Unsuspected Positive Intra-Operative Cultures in Aseptic Revision Hip Arthroplasty: Prevalence, Management, and Infection-Free Survivorship.

Background: This study aimed to describe the management and outcomes of aseptic revision total hip arthroplasty (arTHA) with unsuspected intra-operative positive cultures (UPCs) compared to those with sterile cultures.

Methods: A single tertiary center's institutional database was retrospectively reviewed for arTHA from January 2013 to October 2023. Pre-operative Musculoskeletal Infection Society (MSIS) scores were assigned to patients based on available infectious workup, and those who met the criteria for periprosthetic infection (PJI), received antibiotic spacers, or had less than 1-year follow-up were excluded. Patients were grouped and compared according to intra-operative culture results: sterile cultures, one UPC with a new organism, one UPC with the same organism as prior PJI, ≥ two UPCs with different organisms, and ≥ two UPCs with the same organism.

Results: There was a total of 604 arTHAs included in this study, of which 0.8% [five of 604] had ≥ two UPCs with different organisms, 1.5% [9 of 604] had ≥ 2 UPCs with the same organism, 9.8% [59 of 604] had one UPC with a new organism, 0.2% [one of 604] had 1 UPC with an organism from prior PJI, and 87.7% [530 of 604] of patients had sterile cultures. When comparing 5-year infection-free survival between patients who had one UPC with a new organism and sterile cultures, there was no difference (P = 0.40); however, patients who had ≥ two UPCs with different organisms (P < 0.001), patients who had ≥ two UPCs with the same organism (P = 0.001), and patients who had one UPC of an organism from prior PJI (P < 0.001) had statistically worse infection-free survival compared to patients with sterile cultures.

Conclusion: Infection-free survival at five years was similar between patients who had one UPC with a new organism and those who had sterile cultures; however, ≥ two UPCs and a history of PJI are both significant risk factors for re-revision for infection after arTHA.