Functional outcome instruments used for cervical spondylotic myelopathy: interscale correlation and prediction of preference-based quality of life

Abstract Background context There is limited literature comparing different functional outcome measures used for cervical spondylotic myelopathy (CSM). Purpose To determine the correlation among five functional outcome measures used in CSM patient assessment and their ability to predict preference-based quality of life (QOL). Study design/setting Prospective observational study. Patient sample Patients, aged 40 to 85 years, with CSM and cervical spinal cord compression at two or more levels from degenerative spondylosis were enrolled from seven sites over a 2-year period. Outcome measures The modified Japanese Orthopedic Association scale, Oswestry neck disability index (Oswestry NDI or Oswestry), Nurick scale, norm-based short-form 36 physical component summary, and EuroQol-5D (EQ-5D) were collected. Methods The Jean and David Wallace foundation provided funding for this study. Cervical spondylotic myelopathy patients undergoing either anterior or posterior surgery were prospectively followed with five different functional outcome measures over 1 year. Correlations among scales were tested using the Spearman rank correlation test. The sensitivity and specificity of each scale for predicting the global index of the EQ-5D were determined, and receiver-operating characteristic analysis was used to compare each scale's ability to discriminate QOL. Results A total of 106 patients were initially enrolled; 103 were operated on for CSM and followed for 1 year. Their ages ranged from 40 to 82 years (mean 61.9), and 61.3% were men. Correlations among the various functional outcome instruments were all highly significant (p