellized bone grafting along with revision to a long stemmed tibial component(Stuart and Hanssen, 1999).
Type 3
A fracture of the tibial shaft distal to the prosthesis results from one of three mechanisms: (1) a single episode of trauma, (2) repetitive overload (stress fracture) in the setting of limb malalignment or improper component orientation, or (3) a fracture in association with a tibia tubercle osteotomy ( Felix et al., 2000).
Type 3A fractures should be treated in accordance with the accepted principles of tibial shaft fracture management to ensure proper
limb alignment and maintenance of knee function. Treatment of type 3B fractures needs to be individualized. Management options in-
clude fracture immobilization and delayed revision surgery or combined single-stage revision of the loose tibial component and stabilization of the fracture with a long-stemmed tibial component( Felix et al., 2000).
Type 4
Fractures of the tibial tubercle are potentially catastrophic because the extensor mechanism is disrupted. The two type 4 fractures
reported in one review occurred after a fall in knees with well-fixed components (type 4A). The minimally displaced fracture healed after
immobilization in extension. The displaced fracture healed after open reduction and internal fixation with a tension-band wire. A type 4B fracture that occurred after a tibial tubercle osteotomy was treated with extensor mechanism repair and revision arthroplasty ( Felix et al., 2000).
(B)Intraoperative fractures
Fracture of the tibia during primary or revision knee arthroplasty can result from several mechanisms: (1) removal of cement with an osteotome; (2) trial reduction, (3) bone retraction, (4) intramedullary canal preparation for a tibial stem, (5) insertion of a stemmed tibial component, and (6) application of torsional stress to the limb during the procedure.
Type 1
Fracture of the tibial plateau is frequently caused by an osteotome during cement removal or during a trial reduction. These fractures are usually minimally displaced and may not be recognized until the postoperative radiographs are reviewed. If the fracture is identified during surgery, the treatment of choice is cancellous screw fixation before insertion of the real component. A longer tibial component stem can also be used to bypass the fracture site (Stuart and Hanssen, 1999).
Type 2
Fracture of the proximal metaphyseal-diaphyseal region (type 2) occurs in association with the removal, preparation, or insertion of
a long-stemmed tibial component. Fractures discovered intraoperatively were treated with bone grafting and stem bypass, treatment of postoperative fractures consisted of bracing and limitation of weight bearing for 6 weeks(Stuart and Hanssen, 1999).
Type 3
If an intraoperative fractures of the tibial shaft were identified. The tibia fixed with a plate and screws along with supplemental bone graft.
Type 4
An intraoperative tibial tubercle fracture. The tubercle is secured with suture and the patient treated in a long leg cast until the tibial tubercle healed (Stuart and Hanssen, 1999).
5-Osteolysis
Osteolysis refers to a specific phenomenon that can occur after any form of total joint replacement.Osteolysis is a process where cysts are formed in the bone surrounding total joint replacement component.These cysts are formed when the body reacts to wear debris that is generated at the point of movement of the total joint Arthroplasty.As the body tries to get rid of the debris,there are cells that act similar to a vacuum cleaner to try and clean up this material. The human body has no enzymes that can digest plastic and metal.These matrials will then build up within the cell until the cell ruptures.When the cell bursts,it releases large amounts of enzymes into the local tissue that will then dissolve the tissue and bone in that area.As this occurs,a cyst will be generated( Archibeck et al., 2000).
The most widely accepted theory at the present time regarding osteolysis is that the release of mediators from macrophage engaged in particle phagocytosis stimulate bone resorption at the bone- implant interface. It is the resorption which disrupts the bond formed between implant and bone and which ultimately leads to clinically recognized loosening.Periprosthetic bone loss occurs as a result of an inflammatory reaction to small particles, such as those produced by the various wear modes. Wear modes in total knee replacement have been associated with some design characterized by lower conformity, especially when the tibtil polyethylene is less than six millimeter thickness. Polyethylene wear and osteolysis following total knee replacement surgery may result from many factors, such as, surgical technique, patient selection (young age and high body weigh will subject the polyethylene component to more severe loading conditions), choice of implant design, conformity of articulating surfaces, quality and thickness of the polyethylene component (as thickness decrease, the stress increase), correct alignment of the limb, and proper ligament balance (Argenson and Connor, 2002).
Both processes of stress-shielding and inflammatory reaction occur simultaneously in complex mechanical - biological systems such as joint replacement, and the adverse effects can be additive (Engh et al., 1997).
Cellular mechanism
The tissue adjacent to total hip and knee prosthesis consist of synovial tissue, lymphocytes, and foreign- body inflammatory cells (macrophage and giant cells) that are present roughly in proportion to the number of small particles (Horikoshi et al., 2001).
Most periprosthetic bone resorbtion is affected by osteoclasts, but there is evidence that macrophages and foreign-body giant cells are capable of direct, low-grade bone resorbtion. Invitro studies have indicated that activated macrophages release cytokines, including interlukines (1L-1B, 1L-6) interferone, tumor necrosis factor, and osteoclast secrete prostaglandins (PGE2), and these cytokines play a rule in the recruitment and differentiation of cells and stimulate bone resorbtion .In addition, IL-1B has been shown to stimulate osteoclastic cell formation and increase osteoclast activity (Murry and Rushtan ,2000).
Figure 4-10 osteolysis after T.K.R (Green et al., 1997) .
Although cytokines released by macrophages may directly stimulate bone resorption by osteoclasts, other effect may be mediated by intermediary cells (fibroblasts or osteoblasts). Matrix metalloproteinase (collaginase, gelatinase, and stromelysin), which are capable of effecting bone resorption, are also produced by interfacial membrane tissue around failed total hip and knee replacement (Chiba et al., 1994).
For a given concentration of particles, the stimulatory effect of polyethylene particles in vitro decrease when the particles are larger than about seven micrometers or smaller than about 0.2 micrometer(Green et al., 1997).
Polyethylene wear particles are dispersed in the joint fluid around a prosthetic joint, conceptually, the effective joint space includes all periprosthetic regions that are accessible to joint fluid and, thus, accessible to wear particles.Pattern of joint –fluid flow influence the shape and extent of osteolysis .The local concentration of particles is a factor in the local inflammatory reaction and, hence, the degree of bone resorption in that location. As bone is resorbed, a larger space is produced, encouraging preferential flow of joint fluid and wear particles into that location, which fuels additional bone resorption in that area, leading to an expansile lesion (Thomas et al., 1999 ).
6-Aseptic Loosening
loosening of the components is the most common cause of failure of all types of total knee prostheses. Most often loosens the tibial component, followed by patellar component and femoral component. The loosening is a continuous process causing increasing discomfort (Furnes , 2002).
The loosening rate of total knee prosthese is about one percent per year. That means that after 10 years 10 % of all patients with a total knee joint will have their total knee prostheses failed by loosening and exchanged.Aseptic loosening can be defined as the failure of the bond between an implant and bone in the absence of infection. Historically, the most common cause for revision of a total knee arthroplasty is aseptic loosening of the tibial component (Dorr et al., 1995).
The risk of failure from aseptic loosening in patient who has a total knee replacement increases as the age of the patient at the time of implantation decreases, or if the length of follow- up exceeds 15 years(Stephen, 2000).
Factors responsible for total knee component loosening is technical inadequacy of surgical implantation, other factors include bone quality, patient weigh and activity, prosthetic design, ligamentous instability and wear product.
1- Technical inadequacy of surgical implantation:
Axial malalignment leads to the concentration of stress on one of the compartment, which is neither bone nor cement can withstand in long term component malalignment and malpositioning as well as osteolysis associated with particle debris have been implicated in the development of aseptic loosening (Chiba et al., 1994).
2- Bone quality:
The cancellous bone of the tibia is softer than that of the femur, that is to say the compression strength of the femur exceeds that of the tibial bone and that is why femoral loosening and sinkage is lesser in incidence than tibial loosening (King and Scott ,1995).
Loosening of the femoral component is uncommon whether cemented or uncemented. When it does occur, however, it follows a particular pattern in which the bone resorbs posteriorly, allowing the femur to migrate anteriorly and rotate into flexion (Fukuoka et al., 2000).
Loosening of the patellar component is most often associated with patellar fracture or with dissociation of polyethylene and metal- back component, avascular necrosis of the patella, osteoporosis, loosening of other prosthetic component, and lack of osseous growth into the porous coating (Brick and Scott ,1998).
