Comparison of the patient-derived modified Japanese Orthopaedic Association scale and the European myelopathy score

Abstract

PurposeTo compare the patient-derived modified Japanese Orthopaedic Association (P-mJOA) scale with the European myelopathy score (EMS) for the assessment of patients with degenerative cervical myelopathy (DCM).MethodsIn this register-based cohort study with prospectively collected data, included patients were surgically treated for DCM and had reported both P-mJOA and EMS scores at baseline, 1-year follow-up, and/or 2-year follow-up to the Swedish Spine Register. P-mJOA and EMS scores were defined as severe (P-mJOA 0–11 and EMS 5–8), moderate (P-mJOA 12–14 and EMS 9–12), or mild (P-mJOA 15–18 and EMS 13–18). P-mJOA and EMS mean scores were compared, and agreement was evaluated with Spearman’s rank correlation coefficient (ρ), the intraclass correlation coefficient (ICC), and kappa (κ) statistics.ResultsIncluded patients (n = 714, mean age 63.2 years, 42.2% female) completed 937 pairs of the P-mJOA and the EMS. The mean P-mJOA and EMS scores were 13.9 ± 3.0 and 14.5 ± 2.7, respectively (mean difference –0.61 [95% CI –0.72 to –0.51; p < 0.001]). Spearman’s ρ was 0.84 (p < 0.001), and intra-rater agreement measured with ICC was 0.83 (p < 0.001). Agreement of severity level measured with unweighted and weighted κ was fair (κ = 0.22 [p < 0.001]; κ = 0.34 [p < 0.001], respectively). Severity levels were significantly higher using the P-mJOA (p < 0.001).ConclusionThe P-mJOA and the EMS had similar mean scores, and intra-rater agreement was high, whereas severity levels only demonstrated fair agreement. The EMS has a lower sensitivity for detecting severe myelopathy but shows an increasing agreement with the P-mJOA for milder disease severity. A larger interval to define severe myelopathy with the EMS is recommended.