Femoral Condylar Consumption Index (FCCI): A geometric MRI predictor of lateral meniscal lesion and re-tear.

Abstract

The morphometric relationship between the femoral condyle and lateral meniscus has not been quantitatively characterized. Subtle alterations in femoral geometry may modify load distribution and predispose to meniscal re-tear, yet no reproducible MRI index exists to quantify this phenomenon. To define and validate the Femoral Condylar Consumption Index (FCCI) as a geometric MRI parameter predictive of lateral meniscal lesion and re-tear. A retrospective case-control MRI study was conducted including 120 knees: 60 with arthroscopically confirmed lateral meniscal tears (20 re-tears) and 60 controls. The FCCI was calculated as. FCCI=R₀-R₁R₀x100 where R₀ represents an internal reference radius derived from the medial femoral condyle, and R₁ the measured radius of the lateral condyle on sagittal MRI. Two blinded observers performed independent measurements. Interobserver reliability, receiver operating characteristic (ROC) analysis, and multivariate logistic regression were applied. The mean FCCI was significantly greater in the lesion group than in controls (12.8 ± 3.2% vs. 5.1 ± 2.0%, P < 0.001). An FCCI > 9% predicted meniscal tear with sensitivity 0.86 and specificity 0.82 (AUC = 0.89; 95% CI, 0.83-0.95). Recurrent tears exhibited higher values (15.6 ± 3.4%) than primary tears (11.9 ± 2.8%, P = 0.002). In multivariate analysis, FCCI > 9% remained an independent predictor (OR = 6.4; 95% CI, 2.3-10.8; P < 0.001). Reliability was excellent (ICC_inter = 0.91; ICC_intra = 0.88). The FCCI is a novel, reproducible geometric parameter that quantifies posterior femoral condylar flattening and predicts both primary and recurrent lateral meniscal tears. Incorporation into preoperative MRI assessment may assist in risk stratification and surgical planning. Before FCCI can be applied prognostically, prospective validation is required to establish temporal precedence and causal relevance.