Abstract
The inflammatory response to joint injury has been thought to play a key role in the development of osteoarthritis. In this preclinical study, we hypothesized that synovial fluid presence of inflammatory cytokines, as well as altered loading on the injured leg, would be associated with greater development of macroscopic cartilage damage after an ACL injury. Thirty-six Yucatan minipigs underwent ACL transection and were randomized to: 1) no further treatment, 2) ACL reconstruction, or 3) scaffold-enhanced ACL restoration. Synovial fluid samples and gait data were obtained pre-operatively and at multiple time points post-operatively. Cytokine levels were measured using a multiplex assay. Macroscopic cartilage assessments were performed following euthanasia at 52 weeks. General estimating equation modeling found the presence of IL-1α, IL-1RA, IL-2, IL-4, IL-6, and IL-10 and MMP-2, MMP-3, MMP-12, and MMP-13 in the synovial fluid was associated with better cartilage outcomes. Higher peak pressure for the surgical hind leg and contralateral hind leg aligned with worse cartilage outcomes. A support vector machine built with synovial fluid and gait metrics also demonstrated cytokine presence was predictive of better cartilage outcomes. In conclusion, this preclinical analysis suggests that synovial fluid devoid of cytokines may be a possible indicator that cartilage is more at risk of becoming pathologic after joint injury.