Abstract:
This study details the development and validation of a subject-specific finite element (FE) modeling technique to analyze the three-dimensional stress-strain behavior of the human medial collateral ligament (MCL) during valgus knee loading. Eight cadaveric knees were subjected to experimental varus-valgus loading at 0°, 30°, and 60° of flexion, during which 3D
joint kinematics and MCL surface strains were measured. Following this, each MCL was tested to determine its unique material properties and its in situ strain distribution—the baseline tension present in the ligament within the joint. For each of the eight specimens, a unique FE model of the femur-MCL-tibia complex was constructed using subject-specific geometry from CT scans, experimentally measured material properties (represented by a transversely isotropic hyperelastic model), and the measured joint kinematics and in situ strain as boundary and initial conditions. The FE models' predictions of MCL strain correlated well with the experimental measurements, particularly at 0° flexion (R² =0.83). A key part of the study was a parameter analysis to determine which subject-specific inputs were most critical for model accuracy. It was found that using average material properties had a negligible effect on strain predictions (R² =0.99), but using an average in situ strain distribution resulted in poor correlations (R² =0.44 at 0° flexion). The biomechanical analysis concluded that the highest strains occurred in the posterior part of the MCL near the femur during valgus loading at full extension, identifying it as a region vulnerable to injury.
