Comparative Analysis of Synovial Fluid Microbiome Composition in Primary and Revision Anterior Cruciate Ligament Repair Patients- Madigan Research Day 2026

J Dobrich, R Frenette, M Feldman, F Say, L Gillette, Z Colburn, J Dannenbaum, M Bedrin

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: Anterior cruciate ligament (ACL) injuries are common orthopedic conditions, with revision ACL (RACL) surgeries often required due to graft failure or reinjury. Emerging evidence suggests that the synovial fluid microbiome may play a role in joint health and recovery, yet its composition in ACL and RACL patients remains poorly understood.

Methods: This study analyzed demographic data and synovial fluid microbiome composition from 18 patients enrolled in an orthopedic biorepository. Patients were divided into two groups: primary ACL repair (n=13) and RACL repair (n=5). Synovial fluid samples were collected during surgery, and microbial DNA was extracted for 16S rRNA gene sequencing. Bioinformatics analysis was performed using QIIME 2, and statistical comparisons of microbial diversity and differential abundance were conducted.

Results: Demographic characteristics, including age, sex, race, and ethnicity, showed no significant differences between the ACL and RACL groups. Microbiome diversity metrics (Chao1, Shannon, Inverse Simpson, and Fisher's alpha) revealed no statistically significant differences between groups. However, differential abundance analysis identified several microbial taxa with significantly higher relative abundances in RACL patients, including Sediminibacterium, Bradyrhizobium, and Pseudomonas species. Conversely, taxa such as Corynebacterium kroppenstedtii and Acinetobacter proteolyticus were more abundant in ACL patients.

Conclusion: This study highlights distinct shifts in the synovial fluid microbiome composition between primary and revision ACL surgery patients. These findings provide insights into potential microbial contributions to joint health and recovery, paving the way for future research on microbiome-targeted interventions in orthopedic care.