Influence of hinge position on the effectiveness of open-door expansive laminoplasty for cervical spondylotic myelopathy

【Abstract】Objective: To assess the influence of different hinge positions on clinical results of expansive open-door laminoplasty (EOLP) for cervical spondylotic myelopathy (CSM). Methods: A total of 102 CSM patients who underwent EOLP from February 2006 to February 2007 were enrolled in this randomized controlled trial. Using a random digits table, 57 patients with the hinge located at the inner margin of the lateral mass were classified as wide-open group, while 45 patients with the hinge positioned at the lamina margin served as narrow-open group. All patients were observed over 24 months, and the clinical and radiological results were analyzed statistically. Results: There were no significant differences in operation duration, intraoperative bleeding volume, Japanese Orthopaedic Association (JOA) scores, cervical curvature index, range of motion and neural function recovery rate. The neural functions were satisfactorily improved after surgery in both groups, while the severity of axial symptoms was significantly lower in the narrow-open group than in the wide-open group (P=0.003). The incidence of C5 palsy in the wide-open group was higher than that in the narrowopen group (5.3% vs 0), even though the difference did not reach statistical significance (one tailed Fisher's exact test, P=0.17). Conclusions: Proper inward shift of the hinge can ensure effectiveness of surgical decompression, avoid an excessive backward shift of the spinal cord, decrease the incidence of C5 palsy and alleviate the severity of axial symptoms. Key words: Cervical vertebrae; Spinal cord diseases; Spondylosis; Surgical procedures, operative