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Biomarker Changes in ACL Deficient Knees Compared with Contralaterals

      Introduction

      Though ACLR outcomes are overwhelmingly positive, patients’ recovery processes are highly variable, and typically based off generalized timetables derived from population data. In an attempt to individualize prognostic estimates, we sampled knee joint synovial enzyme concentrations in patients with ACL tears with, and without cartilage injury, and compared them with the contralateral non-injured knee.

      Methods

      480 patients indicated for knee arthroscopy had samples drawn to form a database. If no pathological history existed in the contralateral knee, samples were drawn as well. For this study, only patients that had confirmed ACL injury on arthroscopy were included. Samples were drawn 3-12 weeks after initial injury. Associated cartilage injury was noted. Samples were centrifuged, and concentrations were determined using an Elissa test. Concentrations were then compared between the three study groups (ACL tear with cartilage injury (without cartilage injury, and contralateral) using a Welch ANOVA test with pairwise comparisons.

      Results

      The study included samples from 132 knees which included: 34 ACL tears without cartilage damage (mean age 34.00 years); 28 ACL tears with cartilage damage (36.29 years), and 72 contralaterals (41.06 years). ANOVA testing demonstrated significant differences among groups for: MMP-3 (p,>001); TIMP-1 (p=.001); TIMP-2 (p=.015); FGF-2 (p=.011); IL-6 (p=.001); and MIP-1b (p=.001). Pairwise comparisons demonstrated no significant differences between ACL tears with, and without cartilage damage, but did show both types of ACL tears had significantly higher concentrations of MMP-3, TIMP-1, IL-6, and MIP-1b than contralaterals. ACL tears without cartilage damage had significantly lower concentrations of TIMP-2 and FGF-2 (13).

      Conclusion

      The course from repair to symptomatic relief is highly variable. Cytokine concentrations are shown here to be significantly different between ACL tears (+/- cartilage damage) and healthy knees. These validated differences can help establish these biomarkers as a method for injury stratification ultimately providing patient-specific prognostic data.