The early outcome of surgical treatment for femoroacetabular impingement: success depends on how you measure it

Objective: To evaluate the proportion of "successes" after surgery for femoroacetabular impingement (FAI) using different external criteria, "feeling better" and "feeling good", and to determine the corresponding cut-off scores indicating "success" for the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) (0-10-point response scale), Oxford Hip Score (OHS) and EuroQoL-5D (EQ-5D and EQ-VAS).

Design: Prospective, observational study based in an orthopaedic hospital. Ninety-nine consecutive patients with FAI completed the questionnaires before and 6 months after surgery (arthroscopy or mini-open surgical dislocation). Patient-ratings of change in state ("feeling better") were assessed using a global treatment outcome (GTO) item. Acceptability of the current health state was assessed using the symptom-specific well-being (SSWB) item. Cut-off (threshold) scores for the different instruments indicating the minimal clinically important change (MCIC) and acceptable symptom state were calculated using Receiver Operating Characteristics (ROC) analyses.

Results: Significant improvements in all scores (P < 0.001) were recorded 6 months after surgery. The proportion of good outcomes measured with GTO was 60%; 55% of patients reported having achieved an acceptable symptom state. The MCIC scores for improvement were ≥6 for the OHS (0-48 total score range), ≥15 for EQ-VAS, ≥0.16 for EQ-5D index, and ≥22 for the WOMAC-total score (0-100 total score range); absolute scores of ≥40, ≥80, ≥0.682 and ≤8, respectively, were associated with an acceptable symptom state.

Conclusions: The results show that feeling better does not always equate to feeling good, and that improvements in outcome scores, even large, do not necessarily indicate acceptability of the current state. The cut-off values may help in the interpretation of trial results and individual change-scores recorded in clinical practice.