الفهرس 
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Abstract
Knee arthroscopy is a common orthopedic procedure worldwide. Despite its minimally invasive nature compared to the traditional knee surgery, post arthroscopic pain may be severe and the patients generally require a significant amount of opioid based analgesics after such procedure.
Peripheral nerve blocks offer effective analgesia and decrease the need for opioids, thereby reducing the complications associated with the use of this class of drugs. Moreover, postoperative pain relief is an important factor in the early ambulation and rehabilitation of patients after knee surgery.
The lumbar plexus consists of sensory and motor nerves, which innervates visceral organs in the pelvis and anterior and anterolateral dermatomes of the thigh and the medial dermatome of the lower leg, as well as provides motor control for the quadriceps femoris muscle.
The femoral nerve is one of the most important nerves of the anterior division group of nerves in the lumbar plexus, which mainly supplies the sensation for the anterior and medial parts of the lower extremities. Femoral nerve block (FNB) is a simple technique with a low risk of complications and has a high success rate. This method is appropriate for anterior thigh surgery and pain management after knee surgeries.
The femoral nerve can be anaesthetised at a number of different locations along its course. The main theoretical advantage of blocking the FNB at the level of the adductor canal compared with the more proximal block at the level of the inguinal ligament is sparing of the motor function of the anterior thigh muscles.
Adductor canal block (ACB) is a relatively an alternative for post-knee surgeries pain management. Regional anesthesia is deposited within an adductor canal that can be easily visualized at the middle third of the thigh with use of ultrasonography. Consequently, ACB can be performed with a high success rate. Anatomical study of adductor canal showed that an adductor canal contained multiple afferent sensory nerves (e.g. saphenous nerve, medial femoral cutaneous and medial retinacular nerve etc.) but only a single efferent motor nerve (vastus medialis of the quadriceps muscle) that potentially affected motor function. Therefore, ACB may have a minimal effect on quadriceps muscle strength, but provides a comparable level of pain relief and early mobilization.
Femoral nerve blocks (FNB) can provide effective pain relief but result in quadriceps weakness with increased risk of falls following knee surgeries. Adductor canal block (ACB) is a relatively an alternative providing pure sensory blockade with minimal effect on quadriceps strength.
The present study evaluated and compared the efficacy, duration of sensory block, duration of post operative analgesia and complications between adductor canal block and femoral nerve block.
An equal number of 40 patients were assigned to either the FNB or the ACB group (N =20 in each group). In the adductor canal block (ACB) group, a linear ultrasound probe was placed in inner thigh. The femoral artery is located at one third of the inner thigh under the Sartorius muscle. The ultrasound probe moved to the caudal direction until technically the superficial femoral artery or just femoral artery was identified. After identifying femoral canal, adductor hiatus of the saphenous nerve was visualized as hyperechoic structure superficial and lateral to femoral artery then 12 mL of bupivacaine 0.125% was injected to the nerve sheet.
In the FNB group, the femoral nerve was blocked at level of inguinal ligament. In brief, the femoral artery was identified below inguinal ligament under ultrasound guidance with a linear probe. The femoral nerve was detected adjacent to the artery using subsequently 12 mL of bupivacaine 0.125% was injected along the nerve sheet after negative aspiration.
In this study, we observed that there are statistically non significant differences between the studied groups regarding gender and age. Also, there is statistically non significant difference between the studied groups regarding diagnosis or type of operation
In our study, there is statistically significant difference between the studied groups regarding onset and duration of sensory block peak (both were higher in ACB group). Regarding VAS, there is statistically non-significant difference between the studied groups preoperatively and at 3, 6 and 12 hours postoperatively, while significant difference was detected between them at 24 hours postoperatively (higher VAS score in ACB group at 24 hours). On assessing change overtime in each group, the difference is statistically significant (significant fluctuation over time). But, there is statistically non significant difference between the studied groups regarding modified Ramsey before or one hour after nerve block
In our study, there is statistically non significant difference between the studied groups regarding patient satisfaction with anesthesia. Regarding Bromage score, there is statistically non significant difference between the studied groups at baseline, 3 and 24 hours postoperatively. There is statistically significant difference between the studied groups at 6 and 12 hours postoperatively (gradual improvement in score among patients with ACB, till all patients had no motor weakness on 12 hours, was present in FNB group yet with lesser percentage to reach 75% at 12 hours). On assessing change overtime in each group, there is statistically significant change in bromage score between the studied groups over time.
There is statistically non significant difference between both groups regarding need for analgesia at 24 hours or number of needed doses. Both groups need analgesia at 24 hours and received two grams for each patient.
Conclusion
ACB provides comparable analgesic efficacy and facilitates earlier mobilization by sparing quadriceps strength compared with FNB. Based on current trends in perioperative protocols toward early rehabilitation following knee arthroscopy, ACB may be a reasonable alternative to FNB as part of a contemporary multimodal pain management protocol after knee arthroscopy.
We recommend placing FNB after arthroscopic surgery of the knee joint for its superior analgesia, especially in settings where mild weakness of the thigh muscles would not interfere with postoperative rehabilitation. Early ambulation is not generally limited with the use of femoral block and the theoretical advantage of adductor canal block being ”muscle sparring” was not observed in our study probably due to its suboptimal pain control.
Recommendations
Further studies are needed to determine whether ACB provides superior functional recovery compared with FNB in patients undergoing knee arthroscopy. In addition, the clinical relevance of motor strength during the immediate postoperative period (within 24 hours after knee arthroscopy) should be determined. Further studies with realistic sample sizes and consistent outcome variables are required to determine whether ACB provides clinically relevant functional recovery compared with FNB.
More comprehensive studies are required to examine overall patient satisfaction including a variety of questions asking for the quality of pain, stress, and anxiety and the level of ambulation for these patients before making single shot or continuous FNB as the practice of choice for pain management after arthroscopic knee surgery.