ORIGINAL PAPER Infection risk assessment in patients undergoing primary total knee arthroplasty Lazaros A. Poultsides 1 & Georgios K. Triantafyllopoulos 1 & Vasileios I. Sakellariou 1 & Stavros G. Memtsoudis 2 & Thomas P. Sculco 1 Received: 18 June 2017 /Accepted: 16 October 2017 # SICOT aisbl 2017 Abstract Purpose To determine the incidence and to identify potential risk factors for in-hospital and late infections, as well as for deep periprosthetic joint infection (PJI) following TKA. Methods We identified 17,959 patients treated with primary TKA between 2000 and 2009. We recorded patient demo- graphics, comorbidities and in-hospital complications. The rates of in-hospital, late, and deep PJIs were determined. Different logistic regression models were built to identify risk factors for each of the above types of infection. Results The rates for in-hospital, post-discharge, and deep PJI were 0.65%, 0.41%, and 0.26%, respectively. Younger age, allogeneic blood transfusion, liver disease, and unilateral or staged bilateral TKA were risk factors for in-hospital infec- tion. Renal and pulmonary disease, urinary tract infection, wound dehiscence, and prior in-hospital infection were risk factors for post-discharge infection. Male gender, history of in-hospital infection, prolonged length of stay, and pulmonary disease were identified as risk factors for deep PJI. Conclusion Despite low infection rates after primary TKA, there are patients at higher risk that would benefit by addressing modifiable risk factors for both in-hospital or post-discharge infections, including deep PJIs. Keywords Total knee arthroplasty . Infection . In-hospital . Post-discharge . Risk factors Introduction Total knee arthroplasty (TKA) effectively relieves pain, re- stores function, and improves quality of life in patients with severe knee arthritis [1]. Nonetheless, periprosthetic joint in- fection (PJI) remains one of the most overwhelming compli- cations [2]. The incidence of PJI after primary TKA ranges from 0.4% to 0.9% [3] and remains considerable despite avail- able preventive measures [4]. Infection is also one of the most common causes of revision TKA [5], and has significant med- ical and socioeconomic repercussions [2]. Treatment of PJI may involve multiple interventions, leading to impaired func- tional outcomes and decreased patient satisfaction [4, 6]. In addition, PJI in the elderly population may be associated with an increase in mortality [6]. Of note, the mean annual cost for patients with PJI of the knee may be four times higher than for those without infection [7]. The cost for treating PJIs in the United States will exceed $1.6 billion per annum by the year 2020 [8]. In this context, identification of patients at high risk for PJI of the knee bears great importance. The objectives of our study were to: (a) determine the in- cidence of PJI of the knee occurring during and after hospital- ization; (b) identify potential risk factors for developing either of the previous types of knee PJI; and (c) identify risk factors for deep periprosthetic infections following TKA. * Lazaros A. Poultsides poultsidesl@hss.edu 1 Department of Orthopaedic Surgery, Division of Adult Reconstruction and Joint Replacement, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 East 70th Street, New York, NY 10021, USA 2 Department of Anesthesiology, Hospital for Special Surgery, Weill Medical College of Cornell University, 535 East 70th Street, New York, NY 10021, USA International Orthopaedics (SICOT) https://doi.org/10.1007/s00264-017-3675-z