Reassessing the minimal clinically important differences of patient-reported outcomes in cervical myelopathy: a patient-centered approach from the Canadian Spine Outcomes and Research Network.

Abstract

The objective of this study was to determine minimal clinically important difference (MCID) values for patient-reported outcomes (PROs) including the 12-Item Short-Form Health Survey (SF-12) Physical Component Summary (PCS), SF-12 Mental Component Summary (MCS), and Neck Disability Index (NDI) in patients with degenerative cervical myelopathy (DCM) undergoing surgery, and to assess whether MCID values vary by baseline disease severity. The authors retrospectively analyzed prospectively collected data from the Canadian Spine Outcomes and Research Network for DCM patients treated surgically between 2015 and 2023. Inclusion required a baseline modified Japanese Orthopaedic Association (mJOA) score and 3- or 12-month follow-up PROs with domain-specific anchor responses. Patients were stratified by baseline mJOA score into mild (score ≥ 15), moderate (score 12-14), and severe (score < 12) groups. MCID values for the SF-12 PCS, SF-12 MCS, and NDI were calculated using anchor-based receiver operating characteristic curve analysis, with responder status defined by anchor questions. Discriminative performance was assessed via area under the curve, and 95% confidence intervals were estimated by bootstrapping. Among 290 patients meeting inclusion criteria, 77 (26.6%) were classified as having mild myelopathy, 120 (41.4%) moderate, and 93 (32.1%) severe. In the overall cohort, the MCID values were estimated as 8.9 (95% CI 7.5-10.9) for SF-12 PCS, 4.3 (95% CI 2.3-5.6) for SF-12 MCS, and 13.5 (95% CI 11.5-15.5) for NDI. Stratified SF-12 PCS MCID values increased from an estimated 4.8 (95% CI 1.1-7.7) in mild cases to 8.4 (95% CI 6.1-11.3) in moderate and 14.8 (95% CI 10.4-17.7) in severe cases. The NDI MCID values similarly rose from 10.5 (95% CI 6.5-12.5) to 15.0 (95% CI 10.5-19.0) to 17.5 (95% CI 14.5-21.0) across the mild, moderate, and severe groups, respectively. In contrast, the SF-12 MCS MCID values were 4.5 (95% CI 1.4-7.4) for mild, 3.8 (95% CI 0.4-5.8) for moderate, and 4.4 (95% CI 1.9-8.3) for severe patients, which did not differ significantly across severities. MCID values for PROs in DCM patients undergoing surgery increase with baseline severity. These findings indicate the importance of stratifying patients by disease severity to enhance the clinical relevance of MCID values, facilitate personalized treatment goals, and improve outcome assessments.