To investigate the responsiveness to change of four different elbow-scoring instruments, two Hospital for Special Surgery (HSS) elbow assessment scales, the Mayo Clinic elbow-performance index (Mayo) and the Elbow Functional Assessment (EFA) scale.
A group of 24 RA patients (median age 60 years) undergoing either elbow arthroplasty (22 elbows) or synovectomy with radial head excision (3 elbows), were evaluated both prior and after surgery (median: seven months postoperatively). Score changes, obtained by using the scales under study, were calculated. The patient’s opinion of global perceived effect of the intervention was used as a criterion to classify them as ‘improved’ or ‘non-changed’. Responsiveness was evaluated with use of three approaches: using paired t-statistics (pre- and post-surgery scores), effect size statistics (standardized response mean, effect size and responsiveness ratios) and Receiver Operator Characteristic (ROC) curves.
Each of the elbow rating measures under study proved to be responsive to change when evaluating RA patients undergoing elbow arthroplasty or synovectomy. The EFA scale demonstrated the highest power to detect a clinically meaningful difference and had the best discriminative ability to distinguish improved from non-changed patients, as was revealed by all responsiveness statistics applied.
The HSS, the Mayo and the EFA elbow-scoring scales can all be used as an evaluative instrument to assess the efficacy of surgical treatment of the rheumatoid elbow joint. However, using the EFA scale will require smaller sample sizes to achieve a fixed level of statistical power than the other scales under study.
