Impacts of postoperative changes of segmental mobility on neurological improvement after laminoplasty for cervical ossification of the posterior longitudinal ligament

Several studies have demonstrated that the dynamic factor at the mobile segment affects the severity of myelopathy in patients with cervical ossification of the posterior longitudinal ligament (C-OPLL), and posterior decompression supplemented with posterior instrumented fusion at the mobile segment provides good neurological improvement. However, there have been few reports of changes in range of motion at the mobile segment (segmental ROM) after laminoplasty (LP). The aim of this study was thus to retrospectively investigate changes in segmental ROM after LP and the impacts of these changes on neurological improvement in patients with C-OPLL. A total of 51 consecutive patients who underwent LP for C-OPLL since May 2010 and were followed for at least 2 years after surgery were included in this study. Neurological status was assessed using the Japanese Orthopaedic Association (JOA) score before surgery and at 2-year follow-up. Segmental ROM at the responsible level for myelopathy was measured preoperatively and at 2-year follow-up using lateral flexion-extension radiographs of the cervical spine. The mean JOA score improved significantly from 10.7 points preoperatively to 13.5 points at 2 years after surgery (mean recovery rate, 45.0%). The mean segmental ROM decreased significantly from 6.5 degrees before surgery to 3.2 degrees at 2 years after surgery. In the good clinical outcome group (recovery rate of the JOA score ≥50%; n = 22), the mean segmental ROM decreased significantly from 5.8 degrees preoperatively to 3.0 degrees postoperatively. It also decreased significantly from 7.1 degrees to 3.4 degrees in the poor clinical outcome group (recovery rate of the JOA score <50%; n = 29). This study showed that segmental ROM was stabilized after LP in most patients with C-OPLL. Neither preoperative nor postoperative segmental ROM showed significant differences between the good and poor clinical outcome groups and neither a postoperative increase nor decrease of segmental ROM significantly affected the recovery rate of the JOA score.