Influence of high BMI on functional outcome after total hip arthroplasty

Background High body mass index (BMI) is associated with diseases of the hip joint and subsequent total hip arthroplasty (THA). Less is known about the effects of BMI on the functional postoperative status after THA in obese patients. The purpose of this study was therefore to quantify the role of high preoperative BMI on long-term pain status and functional outcome after THA. Methods In a multi-center cohort, study data of 20,553 primary THAs (18,968 patients) and 43,562 postoperative clinical examinations were analyzed for a follow-up period of up to 15 years. Patients were classified into three BMI groups (normal weight < 25 kg/m(2), overweight 25 to < 30 kg/m(2), and obese = 30 kg/m(2)), and pain status and functional outcome were compared accordingly. Results High preoperative BMI is associated to an almost perfect dose-effect relationship with decreased ambulation during a follow-up period of 15 years, but pain relief of THA is equally efficient for all BMI groups. Conclusion Overweight and obesity are modifiable risk factors that may warrant physicians giving recommendations to patients before or after THA, to improve postoperative functional outcome quality.