311. Low Rate of Microbiologic Relapse in Two-Stage Exchange for Knee Prosthetic Joint Infections

BACKGROUND: Prosthetic joint infection (PJI) is a grave complication of total knee arthroplasty (TKA). Historically, two-stage arthroplasty exchange has been considered to be the definitive approach to eradicating infection and preserving joint function. However, patients are increasingly presenting with higher rates of comorbidities traditionally associated with poorer orthopedic surgical outcome, including advanced age, obesity and diabetes. We investigated whether two-stage exchange remains effective for TKA PJI in this population, and evaluated the microbiology of repeat infections. 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. The primary endpoint was defined as prosthesis retention for 2 years from reimplantation. Microbiologic relapse was defined as a recurrence of a previously treated organism. Descriptive statistics were completed using the Fisher’s exact test for categorical variables and the Mann–Whitney U test for continuous variables. RESULTS: One hundred fifty-nine patients who underwent two-stage exchange for a TKA PJI meeting Musculoskeletal Infection Society International Consensus criteria were identified. The average age was 66 years, and 37% were female. One hundred forty-one underwent reimplantation; 24 of these (17%) had recurrent infection. Of the 24 patients who developed infection after reimplantation, only four relapsed with the same microbe; the other 20 (83%) were diagnosed with new, microbiologically distinct organisms. Thee of these four recurrences were due to Staphylococcus aureus infection. The likelihood of microbiologic relapse was low among reimplanted patients (3%). In univariate analysis, no associations were found between outcome and age, comorbidities, or BMI. CONCLUSION: Two-stage exchange arthroplasty for TKA infection is associated with a very low rate of microbiologic relapse. However, those patients able to undergo reimplantation remain at risk of subsequent infections with new microbes. It remains important to continue to modify risk factors in patients who have undergone a two-stage exchange for PJI. DISCLOSURES: All authors: No reported disclosures.