Body mass index as predictor of health-related quality-of-life changes after total hip arthroplasty: a cross-over study.

The objective of this study was to examine the contribution of patient weight and other preoperative variables to improvements in the general physical health of patients undergoing total hip arthroplasty (THA). Data were prospectively collected on 63 THA patients (28 males and 35 females). The primary outcome measure was the improvement in general health (Short Form-12 Health Survey questionnaire) at three months post-THA. Patients with body mass index >28kg/m(2) showed greater improvements in function and in the physical component of general health after THA. Stepwise regression analyses revealed that the BMI and WOMAC general index were independent and significant predictors of physical function and together explained 34.2% of the variance in physical function scores. These findings suggest that the body mass index before surgery and improvements in hip function are relevant contributors to post-THA improvements in general health.