3- Patient weight and activity
Excessive weight and high activity of the patient have been factors associated with failure of cemented prosthesis and undoubtedly related to the fatigue fracture of methylmetacrylate(Hungerford and Krackow ,1995) .
4- Prosthetic design:
The failure rate due to tibial component loosening represent design problem that is now on the way to solution. The total condylar prosthesis, for example, has a one- piece tibial component and a central fixation peg, and no component loosening was seen in 220 knees followed-up from 3 to 5 years. Kinematic prosthesis has also shown aseptic loosening to be negligible (Wright et al., 1998).
5- Ligamentous instability:
Ligamentous laxity manifested by progressive varus or valgus deformity lead to loosening which occur secondary to development of a significant deformity(Lewallen et al., 1984 ).
6- Wear product:
Small ultra-high molecular weight polyethylene particles inevitably result from motion and wear of an orthopedic prosthesis, then the particles are engulfed by phagocytes in the tissue adjoining the site of prosthesis. The phagocytosis of these particles may result in activated cells that secrete both proinflammatory cytokines (Interlukine-1B and interlukin-2 from mononucleated cells) and proteolytic enzymes and also provide activation signals to lymphocytes.The accumulation of wear particles which had been phagocytosed in the periarticular tissue results in development of foreign-body granulomas with areas of necrosis and fibrosis. Extension of this foreign body response to the bone-cement interface could cause loosening of the implant. Chronic immunologically mediated inflammation may result from the reaction to prosthetic debris and associated immune complexes. Thus damaging the periprosthetic tissue in the region of the prosthesis leading to increase bone resorbtion around the prosthesis and destroying the bone that was formed between the cement and bone (Ali et al., 1999).
Cementing technique is likewise shown to be important in achieving long term good results. Modern proximal tibial resection level where thicker tibial inserts can be used. Femoral component with intramedullary stems to enhance fixation may be appropriate in high-risk patient. Proper soft tissue balancing and correct axial alignment of the component are of major importance in preventing component loosening(Merrill et al.,1999).
The diagnosis of a septic loosening is suggested by comparison of serial radiographs to evaluate prosthetic loosening. Radiographic signs of loosening includes:
- Change in position of the prosthesis.
- Progressive widening of the cement- bone or bone- prosthesis interface. In fact a radiolucency that appears about the tibial stem of any magnitude and a bone- cement or implant- cement radiolucency greater than 2 mm in more than one zone is almost pathognomic for loose implant.
- Cement fragmentation under a component.
- Progressive shedding of beads in a porous- coated prosthesis.
- Areas of osteolysis adjacent to the implant at time associated with an asymmetric decrease in the “Polyethylene clear space” on anteroposterior radiographs (Schenk and Dalinka, 1999).
Serial radiographs may demonstrate progressive tilting of the tibial component into a varus position. Often, the varus tilting is associated with subsidence or sinking of the tibial component medially with collapse or fragmentation of cancellous bone and cement within the medial tibial plateau(Ducheyne et al., 1978).
Differential Diagnosis:
The progressive increase in width and extent of the radiolucent line can occur in infection or mechanical loosening, and differentiation based only on the radiographic finding is usually not possible, as X- ray are usually normal early in the course of infection(Schneider et al., 1982) .
The shift in position of prosthetic component is characteristic of loosening and is more frequent in mechanical loosening than in infectious loosening and radiographic signs of mechanical loosening usually precede clinical symptoms (Schenk and Dalinka, 1999).
7-Limited Range of Motion
(Stiff Knee)
The term stiffness as related to total knee replacement have several different meanings. from the prospective of surgeon, stiffness mean an inadequate or smaller - than- expected range of motion as measured in a standardized fashion with the patient on an examination table. Active or active- assisted ranges of motion routinely are measured under optimum conditions during the recovery period and the norms of motion following total knee replacement have been generated on the basis of these data
(Charles et al., 2005).
Functional capacity also is evaluated to confirm that the clinically derived value for range of motion corresponds with an appropriate level of function (walking, sitting, climbing stairs, and so on).A patient who has a range of motion of 90 degrees of flexion to within 10 degrees of full extension on clinical examination and has no pain or functional difficulties is not said to have a stiff knee. A patient who, at one year after the arthroplasty, have clinically acceptable motion but also has knee stiffness, difficulty getting out of the chair, pain when climbing stair, and an observable stiff- knee gait should be evaluated further for underlying problem involving the knee. Although stiffness is closely related to pain, it has a wider application to the patient’s experience in attempting to move the knee, particularly during the early post operative period. Stiffness therefore is closely related to the patient motivation to achieve a functional range of motion and his or her willingness to endure pain to achieve that goal (Ayers et al., 1997).
As stiffness is nearly always present during the early post operative period and gradually decreases over time, it is a valuable marker for improvement throughout the recovery period. Post operative pain is the most important early cause of knee stiffness. It results in both quadriceps and hamstring guarding and makes passive flexion and extension difficult to perform. This factor was the theoretical basis for the implantation of in- hospital continuous passive motion (Colwell and Morris, 1999).
Post operative stiffness of the knee usually subsides within six to eight weeks. Range of motion generally improves steadily during the first three months, after which less rapid progress may be seen for additional nine months or more (Ayers et al., 1997).
The late onset of knee stiffness after a relatively symptom- free period may suggest one of several conditions including infection, overuse synovitis or tendenitis ( particularly in younger, more active patients ), synovitis secondary to rheumatoid arthritis, particulate wear debris, or recurrent haemoarthrosis, or loosening or breakage of the implant(Fern et al., 1992).
Causes of TKR stiffness
1-Infection
Early infection (within the First six weeks after the operation) is characterized by increasing swelling, erythema, and generalized pain, with or without wound drainage. The progressive nature of the signs and symptoms, especially after two to three days of rest and immobilization, should lead to early recognition of infection. Late infection is recognized more easily because it develops after a relatively asymptomatic period, although aspiration and culture may be necessary to distinguish an indolent infection from the other causes of synovitis (Ayers et al., 1997).
2-Mechanical Problems Related to the Implant or the Soft Tissue
Total knee replacement rarely produces a completely normal gait and that some degree of stiffness is associated with even an excellent result. The proper balance of motion, strength, and stability is the goal for a good functional result. Inadequate bone resection combined with persistent ligamentous imbalance, or tight capsular and ligamentous structure is an important cause of knee stiffness, it can be corrected by revision of the bone cuts or release of the ligaments, or both. If a flexion contracture is present, additional resection of bone from the distal part of the femur or a posterior capsular release, or both, should be performed. If the residual contracture is severe (more than15 degrees), some additional bone may be removed from the proximal part of the tibia, provided that doing so does not make the flexion gap too wide ( Parvizi et al., 2006 ).
Use of an oversized femoral component or posterior placement of the femoral component may lead to a disproportionately narrow flexion gap. Use of a smaller femoral component and resection of more bone from the posterior aspect of the femur expands the flexion gap without affecting stability in extension.In varus deformities, the medial collateral ligament and, in valgus deformities, the lateral collateral ligament and the iliotibial band often must be released in order to prevent asymmetrical wear of the implant and to/promote an optimum range of motion of the knee.External rotation of the femoral component has been found to enhance ligament-balancing in flexion and to facilitate optimum patellar tracking( Laskin, 1995 ).
A number of possibilities related to the patella should be considered during the evaluation of stiffness after a total knee arthroplasty:
- A patella that was not resurfaced,
- Inadequate lateral release,
- Asymmetrical cutting of the patella,
- Excessive elevation of the joint line,
- Internal rotation of the femoral component,
- Formation of intra- articular adhesion that tether the patella to the surrounding structures (thereby altering the normal tracking mechanism),
- Patellar fracture and loosening of the patellar component.
Joint adhesion and quadriceps contracture are known factors that limit knee flexion. Adhesion may occur between the capsule and the muscles and between skin and muscle. Finally the generation of an excessive volume of wear debris over time may cause synovitis, with pain, stiffness, and swelling being the usual clinical result(Kim and Moon, 1999).
Management of stiff knee
Treatment alternatives
Physical therapy
The most important initial treatment of a stiff, non- infected knee is an adequately supervised course of sustained, intensive physical therapy. This therapy may last from three to six months (Ayers et al., 1997).
