Limited cervical laminectomy prevents postoperative delayed motor palsy: an experimental study using a rat model.

Background context: Whether the width of laminectomy is a risk factor for the development of C5 palsy (C5P) remains controversial, partly due to confounding variables inherent in retrospective clinical studies.

Purpose: To investigate the relationship between laminectomy width, posterior shift of the spinal cord, and elongation of the anterior rootlets using an animal model.

Study design: Basic in vivo experimental study.

Methods: Eighteen Sprague-Dawley rats were randomly assigned to three groups: Group L (limited laminectomy, N = 6), Group W (wide laminectomy, N = 6), and Group S (sham surgery, N = 6). Animals were evaluated pre and postoperative days 3, 10, and 14. The widths of the laminectomy, posterior spinal cord shift, and anterior rootlet length were quantified using computed tomography-myelogram images. Motor evoked potentials (MEPs) were recorded from the deltoid (C5-C6 innervated) and triceps brachii (C7-T1 innervated) muscles.

Results: Postoperative posterior shift of the cervical cord was observed in both experimental groups. However, Group W showed significantly greater displacement than Group L at the C4-C6 vertebral levels on postoperative days 10 and 14, corresponding to a greater elongation of the C5-C7 anterior rootlets. MEP latency of the deltoid muscle was significantly longer in Group W than in Group L at postoperative days 10 and 14, and significantly longer than in Group S at all postoperative time points. Conversely, no statistically significant differences in MEP latency of the triceps brachii were observed among all groups.

Conclusions: Limited laminectomy may prevent C5P by minimizing elongation of the intradural anterior rootlets caused by gradual posterior shift of the cervical spinal cord.

Clinical significance: This study provides insights for clinicians regarding C5 palsy prevention. By limiting the width of degree of laminectomy, posterior shift of the spinal cord, and thus elongation of the anterior rootlets, can be reduced. These findings support the hypothesis that root tethering from spinal cord shift is a likely mechanism of C5P.