Impact of the Level of Maximal Spinal Canal Stenosis on Clinical Manifestations and Surgical Outcomes in Cervical Ossification of the Posterior Longitudinal Ligament

STUDY DESIGN: Prospective multicenter cohort study. OBJECTIVES: To clarify whether differences in the level of maximal spinal canal stenosis are associated with distinct patterns of neurological impairment and postoperative functional recovery in patients with cervical ossification of the posterior longitudinal ligament (OPLL). SUMMARY OF BACKGROUND DATA: Although cervical OPLL is a major cause of compressive myelopathy, it remains unclear whether the level of maximal stenosis influences symptom severity and postoperative functional recovery in this disease entity. METHODS: A total of 402 patients who underwent surgery for cervical OPLL were prospectively enrolled from a nationwide multicenter cohort. Patients were stratified according to the level of maximal stenosis into an upper cervical stenosis group (C4/5 or more cranial) and a lower cervical stenosis group (C5 or more caudal). Clinical outcomes were assessed preoperatively and at 2-year follow-up using the Japanese Orthopaedic Association (JOA) score, visual analog scale (VAS), and the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ). Multivariable analyses were performed to adjust for potential confounders. RESULTS: Patients with upper cervical stenosis exhibited significantly worse preoperative neurological function than those with lower cervical stenosis. Despite this baseline difference, postoperative neurological improvement was comparable between groups. Improvement in arm and hand pain or numbness was significantly greater in the upper stenosis group, whereas improvement in lower extremity function, assessed by the JOACMEQ, was significantly poorer in patients with lower cervical stenosis. The incidence of perioperative complications did not differ significantly between groups. CONCLUSION: The level of maximal spinal canal stenosis significantly influences symptom patterns and domain-specific functional recovery in cervical OPLL. These findings provide important information for surgical decision-making and prognostic counseling in cervical OPLL.