310. Assessment of MSIS Diagnostic Criteria as Predictors of Treatment Success in Total Knee Arthroplasty (TKA) Infections Treated With Two-Stage Exchange

BACKGROUND: Prosthetic joint infection (PJI) is a grave complication of total knee arthroplasty (TKA); predicting outcome is difficult. Musculoskeletal Infection Society (MSIS) criteria are sensitive and specific for the diagnosis of PJI. In prior work, we systematically studied the value of each MSIS criterion as a prognostic marker among a large cohort of patients with infected hip and knee arthroplasty treated with debridement, antibiotics, and implant retention (DAIR) at our specialized orthopedic hospital. We found that sinus tract drainage and culture positivity predicted explantation within two years of DAIR; the minor MSIS criteria were not predictive. Here, we sought to evaluate the utility of MSIS criteria in predicting outcomes of infected TKR PJI treated with two-stage exchange arthroplasty. We sought to evaluate whether MSIS criteria can predict the outcome of infected TKR PJI treated with two-stage exchange arthroplasty. METHODS: A retrospective cohort of TKA PJI treated with two-stage exchange was identified by query of hospital coding records from 2009 to 2014, with subsequent chart review. Collected data included demographics and comorbidities, duration of symptoms, implant age, and pathogen. All cases met Musculoskeletal Infection Society International Consensus criteria for PJI. The primary endpoint was defined as prosthesis retention for 2 years from reimplantation. Descriptive statistics were completed using the Fisher’s exact test for categorical variables and the Mann–Whitney U test for continuous variables. RESULTS: 159 patients who underwent 2-stage exchange for TKA PJI meeting MSIS criteria were identified. 116 patients (73%) remained infection-free after two years of observation. Neither of the major criteria [presence of sinus drainage (P = 0.6); >1 positive culture (P = 1.0)], nor any of the minor criteria (individually or in composite) reached statistically significant association with treatment outcome. CONCLUSION: Individual MSIS diagnostic criteria, which have prognostic utility in TKA PJI treated with DAIR, are not powerful predictors of outcome of TKA PJI after two-stage exchange. DISCLOSURES: All authors: No reported disclosures.