Thirty-Day Periprosthetic Joint Infection After Hip and Knee Arthroplasty: Clinical Correlates and Microbiology in a Tertiary Referral Cohort

Background : Early periprosthetic joint infection (PJI) is often pooled with later events despite distinct surveillance implications. We evaluated the burden, correlates, and microbiology of PJI diagnosed within 30 days after hip or knee arthroplasty. Methods : This secondary retrospective cohort included 975 primary or revision total hip and knee arthroplasty procedures performed at our institution in 735 adults from 2008 through 2023. The primary outcome was registry-recorded PJI on days 0-30. Patient-clustered logistic regression included revision status, age, diabetes, rheumatic disease, and corticosteroid exposure. Modified Poisson and sensitivity analyses assessed robustness; pathogen distributions were compared by timing. Results : Thirty-six procedures developed 30-day PJI (3.7%; 95% confidence interval [CI], 2.7%-5.1%), representing 59.0% of 61 first-year events; 58/61 (95.1%) were diagnosed by day 90. Early PJI occurred after 8/87 revisions (9.2%) and 28/888 primary procedures (3.2%). Revision arthroplasty was the most consistent correlate (adjusted odds ratio [aOR], 3.28; 95% CI, 1.49-7.24). Rheumatic disease showed a positive but imprecise association (aOR, 2.73; 95% CI, 0.98-7.63) that varied across model specifications. Gram-negative organisms accounted for 15/36 (41.7%) early and 3/25 (12.0%) later events (exploratory odds ratio, 5.24; 95% CI, 1.32-20.74). Conclusions : Most first-year PJIs were diagnosed within 90 days, with nearly 60% occurring during the first month. Revision arthroplasty was the most consistent correlate of 30-day PJI, supporting intensified early surveillance and continued first-year follow-up in complex revision patients. Clinical trial number: not applicable.