Patterns of Neurological Recovery after Posterior Decompression Without Fusion for Degenerative Cervical Myelopathy According to the Timing of Minimum Clinically Important Difference Achievement

Study DesignProspective cohort study.ObjectivesThe significance of failing to achieve the minimum clinically important difference (MCID) early after surgery for degenerative cervical myelopathy (DCM) remains unclear. To compare postoperative clinical outcomes among early-, delayed-, and persistent non-responders for DCM and to clarify the clinical significance of delayed neurological recovery.MethodsA total of 655 patients with moderate-to-severe DCM were categorized according to the achievement of the MCID in the Japanese Orthopaedic Association (JOA) score: early responders (MCID at 6 months), delayed responders (no MCID at 6 months but MCID at 2 years), and persistent non-responders (no MCID at either time point). Neurological, pain-related, and patient-reported outcomes were compared among the groups. Among patients without MCID achievement at 6 months, binary logistic regression analysis was performed to identify the factors associated with delayed MCID achievement.ResultsAmong patients without MCID achievement at 6 months, 36.9% achieved the MCID by 2 years. Binary logistic regression identified the 6-month JOA score, upper extremity function in the JOA Cervical Myelopathy Evaluation Questionnaire, and physical component summary of the 36-Item Short Form Health Survey as associated factors. Pain-related measures, autonomic function, and mental health status did not differ significantly among the groups.ConclusionsApproximately one-third of patients without early MCID achievement subsequently achieved the MCID within 2 years. Failure to achieve the MCID at 6 months does not necessarily indicate poor long-term outcomes, supporting the importance of continued postoperative follow-up.