Risk Factors for Surgical Site Infections After Orthopaedic Surgery in the Ambulatory Surgical Center Setting

Robert H. Brophy, MD; Anchal Bansal, MD; Brandon L. Rogalski, MD; Michael G. Rizzo, MD; Eric J. Weiner, MD; Brett D. Wolff, MD; Charles A. Goldfarb, MD


J Am Acad Orthop Surg. 2019;27(20):e928-e934. 

In This Article

Abstract and Introduction


Introduction: This study was designed to determine the incidence of surgical site infections (SSIs) after orthopaedic surgery in an ambulatory surgery center (ASC) and to identify patient and surgical risk factors associated with SSI.

Methods: Patients who underwent orthopaedic surgery at an ASC over a 6.5-year period were reviewed for evidence of SSI. Data on patient and surgical factors were collected, and stepwise multivariate logistic regression determined the risk factors for SSI.

Results: The incidence of SSIs was 0.32%. Five independent factors were associated with SSI: anatomic area (odds ratio [OR] = 18.60, 11.24, 6.75, and 4.01 for the hip, foot/ankle, knee/leg, and hand/elbow versus shoulder, respectively), anesthesia type (OR = 4.49 combined general and regional anesthesia versus general anesthesia), age ≥70 (OR = 2.85), diabetes mellitus (OR = 2.27), and tourniquet time (OR = 1.01 per minute tourniquet time).

Discussion: The risk of infection after orthopaedic surgery in ASCs is low, but patient and surgical factors are independently associated with SSIs.


Outpatients may have safer, more efficient, and more cost-effective surgical procedures than their inpatient counterparts, providing an attractive alternative to traditional inpatient surgery for surgeons and patients alike.[1–3] Given these advantages, the availability of outpatient surgery has expanded, and the recent data from the 2016 Medicare payment advisory commission report based on the Centers for Medicare & Medicaid Services data show that the number of Medicare-certified ambulatory surgery centers (ASCs) increased by 15% from 4,740 to 5,446 between 2007 and 2014.[4] Orthopaedic surgery has been a leader in this transition of services from the inpatient to ASC setting. Between 2000 and 2007, this shift led to a 77% increase in the volume of ASC-based orthopaedic procedures, second only to ophthalmologic procedures.[3] From 1996 to 2006, outpatient rotator cuff repairs increased by 272% and inpatient repairs dropped by 67%.[5] Similar data have been found for other orthopaedic surgeries.[6–8]

Despite this shift in case volume to the ASC environment, little literature is available in examining risk factors for adverse outcomes in orthopaedic ASCs. Studies from plastic surgery outpatient centers have identified increasing body mass index (BMI), preoperative infection, and increased American Society of Anesthesiology (ASA) class as risk factors for unplanned readmission, but few confirmatory studies show that these factors are also relevant for patients receiving outpatient orthopaedic surgery.[9–11] As the surgical volume of ASCs continues to increase, the ability to preoperatively stratify patients at risk for adverse outcomes using risk factors specific to orthopaedic ASCs becomes increasingly important.

The purpose of this study was to assess the incidence of surgical site infections (SSIs) at a high-volume ASC and to identify patient and surgical risk factors associated with increased risk of infection. We hypothesized that patient factors such as the BMI, smoking status, increased age, the presence of diabetes mellitus (DM), and ASA score as well as surgical factors such as operation length, tourniquet time, and a lack of administration of antibiotics would each be associated with increased risk of SSI.