Sequential Exposure to Acute, Intermediate, and Late Synovial Fluid Fracture Hematoma after Ankle Fracture Promotes Cartilage Damage in Vitro Partially Attenuated by Anti Inflammatory Agents

BackgroundPost-traumatic osteoarthritis (PTOA) following intra-articular fractures (IAFs) remains a common sequela after injury. Cartilage degeneration after injury is influenced by multiple factors, including elevated proinflammatory cytokines produced by synovial fluid fracture hematoma (SFFH). Targeting this inflammatory response may reduce cartilage damage. This study evaluated cartilage injury and inflammatory mediator changes caused by SFFH, assessing whether commercially available anti-inflammatory agents can suppress the inflammatory cascade implicated in PTOA and reduce chondrocyte death.MethodsAnkle synovial fluid was collected from 54 patients with IAFs. Human cartilage discs harvested from talar allografts were cultured in standard chondrocyte media (SCM) and initial media was collected. Explants were randomized into five groups: (1) control (SCM only), (2) sequential exposure SFFH representing acute (days 0-2), intermediate (days 3-9), and late (≥10) phases, (3) Group 2 with interleukin-1 receptor antagonist (IL-1Ra), (4) Group 2 with dexamethasone, and (5) Group 2 with doxycycline. After exposure, spent media was collected. Samples were analyzed for cytokines, matrix metalloproteinases (MMPs), C-terminal telopeptides of type II collagen (CTX-II), and sulfated glycosaminoglycans (sGAGs), with histological assessment performed to evaluate viability and proteoglycan content.ResultsSFFH exposed cartilage showed increased levels of proinflammatory cytokines, MMPs, and cartilage breakdown products compared to controls. Treatment with IL-1Ra, dexamethasone, or doxycycline all reduced inflammatory cytokines and MMP levels. Safranin O staining, indicating proteoglycan content, was lowest in group 2. No significant difference in chondrocyte survival was observed among groups.ConclusionSequential exposure to SFFH creates a sustained proinflammatory and catabolic environment that promotes biochemical cartilage degradation. IL-1Ra, dexamethasone, and doxycycline reduced inflammatory cytokine and MMP concentrations while cartilage matrix degradation markers remained elevated and histologic preservation was not significantly improved. These findings suggest that suppression of inflammatory pathways alone may be insufficient to fully prevent cartilage injury under cumulative SFFH exposure.Clinical RelevanceAcute anti-inflammatory therapy following IAF may modulate inflammatory and catabolic mediator production within the post-fracture joint environment. Further in vivo investigation is required to determine whether these biological effects translate into durable cartilage preservation or altered PTOA risk.Level of EvidenceLaboratory study.