Moore, Lane

Introduction 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 with chronic periprosthetic joint infection (PJI) of the knee that underwent two-stage exchange arthroplasty with a minimum 1-year follow-up. PJI was defined using the 2013 Musculoskeletal Infection Society (MSIS) criteria. Patients with a time to reimplantation >180 days from resection arthroplasty (n=76) and those that 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. Results 451 patients with a mean follow-up time of 5.8 ± 3.6 years were included. Of these, 71 (15.7%) patients experienced failure and 380 (84.3%) experienced success. ROC curve analyses demonstrated that the optimal interstage duration was longest for patients infected with “high-virulence” pathogens (129 days), followed by those with MSSA (117 days), culture negative PJI (98 days), and coagulase-negative Staphylococci (86 days). After controlling for co-variates, 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.

Introduction The alpha-defensin test has witnessed a surge in popularity following reports of its superior diagnostic capabilities, when compared to more conventional synovial markers. Despite this, no study to date has evaluated the utility of alpha-defensin for the diagnosis of acute periprosthetic joint infection (PJI). The purpose of this multicenter study was to determine whether the alpha-defensin test provided additional clinical benefit, when compared to synovial white blood cell (WBC) count and polymorphonuclear leukocyte percentage (PMN%), in the diagnosis of acute postoperative PJI. Methods This retrospective study identified all patients who underwent arthrocentesis within 90 days of their primary total joint arthroplasty (TJA) at three institutions. PJI was defined as revision TJA for infection within 2-weeks of joint aspiration with >=1 positive intraoperative culture. Patients were considered aseptic if they had no reoperation for >=1-year after arthrocentesis. Receiver operator characteristic (ROC) curves were used to assess the utility of alpha-defensin, WBC count, and PMN% in the diagnosis of acute PJI. Pairwise comparison was performed to compare whether the area under the curve (AUC) was significantly different between the three markers. Results A total of 143 patients were included. Of these, 85 (59.4%) were infected and 58 (40.6%) were aseptic. After plotting ROC curves, WBC count was found to have the highest diagnostic utility (AUC 0.912, sensitivity 80.0%, specificity 91.2%), followed by PMN% (AUC 0.869, sensitivity 70.5%, specificity 93.0%), and alpha-defensin (AUC 0.812, sensitivity 62.4%, specificity 100%). Using pairwise comparison, the AUC for WBC count was found to be significantly higher than that of alpha-defensin (p=0.005). However, there was no difference in the AUC between alpha defensin and PMN% (p=0.154). Conclusion Based on our findings, it appears that alpha-defensin provides little to no additional clinical benefit in the diagnosis of acute PJI, when compared to synovial WBC count and PMN%.