Inflammatory Cytokines and Biomarkers of Cartilage Metabolism 8 Years After Anterior Cruciate Ligament Reconstruction

Abstract

Background: Patients who sustain an acute anterior cruciate ligament (ACL) rupture are at increased risk to develop posttraumatic arthritis (PTA) in the injured knee whether the ACL is reconstructed or treated nonoperatively. Inflammatory cytokines and cartilage degradation biomarkers are elevated at the time of acute injury and postoperatively. This suggests that one mechanism for PTA may be an inflammatory degradative process initiated on the acute injury and sustained for some length of time independent of whether adequate joint stability is restored. Hypothesis: Inflammatory cytokines and biomarkers of cartilage degradation are elevated in the synovial fluid several years after reconstruction of the ACL, indicating an ongoing imbalance between extracellular matrix destruction and repair. Study Design: Cross-sectional study; Level of evidence, 3. Methods: In 11 patients who had undergone ACL reconstruction 8 years earlier, knee synovial fluid was aspirated from the operated knee and the contralateral nonoperated knee. The synovial fluid was analyzed for interleukin (IL)–1β, IL-6, tumor necrosis factor (TNF)–α, sulfated glycosaminoglycans (sGAG), aggrecan neoepitope fragment (ARGS-aggrecan), and cartilage oligomeric matrix protein (COMP). At follow-up, the patients underwent bilateral weightbearing radiographs and bilateral MRIs of their knees. Results: No significant differences between the operated and the contralateral knee were found for the synovial fluid concentrations of IL-1β, IL-6, TNF-α, sGAG, ARGS-aggrecan, or COMP. There were significantly more radiographically visible osteoarthritic changes in the operated knees compared with the contralateral knees. MRIs revealed that all grafts and all contralateral ACLs were intact and, furthermore, that there was significantly more meniscal and cartilage damage in the index knees than the contralateral knees. Conclusion: Eight years after ACL reconstruction, there were no significant differences in inflammatory cytokines and biomarkers for cartilage degeneration between the nonoperated and the ACL-reconstructed knee, even though there were more osteoarthritic changes and meniscal and cartilage damage in the operated knee, as seen on weightbearing radiographs and MRI.