A comparison of modeling approaches when estimating tibial loading during running with different foot strike patterns

Area of Science:

• Biomechanics
• Orthopedics
• Sports Medicine

Background:

• Foot strike mechanics influence tibial loading, a risk factor for tibial stress injuries.
• Accurate tibial geometry is crucial for load analysis but often requires medical imaging.
• Open-source statistical shape modeling (SSM) offers a non-imaging alternative for tibial reconstruction.

Purpose of the Study:

• To quantify the accuracy of a 4-marker SSM for tibial geometry reconstruction.
• To compare internal tibial loading estimates from 2D beam theory and 3D finite element analysis (FEA).
• To evaluate the consistency of loading responses under different foot strike conditions.

Main Methods:

• Assessed 4-marker vs. 9-marker SSM accuracy against MRI-based geometries using Jaccard index and surface error.
• Generated 4-marker SSM tibial geometries for participants running under habitual and imposed foot strike conditions.
• Estimated tibial stress/strain using 2D beam theory and 3D FEA with identical loading inputs.

Main Results:

• The 4-marker SSM showed a 17.1% lower Jaccard index than the 9-marker configuration.
• Reconstructed tibial lengths had a mean absolute error of 13.8 mm compared to marker-based measurements.
• Forefoot striking increased peak anterior tibial stress by ~17-19%, with consistent directional changes between 2D and 3D models.

Conclusions:

• Relative changes in tibial loading were directionally consistent between 2D and 3D models across foot strike conditions.
• Simplified 2D beam theory offers a practical, non-imaging alternative for estimating loading changes in healthy runners.
• 4-marker SSM provides a viable method for tibial geometry reconstruction when imaging is unavailable.