الفهرس 
Detailed Anatomy of the Lumbar Intervertebral Foramen and Detailed Anatomy of the Lumbar Intervertebral Foramen andOnly 14 pages are availabe for public view
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Abstract
The Intervertebral foramen is a door between the spinal canal and periphery. from medial viewpoint, intervertebral foramen is seen as circular, oval or upside-down tearDROP shape. It is a unique dynamic structure related to two different kinds of joints and surrounded by osseous structures. Its shape and diameter changes during movements of the body. The `extraforaminal space is anatomically defined as the area lateral to the superior and inferior pedicles. The boundaries of the extraforaminal space could then be defined: medially, the pars interarticularis; laterally, the medial free edge of the intertransverse ligament; superiorly, the inferior border of the pedicle and inferior aspect of the superior articular process above; and inferiorly, the superior border of the pedicle below and the superior aspect of the superior articular facet below. The intervertebral foramen and extraforaminal space contain segmental mixed spinal nerve and its dural sheath, dorsal root ganglion, sinuvertebral nerves (recurrent meningeal nerves), spinal branch of posterior ramus of a lumbar artery, communicating veins between internal and external venous plexuses.
In the present study, the presence of ligamentous bands running across foramina of the lumbar spine were discussed. Such transforaminal ligaments are documented at all foraminal levels where they divide the foramen into many compartements. The attachments and the arrangments of the ligaments were described. The ligaments are arranged spatially from medial to lateral and designated as: (i) internal, (ii) intraforaminal and (iii) external foraminal. In the literature, many authors claimed that these ligaments help in protection and support of the nerve root; however, other authors reported that they may be a cause of nerve root compression in some cases.
In the present work, the anatomy of zygapophyseal joint, clinicaly known as joints (FJ), was considered in details as they share in formation of the intervertebral foramen and extraforaminal space. These articulations are plane synovial joints. Each joint is surrounded by a thin, loose articular capsule. Dynamically, the capsule serves to limit rotation and resists a backward sliding motion during extension. The facet joint contains two types of intraarticular structures which have clinical importance; subcapsular fat and meniscoid. Moreover, each lumbar FJ is innervated by the medial branches of the primary dorsal rami from the same level and the level above.
Familiarity with both basic anatomy and radiologic anatomy of the spine is necessary to understand the various disorders and pathologies that affect the spine and its components. Therefore, the present study focused on correlating the anatomical facts with the main modalities currently in use for spinal imaging in medicine; X-rays, computed tomography (CT), and magnetic resonance imaging (MRI).
Most disorders of the spine come from degenerative changes that may arise in bone, ligaments, or soft tissue of the spine. They are visualized by X- ray, CT-scan and MRI. Structural changes of the intervertebral disc often initially occur in small, localized regions. Over time, tissue disruption can spread diffusely throughout the disc and lead to a reduction in stiffness and loss of fluid pressure, as well as various combinations of bulging, herniation, and decreased disc height. In plane X- ray and CT-scan space narrowing and osteophytosis are characteristic. The accuracy of magnetic resonance imaging in the diagnosis of disc degeneration approached 100%. Severity of disc degeneration is divided into five grades according to the extent of the reduced signal strength: grade I, which represents a normal disc, and grades II, III, IV and V, which respectively represent light to severe degeneration. Dynamic MRI as compared to conventional MRI is more sensitive in demonstrating the presence of high intensity zone (HIZ) which represents radial annular tear.
Degenerative changes of the facet joint may result from primary osteoarthritis or may be secondary to degenerative changes within the intervertebral disc. Repetitive stress and osteoarthritic changes to the facet joint can lead to zygapophyseal hypertrophy. Like any synovial joint, degeneration, inflammation, and injury can lead to pain with joint motion, causing restriction of motion secondary to pain and, thus, deconditioning. In addition, Z-joint arthrosis, particularly trophic changes of the superior articular process, can progress to narrowing of the neural foramen. Degenerative changes of the facet joint may result in the formation of two types of juxtaarticular cysts; synovial and ganglionic cysts. standard radiographs are highly accessible, inexpensive, and a relatively harmless imaging method, they can only be used for preliminary screening for FJ OA. CT improves anatomical evaluation; Abnormalities of the facet joints that can be demonstrated and categorized by CT include osteophyte formation, hypertrophy of articular processes, articular cartilage thinning, vacuum joint phenomenon, synovial and subchondral cysts, and calcification of the joint capsule. MRI may illustrate nerve root entrapment secondary to Z-joint hypertrophy or a synovial cyst and may help visualize the intervertebral foramen.
