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.

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

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: Intra-articular injections are frequently used in the management of joint conditions prior to total knee arthroplasty (TKA). However, their impact on systemic inflammatory and immunological biomarkers remains unclear. This study aimed to evaluate plasma cytokine and chemokine profiles in TKA patients with varying histories of joint injections.

Methods: Peripheral blood samples were collected from 41 TKA patients categorized into three groups based on injection history: no prior injection (None, n=10), injection within six months (<6 mo, n=14), and injection more than six months prior to surgery (>6 mo, n=17). Plasma was isolated and analyzed using the Bio-Plex Pro Human Immunotherapy Panel, which quantifies 20 cytokines and chemokines. Biomarkers with more than 10% missing or out-of-range (OOR) values were excluded. Statistical comparisons of demographic characteristics and biomarker concentrations were performed using ANOVA, Kruskal-Wallis tests, and two-way ANOVA controlling for sex. False discovery rate (FDR) adjustments were applied to account for multiple comparisons.

Results: Demographic analysis revealed significant differences in sex distribution across groups (Fisher's exact test, p=0.0017), while age, race, and ethnicity showed no significant differences. Of the 20 biomarkers analyzed, seven were excluded due to high percentages of missing or OOR values. Statistical analysis of the remaining biomarkers revealed no significant differences across groups after FDR adjustment. However, several biomarkers, including IL-2, IL-18, and MCP-1, approached significance across multiple tests.

Conclusion: This study provides insights into the potential effects of joint injection history on systemic inflammatory biomarker profiles in TKA patients. While no significant differences were observed, trends in specific biomarkers suggest avenues for further investigation into the immunological impact of intra-articular injections.

B Kowalski, M Deegan, H Johnson, F Say, L Gillette, Z Colburn, J Dannenbaum, M Bedrin

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: Cytokines and chemokines play critical roles in inflammation and tissue repair, yet their plasma concentrations in patients undergoing primary anterior cruciate ligament (ACL) repair and revision ACL (RACL) repair remain poorly understood. This pilot study aimed to compare plasma biomarker profiles between ACL and RACL patients to identify potential differences in inflammatory and immunological responses.

Methods: Peripheral blood samples were collected from 21 patients (ACL group: n=15; RACL group: n=6) at the time of surgery. Plasma was isolated and analyzed using the Bio-Plex Pro Human Immunotherapy Panel, a multiplex immunoassay measuring 20 cytokines and chemokines. Biomarker concentrations were reported in pg/mL, and values outside the detection range were flagged and processed. Statistical comparisons of demographic characteristics and biomarker concentrations were performed using t-tests, Wilcoxon rank-sum tests, and ANOVA controlling for sex. False discovery rate (FDR) adjustments were applied to account for multiple comparisons

Results: No significant differences in demographic characteristics, including age, sex, race, and ethnicity, were observed between the ACL and RACL groups. Of the 20 biomarkers analyzed, six were excluded due to missing or out-of-range values. Statistical analysis of the remaining biomarkers revealed no significant differences between the groups after FDR adjustment. However, several biomarkers, including CCL3, CCL4, and RANTES, approached significance across multiple tests, suggesting potential trends in inflammatory marker expression.

Conclusion: This study provides the novel comparison of plasma cytokine and chemokine profiles in ACL and RACL patients, highlighting potential trends in biomarker expression that warrant further investigation. These findings contribute to the understanding of inflammatory processes in primary and revision ACL repair and may inform future research on targeted therapeutic strategies.

C Gerber, M Feldman, R Frenette, F Say, L Gilette, Z Colburn, J Dannenbaum, M Bedrin

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: Intra-articular injections are commonly administered prior to total knee arthroplasty (TKA) to manage pain and inflammation, yet their impact on the synovial fluid microbiome remains unclear. We aimed to investigate the influence of pre-operative intra-articular injections on the synovial fluid microbiome composition in TKA patients.

Methods: Twenty-six TKA patients were divided into two cohorts: those who received an intra-articular injection within six months prior to surgery (injection group, n=13) and those who did not (non-injection group, n=13). Synovial fluid samples were collected during surgery, and microbial DNA was extracted for 16S rRNA gene sequencing targeting the V3-V4 hypervariable regions. Bioinformatics analysis was performed using QIIME 2, and microbial diversity metrics and differential abundance of taxa were compared.

Results: Demographic comparisons revealed significant differences in sex distribution and beneficiary category between the injection and non-injection groups, while age, race, and ethnicity showed no significant differences. Alpha diversity metrics, including Chao1, Shannon, Inverse Simpson, and Fisher's alpha, demonstrated no statistically significant differences between the two groups. However, differential abundance analysis identified several microbial taxa with significantly altered relative abundances between the injection and non-injection groups. Specifically, 30 taxa were enriched in the injection group, while 16 taxa were more abundant in the non-injection group.

Conclusion: We identified specific differences in the synovial fluid microbiome associated with pre-operative intra-articular injections in TKA patients. These findings provide insights into the potential microbiome-related effects of intra-articular injections, paving the way for further research on their implications for joint health and surgical outcomes.

M Deegan, B Kowalski, R Frenette, F say, L Gillette, Z Colburn, J Dannenbaum, M Bedrin

Abstract accepted for poster presentation at Madigan Research Day 2026

Background: The synovial fluid microbiome is becoming increasingly recognized for its role in joint health and disease, yet how its composition differs relates to different joint conditions such as in patients undergoing primary anterior cruciate ligament (ACL) repair and total knee arthroplasty (TKA) remains poorly characterized. We aimed to compare synovial fluid microbiome profiles between these two distinct patient groups.

Methods: Synovial fluid samples were collected from 13 ACL patients and 13 TKA patients during surgery. Microbial DNA was extracted and analyzed using 16S rRNA gene sequencing targeting the V3-V4 hypervariable regions. Bioinformatics analysis was performed using QIIME 2, and microbial diversity metrics were calculated. Statistical comparisons of demographic attributes, alpha diversity indices, and differential abundance of microbial taxa were conducted.

Results: Significant demographic differences were observed between the groups, with ACL patients being younger (median age: 25 years) and predominantly male, while TKA patients were older (median age: 67 years) and exclusively female. Alpha diversity metrics revealed significantly higher microbial richness and evenness in TKA patients compared to ACL patients, as evidenced by Chao1, Shannon, and Inverse Simpson indices. Differential abundance analysis identified several taxa enriched in TKA patients, including Burkholderia, Aquabacterium, and Moraxella cinereus, while taxa such as Acinetobacter proteolyticus and Pseudomonas alloputida were more abundant in ACL patients.

Conclusion: Our results reveal distinct synovial fluid microbiome profiles between ACL and TKA patients, with significant differences in microbial diversity and taxa abundance. These findings provide insights into the potential role of the microbiome in joint health and recovery, paving the way for future research on microbiome-targeted therapies in orthopaedic care.