Obesity, Morbid Obesity and their Related Medical Comorbidities are Associated with Increased Complications and Revision Rates after Unicompartmental Knee Arthroplasty Abdurrahman Kandil, MD ⁎, Brian C. Werner, MD, Winston F. Gwathmey, MD, James A. Browne, MD Department of Orthopaedic Surgery, University of Virginia Health System, Charlottesville, Virginia abstract article info Article history: Received 29 July 2014 Accepted 11 October 2014 Available online xxxx Keywords: obesity morbid obesity unicompartmental knee arthroplasty revision knee arthroplasty complications Recent studies have demonstrated clinical success in expanding the indications for unicompartmental knee arthroplasty (UKA) to patients with increased body mass index (BMI). This study utilized national databases to identify 15,770 unique patients who underwent UKA between 2005 and 2011. 18.7% of patients undergoing a UKA were obese or morbidly obese. Univariate analysis demonstrated that obesity and morbid obesity were as- sociated with significantly higher complication rates within 90 days postoperatively compared to non-obese patients. The overall short-term revision rate in obese and morbidly obese patients undergoing UKA was almost twice as high as the revision rate in non-obese patients. Obese and morbidly obese patients being considered for UKA should be counseled preoperatively regarding their increased risk of postoperative complications and revi- sion surgery. © 2014 Elsevier Inc. All rights reserved. Unicompartmental knee arthroplasty (UKA) is a valuable surgical option in patients with arthritis limited to a single compartment of the knee. UKA has several proposed advantages over total knee arthroplasty (TKA), including preservation of bone stock, shorter recovery, lower perioperative complications, improved function, and lower cost [1,2]. While knee arthroplasty utilization has increased over the past couple of decades, so too has obesity [3]. Not surprisingly, many patients un- dergoing total joint arthroplasty are obese and the effect of obesity on surgical outcomes is of interest to providers and patients. Body weight is a potentially modifiable risk factor for knee osteoar- thritis (OA) and obesity increases the risk for the initiation and progres- sion of knee OA [4–6]. In the studies of patients who have undergone total knee and hip arthroplasty, adverse events have been demonstrated to occur more commonly in obese patients, including dislocation, asep- tic loosening, superficial infection, and revision surgery [7–10]. Less is known about the influence of obesity on UKA outcomes. Historically, the indications for UKA were older (N 60 years), lower- weight (less than 82 kg), lower-demand patients [11]. Multiple studies have corroborated these strict indications and have shown that in- creased weight leads to worse functional outcome scores, implant fail- ure, and higher revision rates in patients undergoing UKA [12–14]. However, the indications for UKA are changing and many historical con- traindications, such as weight less than 82 kg, are being challenged. Re- cent studies have demonstrated success in expanding the use of UKA to heavier patients [15–17]. A recent study retrospectively reviewed 1000 mobile bearing UKAs and found no significant outcome difference, fail- ure rate or survival between UKAs performed in ideal weight patients compared to non-ideal [16]. Another retrospective series of nearly 500 patients found that BMI greater than 30 did not affect clinical outcome or implant survivorship [18]. A retrospective review of 212 mobile bear- ing UKAs found that 10-year survival rates were similar between sub- groups, whether stratified by BMI or weight [17]. While informative, all of these studies have been small and retrospective in nature and re- sults have often been contradictory. To our knowledge, there is no large national database study looking at the effect of obesity or morbid obesity on postoperative complications in patients undergoing UKA. The goal of this study is to assess the asso- ciation of obesity, morbid obesity and their related medical comorbidi- ties with the risk of postoperative complications and need for revision surgery in patients undergoing UKA. Materials and Methods Data in this study were collected from the PearlDiver Patient Record Database (PearlDiver Inc, Fort Wayne, IN). The PearlDiver database is a publicly available, Health Insurance Portability and Accountability Act (HIPAA)-compliant national database. The database specifically has more than 2 billion individual patient records and contains Current Pro- cedural Terminology (CPT) and International Classification of Diseases, 9th Revision (ICD-9) codes related to orthopedic procedures. There are two sub-databases within PearlDiver: a private-payer da- tabase and a Medicare-based database. The private-payer database has over 30 million individual patient records from 2007 to 2011. The The Journal of Arthroplasty xxx (2014) xxx–xxx The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2014.10.016. Reprint requests: Abdurrahman Kandil, MD, Department of Orthopaedic Surgery, University of Virginia Health System, Ray C. Hunt Drive, Charlottesville, VA 22908. http://dx.doi.org/10.1016/j.arth.2014.10.016 0883-5403/© 2014 Elsevier Inc. All rights reserved. Contents lists available at ScienceDirect The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org Please cite this article as: Kandil A, et al, Obesity, Morbid Obesity and their Related Medical Comorbidities are Associated with Increased Compli- cations and Revision Rates aft..., J Arthroplasty (2014), http://dx.doi.org/10.1016/j.arth.2014.10.016