Neural space integrity of the lower cervical spine: effect of anterior lesions.

Abstract

A repeated measures study design was used to evaluate intervertebral foramen and spinal canal neural space integrity subsequent to sequential surgical anterior lesions of the lower cervical spine in a human cadaver model. To investigate the degree to which sequential ablation of anterior vertebral elements places the neural structures at risk of injury. Classic instability management utilizing functional-structural criteria has been widely examined associating specific lesions or pathologies to a degree of mechanical instability. Unfortunately, these studies have not assessed the neuroprotective role of the vertebral column. Eight human cadaveric lower cervical spines were instrumented with transducers to measure geometrical changes in the intervertebral foramen and spinal canal. Sequential lesions were performed anteriorly on the anterior and middle column structures (C4-C5 disc and C5 vertebra), and their effects on neural space integrity and range of motion were measured under physiologic loading. Range of motion significantly increased with successively more destructive lesions, whereas the spinal canal exhibited few changes. Intervertebral foramen integrity was statistically reduced for corpectomy (66% intact), hemivertebrectomy (62% intact) and full vertebrectomy (57% intact) lesions when loaded in concomitant extension and ipsilateral bending (4 Nm). Lesions more extensive than a surgical discectomy have significant effects on the cervical neural foramens specifically when the spine is placed in extension, ipsilateral bending, and coupled ipsilateral bending and extension. Our study establishes a quantitative relationship between the risk of neural structure compression and anterior lesions of the spinal column under physiologic loading.