Primary Total Hip Arthroplasty in Patients Who Have a Body Mass Index > 50: Is the Risk Worth the Reward?

Abstract

The obesity epidemic has given rise to a growing number of patients who have a body mass index (BMI) exceeding 50. As BMI cutoffs are no longer recommended, arthroplasty surgeons continue to push the limits of surgical feasibility in total hip arthroplasty (THA) despite possible risks. A retrospective cohort study of patients who underwent primary THA for degenerative arthritis (N = 7,458) was developed, comparing outcomes between patients who had a BMI ≥ 50 (N = 147) and those of other weight classes. We used Cox proportional hazard models to estimate the association between patient BMI and revision risk using overweight patients (BMI 25 to 30) as the reference group. Patients entered the study cohort on their date of surgery and exited on the earliest of the date of revision, date of death, or the end of the study. Patient Oxford-12 hip scores (OHS) were compared pre- and postoperatively. Increased obesity class led to a gradient of elevated revision risk. In the first year after surgery, THA patients who had a BMI ≥ 50 demonstrated an adjusted hazard ratio (HR) for revision of 11.8 (95% confidence interval [CI] 5.3 to 26.2). This risk was also elevated in patients who had a BMI of 40 to 50 (N = 635, hazard ratio (HR) = 3.8, 95% CI = 1.9 to 7.7). Although the patients who had a BMI ≥ 50 had a significantly worse preoperative OHS than other overweight patients, at five years, this difference was negligible. There was an increased risk of early THA revision surgery in patients who had a BMI ≥ 50. This risk plateaued after the first year and was equivalent to other weight classes afterwards. Despite worse preoperative function and greater failure rates, this population reports major benefits and high satisfaction with THA. The risk of THA appears to be worth it for most patients who have a BMI ≥ 50.