Predictors of functional outcome two years following revision hip arthroplasty.

BACKGROUND: Little is known about factors that might predict functional outcome following revision hip arthroplasty. The purpose of this study was to identify predictors of pain and physical function at two years following revision total hip arthroplasty and to evaluate whether the time that the patient waited for the surgery and whether the patient had complications were significant predictors of outcome.
METHODS: One hundred and twenty-six patients (126 hips) were entered prospectively into the study when their name was placed on the waiting list for surgery. Baseline measures included demographic factors, comorbidities, and the responses to the Short Form-36 (SF-36) and Western Ontario and McMaster Universities Osteoarthritis (WOMAC) questionnaires. Follow-up was carried out at six-month intervals while the patient was waiting for the surgery; within one week prior to the surgery; and at six, twelve, and twenty-four months after the surgery. Patient age and gender, the preoperative WOMAC pain and function scores, the physical and mental component scores of the SF-36, comorbidities, the number of revisions, bilateral joint replacement, and the severity of the revision were evaluated as possible predictors of ultimate pain and function as measured with the WOMAC instrument.
RESULTS: The mean age of the patients was 68.6 years. Improvement in WOMAC pain and function scores plateaued at six months. The mean pain score (and standard deviation) improved from 9.4 +/- 4.1 points preoperatively to 3.9 +/- 3.9 points at six months postoperatively, and the mean function score improved from 35.4 +/- 14.1 to 19.1 +/- 13.2 points. Preoperative pain (p = 0.002) and comorbidity (p = 0.02) were significant predictors of pain at two years. There was a trend toward preoperative function predicting function at twenty-four months (p = 0.07). There was no significant deterioration in the WOMAC pain or function score while the patients waited for surgery. Twenty-eight patients had complications. When the time that the patient waited for the surgery and complications were added to the models, only complications were found to be predictive of outcome (p = 0.04 for pain and p = 0.05 for function). Four patients required repeat revision during the follow-up period.
CONCLUSIONS: Patients with better preoperative pain scores and fewer comorbidities have better outcomes following revision total hip arthroplasty. Although the time that the patient waited for the revision was not predictive of the ultimate WOMAC pain and function scores, we believe that performing revision arthroplasty before the patient has substantial functional compromise potentially improves the outcome.