gms | German Medical Science

Objectives: Treatment of periprosthetic joint infections (PJI) caused by pathogens, for which no biofilm-active antibiotics exist, is challenging. The outcome of these difficult-to-treat (DTT) PJI is unknown. Therefore, we performed an outcome analysis in patients with DTT PJI, which were treated according to an adjusted surgical and antimicrobial treatment concept.

Methods: In this prospective cohort, consecutive patients with hip and knee PJI treated at our institution from 2013 to 2015 were analyzed. DTT pathogens included rifampin-resistant staphylococci, enterococci, ciprofloxacin-resistant gram-negative bacteria and fungi. The difference in outcome was compared between DTT and non-DTT PJI by follow-up evaluation after two-stage exchange arthroplasty. A DTT PJI was diagnosed when at least one of the causing microorganisms was resistant to biofilm-active antimicrobial therapy. A standardized treatment-algorithm including surgical procedures and antimicrobial therapy was applied in all patients. Treatment failure was assessed according to the Delphi-based consensus definition. Chi square and Fisher's exact tests were employed to find significant differences between categorical variables. The Mann Whitney U test (non-parametric) or two-sample t-test (parametric) was used to compare continuous variables. Logistic regression analysis was performed to assess the predictors of a DTT PJI. The Kaplan-Meier survival method was used to compare the probability of infection-free survival between groups.

Results and Conclusion: A total of 35 DTT PJI were identified in 182 patients with hip (n=93) and knee (n=89) PJI. The overall treatment success rate for DTT PJI was 82.9% and for non-DTT PJI 85.7% with a median follow-up of 27.2 months (range, 14-42 months) (p=0.67). The number of revision surgery in prosthesis-free interval because of persistent infection was significantly higher in DTT than in non-DTT PJI group (1.9 vs. 1.1 p=0.04). As a result the hospital stay (mean 43.14 days vs. 28.39 days, p=0.015) and the prosthesis-free interval (mean 85.8 days vs. 58.8 days, p=0.003) were significantly prolonged. Multiple regression analysis showed sinus tract as the only independent risk factor predictive of DTT PJI (odds ratio [OR] = 1.6; 95% confidence interval [95% CI]= 1.03 to 2.4; p=0.04). With standardized therapeutic algorithm using a two-stage exchange, no difference in outcome between patients with and without DTT PJI was found. Due to the pattern of resistance more revision surgeries and longer intervals are needed for adequate treatment of DTT PJI.