Background: The effect of body mass index (BMI) on the outcome of total hip arthroplasty (THA) remains controversial. The purpose of this study was to examine whether revision rate and postoperative outcomes following THA were influenced by BMI.
Materials and methods: We retrospectively evaluated 714 patients (751 hips) who underwent primary THA in our department between March 1991 and April 2006. They were followed prospectively for 5-20 years with 24 deaths (24 hips) and 33 losses (34 hips). Patients were separated into three groups based on BMI: underweight, normal and obese groups. A survival analysis was performed using revision as the endpoint, and a case-matched study that was matched for age, gender, and laterality was designed; outcomes were assessed with the Harris Hip score, 36-item short-form health survey, complication rate and radiological examination.
Results: The preoperative scores were lower for the obese group, and the postoperative scores were higher for the normal group. Patients in the obese group obtained the greatest overall improvement in clinical scores from admission to the last follow-up. We found a significantly higher complication rate in the obese group and underweight group. It appears that being underweight was associated with an increased dislocation rate, and obese patients were more likely to have osteolysis, deep vein embolism, and pulmonary thrombosis. The log rank test for survival showed no significant differences among the three groups.
Conclusions: Abnormal BMI does not prevent functional rehabilitation after THA; however, patients with abnormal BMI have to face higher complication rates and poorer clinical outcomes following this operation.