Manipulation
If a range of motion reaches a plateau during the first three months, manipulation of the knee with the patient under regional or general anesthesia should be considered, because of the need for full muscle relaxation. If tone remains in the quadriceps muscle the increased resistance may damage the patellar ligament or its insertion and possibly cause a fracture adjoining the prosthesis during manipulation. In a patient with normal preoperative range of motion, a stiff total knee replacement can result from technical difficulties, arthrofibrosis, or poor postoperative patient complaince. Currently manipulation is most effective if performed within 6 to 12 weeks of primary total knee arthroplasty(Haas and Insall, 1993).
In an assessment of the range of motion one year after total knee replacement, Fox and Poss in 1981 found that knees that had been manipulated two weeks postoperatively could not be distinguished from
these that had not. The preoperative range of motions is an important predictor of the range after total knee arthroplasy (Parsley et al., 1992).
It is clear that those patients with high range of motion preopertatively will loose motion, whereas those with poor preoperative motion will gain, and those in the mid range stay in the mid range(Ayers et al., 1996).
Debridement
If manipulation of the knee does not lead to a sustained, acceptable improvement in the range of motion, exploration and debridement of the knee may be performed with either open or arthroscopic technique(Linter et al., 1994).
Revision
Revision with a modular tibial polyethylene spacer in conjugation with a capsular or ligamentous release may improve the range of motion of the knee, particularly when the procedure is performed to correct a flexion contracture. Intraoperatively the deformity should be corrected completely with new, trial spacer in place. If complete correction can not be achieved, the tibial or the femoral component, or both should be revised after new cuts are made in the bone to provide optimum flexion and extension gaps.
A posterior cruciate- substituting design should be used whenever both components are revised. This design more readily accommodates alteration in the joint line caused by the new cuts in the bone, and it has the inherent stability to allow generous flexion and extension gaps as well as ligamentous release (Becker et al., 1991).
During revision, it is very important to release fully all structures that may have contributed to stiffness of the knee, including the quadiceps tendon and the vastus intermedius adhesion to the femur and suprapatellar pouch, the medial and lateral gutters, the collateral ligaments, and the lateral patellar retinaculum.( Ranawat and Flynn, 1995 ).
8-Polyethylene Wear
Wear is the removal of material, with the generation of wear particles that occur as a result of relative motion between two opposing surfaces under load (Thomas et al., 1999).
Structure of Polyethylene
Polyethylene is a long -chain polymer composed of a carbon chain backbone with hydrogen sub-group. The current material of choice remains ultra high molecular weight polyethylene (UHMWPE).
originally Charnley used High Density Polyethylene and later this was changed to UltrahighMolecularWeightPolyethylene. UHMWPE has better abrasion resistance, strength, resistance to deformation, and fatigue strength ( Mckellop et al., 2000).
Conformation of the bearing surfaces is important because it is factor in the determination of contact stress, increases in material strength, will usually result in increases in stiffness and increases in contact stresses, hence, it is important that gains in strength offset increases in surface contact. increases in the modulus of the polymer (or increases in the density) will have the effect of increasing contact stress and may result in increased wear. higher contact stresses between ultra-high molecular wt poly & other biomaterials are thought to result in greater polymeric wear,over the lifetime of an implant, polyethylene becomes stiffer near the surface, and therfore, contact forces will increase with time.
Thermoplastic properties:
Deformation of polyethylene is dependent on temperature.
Heat pressing alters the physical properties of polyethylene near the surface of the component and makes the device more susceptible for fracture at the subsurface juncture of heat-press material and the bulk polyethylene( Mckellop et al., 2000).
Wear and Damage to UHMWPE in Total Knee Replacements.
There have been seven different polyethylene damage mechanisms. These are abrasion, burnishing, scratching, delamination, pitting, deformation, and third body abrasion with bone cement.
The dominant modes of this damage in total knee prosthesis are pitting and delamination. Pits may be caused by cracks that start at the surface and propagate into the material, or by sub-surface cracks that propagate toward the surface. Delamination is caused when sub-surface cracks continue to propagate tangent to the surface (Bartel et al., 1995) .
In a specific joint, there may be different types of wear occurring at different times over the service life of the implant.
The damage to an implant is a result of all of the mechanisms of wear:
Mode-1 wear results from motion that is intended to occur between the two primary bearing surfaces. It represents the most potential source of
Wear in total hip and knee replacement.
Mode-2 wear refers to the condition of a primary bearing surface that moves against a secondary surface that is not intended to move against.
Mode-3 wear refer to the condition of the primary surfaces as they move against each other but with the interposition of third-body particles. mode-3 wear, the contaminant particles directly abrade one or both of the primary bearing surfaces. This type of wear is known as three body wear.
Mode-4 wear refers to two secondary (non-primary) surfaces rubbing together.
The particles that are produced by these types of wear may be composed of bone, polymethylmethacrylate, metal alloys, metallic corrosion products or hydroxyapatite (Agins et al., 1988).
A total hip or knee prosthesis that is well fixed and well functioning has a low rate of mode-1 wear of the polyethylene. The gradual release of polyethylene particles into the periprosthetic tissues can results in a slow rate of interficial bone resorbtion, which can lead to an increase in the relative motion between the implant and the adjacent bone. Such relative motion causes mode-4 wear, which can generate particles of bone, cement, and metal. These hard particles can affect the base line mode-1 wear by passing through the articulation and resulting in a transient three-body wear mechanism. The femoral component can be scratched by this interaction.
Additionally, hard particles may become embedded in the polyethylene and act as an ongoing abrasive source. The increased roughness of the bearing surface of the femoral component can then increase the rate of polyethylene wear (Engh et al., 1997).
Higher rate of wear in total knee replacements have been associated with some designs characterized by lower conformity, especially when the tibial polyethylene is less then six millimeters thick and when the so called heat-pressing of the tibial articular surface has been used (Jones et al., 1992).
This type of rapid wear tends to involve only the medial or lateral compartment. The type of wear that occur is predominantly due to subsurface fatigue resulting in delamination (and the production of large particles of polyethylene) (Schmalzried et al., 1994).
Wear through or gross mechanical failure of the polyethylene component can result in mode-2 wear with abrasive damage to the femoral component and substantial generation of metal particles .The clinical triad of effusion, pain, and progressive change in the coronal alignment of the knee (most commonly into varus alignment) is the characteristic of accelerated polyethylene wear (Jones et al., 1992).
The joint fluid is loaded with polyethylene particles of various sizes, and aspiration can confirm the diagnosis of polyethylene induced synovities. Arthroscope can be helpful in assessing the degree of polyethylene wear and the damage of the femoral component as well as in planning the revision operation (Mintz et al., 1991).
Sterilization and Oxidation of UHMWPE
Since its commercial availability in the late 1960, the dominant method for sterilization of UHMWPE component has been gamma irradiation from a cobalt-60 source. Gamma sterilization in air may initiate a long term oxidative process which have a negative impact on the implants mechanical properties and reduces the static strength and elongation properties of polyethylene and decrease the resistance of polyethylene bearings to fatigue, and which can increase the propensity for wear. As radiation does promote polyethylene cross-linking: with low oxygen environment, free radicals created during irradiation can form carbon- carbon cross- links between polyethylene molecules, this cross-linking improves the wear resistance of the polymer (James et al., 1996).
Radiographically, a ”metal line” sign is appreciated as thin curvilinear dense, white line most commonly seen on lateral radiographs outlining the region of infrapatellar synovium and the synovium of the suprapatellar bursa. A knee effusion is usually present (Engh et al.,1996).
9-Patellar Problems
Patellar complication has become the major source of failure after total knee arthroplasty . It has been estimated as 50 % of complications after total knee arthroplasty (Doolittle and Turner 1998).
These complications are:
1- Patellofemoral instability.
2- Patellar fracture.
3- Loosening or failure of the patellar component.
4- Patellar clunk syndrome.
5- Tendon rupture.
6- Infrapatellar scaring and soft tissue impingement.
7- Patellar osteonecrosis(Hozack et al., 1999).
8-
(1) Patellofemoral Instability
Patellofemoral instability most commonly results from imbalance in the extensor mechanism characterized by excessive tightness of the lateral retinaculum and associated weakness of the vastus medialis muscle (Doolittle and Turner, 1998).
Placement of prosthetic component in an excessive valgus position increases the Q angle and results in an increased lateral force – vector on the patella (Dowd et al., 1982).
