Effect of Bariatric Surgery on Risk of Complications After Total Knee Arthroplasty: A Randomized Clinical Trial

IMPORTANCE: People with severe obesity who undergo a total knee arthroplasty (TKA) for osteoarthritis (OA) are at higher risk of short-term and long-term complications compared with people with reference (<30) body mass index (BMI; weight in kilograms divided by height in meters squared). It is not known whether weight loss before TKA modifies this risk. OBJECTIVE: To determine whether outcomes are improved by undergoing bariatric surgery before TKA in people with BMI greater than or equal to 35 and end-stage OA. DESIGN, SETTING, AND PARTICIPANTS: This parallel-group, assessor-blinded, randomized clinical trial was conducted between May 2012 and June 2020 with a minimum follow-up of 12 months after TKA. TKA was performed at a tertiary referral university-affiliated public hospital, and bariatric surgery was performed at a private hospital facility and a university-affiliated private practice. Data analysis was performed from February to July 2021. INTERVENTIONS: Bariatric surgery compared with usual weight management advice (treatment as usual [TAU]) in people scheduled for TKA. MAIN OUTCOMES AND MEASURES: The primary outcome was complications of TKA measured by a composite of death from any cause, perioperative or postoperative complications resulting in a discharge delay, unplanned procedure, or readmission for at least 12 months after TKA. Secondary outcomes included hospital bed day utilization, anthropomorphic measures, and patient-reported outcomes. RESULTS: Eighty-two patients waiting for TKA were randomized to undergo bariatric surgery (41 patients) or TAU (41 patients). Of the 82 participants, 66 (80.5%) were women, the mean (SD) age was 57.8 (4.9) years, and the mean (SD) BMI was 43.8 (5.5). Thirty-nine participants (95.1%) in the intervention group underwent laparoscopic adjustable gastric banding, and 29 (70.7%) subsequently underwent TKA. Thirty-nine patients (95.1%) in the TAU group underwent TKA. Six patients (14.6%) in the intervention group incurred the primary outcome (median follow-up, 24 months), compared with 15 (36.6%) in the TAU group (median follow-up, 27 months) (difference, 22.0%; 95% CI, 3.7% to 40.3%; P = .02). The between-group difference in BMI at 12 months was −6.32 (95% CI, −7.90 to −4.50; P < .001) in favor of the intervention group. TKA was declined by 12 participants (29.3%) in the intervention group because of symptom improvement, whereas 2 participants (4.9%) in the TAU group declined TKA (difference, 24.4%; 95% CI, 9.0% to 39.8%; P = .003). CONCLUSIONS AND RELEVANCE: Weight loss following bariatric surgery reduced the risk of complications of TKA in people with BMI greater than or equal to 35. Significantly fewer participants required TKA following weight loss, contributing to this finding. TRIAL REGISTRATION: Australian New Zealand Clinical Trials Registry Number: ACTRN12611001178932