Although it has been shown that morbidly obese patients experience good outcomes following primary total hip arthroplasty (THA), it is unclear whether this also applies to revision surgery. The purpose of this study was to examine the effect of a high body mass index (BMI) on the outcome of revision THA.
We identified 56 patients with a BMI >40 kg/m2 who had undergone revision THA between 1994 and 2009 at our hospital (group B). Mean age, BMI, and follow-up were 66.4 years, 45.7 kg/m2, and 11.7 years, respectively. This was matched with a second group of patients with a BMI between 30 and 40 kg/m2 according to age, gender, and date of index procedure (group A). Mean age, BMI, and follow-up were 66.6 years, 33.6 kg/m2, and 12 years, respectively. Outcome measures included the rate of subsequent revision, implant survival, and the Harris hip score (HHS).
Patients with a BMI >40 kg/m2 had a significantly increased risk of revision surgery (27% vs 12%, P = .036). Cumulative implant survival was 85% (95% CI, 69-92) in group A and 69% (95% CI, 54-80) in group B at 15 years. HHS increased significantly following surgery in both groups (group A: 26.3-79.3) and (group B: 37.6-69.9; P < .001). However, HHS at last follow-up was significantly higher in group A (79.3 vs 69.9, P = .042).
Morbid obesity appears to be associated with an increased risk of failure and lower functional scores following revision THA. Patients should be well informed of this before surgery.