Understanding the design differences between multisegmented foot models and their impact on joint kinetic outcomes

Multisegmented foot models (MSFMs) are used to capture data of specific regions of the foot instead of representing the foot as a single, rigid segment. It has been documented that different MSFMs do not yield the same joint kinematic data, but there is little information available regarding their use for kinetic analysis. We compared the moment and power at the tibiotalar, midtarsal, and metatarsophalangeal joints of four MSFMs using motion capture data of young adult runners during stance phase of barefoot walking and jogging. Of these models, three were previously validated: the Oxford, Milwaukee, and Ghent Foot Models. One model was developed based upon literature review of existing models: the "Vogel" model. We performed statistical parametric mapping comparing joint measurements from each model to the corresponding results from the Oxford model, the most heavily studied MSFM. We found that the Oxford, Milwaukee, Vogel, and Ghent Foot Models do not provide the same kinetic results. The differences in segment definitions impact the degrees of freedom in a manner that alters the measured kinematic function of the foot, which in turn impacts the kinetic results. The results of this study capture the variability in performance of MSFMs as it relates to kinetic outcomes and emphasize a need to remain aware of model differences when interpreting results.