MICROSURGICAL ANATOMY OF THE LOWER CERVICAL-SPINE AND CORD

THE AUTHORS DISSECTED the cervical spine and its surrounding structures from 40 adult cadavers under a surgical microscope. The anterior part of the spine and spinal cord was examined after vertebrectomy. The posterior longitudinal ligament (PLL) consists of two layers; the anterior one is termed the deep layer, and the posterior one is termed the superficial layer. These two layers adhered together loosely, In the lateral portion of the spinal canal, the superficial layer joined the periradicular sheath at the level of the intervertebral disc spaces and joined the dura mater at the level of the vertebral bodies. After the removal of the deep layer, the anterior internal vertebral venous plexus was seen on top of the lateral part of the superficial layer. The venous plexus was embedded between the double-layered PLLs, was not located in the epidural space, and was not seen in the medial part of the PLL. The PLL without venous channels on top of it was about 10 mm in width at the levels of the intervertebral disc and about 5 mm at the levels of the vertebral body. The anterior root exit zone (AREZ) was an elliptical shape; the transverse length of the AREZ was about 2 mm, and the longitudinal length was 10 to 15 mm. The average number of anterior rootlets on the AREZ was 17 to 25 and tended to decrease in the lower cervical spinal cord. The posterior structures were examined after en bloc laminectomy. The posterior root entry zone was linear, and the longitudinal length was 6 to 14 mm; the average number of posterior rootlets on the posterior root entry zone was 7 to 12. The intersegmental anastomoses between the spinal rootlets were common throughout the lower four cervical segments. The C7 AREZ faced the C5-C6 disc in most cases, and the C8 AREZ faced the C6-C7 disc in 80%. Knowledge of microsurgical anatomy should be considered essential for spinal surgery.