Q angle is the angle formed by a line drawn from the ASIS to the central patella and a second line drawn from the central patella to the tibial tubercle, an increased Q angle is a risk factor for patellar subluxation.Normally Q angle is 14 deg for males and 17 deg for female.biomechanics of patellofemoral joint are effected by patellar tendon length & the Q angle.
Q.angle.is.increased.by:
(1)genu.valgum
(2)increased.femoral.anteversion
(3)external.tibial.torsion
(4)laterally.positioned.tibial.tuberosity (5)tight lateral retinaculum (Berger et al., 2001).
Disruption of the capsular repair, by intensive physiotherapy, injury or hemarthrosis. A symmetrical patellar resection can lead to patellofemoral instability as well. Malpositioning of the femoral, tibial or patellar component also can predispose to patellofemoral instability (Merkow et al., 1995).
Patellofemoral instability can be caused by a number of factors, including extensor mechanism imbalance with a tight lateral retinaculum associated with preoperative valgus deformity,excessive lateral patellar facet resection, lateral placement of the patellar component with failure to reproduce the normal position of the median eminence, and early postoperative rupture of the medial capsular repair . If the lateral retinaculum is tight, lateral release is indicated, sparing the superior lateral geniculate artery if possible . The ‘‘no thumb’’ test of patellar tracking (see Patellofemoral Tracking) should be done intraoperatively. Excessive lateral patellar facet resection is frequent because of the normal asymmetry of the medial and lateral patellar facets. Often the level of the lateral facet resection must be much shallower than the medial facet resection (Figure 4-8). Removing equal amounts both medially and laterally can tilt the patellar component. Lateral placement of the patellar component on the cut surface of the patella fails to reproduce the normal median eminence of the patella and can lead to subluxation of the patella in extension and capture of the patella in the trochlear groove during flexion. Postoperative rupture of the medial capsular repair can be caused by a closure that is too tight or by a traumatic event in the early postoperative period. Some authors have advised closing the retinacular-capsular layer with the knee in 90 degrees of flexion to ensure proper medial tensioning. The knee should be placed through a full range of motion after the medial capsular closure to evaluate patellar tracking and the adequacy of the repair (Beight et al., 1994).
Figure 4.11 Lateral patellar subluxation demonstrated on skyline view( Dennis ,1992).
Figure 4.12 Often lateral facet resection must be much shallower than medial facet resection because of normal asymmetry of patellar facets( Dennis ,1992).
Another frequent cause of patellar instability is malposition of either the femoral or tibial component. Malposition of the tibial component in an internally rotated position increases the Q angle by moving the tibial tubercle laterally. The increased Q angle leads to lateral subluxation. The tibial component should be centered on the medial border of the tibial tubercle, with any deviation into slight external rotation. Similarly, internal rotation and medial translation of the femoral component both move the trochlea more medial relative to the extensor mechanism, leading to lateral subluxation( Dennis ,1992).
The intraoperative evaluation of femoral component rotational alignment is based on anatomical landmarks. Femoral component rotation is determined primarily by ligamentous tensioning in flexion or by slight external rotation from the posterior condylar axis as a part of the measured resection technique.Other landmarks include the epicondylar axis and the anteroposterior axis described by Whiteside and Arima. Berger et al., in an anatomical study of normal distal femurs, demonstrated that the epicondylar axis, defined as the line from the medial sulcus of the medial epicondyle to the lateral epicondyle, is rotated approximately 3.5 degrees externally from the posterior condylar axis in males . In females, the epicondylar axis was externally rotated only 0.3 degrees from the posterior condylar axis. Arima et al. have argued that the epicondyles can be difficult to palpate and that considerable variation is present in interobserver accuracy in the determination of the epicondylar axis. They believe that the anteroposterior axis, drawn from the center of the trochlea to the intercondylar notch when viewing the femur from its distal aspect, is a reliable indicator of appropriate femoral rotation, especially in valgus knees, where the posterior condylar axis is internally rotated because of a hypoplastic lateral condyle. They described the anteroposterior axis as perpendicular to a line externally rotated 4 degrees from the posterior condylar axis in normal knees, with a slightly more constant relationship than the relationship of the epicondylar axis to the posterior condylar axis. Insall has come to exactly the opposite conclusion, that the epicondylar axis, although it has some variation, is more constant in its relationship to the posterior condylar axis than is the anteroposterior axis and thus is more useful in determining femoral component rotation. Frequently, in the revision setting with bone loss, the epicondylar axis is the only remaining bony landmark to determine femoral component rotation. Even though the primary consideration of femoral component rotation is tibiofemoral flexion stability, care must be taken not to internally rotate the femoral component, since this can lead to lateral patellar instability( Berger et al., 1993) .
Figure 4.13 Posterior condylar angle. Axial view of right distal femur as seen from below by surgeon during TKA with knee flexed 90 degrees.Posterior condylar angle is angle between posterior condylar surfaces and surgical epicondylar axis, defined using medial sulcus on medial epicondyle( Berger et al., 1993) .
(2) Patellar fractures
The prevalence of patellar fracture following total knee replacement has been reported between 0.05 % and 8.5 %. (Ayers et al., 1997).
Various causes of patellar fracture have been proposed , including trauma, patellar subluxation , improper patellar resection , vascular compromise , component design , component malpositioning , increased flexion , thermal necrosis and revision arthroplasty ( Rand, 1998 ).
. The classification espoused by Goldberg et al .,1988 is helpful for planning appropriate intervention.
Type I fracture are avulsion-type fractures, generally involving the periphery of the patella, without involving the implant, cement, or quadriceps mechanism.
Type II fractures disrupts the cement-prosthesis interfaces or the quadriceps mechanism.
Type 111-A fractures involve the inferior pole of the patella with disruption of the patellar ligament.
Type 1II-B is nondisplaced fractures of the inferior pole of the patella with an intact patellar ligament.
Type IV fractures is fracture dislocation of the patella.
Figure 4.14 A, Patella is intact in postoperative lateral roentgenogram. B, Six weeks later, patellar fracture with displacement is clearly visible(Canale,2003).
(3-a) Patellar component loosening
The prevalence of patellar component loosening that was inserted with cement during total knee arthroplasty is less than 2 % in most studies (Ranawat, 1986).
Factors associated with loosening of the patellar component include insertion of the prosthesis with cement into worn , sclerotic bone ; malpositioning of the patellar component ; subluxation , fracture or avascular necrosis of the patella ; osteoporosis , asymmetrical resection , loosening of other prosthetic components ; and a lack of osseous growth into the porous coating ( Brick and Scott, 1998 ).
(3-b) Failure of the patellar component
Failure of the polyethylene patellar components has been associated with metal backed design (Goldstein et al., 1996).
These designs have failed because of wear and fracture of the polyethylene, dissociation of the polyethylene from the metal plate, dissociation of the pegs from the metal plate (Bayley et al., 1988).
Risk factors for failure of patellar component include excessive body weight, increased post operative knee flexion (more than 115 degrees) a high level of activity, and male gender.
( Stulberg et al., 1998 ).
Additional risk factors associated with increased patellofemoral loading and subsequent failure of the component include patellofemoral malalignment, increased thickness of the patella – patellar component composite, an over sized femoral component, malpositioning of the femoral component in flexion, and failure to restore the prosthetic joint line to an anatomical level. Failure of metal – backed patellar components often occur early, usually within two years after the arthroplasy(Rosenberg et al., 1988).
Clinical signs of failure of the patellar component include effusion as well as crepitus, which occasionally is audible (Dennis, 1992).
Failure of metal-backed patellar components has been discussed by multiple investigators, including Rosenberg et al., Bayley et al., Firestone et al., and Stulberg et al. The components failed by various mechanisms, including fatigue fracture of the metal baseplate from the fixation lugs, delamination of the polyethylene from the baseplate, failure of the ingrowth interface, and wear in areas of thin polyethylene, exposing the underlying metal baseplate and leading to metal-on-metal wear between the baseplate and the femoral component (Figure 4-11). Factors that have been correlated with metal-backed patellar component failure include maltracking and component mal position, excessive thickness of the patellar construct, joint line elevation, obesity, osteoarthritis, and specific metal-backed patellar component designs. Few of the current metal-backed prostheses are designed to be implanted with a recessed technique; most are cemented, all-polyethylene implants (Bayley et al., 1988).
