Weight change following total hip replacement: a comparison of obese and non-obese patients.

BACKGROUND: Weight loss is desirable in obese patients prior to hip replacement but poor mobility secondary to hip dysfunction may limit attempts at weight reduction because of reduced exercise tolerance.
METHODS: We followed 140 patients prospectively to investigate weight change and functional outcome in obese and non-obese patients following total hip arthroplasty. Weight and the Harris hip score was measured one week prior to surgery and three years post-operatively.
RESULTS: Fifty nine patients were obese (BMI > or = 30). The mean weight of obese patients increased from 88 kg pre-operatively to 92 kg following surgery (p<0.001). In non-obese patients pre-operative weight was 69 kg and post-operative weight 70 kg (p=0.106). In the obese group 75% of patients gained a mean of 6.77 kg (p<0.001) and 19% of patients lost a mean of 4.8 kg (p<0.01). In the non-obese group, 60% of patients gained a mean of 4.2 kg (p<0.001) and 31% of patients lost an average of 4.7 kg (p<0.001). The mean Harris hip score was 90 in non-obese patients and 85 in obese patients three years post-operatively (p<0.01).
CONCLUSION: Weight increase is common following total hip replacement despite improved function but the magnitude of weight increase appears to be greater in patients who are obese. Obesity was also associated with lower functional hip scores but the differences were small and unlikely to be of clinical significance.