Analysis of Tibial Curvature, Fibular Loading and the Tibia Index


Dr. James R. Funk, Dr. Rodney W. Rudd, Dr. Jason R. Kerrigan, Dr. Jeff R. Crandall


Proceedings of the 2003 IRCOBI Conference on the Biomechanics of Impact, Lisbon, Portugal, September 25-26, 2003. Bron, France, IRCOBI Secretariat. 2003; 135-148. SAE Paper #2003-13-0010.


The tibia index (TI) is commonly used to predict leg injury based on measurements taken by an anthropomorphic test device (ATD). The TI consists of an interaction formula that combines axial loading and bending plus a supplemental compressive force criterion. Current ATD lower limbs lack geometric biofidelity with regard to tibial curvature and fibular load-sharing. Due to differences in tibial curvature, the midshaft moments induced by axial loading are different in humans and ATDs. Midshaft tibial loading in the human is also reduced by load-sharing through the fibula, which is not replicated in current ATDs. In this study, tibial curvature and fibular load-sharing are quantified through CT imaging and biomechanical testing, and equations are presented to correct ATD measurements to reflect the loading that would be experienced by a human tibia.