Type of acute periprosthetic joint infection may not affect failure of debridement, antibiotics, and implant retention after total knee arthroplasty.

Introduction: In periprosthetic joint infection (PJI) following total knee arthroplasty (TKA), debridement, antibiotics, and implant retention (DAIR) is a common procedure with a high rate of failure. Timing of infection can be used to stratify acute PJI into acute postoperative, intermediate, and hematogenous infections. Potential differences in prognosis between classifications remain unclear. This investigation assessed the current overall failure of DAIR procedures, compared DAIR failure between three types of acute PJI, and analyzed DAIR outcomes in an "optimal" cohort of patients with a minimal number of medical comorbidities. Methods: This retrospective study compared 122 patients with acute TKA PJI who underwent DAIR between 2016 and 2022. Categorization was based on timing between index TKA and PJI diagnosis, with $<$ 6 weeks termed postoperative ( $n=$ 43), 6 weeks to 1 year termed intermediate ( $n=$ 19), and $>$ 1 year termed hematogenous ( $n=$ 60). The primary outcome was DAIR failure, defined as reoperation for PJI. Subgroup analysis was performed after removing patients with high-risk comorbidities. Results: The overall failure rate was 42 %; 78.4 % of failures occurred within 1 year. No significant differences in the failure rate were found between PJI types at any time point. At 1 year, 58 % postoperative, 58 % intermediate, and 77 % hematogenous cases remained failure-free ( $p=$ 0.09). Failure rates of 45 % postoperative, 44 % intermediate, and 36 % hematogenous cases were seen in the optimal cohort, without significant differences. Conclusions: DAIR failure for acute TKA PJI is high. Although no differences in failure rates were observed based on the PJI type, DAIR failure trended lower for the hematogenous group in this study. Outcomes for DAIR appear similar regardless of the PJI type in optimal patients.