Evaluating the importance of load and morphology to regional tibial strength.

Monitoring tibial bone strength is critical for assessing fatigue fracture risk. This study aimed to evaluate the contributions of morphological features, muscle forces, and ankle contact forces to tibial stress-strain distribution and to analyse the effect of feature quantity on tibial stress-strain prediction accuracy. Tibial cortical morphologies were described using a statistical shape model based on CT scans from 40 young males. Regional stress-strains were calculated via finite element analysis (FEA), with loads estimated from optical motion capture data across six activities. Variable Importance in Projection (VIP) scores using a Partial Least Squares Regression (PLSR) model were employed to evaluate the importance of load and morphological features. The anterior-posterior (2.15 ~ 2.44) and vertical (1.74 ~ 2.34) components of ankle contact forces showed the highest VIP scores to stress-strain in high-risk regions. Using only ankle joint contact forces (anterior-posterior and vertical components) as predictors, the PLSR model achieved a mean R2 of 0.79 ~ 0.83 and RMSE < 5% for von Mises stress, tensile strain, and compressive strain. Ankle contact forces are the primary contributors to tibial stress-strain distribution and can effectively predict stress-strain in high-risk regions using the PLSR approach.