Patients with metal-backed patellar implants require close follow-up to watch for signs of failure. Roentgenographically, the skyline and lateral views of the knee demonstrate polyethylene wear, interface failure, and patellar subluxation. Clinically, the onset of a knee effusion, patellofemoral crepitis, or audible squeaking and scraping all suggest component failure. Early revision of the failed components is recommended to prevent extensive metallosis of the knee. Usually, revision consists of exchange of the tibial polyethylene insert only, synovectomy, and revision or removal of the patellar component. Occasionally, metal-on-metal wear damages the femoral component to the extent that revision of the femoral component also is necessary. Techniques for removal of well-fixed metal-backed patellar components have been described using diamond-tipped saws and high-speed burrs to separate the fixation pegs from the baseplate (Bayley et al., 1988).
Figure 4.15 Frequent mechanisms of patellar component failure. A, Failure of metal fixation lugs with inadequate ingrowth fixation of baseplate. B, Delamination of polyethylene from metal baseplate. C, Polyethylene wear in areas where design factors caused thin polyethylene overlying metal baseplate ( Rosenberg et al., 1988).
(4) Patellar clunk syndrome
Patellar clunk syndrome is a common complication relating to the patellofemoral articulation. This syndrome is the painful crepitus under the quadriceps tendon at the anterior knee that is caused by soft tissue catching in the intercondyler notch of the femoral component. A fibrous nodule (hypertrophic scar tissue) developed at the junction of the posterior aspect of the quadriceps tendon and the proximal pole of the patella (Reilly, 2000).
With flexion of the knee, this fibrous nodule enters the intercondyler notch of the femoral prosthesis. At 30 to 45 degrees from full extension, enough tension is placed on the fibrous nodule to cause it to clunk out of the inter condylar notch .Possible causes of this condition include a femoral component with a sharp anterior edge at the superior aspect of the intercondyler notch, malpositioning of the patellar component beyond the proximal border of the patella, postoperative scaring, ad alteration of the joint line or the patellar height or thickness (Ayers et al., 1997).
Figure 4.16 Patellar clunk syndrome. Synovium just superior to patella can form hypertrophic nodule that catches in box cut-out of posterior stabilized total knee design ( Dennis , 1992).
(5) Patellar tendon rupture
Rupture of the quadriceps tendon or the patellar ligament is an infrequent complication of total knee arthroplasty, with a repeated prevalence of 0.17 % to 2.5 % (Rand et al., 1989).
The risk of rupture of the patellar ligament is increased in patient who have had a previous operation involving the knee and in those who have had a partial release of patellar ligament to enhance exposure at the time of an arthroplasty. Additional risk factors include closed manipulation of the knee and osteotomy of the tibial tubercle for a realignment of the extensor mechanism.Rupture of either the quadriceps or patellar tendon is an infrequent but severe complication of TKA. Quadriceps rupture may be related to lateral release in part because of vascular compromise of the tendon and possibly with extension of the release anteriorly that weakens the tendon. Surgical repair is suboptimal, with frequent diminished range of motion, weakness, extensor lag, and re-rupture. Patellar tendon rupture is associated with previous knee surgery, knee manipulation, and distal realignment procedures of the extensor mechanism. Multiple procedures have been described to treat patellar tendon rupture after TKA, including direct repair, augmentation with hamstring tendons, and the use of an allograft patella with attached patellar tendon and tibial tubercle. None of these procedures has been routinely successful without further difficulties.There were persistent rupture in 11 of 18 surgically treated patellar tendon ruptures after TKA(Cadambi et al .,1992).
Systemic disorders such as rheumatoid arthritis, lupus, chronic renal failure, diabetes and long term corticosteroids are known to weaken collogenous tissues and increase the likelihood of tendon rupture(David et al., 1999).
(6) Infra patellar scaring and soft tissue impingement
Soft -tissue impingement at the surface of the prosthesis can result in pain. Pain in the popliteal fosa can result from soft -tissue impingement in the area of hamstring or entrapment of the popliteus tendon(Geoffrey and Windsor, 1999).
Radiographically, patient with persistent knee pain at the extremes of flexion and extension may show an apparent acquired shortening of the patellar tendon in comparison with the immediate postoperative films.
( Pertine and Bryan, 1986 ).
(7) Osteonecrosis of the patella and its resorption
A rare complication of total knee arthroplasty with a dramatic recovery after a relative simple revision surgery. It is due to disruption of the patellar blood supply resulting in avascular necrosis.Physical examination reveals an effusion and tenderness on the anterior aspect of the knee joint. It has been shown that increased quadriceps activity increase the joint reactive forces on the patello-femoral joint, thereby increasing the stress on the patella. This increased stress with an avascular patella may play a significant role in its resorption (Kayler and Lyttle, 1988).
Management of Patellar problems
1- Patellofemoral Instability
Nonsurgical treatments for patellar subluxation or dislocation include physiotherapy focused on strengthening of the quadriceps (particularly the vastus medialis obliqus), patellofemoral bracing, and activity modification to avoid activities that require hyperflexion, such as squatting or stair climbing.
When nonoperative measures fail to relieve the patient’s symptoms, surgical efforts must be directed at the underlying cause of the problem. Malaligned or malrotated femoral or tibial components need to be revised, condylar deficiencies may require augmentation with metal wedges, bone graft, or cement. Most commonly, a posterior wedge is necessary to augment the posterior lateral femoral condyle, to ensure adequate component rotation. Additionally, the femoral component should be applied in approximately 5 to 7 degrees of valgus with respect to the mechanical axis based on preoperative radiographs. Stems are commonly used in revision arthroplasry. With augments utilized if necessary.If the tibial component requires revision for malrotation, it is implanted according to anatomic landmarks as well. It is externally rotated with respect to the long axis of the tibia so that its midportion generally aligns with the medial third of the tibial tubercle. In the even that the patella had been implanted centrally or laterally, revision and reimplantation in more medialized position may be advisable- provided that bone stock is adequate. Obliquely resurfaced patellar components should be revised as well, so that the resurfacing is parallel to the nonarticular surface of the patella. In the absence of component malposition, a lateral retinacular release may be all that is necessary to improve patellar tracking( Rand, 1998 ).
(2)Treatment of Patellar Fractures
Treatment of patellar fractures is dependent on fracture pattern, location, remaining bone stock, integrity of the component-cement-bone interface, and competence of the extensor mechanism.Nonoperative treatment is preferred when fractures are nondisplaced. Unfortunately, the definition of displacement has varied in reports in the literature, from 2 mm to 2 cm.( Hozack et al., 1988).
In general, fractures displaced less than 2 mm anywhere along the patella, provided that the patellar implant is intact, are treated in a long leg cylinder cast with the knee fully extended for 6 to 8 weeks. These patients are allowed to bear weight as tolerated with the assistance of crutches or a walker. Isometric quadriceps sets are encouraged. Considering the experience of Windsor et al 1988, comminuted patellar fractures, regardless of the extent of fragment displacement, can be treated in a long leg cylinder cast as well. Unless there is compromise of the prosthesis-patella composite. In the latter scenario, a patellectomy has superior results than attempted open reduction and internal fixation, which may predispose the patella to osteonecrosis or nonunion. Another option for these situations is to remove the patellar component and allow healing of the comminuted bone fragments in a cast.Transverse fractures. with displacement of more than 1 cm may be treated with cerclage tension band wiring provided that the native bone stock is adequate. Otherwise, patellectomy and tubing of the salvaged extensor mechanism is preferable. Finally, displaced avulsion fractures of either the proximal or distal poles of the patella. With an intact patellar component, can be fixed with No, 5 non absorbable sutures passed through the quadriceps tendon or patellar- tendon and secured to the patella through drill holes. The free suture ends can then be passed through parallel longitudinal drill holes in the major patellar bone fragment and tied at the edge of the patella, in order to protect the repair, a check-reign-type figure-of-eight stitch may be tied over the anterior aspect of the extensor mechanism. The proximal extent of the check-reign passes through the quadriceps tendon; the distal extent is through a drill hole beneath the tibial tubercle . Postoperativly, pasive knee motion and quadriceps exercise are permitted ( Lonner, 1999)
The results of operative treatment of patellar fractures after TKA vary significantly from the results of treatment of patellar fractures in normal knees. Nonunion and hardware failure are frequent after internal fixation. Hozak et al. recommended nonoperative treatment of both displaced and nondisplaced fractures with no extensor lag and no loosening of the patellar component from a large fracture fragment. They had poor results with operative repair of displaced patellar fractures and recommended patellectomy and extensor mechanism repair (Hozack et al., 1999).
