Spinal posterior movement after posterior cervical decompression surgery: clinical findings and factors affecting postoperative functional recovery.

This study investigated the posterior movement of the spinal cord after posterior decompression surgery and evaluated factors affecting postoperative functional recovery in patients with cervical spondylotic myelopathy (CSM). Thirty-two patients with CSM underwent posterior decompression from C3 to C7 through laminectomy (n=12) and single, open-door laminoplasty (n=20). There were no significant differences between laminectomy and laminoplasty in degree of spinal posterior movement, recovery rate, and curvature index. Japanese Orthopedic Association (JOA) scores improved from preoperative (10.63±1.77; range, 7-14) to 3-months postoperative (13.57±1.50; range, 11-16) (n=32, P<.05) and from preoperative (10.24±1.87; range, 7-14) to 6-months postoperative (14.16±1.54; range, 12-16) (n=21) (P<.05). C5 palsy was observed in 1 (3.1%) patient. The vertebral body-to-spinal cord distances significantly increased after operations, with the greatest posterior movement at C5 and the least posterior movement at C3 and C7. However, the difference in the degree of the spinal movement of C3 to C7 was not statistically significant (P>.05). Furthermore, no correlation was found between the magnitude of spinal posterior movement and the curvature index. In addition, the magnitude of posterior movement and age were not correlated with the postoperative JOA improvement, but the preoperative JOA scores were. Our study shows that both laminectomy and laminoplasty can produce a similar degree of posterior movement of the spinal cord. Cervical lordosis is not associated with the posterior movement of the cord. The preoperative JOA scores, but not posterior movement of the cord and age, are important determinants for postoperative outcome.