Bariatric Orthopaedics: Total Knee Arthroplasty in Super-obese Patients (BMI > 50 kg/m2). Survivorship and Complications

Background Some studies have suggested that patients who are super obese (BMI > 50 kg/m²) may have poorer outcomes and more frequent complications when undergoing TKA compared with those who have lower BMI, however, the literature on this is scant.

Questions/purposes The purpose of this study was to compare a group of super-obese patients undergoing TKA with a matched group of patients with BMI less than 30 kg/m² in terms of (1) implant survivorship, (2) complications, (3) functional parameters, and (4) intraoperative variables (including operative time and estimated blood loss).

Methods One-hundred one knees in 95 patients (21 men, 74 women) who had a minimum BMI of 50 kg/m² and who had undergone a primary TKA at one of the four high-volume institutions were compared with a group of patients who had a BMI less than 30 kg/m² who were matched by age, gender, preoperative clinical scores, and mean followup. End points evaluated by chart review included implant survivorship, medical and surgical complications, functional parameters (The Knee Society outcome scores and ROM), and intraoperative variables at a mean followup of 62 months (range, 36-85 months).

Results With the numbers available, there were no differences in aseptic implant survivorship (94% versus 98%, p = 0.28), however, medical and surgical complication rates (14% versus 5%, OR: 3.1, 95% CI=1.07-8.9; p = 0.037) were significantly higher in the super-obese patients compared with the nonobese matching group, respectively. Super-obese patients also achieved lower mean Knee Society functional scores (82 versus 90 points, p = 0.004) and smaller gains in flexion arc ROM (14° versus 21°, p = 0.009); they also lost more blood during surgery and experienced longer surgical anesthesia times compared with the matched group, respectively.

Conclusions With the numbers available, we could not identify what might have been modest differences in implant survivorship, however, complications were more frequent and functional outcomes were significantly lower in super-obese patients. Other studies similarly have found inferior outcomes in this challenging group of patients. Our data may be considered pilot data for future prospective studies with longer followup.

Level of Evidence Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.