Synovial Fluid Ghrelin Levels in Patients With or Without Cartilage Injury Undergoing Anterior Cruciate Ligament Reconstruction

Abstract Objectives The aim of our study was to measure synovial fluid levels of ghrelin in patients with ACL injury to evaluate its potential function as a diagnostic biomarker for cartilage injury. Methods Patients were prospectively recruited in this study, compromising a cohort of subjects that had synovial fluid samples collected. Patients’ synovial fluid sampling was collected to evaluate ghrelin level. Venous blood samples were taken from all subjects to test inflammation markers IL-6, TNF-α, MMP-3, MMP-13 and also serum ghrelin level. Correlation between synovial fluid ghrelin level and inflammatory biomarkers were analyzed using spearman’s correlation analysis. The best cut-off of synovial fluid ghrelin level was defined using Medcalc. Results Patients in the ACL reconstruction with cartilage damage had lowest synovial fluid ghrelin level (ACL reconstruction with cartilage damage group: 264.6±65 pg/ml, ACL reconstruction without cartilage damage group: 466.8±92.6 pg/ml, healthy controls: 471.5±89.3 pg/ml, P < 0.001). Synovial fluid ghrelin level was negatively associated with IL-6 (r=-0.700, P < 0.001), MMP-3 (r=-0.702, P < 0.001) and MANKIN score (r=-0.768, P < 0.001). Patients with synovial fluid ghrelin level ≤ 333 pg/ml had higher chance of cartilage injury with specificity of 91.7% and sensitivity of 87.5%. Discussion In conclusion, synovial fluid ghrelin was a useful biomarker to predict cartilage injury for patients undergoing ACL reconstruction. Synovial fluid ghrelin was negatively correlated with IL-6, MMP-3 and MANKIN score. Synovial fluid ghrelin ≤ 333 pg/ml was a useful biomarker for cartilage damage in patients with ACL injury.