Postoperative instability after laminoplasty for cervical myelopathy with spondylolisthesis

Objective: 76 patients who underwent laminoplasty for cervical spondylotic myelopathy were investigated regarding the impact of preoperative and postoperative degenerative spondylolisthesis on their neurologic outcome. Methods: Radiographs were obtained 1 year postoperatively to investigate range of motion (ROM), lordotic curvature, and postoperative spondylolisthesis. Results: By 1 year after surgery, 85% of those spondylolistheses present preoperatively had either resolved or improved on neutral lateral radiographs. The cross-sectional area of the spinal cord at the site of spondylolisthesis was measured using preoperative computed tomography myelography. Clinical results were evaluated by the recovery rate using Japanese Orthopaedic Association score. Patients with posterior spondylolisthesis showed a significantly poorer postoperative recovery rate. Intervertebral ROM in patients with preoperative spondylolisthesis was reduced, whereas cervical alignment had not deteriorated after laminoplasty. The group with posterior spondylolisthesis showed a significant reduction in the cross-sectional area of the spinal cord at the site of spondylolisthesis. Postoperative spondylolisthesis appeared in 15 patients, 10 of whom had preoperative spondylolisthesis at an adjacent site. Conclusion: The cause of poorer surgical results of those patients with preoperative posterior spondylolisthesis appears to be related to a higher degree of spinal cord compression than with preoperative anterior spondylolisthesis.