Fig. 31.5. A sagittal CT scan reconstruction of the mid-cervical spine. The patient underwent a previous laminectomy and had transient improvement of his symptomatology, followed by progressive myelopathy. The kyphotic configuration of the spine and the anterior osteophyte have prevented adequate decompression of the spinal cord by the laminectomy.
retrieved by retracting the nerve root and incising the posterior ligament, which typically contains the herniated fragment. Osteophyte usually cannot be removed by the posterior approach.
The genesis of anterior decompressive procedures has contributed significantly to the ability to directly decompress the neural elements in the cervical spine. Most degenerative pathology originates anterior to the thecal sac or the cervical nerve roots. In particular, the degenerative process typically begins in the disk space. Spinal cord and/or nerve root compression can result from the accumulation of osteophytes or from protruding disk material. Facet hypertrophy can also contribute to foraminal compression, although this is much less common in cervical spondylosis as opposed to its frequency in lumbar spondylosis. Compressive pathology can also be located posterior to the vertebral body, contributing to canal stenosis. Disk material can herniate vertically and be positioned behind the vertebral bodies. Osteophyte can proliferate from the interspace and extend behind the vertebral body, as can ossification of the posterior longitudinal ligament. Since compressive pathology typically originates anterior to the spine, the anterior decompres-sive techniques are a logical option to directly decompress the neural elements.
If the compressive pathology is confined to the level of the interspace, either in the central canal or the intervertebral foramen, a diskec-tomy and osteophytectomy confined to the interspace can be utilized to effect spinal cord and/or nerve root compression, respectively. The original anterior decompression technique was devised by Cloward, where a large burr-type hole was made over the mid portion of the disk, extending into the adjacent vertebral bodies and extending posteriorly to the annulus . From this midline channel, lateral decompression could be carried out to decompress the lateral aspects of the spinal canal and perform foram-inal decompressions. Following the decompression, a bone dowel was harvested from the iliac crest and placed into the hole to effect fusion. A modification of the Cloward procedure has since been devised and is called the Smith-Robinson technique [14,15]. Instead of a cylindrical hole, disk material and the endplate are removed in a rectangular shape. The decompression can be extended laterally to perform foraminotomies. Following the decompression, bone graft can be inserted into the interspace to maintain the disk space height and produce a fusion. Some authors perform decompression without fusion. Apparently, a majority of patients who do not have fusion bone inserted following the decompression will go on to a spontaneous fusion . It is not uncommon to develop collapse across the interspace following a decompression without fusion. This can result in a cervical kyphosis or foraminal stenosis .
In an attempt to eliminate the extent of disk removal for radiculopathy, a technique for lateral diskectomy and foraminal decompression has been developed [18,19]. The technique involved a lateral exposure to the anterior aspect of the spine and resection of the lateral aspect of the disk and uncovertebral joint to access the intervertebral foramen. The rationale for this procedure is to avoid a complete diskec-tomy and maintain the mobility of the motion segment. The risks of the procedure are injury to the vertebral artery and nerve root, and probably a higher risk of incomplete decompression because of the limited exposure.
Re-establishment of normal spinal alignment, or reduction of spinal deformity, has been a principle of spinal reconstructive surgery for trauma. In the setting of trauma, spinal realignment frequently achieves neural decompression. Besides decompressing the spinal cord and nerve roots, reduction of spinal deformity and re-establishment of a normal cervical lordosis appear to have other benefits in patients with cervical spondylosis. Cervical kyphosis, as discussed above, can contribute to anterior compression of the spinal cord, contributing to myelopathy. In addition, kyphosis probably also contributes to the likelihood of axial pain from spondylosis. In a kyphotic configuration, the paraspinal musculature, positioned posterior to the spine, is at a mechanical disadvantage and requires continuous contraction to maintain the head in a neutral position. This increased paraspinal muscle activity can contribute to axial neck pain. A posterior decompression, with removal of the posterior bony elements and detachment and manipulation of the posterior musculature, can also diminish the effectiveness of the extensor musculature and contribute to a progressive cervical kypho-sis. Based on these biomechanical factors, a laminectomy in the presence of cervical kyphosis can predispose to delayed complications.
The presence of kyphosis also adds to the amount of translational force applied to the individual motion segments. This can accelerate the deformity, as discussed above, but also impair the ability to achieve fixation and fusion of the cervical spine. The translational
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