Total Hip Arthroplasty in Patients Who Have a Body Mass Index ≥ 40: Outcomes at an Institution Without Cutoffs

Morbid obesity (body Mass Index [BMI] ≥ 40) has been associated with increased perioperative risk following total hip arthroplasty (THA), leading many institutions to impose strict BMI cutoffs. Our institution does not restrict THA based on BMI.

A retrospective review was conducted of 3,577 primary THAs performed between June 2016 and April 2024 at a single academic center. Patients were stratified by BMI less than 40 (n = 3,169) and BMI ≥ 40 (n = 408). Primary outcomes were return to the operating room (OR) and revision surgery. Secondary outcomes included infection and aseptic implant failure. Multivariable Cox and logistic regression analyses were performed, including a sensitivity analysis using three BMI categories (less than 30, 30 to 39.9, and ≥ 40).

Patients who had a BMI ≥ 40 were younger, and had higher American Society of Anesthesiologists (ASA) classifications (83.1% ASA 3 to 4 versus 42.5%, P < 0.01). Infection (2.9 versus 1.1%, P < 0.01), return to OR (6.4 versus 3.0%, P < 0.01), and revision surgery (4.7 versus 2.2%, P < 0.01) were more common in the BMI ≥ 40 cohort. A body mass index ≥ 40 independently predicted return to OR (HR [hazard ratio] 1.63, P = 0.03) and infection (odds ratio [OR] 2.94, P < 0.01). Sensitivity analyses demonstrated that increased perioperative risk was primarily driven by the BMI ≥ 40 cohort, whereas BMI 30 to 39.9 was not associated with increased risk compared with BMI less than 30.

Morbid obesity is associated with increased postoperative infection and return to the OR following THA. However, patients who had a BMI ≥ 40 demonstrated substantially greater medical complexity, suggesting that perioperative risk is influenced by both BMI and associated comorbidity burden. These findings support individualized, risk-adjusted patient selection and perioperative optimization.