Patellar resection that results in an osseous thickness of less than fifteen millimeters substantially increases anterior patellar strain, predisposing to patellar fracture especially if subchondral bone is removed. Conversely too little patellar resection creates a thick patella – patellar component composite and increases patellofemoral joint reaction force as well as tension within the quadriceps tendon .When the patella is prepared for component fixation, the creation of a large central peg-hole increases anterior patellar strain more than the creation of smaller peripheral peg- hole; the former technique is associated with an increased risk of fracture (Rand, 1998).
Operative disruption of the patellar blood supply resulting in a vascular necrosis also has been associated with patellar fracture(Kayler and Lyttle ,1988).
(3) Patellar Component Loosening
A reduction in the rate of loosening of the patellar components requires improved bone preparation and cementing techniques, proper patellar resection , avoidance of asymmetrical or excessive bone removal, and central patellar tracking .Options for the treatment of loosening of the patellar component include revision of the component , removal of the component and patellar arthroplasty ( smoothing of the remaining patella without resurfacing ) if the remaining bone stock is unsatisfactory , and patellectomy . Some patients are asymptomatic and need no treatment (Ayers et al., 1997).
(4) Patellar Clunck Syndrom
Nonoperative treatment of patellar clunk syndrome include:
Physiotherapy to encourage patellar mobilization. Quadriceps and hamstring strengthening and a trial of anti-inflammatory medications. If nonoperative measures fail to adequately relieve the patients symptoms, then surgical options need to be entertained, including arthroscopic debridement or arthrotomy with debridement and excision of hypertrophic tissue ( Donald Reilly ,2000 ).
(5) Treatment of Patellar Tendon Ruptures
Distal ligament avulsions occur most commonly, if they involve less than 30% of the tibial tubercle insertion, then a primary repair to the medial capsuloretinacular sleeve should suffice without any need for alteration in normal postoperative physiotherapy. For complete avulsions, primary repair with staples, transosseous sutures, and screws with washers have all been utilized, but the incidence of rerupture remains high and functional impairment is unavoidable.The decision for reconstruction is usually predicated on the quality of the remaining patellar bone stock. When there is adequate patellar bone stock, primary repair and augmentation with an autogenous semitendonosis graft is effective. Technique modified from Cadambi and Engh (1992) whereby the standard total knee incision can be used to harvest the semitendinosis, leaving its insertion point on the pes anserinus intact. The tendinous bands and then a tendon stripper is used to harvest a strip of semitendinosis tendon as far proximal as possible. The attached graft is then routed proximally along the medial aspect of the patella tendon and then passed transversely through a 0.5-cm hole drilled along the superior or inferior pole of the patella, if bone stock allows. The remainder of the tendon is then passed along the lateral aspect of the patella and tendon, and then passed through a 0.5-cm transverse drill hole beneath the tibial tubercle. Before suturing it back to its insertion anteromedially. Postoperatively the knee is immobilized in extension for 6 to 8 weeks.A locked hinge brace should be utilized while the quadriceps are strengthening by physitherapy.
Alternatively, when the patellar bone stock is extremely deficient and soft tissues are compromised, a complete extensor mechanism allograft that incorporates the quadriceps tendon, patella, patellar tendon, and a tibial tubercle bone block may be preferable. First the allograft tibial tubercle is fashioned to fit into a mated trough created in the host tubercle region, or slightly medial to it, in order to enhance patellar tracking. The position of this trough needs to be carefully determined so that the patella will be in an appropriate position with respect to the Joint line. Once this is completed, the bone plug may be secured with one or two screws. The patella should rest comfortably on the patellar flange of the femoral component.Finally, the quadriceps component of the allograft is secured to the host quadriceps tendon with sutures .Postoperative immobilization and isometric exercises continue for 6 to 8 weeks before allowing protected range of motion. A hinged knee brace should be utilized while ambulating, and it should be worn for approximately 3 months until quadriceps strength recovers(Lonner, 1990).
Materials and methods
This study will be carried out as a systematic review.
Materials
Fulfillment the most recent topics in different modalities in complications of total knee replacement that will be found in:
(1)Literatures from orthopaedic textbooks.
(2)Published articles from orthopaedic journals.
(3)Papers and websites published on intrnet protocol and ethics.
(4)Technical guids of medical instruments companies.
Search strategy
We will search pub med and e-medicine using standardized methodological filter for identifying trials-which represent the most famous scientific sites on the internet.
We will search the most famous journals and internet sites which represent honest references to most of the orthopaedic surgeons as:
+AO orthopaedic journals .
+Journal of bone and joint surgery.
+American journal of orthopaedic.
+American academy of orthopaedi surgery.
Studies identified by the search strategy will be scrutinized independently for eligibility.
Criteria for selectingthose studies
+Initial screen to exclude studies not relevant to the review questions.
+Second screen determines which of the relevant studies are strong enough and of the highest quality to be included in the systematic review to be as free from bias as possible.
Study preparation
Using Microsoft office 2000 program in typing and preparation of the essay.
Discussion
The primary indication for total knee arthroplasty is to relieve pain caused by severe arthritis, with or without significant deformity. Other sources of knee and leg pain must be sought and systematically excluded.
Patients who do not have complete cartilage space loss before surgery tend to be less satisfied with their clinical result after total knee arthroplasty. Before surgery is considered, conservative treatment measures should be exhausted, including antiinflammatory medications, activity modifications, and the use of a cane for ambulation.Because knee replacement has a finite expected survival that is adversely effected by activity level, it generally is indicated in older patients with more sedentary life-styles. It also is clearly indicated in younger patients who have limited function because of systemic arthritis with multiple joint involvement.Severe pain from chondrocalcinosis and pseudogout in an elderly patient is an occasional indication for arthroplasty in the absence of complete cartilage space loss. Rarely, severe patellofemoral arthritis in an elderly patient may justify arthroplasty because the expected outcome of arthroplasty is better than that of patellectomy in these patients(Canale, 2003).
The success of total knee arthroplasty (TKA) in relieving pain and improving function has led to its widespread use worldwide. In addition, the increasing size of the aging population, especially in the United States, will only further test the longevity and durability of TKA. With the increasing demands placed on TKA in terms of longevity and function, the problem of failure has manifested itself as a substantial reconstructive challenge in the last decade. The most common indications for revision TKA are infection, mechanical loosening, and instability( Chritranjan et al., 2000).
Absolute contraindications to total knee arthroplasty include recent or current knee sepsis, a remote source of ongoing infection, extensor mechanism discontinuity or severe dysfunction, recurvatum deformity secondary to muscular weakness, and the presence of a painless, well-functioning knee arthrodesis. Relative contraindications are numerous and debatable. These include medical conditions that compromise the patient’s ability to withstand anesthesia, the metabolic demands of surgery and wound healing, as well as the significant rehabilitation necessary to ensure a favorable functional outcome. Other relative contraindications include monarticular disease in young patients, significant atherosclerotic disease of the operative leg, skin conditions such as psoriasis within the operative field, neuropathic arthropathy, morbid obesity, recurrent urinary tract infections, and a history of osteomyelitis in the proximity of the knee. This list is not all-inclusive, and any preoperative condition that can adversely affect the patient’s outcome can be considered a relative contraindication(Canale, 2003).
The mechanics of joint loading in the limb with a total knee prosthesis do not differ substantially from those of the natural limb. As the joint surfaces are replaced by artificial components, the resulting forces will be much the same. The concept of the point of application of the joint compressive load needs closer examination. Condylar style prosthesis are available with a wide range of antroposterior tibial condyle curvatures. They vary from the relatively flat geometry, used most frequently in cruciate-retaining prosthesis, to the more curved geometry commonly associated with cruciate-sacrificing and curciate substituting prosthesis. In either case, the principles of mechanics do not change and if the joint reaction force is composed mainly of transmitted compressive load between the femur and the tibia, the load line must lie perpendicular to the surface of the joint at its point of contact. For the natural joint, with its remarkable low coefficient of friction, deviation from perpendicularity condition of approximately one part per thousand can not be exceeded if no cruciate force is applied. For total joint prosthesis with somewhat higher coefficient of friction, deviation from perpendicularity could be several parts of hundred (lnsall et al., 1993).
