Prevalence and Outcomes of Unexpected Positive Intraoperative Cultures in Presumed Aseptic Revision Hip Arthroplasty

Background: The prevalence and outcomes of unexpected positive cultures (UPCs) of specimens taken during presumed aseptic revision total hip arthroplasty (THA) are unclear. The purpose of this study was to determine the prevalence of UPC and infection-free implant survival in this patient population. Secondary aims included identifying factors associated with subsequent infection-related failure in patients with UPC.

Methods: We reviewed all THA revisions (n = 2,288) performed at our institution from 2006 to 2019. Presumed aseptic revision THAs with intraoperative culture(s) were eligible (n = 1,196), and those with UPC were included in a Kaplan-Meier analysis to determine the infection-free implant survival and in Cox regression analysis to identify factors associated with infection-related failure.

Results: UPC(s) were documented for 9.2% (110) of 1,196 aseptic THA revisions. The 2- and 5-year infection-free implant survival in the entire UPC cohort was 93.1% (95% confidence interval [CI] = 90.5% to 95.7%) and 86.8% (95% CI = 82.9% to 90.7%), respectively. The 2- and 5-year infection-free survival with failure due to infection with the same microorganism as identified in the UPC as the end point was 95.8% (95% CI = 93.7% to 97.9%) and 94.3% (95% CI = 91.7% to 96.9%), respectively. Subsequent infection-related failures caused by the same microorganism as identified in the UPC were more likely to occur after revisions with ≥2 UPCs than after those with 1 UPC (p = 0.024). Revision due to adverse metal reaction was a risk factor for subsequent infection-related failure (hazard ratio [HR] = 14.49, 95% CI = 2.69 to 78.04). Patients with a single UPC who were not treated with antibiotics had no subsequent periprosthetic joint infections (PJIs) caused by the same microorganism as identified in the UPC.

Conclusions: The prevalence of UPC was 9.2%, and the infection-free implant survival in patients with UPC is encouraging. Implant survival free of PJI caused by the same microorganism as identified in the UPC was excellent. Aseptic revision for adverse metal reaction was a risk factor for subsequent PJI in patients with UPC. No patient with a single UPC who was not treated with antibiotics developed PJI caused by the UPC-identified microorganism, suggesting that in the absence of other signs of infection a single UPC does not warrant antibiotic treatment.

Level of evidence: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.