Clinical Outcomes of 1.5-Stage Arthroplasty for Native Joint Septic Arthritis of the Hip and Knee: A Retrospective Cohort Study.

Background: Native joint septic arthritis (NJSA) requires joint excision and arthroplasty when debridement fails or irreversible joint damage is present. Traditionally, this is performed as a staged procedure with a spacer and antibiotics prior to definitive arthroplasty. While effective, this approach is associated with multiple operations, prolonged treatment, and increased morbidity. The 1.5-stage arthroplasty has recently emerged as a potential alternative in treating periprosthetic joint infections, but its role in NJSA remains unexplored. This study evaluated the clinical outcomes of 1.5-stage arthroplasties in hips and knees for NJSA. Methods: A retrospective analysis was conducted on patients who underwent a 1.5-stage (n = 45) arthroplasty for NJSA between 2015 and 2024. Primary outcome was the revision rate at 12 months postoperatively. Secondary outcomes included surgical complication rates, length of hospital stay, rate of progression to second stage, 30-day emergency department and hospital readmission rates, and 1-year mortality. Results: At 1 year, the revision rate was 26.7%, with only 2 revisions performed for surgical complications (6.7%). Overall, 24.4% of patients progressed to a planned second stage within 1 year, primarily for functional optimization. The median length of stay was 13.5 days (interquartile range: 8-16). Thirty-day emergency department presentations (11.1%), readmissions (6.7%), and 1-year mortality (4.4%) were low and did not differ between hip and knee cohorts. No baseline demographic or clinical factors were significantly associated with revision risk. Conclusions: These findings suggest that 1.5-stage arthroplasty is a safe and effective option for NJSA, potentially avoiding additional surgery in selected patients.