An anatomical study of the different neurosurgical approaches of the cervical spinal cord

Abstract

Introduction: There has been long standing controversy about the best approach for the cervical spinal cord, however there is no doubt that the clinical indication and the surgical procedure required will determine for most cases the best surgical approach.
Objective: This study was done to study the feasibility of the various neurosurgical approaches of the cervical spinal cord.
Methods: Ten cadaveric specimens obtained from the dissecting room of the Faculty of Medicine, University of Alexandria were dissected both anteriorly and posteriorly in the cervical region to compare between the anterior and posterior approaches for the cervical spinal cord and to identify the various anatomical structures met with during both approaches. Also various techniques of laminoplasty and laminectomy with lateral mass screw fixation had been performed.
Results: A posterior midline incision cuts through the skin, subcutaneous tissue, trapezius fascia and liqamentum nuchae, bilateral subperiosteal dissection of cervical paraspinal muscles. Keyhole laminoforaminotomy was done by removing the lateral portion of two adjacent laminae to expose
foraminal course of the nerve root. Unilateral open door laminoplasty was done using non absorbable sutures, bone graft, or plate and screws. Then the laminae and spinous processes were cut in the midline with either drill or Gigli saw and opened bilaterally, then the defects were filled between the separated laminae by bone grafts and fixed by sutures (bilateral open door laminoplasty). Laminectomy was done to expose the dura mater and the cervical spinal cord. In lateral mass screw fixation the screw entry point was located 1 mm medial to the center of each lateral mass. The
screws were directed 20 superior and 30 lateral to the screw entry point. The average screw length that can be used for bicortical fixation without injuring the vertebral artery or nerve root was about 13.5 mm and average screw thickness was about 3.5 mm. After making an anterior incision through the skin and the investing layer of deep cervical fascia,
the strap muscles were exposed. The sternomastoid muscle appeared on the lateral side of the neck
with the carotid triangle between it and the strap muscles. After peeling off longus colli from the
cervical vertebrae, their bodies and the intervening intervertebral disks can be seen. Partial corpectomies and anterior discectomy of the vertebral body and the intervertebral disk was done to expose the dura mater and the cervical spinal cord using either drill or Kerrison rongeurs.
Conclusion: The choice of the surgical approach to the cervical spine should be dictated by the site of the primary pathology. Cervical laminoplasty is an alternative to standard laminectomy allowing
for a reasonable decompression of the vertebral canal with preservation of the supportive function of the vertebral column posteriorly. For a posterior approach to be successful the cervical lordosis should be intact and if affected the laminectomy must be combined with lateral mass screw fixation. The anterior approach has technical advantage that the decompression, fusion and immediate stabilization can be performed through one exposure, at one operation.