Background: Synovial fluid biomarkers can highlight the molecular milieu associated with knee pathology and have been shown to be significantly different in patients with anterior cruciate ligament (ACL) injuries compared to uninjured controls. The purpose of the current study was to establish how synovial fluid biomarker concentrations change in patients undergoing ACL reconstruction between the immediate preoperative period to the acute postoperative period.
Methods: Patients were prospectively enrolled at the time of surgery from September 2016 to March 2017. Patients who had an operative knee synovial fluid sample obtained at the time of ACL reconstruction and provided a synovial fluid sample at their first postoperative appointment were included. The concentrations of 10 biomarkers were determined using a multiplex magnetic bead immunoassay. Biomarker concentrations before and after surgery were compared using a paired sample t-test.
Results: Eight patients with mean age of 33.4 years who underwent isolated ACL reconstruction using a bonepatellar tendon-bone autograft were included. The mean time between surgery and postoperative office visit was 10.4 days. There was a statistically significant increase in the concentrations of interleukin-6 (IL-6, p = 0.014), monocyte chemoattractant protein-1 (MCP-1, p = 0.024), human matrix metalloproteinase 3 (MMP-3, p = 0.00002), macrophage inflammatory protein-1 beta (MIP-1β, p = 0.006), human interleukin-1 receptor antagonist (IL-1Ra, p = 0.017), and vascular endothelial growth factor (VEGF, p = 0.023) between the time of surgery and the first postoperative visit and a decrease in the concentration of tissue inhibitor of metalloproteinase-2 (p = 0.050).
Conclusion: The molecular profile of the synovial fluid changes in the early postoperative period following arthroscopic ACL reconstruction. The concentration of proinflammatory markers (such as IL-6, MCP-1, MMP-3, and MIP-1β) and growth factors including VEGF increases. The concentration of the anti-inflammatory marker tissue inhibitor of metalloproteinase-2 (TIMP-2) appears to decrease postoperatively.