Effects of lower limb parameters on femoral bone tunnel biomechanics after anterior cruciate ligament reconstruction during dynamic tasks.

Tendon-bone healing after anterior cruciate ligament (ACL) reconstruction is influenced by the local mechanical environment. This study aimed to investigate the effects of lower limb kinematics, kinetics, and muscle force on femoral bone tunnel strain, and identify parameters that can predict high bone tunnel strain during three dynamic tasks. Motion data from twelve lower limbs were collected during gait, lunge, and squat using a three-dimensional motion capture system. Lower limb biomechanical parameters were obtained using inverse dynamics methods. A finite element model of single-bundle ACL reconstruction was established to calculate the bone volume around the femoral tunnel within the 2000-4000 μ-strain range. The Spearman correlation coefficient assessed relationships between lower limb parameters and bone tunnel biomechanics. Receiver operating characteristic curve analyses and multivariate binary logistic regressions identified lower limb parameters that distinguished between high and low strain values. Higher semitendinosus muscle force (ρ = 0.895), greater anterior tibial translation (ρ = 0.937), and greater peak knee valgus moment (ρ = 0.872) demonstrated the strongest associations with high bone tunnel strain during gait, lunge, and squat tasks, respectively. The regression model using kinetics to predict high bone tunnel strain trials during the lunge task yielded the highest accuracy (82.6 %), sensitivity (0.424), and specificity (0.960) among all models. Key parameters strongly associated with and predictive of beneficial bone tunnel biomechanics included higher knee lateral contact force during gait, greater hip flexion angle and extension moment during the lunge, and greater lateral tibial rotation angle during the squat.