Disc herniation is defined as focal eccentricity of the disc contour due to displacement of disc material beyond the intervertebral disc space. The present work demonstrated that, there are five types of lumbar disc herniation: protrusion, subannular extrusion, extrusion, sequestration, and migration. The location of the herniated disc is described in horizontal plane is central, left. or right. paracentral, subarticular (lateral recess), foraminal and extraforaminal (far lateral); in the craniocaudal plane the disc level may be infrapedicular, pedicular or suprapedicular. In plane X-ray narrowing of an intervertebral disc space, in the absence of other evidence of chronic discopathy, is the only detectable sign suggesting the presence of a disc herniation. Computed tomography aids in the diagnosis of far lateral disc herniations. Isolated far lateral fragments appear isointense. There are four parameters on axial T1- and T2-weighted images should be looked for in evaluation of these cases on the basis of the following MRI findings: (1) focal eccentricity of the disc contour; Eccentricity is defined as obviously focal extension of the disc beyond the boundary of the circumferential margin of the disc around the vertebral endplates, (2) obliteration of epidural fat surrounding the nerve root; epidural fat plane is obliterated by the herniated disc material in the medial, lateral, or both aspects of the nerve root, (3) changes in the thickness of the nerve root related to the herniated disc in comparison with the contra lateral nerve root, and (4) displacement of the nerve root by the herniated disc. In dynamic MRI, pain in disc herniation is more severe in extension than in flexion. This positional pain difference may be due to the change from disc protrusion to extrusion that is better demonstrated by dynamic MRI than conventional MRI.
Foraminal stenosis is defined as narrowing of the bony exit of the nerve root. The present investigation demonstrated that foraminal stenosis is graded according MRI appearance into four grades: grade 0, refers to the absence of foraminal stenosis; grade 1 refers to mild foraminal stenosis ; Grade 2 refers to moderate foraminal stenosis, and Grade 3 refers to severe foraminal stenosis. In addition MR imaging may reveal compression of the nerve root in the extraforaminal zone. in that respect, foraminal or extraforaminal stenosis are frequently overlooked as a cause for failed back surgery syndrome.
Spondylolisthesis is defined as anterior displacement of a vertebra relative to the vertebra below. It is divided into dysplastic, isthmic, degenerative, traumatic, pathological, and iatrogenic. A lytic defect of the pars interarticularis at any given level allows for separation of that vertebral body from its inferior facet, thus allowing the vertebra to slip forward. The pathophysiology of degenerative spondylolisthesis involves degeneration of the intervertebral disc and the facet joints, permitting displacement of the vertebrae with characteristic forward slippage and instability. In plane X-ray it is graded into 5 grades : Grade 1: 1- 25% slippage, Grade 2: 26-50% slippage, Grade 3: 51-75% slippage, Grade 4: 76-100% slippage, Grade 5: Greater than 100% slippage in DS. Isthmic spondylolisthesis is best visualized in oblique view showing fracture of the scottie dog’s neck. In degenerative spondylolisthesis CT will show the alignment of the facet joints and their degenerative changes. In isthmic spondylisthesis CT can demonstrate the detail of the pars defects. MR imaging is used to detect the degenerative changes and used for assessment of the nerve root and evaluation of the spinal canal.
The present work elucidated the anatomical basis of interventional radiology. Interventional radiology includes several modalities; transfroaminal steroid injection, medial branch block and facet joint injection. High concentration of corticosteroid injected precisely in the posterior epidural space is one of the lines of treatment of lumbar spinal stenosis. Transforaminal epidural steroid injection (subpedicular approach) is targeted to reach the safe triangle bounded by the pedicle, the exiting nerve root, and the lateral border of the vertebral body and then advanced to the outer third of the pedicle. There are two alternative approaches for the subpedicular transforaminal epidural steroid injection (TFESI); retroneural and retrodiscal. The retroneural TFESI approach describes the optimal target area more dorsal in the intervetebral foramen compared to the subpedicular technique. The retrodiscal TFESI approach places the needle past the lateral surface of the superior articular process (SAP) into the intervertebral foramen.
Under fluoroscopic guidance the target location for the L3 and L4 medial branch block was the osseous groove at the junction of the superior articular process and the transverse process of the corresponding vertebra. For the L5 dorsal ramus block, the junction of the superior articular process and the ala of the sacrum was the target.
Facet joint image-guided injection is an outpatient procedure that has a high diagnostic accuracy and safety. This technique is used to identify facet joints as the source of spinal pain. Moreover, it is used as a management tool for facet related spinal pain through the injection of local anesthetic and steroid into or around the facet joint. The major indications for facet injections include strong clinical suspicion of the facet syndrome.
The above mentioned description of these detailed anatomical facts, radiological findings and pathological conditions of the spine may serve as a useful foundation for a better understanding of the workspace in several spinal procedures and endoscopic access of the lumbar spine.