Achieving the Minimum Clinically Important Difference in Japanese Orthopaedic Association Score After Surgery for Degenerative Cervical Myelopathy: Predictive Factors and Impact on Patient-Reported Outcome Measures

Study DesignProspective multicenter cohort study.ObjectivesAlthough surgery for degenerative cervical myelopathy (DCM) often improves neurological function, predicting clinically meaningful recovery remains challenging. To identify preoperative predictors of achieving the minimum clinically important difference (MCID) in the Japanese Orthopaedic Association (JOA) score and to evaluate its association with patient-reported outcomes.MethodsWe prospectively analyzed 762 patients with moderate to severe DCM (defined by preoperative JOA score <15) who underwent surgery at 10 high-volume centers in Japan, with a 2-year follow-up. MCID was defined as a ≥2.5-point improvement in JOA score. Logistic regression identified independent predictors. Outcomes included JOA score, Visual Analog Scale (VAS), the JOA Cervical Myelopathy Evaluation Questionnaire (JOACMEQ), and the 36-Item Short Form Health Survey (SF-36).ResultsMCID was achieved in 63.0% of patients. Independent predictors included younger age (Odds ratio = 0.973 [95% confidence interval: 0.956-0.990]; <i>P</i> = 0.002), absence of cerebrovascular (0.466 [0.224-0.960]; <i>P</i> = 0.039) and cardiac disease (0.510 [0.285-0.912]; <i>P</i> = 0.023), greater cervical lordosis (1.021 [1.004-1.037]; <i>P</i> = 0.013), lower baseline JOA score (0.547 [0.485-0.617]; <i>P</i> < 0.001), and higher JOACMEQ scores for upper extremity function (1.011 [1.000-1.022]; <i>P</i> = 0.044) and QOL (1.021 [1.009-1.033]; <i>P</i> < 0.001). MCID achievement was associated with significantly greater improvements in VAS, most JOACMEQ domains, and all SF-36 subscales.ConclusionsYounger age, absence of cerebrovascular and cardiac disease, greater cervical lordosis, lower baseline JOA score, and higher preoperative JOACMEQ scores for upper extremity function and QOL were associated with achieving MCID in JOA score.