To assess long-term outcome and predictors of prognosis following total hip arthroplasty (THA) for osteoarthritis (OA).
We studied 282 patients from 2 English health districts approximately 8 years after THA, along with 295 controls selected from the general population. Baseline data were collected by interview and examination, on sex, age, comorbidity, body mass index (BMI), and Short Form 36 (SF-36) functional status, and preoperative radiographic severity of OA was graded. Functional status was reassessed at followup by postal questionnaire. Predictors of change in physical functioning were analyzed by linear regression.
Over followup, cases who had THA reported a median improvement of 10 points in SF-36 score for physical functioning, whereas in controls there was a median deterioration of 10 points (P < 0.0001). Mental health improved by a median of 12 points in both cases and controls. Change in physical functioning was significantly worse in women and at older ages among both cases and controls. In cases, Croft grade 5 OA was associated with a physical functioning score improvement 19.4 points (95% confidence interval 7.7, 31.2) greater than the improvement in grades 0-3, but BMI was unrelated to change in physical functioning.
Improvements in physical functioning following THA for OA are sustained in the long term and are more frequent in patients with more severe radiographic features preoperatively. We found no indication that patients who are overweight benefit less from THA, but further evidence is needed on the prognostic influence of more severe obesity.