Total Knee Arthroplasty in Post Bariatric Surgery Patients - Outcomes Using Administrative Medicare Data

Introduction: Joint replacement pathways now include guidelines or hard-stops in allowing patients` access to TKA. A BMI of over 40 kg/m² has been identified as a threshold, if exceeded, to be referred for weight loss and bariatric surgery. We present data identifying the risks in individuals who have undergone bariatric surgery prior to submitting to a TKA. Specifically, we have asked the following questions: 1. Have the risks been normalized following bariatric surgery?, 2. Does the type of Bariatric procedure matter?, and 3. In instances where complications occurred was it due to persistence or recurrently elevated BMI?

Methods: A retrospective cohort study was conducted of patients who underwent TKA using Medicare hospital claims data from 2004 to 2016. CPT codes for bariatric surgery 43770, 43775 and 43644, were cross referenced with individuals who subsequently underwent a TKA 27447. Twelve complications occurred in the 90 day period following the TKA and were analyzed using multivariate Cox models, adjusting for patient demographic, morbidity and institutional factors.

Results: During this study period there were 2,675,575 TKA`s performed without a prior gastric bypass, and 2,044 with banding gastroplasties, 1,025 with sleeve gastrectomies 1,671 Roux-en-y gastric bypasses and 21,112 bariatric procedures of unknown type. The complications are listed in table 1 and figures 1 and 2. The surgical and cost utilization are represented by the values for infection, revision, implant failure, and readmission. The readmission baseline was 7.6% compared to 9.4%, 9.1%, 10.1% and 9.6% respectively.

Conclusion: This study demonstrates that while bariatric surgery does improve the risk profile, the risks are elevated above baseline. It also demonstrates that the more aggressive bypasses come with increased risks and that the increased risks often accompany failure to achieve and maintain the target BMI.