Michael E. Neufeld, MD, MSc, FRCSC, Brent A. Lanting, MD, MSc, FRCSC, Michael Shehata, MD, BCh, BAO, James L. Howard, MD, MSc, FRCSC, Steven J. MacDonald, MD, FRCSC, Matthew G. Teeter, PhD, and Edward M. Vasarhelyi, MD, MSc, FRCSC
The Journal of Bone and Joint Surgery, Volume 103, Issue 11, May 11, 2021
Summary: Ilan Small, BS
An estimated 12% of primary total hip arthroplasties (THA) are expected to be revised within 10 years postoperatively (1). Periprosthetic joint infection (PJI) is a common indication for revision and is associated with morbidity and economic cost (2). There is currently no ideal test for PJI diagnosis, and it remains unclear how many aseptic failures occur from undiagnosed PJI (3). Unexpected positive intraoperative cultures (UPCs) that occur during what are thought to be aseptic revisions represent a challenge for treatment (4). The objectives of Neufeld’s et al. study was to determine the incidence of UPCs in aseptic revision THA, examine infection-free implant survival rate, and identify risk factors for infection-related revision failure.
The authors retrospectively reviewed 2,228 revision THAs from January 2006 to April 2019 at a single institution. Those with at least one UPC were eligible for inclusion. Infection-related implant failure occurred if any infection after aseptic revision necessitated antibiotics or PJI revision surgery. Microorganisms from the PJI were compared to the UPC microorganism. Kaplan-Meier curves were used to determine implant survival at 2 and 5 years for PJI and survival analysis was calculated for PJI for the same microorganism from the UPC. A cox regression analysis was used to classify risk factors for infection-related failures after UPC.
There were 1,196 aseptic THA revisions. Of those, 110 THA (9.2%) with UPC were eligible for inclusion. Infection-free implant survival in the UPC cohort at 2-years was 93.1% (95% confidence interval [CI] = 90.5% to 95.7%) and at 5-years was 86.8% (95% CI = 82.9% to 90.7%). Infection-free survival with failure due to infection with the same microorganism identified in the UPC was 95.8% at 2-years (95% CI = 93.7% to 97.9%) and 94.3% at 5-years (95% CI = 91.7% to 96.9%). Infection-related failures with the same microorganism in the UPC were more likely to occur after revisions with ≥2UPCs than those with 1 UPC (p = 0.024). Revision due to adverse metal reaction was found to be a risk factor for infection-related failure (hazard ratio = 14.49, 95% CI = 2.69-78.04). No patient with a single UPC but not treated with antibiotics developed PJI from the same UPC microorganism.
Infection-free survival of patients with UPC is encouraging, as well as implant survival free of PJI from the UPC microorganism. UPC without signs of infection may not necessitate antibiotic treatment. Limitations of this study included its retrospective design, small cohort size, lack of standardized PJI screening in treatment following UPC, and samples taken from surgery are not standardized.
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