Changes in body weight after total hip arthroplasty: short-term and long-term effects.

Background: Elevated body weight is associated with hip osteoarthritis (OA) and subsequently with total hip arthroplasty (THA). Patients with hip OA who are overweight often mention their restricted mobility as a factor that thwarts their attempts to be physically active and lose weight. There is some evidence that THA increases physical activity, but none for losing body weight after THA.

Objective: The purpose of this study was to analyze the short-term (1-year) and long-term (4.5-year) effects of a THA on body weight.

Design: This was an observational, multicenter cohort study.

Methods: For the short-term effect, all patients (N=618) were analyzed; for the long-term effect, a random subgroup (n=100) was analyzed. Preoperative and postoperative body weight and height were self-reported. Patients were categorized according to their preoperative body mass index (BMI <25 kg/m(2)=normal weight, 25-30 kg/m(2)=overweight, >30 kg/m(2)=obese). Clinical relevancy was set at a minimum of 5% weight loss compared with baseline.

Results: The mean age of the study group was 70 years (SD=8), 74% were women, and mean preoperative body mass was 79 kg (SD=14). One year after THA, a significant decrease in body weight of 1% and 3.4% occurred for the overweight and obese BMI categories, respectively. After 4.5 years, a significant decrease in body weight of 6.4% occurred for the obese BMI category.

Limitations: Height and weight-and thus BMI-were self-reported.

Conclusion: Patients in the overweight and obese groups showed a decrease, albeit not clinically relevant, in body weight after 1 year. After 4.5 years, a decrease that was relevant clinically was observed in the patients who were obese. It can be concluded that no clinically relevant reduction of weight occurred after THA, except in the long term for patients who were obese.