Abstract
Minimum clinically important differences (MCIDs) for patient-reported outcome metrics (PROMs) in patients with cervical spondylotic myelopathy (CSM) lack consensus on the most appropriate calculation method. This retrospective study aimed to identify the optimal MCIDs for commonly used PROMs in CSM.
The CSM database from the Quality Outcomes Database SpineCORe Study Group was analyzed. Baseline, 3-month, and 24-month PROM values for Neck Disability Index (NDI), 5-dimension Euro-quality of life (EQ-5D) in quality-adjusted life years, modified Japanese Orthopaedic Association (mJOA) score, and neck/arm pain numeric rating scale (NRS) were collected. MCIDs were calculated for each PROM using previously validated techniques. MCID values were compared using the area under the curve (AUC) with the North American Spine Society satisfaction scale as an anchor.
A total of 1141 patients with CSM undergoing surgery were included in this analysis. Improvement of ≥30% from baseline was the optimal MCID for NDI and neck/arm NRS. At 24 months, the optimal percentage cutoff MCID for these instruments resulted in AUCs of 0.76, 0.72, and 0.67, similar to the 30% improvement method, with AUCs of 0.73, 0.71, and 0.67, respectively. Numeric cutoffs (0.065 at 3 months; 0.149 at 24 months) were the superior MCIDs for EQ-5D. For mJOA score, a severity-adjusted MCID outperformed other methods, yielding an AUC of 0.67 at 24 months. MCIDs were achieved in 63% of patients for NDI, 59% for neck pain NRS, 61% for arm pain NRS, 52% for EQ-5D, and 59% for mJOA score at 24 months.
Using the Quality Outcomes Database SpineCORe data set, we defined optimal MCIDs for key PROMs in CSM. A ≥30% improvement from baseline was optimal in NDI and arm/neck NRS. An absolute numeric cutoff was superior for EQ-5D (0.149 at the 24-month follow-up). A severity-adjusted MCID performed best for mJOA score. These redefined benchmarks better capture the treatment impact and guide care decisions for patients with CSM.