Total Joint Arthroplasty in the Morbidly Obese: How Body Mass Index ≥40 Influences Patient Retention, Treatment Decisions, and Treatment Outcomes

The United States is in an obesity epidemic. Obesity has multiple common comorbid conditions, including lower extremity arthritis. We sought to examine the course of treatment for a population with body mass index (BMI) ≥40 kg/m² and osteoarthritis (OA) of the hip or knee. We investigated decision criteria that influenced arthroplasty surgeons to recommend nonoperative management vs total joint arthroplasty (TJA). For those patients who ultimately received TJA, we compared outcomes in this population to those with BMI <40 kg/m².

This study retrospectively reviewed 158 new patients with BMI ≥40 kg/m² and moderate/severe OA of the hip or knee. Demographics, comorbidity profiles, and weight loss were compared between groups that underwent TJA and those that did not. The arthroplasty database was used to identify patients who underwent TJA during 2016-2018 (N = 1473). Comorbidities, readmissions, surgical site infections, and overall complications were compared between those with BMI ≥40 kg/m² and BMI <40 kg/m².

About 51.3% of new patients with BMI ≥40 kg/m² and moderate/severe OA did not return for a second clinic visit. Of those who did return, 42.9% eventually underwent surgery. BMI was higher in single visit patients vs those with multiple visits (49.5 vs 46.3 kg/m², P < .001), no difference in those scheduled on an “as-needed” basis vs a specific return date (P = .18), and did not change significantly during the 2-year follow-up (P = .41). Patients who underwent TJA had a lower mean BMI at presentation than their nonoperative counterparts (44.5 vs 47.6 kg/m², P < .01) and demonstrated significant weight loss prior to surgery (44.5 vs 42.6 kg/m², P < .05). When comparing patients with BMI ≥40 kg/m² vs BMI <40 kg/m², overall complications were not higher in the BMI ≥40 kg/m² group, although surgical site infections were higher in those undergoing total hip arthroplasty with BMI ≥40 kg/m² (0.3% vs 3.1%, P < .05).

A majority of patients with BMI ≥40 kg/m² and moderate/advanced OA will be lost to orthopedic follow-up. A relatively lower BMI indicates a greater chance of retention in care, and ultimately surgery, but does not influence surgeons’ recommendations to continue orthopedic management. Patients who persist in seeking treatment, lose significant weight, and exhaust nonoperative alternatives may be suitable for TJA despite a BMI ≥40 kg/m², with an overall complication rate of 4.3%. However, only 9% of patients at 2-year follow-up achieved BMI <40 kg/m² and only 20% of surgeries were performed on patients who had achieved this proposed cutoff.