Modern knee arthroplasty began in the early 1970s with the development of the condylar total knee prosthesis. The studies of prosthesis longevity with this prosthesis are the standard to which modern knee replacement is compared. Long-term series by Ranawat, Flynn, and Deshmukh, Scuderi et al., and Ranawat et al. have documented the longevity of the original total condylar prosthesis to be 91% to 96% at 14- to 15-year follow-up. The reported prevalences of early failure because of tibial loosening, polyethylene wear, and osteolysis has been higher in cementless TKA than in cemented designs. However, Buechel reported 95% clinical survivorship at 12 years for an assorted group of cementless low-contact-stress (LCS) knee prostheses that included unicondylar prostheses, meniscal-bearing prostheses, and a rotating platform version. Whiteside reported a 10-year survival rate of 96% with an earlier cementless design that included a tibial intramedullary stem and additional pegs but lacked tibial screw fixation. Subsequent modification of the tibial trays to include screw fixation has resulted in minimal short-term tibial loosening ( Rand and Ilstrup , 1991).
Factors frequently associated with a higher rate of infection after TKA include rheumatoid arthritis (especially in seropositive males), skin breakdown, prolonged wound drainage (more than 6 days), previous knee surgery, use of a hinged knee prosthesis, obesity, concomitant urinary tract infection, steroid use, renal failure, diabetes mellitus, malignant disease, and psoriasis( Quanjun et al., 2007).
Infection should be considered in any patient with a consistently painful TKA and especially in a patient with a previously pain-free arthroplasty. A history of swelling, erythema, or prolonged wound drainage is suggestive of TKA sepsis, but these signs are not uniformly present.
In the report by Peersman and his coworker (2001), 6489 TKR were done in 6120 patients of these knee replacements, 116 knees became infected and 113 were available for followup; 97 of these knees (86%) had deep periprosthetic infections and the remaining 16 knees had superficial wound infections; one third of the deep infections occurred within the first 3 months after surgery and the remaining 2/3 occurred after 3 months.Overall early deep infection rate for patients undergoing a primary knee replacement was 0.39%, whereas the rate for patients undergoing a revision knee replacement was 0.97%;predominant infectious organisms were gram-positive (staph aureus, staph epidermidis, and strept group B); 20% percent of the knees that were infected clinically had no organisms that could be identified in each case, the patient had been treated empirically at another institution with antibiotic before a culture of the joint was obtained( Peersman et al., 2001).
Two additional mechanisms can lead to an early wound infection:
(1)-A leading hematoma that initially is sterile and subsequently becomes culture positive.
(2)-Defective skin healing that allows the contamination of the underlying soft tissues and prosthesis from the outside environment. Or remote sites of infection such as the oral cavity, the genito- urinary tract, the pulmonary system, and skin ulcers.
Three main portal of entry for infection after total joint replacement have been suggested:
- Intraoperative contamination.
- Postoperative inoculation of the joint.
- Haematogenous seading ( Peersman et al., 2001).
Prevention of infection in TKA begins in the operating room, which should be controlled with strict adherence to aseptic technique. Personnel within the operating room should be kept to the smallest number that can efficiently perform the procedure, and traffic in and out of the room should be held to a minimum. Operating room surveillance with adherence to such policies has been demonstrated to decrease the incidence of postoperative infection in total joint replacement. The use of ultra-clean air operating rooms has greatly affected postoperative infection rates in total joint arthroplasty. Filtered vertical laminar flow rooms with high rates of air exchange were widely used,this reduce the postoperative infection rate from around 10% to 1% to 2% by this measure alone. In a series of articles, Lettin .(1990) described the use of vertical laminar flow in operating rooms and the use of prophylactic antibiotics and reported similar effects in lowering the rates of postoperative deep infection in both hip and knee replacement. They stated that the combination of vertical laminar flow with prophylactic antibiotics has an additive effect in preventing deep infection. Statistically, this is difficult to prove because of the low incidence of infection with either prophylactic measure alone. In one clinical series, the use of horizontal laminar flow was demonstrated to actually increase the postoperative infection rate in TKA, probably because of positioning of operating room personnel upstream in the air flow from the operative field. Attention to better personnel positioning may improve results with horizontal laminar flow. Although not widely used, ultraviolet light is preferred by some centers to create an ultra-clean air environment, with infection rates similar to those with vertical laminar flow. The use of body exhaust systems has become wide spread in total joint arthroplasty and has resulted in low levels of bacterial shedding into the operative field. The effectiveness of these systems in preventing postoperative wound infection is again difficult to prove statistically because of the already low postoperative infection rate (Lettin , 1990) .
The treatment options for an infected total knee replacement include:
Antibiotic treatment based on organism, ggressive wound debridement, drainage, and antibiotic suppression therapy, Staged revision with antibiotic spacer, Knee arthrodesis, Resection arthroplasty and Amputation(James, 1996).
One of the most significant complications after total knee arthroplasty is the development of deep venous thrombosis (DVT), with subsequent life-threatening pulmonary embolism (PE). Factors that have been correlated with an increased risk of DVT include age over 40 years, female gender, obesity, varicose veins, smoking, hypertension, diabetes mellitus, and coronary artery disease. The overall incidence of DVT after TKA without any form of mechanical or pharmaceutical prophylaxis has been reported to range from 40% to 88%. The risk of asymptomatic PE may be as high as 10% to 20%, with symptomatic PE reported in 0.5% to 3% of patients and a mortality rate of up to 2%. Proximal thrombi, in the popliteal vein and above, occur in 3% to 20% of patients and have been thought to pose a greater risk of PE than thrombi in calf veins, which have been reported in 40% to 60% of patients. Thrombi in the calf veins do have a propensity to propagate proximally, as documented in 6% to 23% of patients. Routine duplex ultrasonic screening can detect asymptomatic thrombi, as well as proximal propagation of calf thrombi, and that full-scale anticoagulation should be used only in patients with proximal clots( Khaw et al., 1993).
Venography is the classic method of detection of DVT and may still be considered the gold standard, especially for research purposes. It does carry the risk of anaphylactic reaction to the contrast media and a small risk of actually inducing DVT. Duplex ultrasonography has excellent sensitivity in the detection of DVT after total joint arthroplasty.It has been documented that sensitivities of 89% or better with duplex ultrasound using venography for comparison ( Kraay et al., 1993).
Many current methods of DVT prophylaxis are available, including mechanical compression stockings or foot pumps and pharmaceutical agents including low-dose warfarin, low-molecular-weight heparin, and aspirin. Interestingly, continuous passive motion has not been proven to significantly affect the incidence of DVT (Clagett et al.,1995).
In the report by Comp et al.,(2001) the authors evaluated the efficacy and safety of a prolonged post-hospital regimen of enoxaparin;following elective total hip or knee replacement, 968 patients received subcutaneous enoxaparin (30 mg twice daily) for seven to ten days, and 873 were then randomized to receive three weeks of double-blind outpatient treatment with either enoxaparin (40 mg once daily) or a placebo.
- of the 873 randomized patients, 435 underwent elective total hip replacement and 438 underwent elective total knee replacement, enoxaparin was superior to the placebo in reducing the prevalence of venous thromboembolism in patients treated with THR. Eighteen of the 224 (8.0%) patients treated with enoxaparin had venous thromboembolism compared with 23.2% (forty-nine) of the 211 patients treated with the placebo - enoxaparin had no significant benefit in the patients treated with knee replacement.Thirty eight of the 217 patients(17.5%) treated with enoxaparin had venous thromboembolism compared with 46 of the 221 patients(20.8%) treated with the placebo.Symptomatic PE developed in three patients, one with a hip replacement and two with a knee replacement, all had received theplacebo.Arterial complications after total knee arthroplasty are relatively uncommon. Various mechanisms of arterial injury have been described, of which intraoperative or early postoperative arterial thrombosis is the most frequently reported (Calligaro et al., 1994).
Peroneal nerve palsy is the only commonly reported nerve palsy after TKA. It occurs primarily with correction of combined fixed valgus and flexion deformities, and are common in patients with rheumatoid arthritis. The incidence of peroneal nerve palsy in the Swedish Knee Arthroplasty project was 1.8% in 2273 rheumatoid patients. The true incidence may be somewhat higher reported in 0,3% to 4% of all total knee operations because mild palsies may recover spontaneously and not be reported(Idusuyi 1996). The value of intraoperative exposure and possible decompression of the peroneal nerve is questionable. When a peroneal nerve palsy is discovered postoperatively, the dressing should be checked for peroneal nerve constriction and the knee should be flexed. Asp and Rand (1999) suggested that such conservative measures, though appropriate, are not very effective in restoring nerve function( Asp and Rand , 1999).
