Levels of Synovial Fluid Inflammatory Biomarkers on Day of Arthroscopic Partial Meniscectomy Predict Long-Term Outcomes and Conversion to TKA

BACKGROUND: The purpose of the present study was to evaluate the relationships of the concentrations of pro- and anti-inflammatory biomarkers in the knee synovial fluid at the time of arthroscopic partial meniscectomy (APM) to long-term patient-reported outcomes (PROs) and conversion to total knee arthroplasty (TKA). METHODS: A database of patients who underwent APM for isolated meniscal injury was analyzed. Synovial fluid had been aspirated from the operatively treated knee prior to the surgical incision, and concentrations of pro- and anti-inflammatory biomarkers (RANTES, IL-6, MCP-1, MIP-1β, VEGF, TIMP-1, TIMP-2, IL-1RA, MMP-3, and bFGF) were quantified. Prior to surgery and again at the time of final follow-up, patients were asked to complete a survey that included a visual analog scale (VAS) for pain and Lysholm, Tegner, and Knee injury and Osteoarthritis Outcome Score-Physical Function Short Form (KOOS-PS) questionnaires. Clustering analysis of the 10 biomarkers of interest was carried out with the k-means algorithm. RESULTS: Of the 82 patients who met the inclusion criteria for the study, 59 had not undergone subsequent ipsilateral TKA or APM, and 43 (73%) of the 59 completed PRO questionnaires at long-term follow-up. The mean follow-up time was 10.6 ± 1.3 years (range, 8.7 to 12.4 years). Higher concentrations of individual pro-inflammatory biomarkers including MCP-1 (β = 13.672, p = 0.017) and MIP-1β (β = -0.385, p = 0.012) were associated with worse VAS pain and Tegner scores, respectively. K-means clustering analysis separated the cohort of 82 patients into 2 groups, one with exclusively higher levels of pro-inflammatory biomarkers than the second group. The "pro-inflammatory phenotype" cohort had a significantly higher VAS pain score (p = 0.024) and significantly lower Lysholm (p = 0.022), KOOS-PS (p = 0.047), and Tegner (p = 0.009) scores at the time of final follow-up compared with the "anti-inflammatory phenotype" cohort. The rate of conversion to TKA was higher in the pro-inflammatory cohort (29.4% versus 12.2%, p = 0.064). Logistic regression analysis demonstrated that the pro-inflammatory phenotype was significantly correlated with conversion to TKA (odds ratio = 7.220, 95% confidence interval = 1.028 to 50.720, p = 0.047). CONCLUSIONS: The concentrations of synovial fluid biomarkers on the day of APM can be used to cluster patients into pro- and anti-inflammatory cohorts that are predictive of PROs and conversion to TKA at long-term follow-up. LEVEL OF EVIDENCE: Prognostic Level III . See Instructions for Authors for a complete description of levels of evidence.