Impact of Organism Profile on Ideal Timing of Reimplantation in Patients Undergoing Two-Stage Exchange Arthroplasty.

INTRODUCTION: To our knowledge, no study to date has examined the association between organism profile and ideal interstage duration in patients undergoing two-stage exchange arthroplasty. The purpose of this study was to evaluate the impact of the type of infecting organism on the optimal timing of reimplantation in this patient population.

METHODS: This retrospective study identified 576 patients who had a chronic periprosthetic joint infection (PJI) of the knee and underwent two-stage exchange arthroplasty with a minimum one-year follow-up. A PJI was defined using the 2013 Musculoskeletal Infection Society (MSIS) criteria. Patients who had a time to reimplantation greater than 180 days from resection arthroplasty (n = 76) and those who underwent spacer exchange were excluded (n = 49). Treatment failure was defined as any reoperation for infection or PJI-related mortality. Receiver operator characteristic (ROC) curve analyses were used to identify whether the optimal interstage duration differed by infecting organism. Multivariate regression analyses were performed to identify risk factors for failure. There were 451 patients who were included who had a mean follow-up time of 5.8 years.

RESULTS: Of the 451 included patients, 71 (15.7%) patients experienced failure and 380 (84.3%) experienced success. The ROC curve analyses demonstrated that the optimal interstage duration was longest for patients infected with "high-virulence" pathogens (129 days), followed by those who had methicillin-sensitive Staphylococcus aureus (MSSA) (117 days), culture negative PJI (98 days), and coagulase-negative Staphylococci (86 days). After controlling for covariates, regression analyses showed that an interstage duration above the identified cutoff for each pathogen group was a predictor of treatment failure (all P < 0.05).

CONCLUSION: We found that the ideal interstage duration varied considerably by the type of infecting organism in patients undergoing two-stage exchange. Greater awareness of this data may help guide the optimal timing of reimplantation in this patient population.