Peroneal nerve palsy following TKR usually presents acutely but in some cases there will be a delayed presentation(Furnes , 2002).
The predisposing risk factors for fractures in TKR patients are rheumatoid arthritis, chronic steroid therapy, and other condition that results in osteopenia of the distal part of the femur. Other less contributing factors have included medication- induced osteopenia or an unsteady gait in patient who have a neurological disorder. Also, arthrofibrosis after a total knee replacement may predispose to fracture by increasing stress in the distal femoral metaphysic (Clup et al., 2001).
Supracondylar fractures of the femur occur infrequently after TKA (0.2% to 1%) (Figure 4-5). Reported risk factors include anterior femoral notching, osteoporosis, rheumatoid arthritis, poor flexion, revision arthroplasty, and neurological disorders. The anterior femoral flange of condylar-type prostheses creates a stress riser at its proximal junction with the relatively weak supracondylar bone.Many patients with supracondylar fractures after TKA have prior anterior femoral notching, especially rheumatoid patients (DiGioia and Rubash , 1991).
Tibial fracture following total knee arthroplasty is an infrequent
complication with a reported prevalence of 0.40 to 1.7 %(Felix et al., 2000).
The goal of treatment of a supracondyler fracture proximal to a total knee arthroplasty are union of the fracture and a return to the pre-fracture level of function while maintaining the range of motion of the knee Non-operative treatment is recommended for non-displaced fractures as well as for minimally displaced fractures when alignment of the fracture and mechanical axis of the limb are easily achieved and maintained with closed reduction ( Rolston et al., 1995 ).
Multiple options are available to provide secure internal fixation of supracodylar fractures of the distal part of the femur. The supracondylar blade-plate and the condylar compression screw and side-plate have been
used for many years to treat these fractures (Zehntne and Ganz, 1993).
Osteolysis refers to a specific phenomenon that can occur after any form of total joint replacement.Osteolysis is a process where cysts are formed in the bone surrounding total joint replacement component.These cysts are formed when the body reacts to wear debris that is generated at the point of movement of the total joint Arthroplasty.As the body tries to get rid of the debris,there are cells that act similar to a vacuum cleaner to try and clean up this material. The human body has no enzymes that can digest plastic and metal.These matrials will then build up within the cell until the cell ruptures.When the cell bursts,it releases large amounts of enzymes into the local tissue that will then dissolve the tissue and bone in that area.As this occurs,a cyst will be generated( Archibeck et al.,2000).
The most widely accepted theory at the present time regarding osteolysis is that the release of mediators from macrophage engaged in particle phagocytosis stimulate bone resorption at the bone- implant interface. It is the resorption which disrupts the bond formed between implant and bone and which ultimately leads to clinically recognized loosening.Periprosthetic bone loss occurs as a result of an inflammatory reaction to small particles, such as those produced by the various wear modes. Wear modes in total knee replacement have been associated with some design characterized by lower conformity, especially when the tibtil polyethylene is less than six millimeter thickness. Polyethylene wear and osteolysis following total knee replacement surgery may result from many factors, such as, surgical technique, patient selection (young age and high body weigh will subject the polyethylene component to more severe loading conditions), choice of implant design, conformity of articulating surfaces, quality and thickness of the polyethylene component (as thickness decrease, the stress increase), correct alignment of the limb, and proper ligament balance (Argenson and Connor, 2002).
The loosening rate of total knee prosthese is about one percent per year. That means that after 10 years 10 % of all patients with a total knee joint will have their total knee prostheses failed by loosening and exchanged.Aseptic loosening can be defined as the failure of the bond between an implant and bone in the absence of infection. Historically, the most common cause for revision of a total knee arthroplasty is aseptic loosening of the tibial component (Dorr et al., 1995).
Factors responsible for total knee component loosening is technical inadequacy of surgical implantation, other factors include bone quality, patient weight and activity, prosthetic design, ligamentous instability and wear product (canale,2003).
The term stiffness as related to total knee replacement have several different meanings. from the prospective of surgeon, stiffness mean an inadequate or smaller - than- expected range of motion as measured in a standardized fashion with the patient on an examination table. Active or active- assisted ranges of motion routinely are measured under optimum conditions during the recovery period and the norms of motion following total knee replacement have been generated on the basis of these data(Charles et al., 2005).
Post operative stiffness of the knee usually subsides within six to eight weeks. Range of motion generally improves steadily during the first three months, after which less rapid progress may be seen for additional nine months or more (Ayers et al., 1997).
The Causes of TKR stiffness are nfection and Mechanical Problems Related to the Implant or the Soft Tissue (Kim and Moon, 1999).
Treatment alternatives are Physical therapy Manipulation, Debridement and Revision Ranawat and Flynn, 1995 ).
Patellar complication has become the major source of failure after total knee arthroplasty . It has been estimated as 50 % of complications after total knee arthroplasty (Doolittle and Turner, 1998).
These complications are : Patellofemoral instability, Patellar fracture, Loosening or failure of the patellar component, Patellar clunk syndrome, Tendon rupture, Infrapatellar scaring and soft tissue impingement and Patellar osteonecrosis (Hozack et al., 1999).
Nonsurgical treatments for patellar subluxation or dislocation include physiotherapy focused on strengthening of the quadriceps (particularly the vastus medialis obliqus), patellofemoral bracing, and activity modification to avoid activities that require hyperflexion, such as squatting or stair climbing.
When nonoperative measures fail to relieve the patient’s symptoms, surgical efforts must be directed at the underlying cause of the problem.
Treatment of patellar fractures is dependent on fracture pattern, location, remaining bone stock, integrity of the component-cement-bone interface, and competence of the extensor mechanism.Nonoperative treatment is preferred when fractures are nondisplaced. Unfortunately, the definition of displacement has varied in reports in the literature, from 2 mm to 2 cm( Hozack et al., 1988).
The results of operative treatment of patellar fractures after TKA vary significantly from the results of treatment of patellar fractures in normal knees. Nonunion and hardware failure are frequent after internal fixation. Hozak et al.,1999 recommended nonoperative treatment of both displaced and nondisplaced fractures with no extensor lag and no loosening of the patellar component from a large fracture fragment. They had poor results with operative repair of displaced patellar fractures and recommended patellectomy and extensor mechanism repair.
A reduction in the rate of loosening of the patellar components requires improved bone preparation and cementing techniques, proper patellar resection , avoidance of asymmetrical or excessive bone removal, and central patellar tracking .Options for the treatment of loosening of the patellar component include revision of the component , removal of the component and patellar arthroplasty ( smoothing of the remaining patella without resurfacing ) if the remaining bone stock is unsatisfactory , and patellectomy . Some patients are asymptomatic and need no treatment (Ayers et al., 1997).
Nonoperative treatment of patellar clunk syndrome include:
Physiotherapy to encourage patellar mobilization. Quadriceps and hamstring strengthening and a trial of anti-inflammatory medications. If nonoperative measures fail to adequately relieve the patients symptoms, then surgical options need to be entertained, including arthroscopic debridement or arthrotomy with debridement and excision of hypertrophic tissue ( Donald Reilly, 2000 ).
Summary
The knee joint is a freely mobile joint composed of tibio-femoraland patello-femoral articulation.The tibio-femoral joint permit flexion,extention and varus,valgus motion.
The mechanics of TKR do not differ substantially from those of the natural limb with the mechanism producing varus-valgus stability of the normal joint still applicable for most prosthesis,however with some important destinctions.
Careful preoperative evaluation of the patient,adequate operative procedure,and postoperative follow up,and rehabilitation should be promptly fullfield so as to achieve a successful TKR.
The different complications of TKR have been discussed in view of their presentation,causes and management,they had been categorized into nine major groups:
The first group include the infected TKR.
The second group include the thrombombolism complication.
The third group include the neurovascular complication.
The fourth group include the periprosthetic fracture.
The fifth group include the osteolysis problem.
The six group include the asepic loosening .
The seventh group include the stiff knee complication.
The eighth group include the polyethylene wear.
The ninth group include the patellar problems.
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