Estimating the paths and mechanical behaviors of the plantar aponeurosis during dynamic movements using a multiple-marker foot model incorporating anatomically-detailed plantar aponeurosis morphology

Background

Several foot models have been developed to estimate the behaviors of the plantar aponeurosis (PA) during movements. However, these models did not consider the actual path of the PA, and their validity remains insufficiently investigated due to the absence of direct PA measurement during movements.

Research question

Would developing a foot model that considers the actual path of the PA improve the accuracy of estimating the PA behavior during movements?

Methods

The foot model was developed based on the CT scans of the six feet with 20 markers attached. An average foot model was created by calculating the mean positions of the 20 markers and 21 PA landmarks.　The PA on the average foot model was warped onto the motion-captured foot based on the marker positions using the thin-plate spline function to create the subject-specific model of the PA. To estimate the PA behaviors during movements, each of the PA landmarks was represented in an adjacent local coordinate system, and the time changes in the positions of the PA landmarks in the laboratory coordinate system were calculated.

Results

The present foot model incorporating the anatomically-detailed PA morphology estimated paths and lengths of the PA more accurately than the conventional PA model. Dynamic behaviors of the PA during walking and drop-jump were also successfully estimated.

Significance

Incorporating the anatomically detailed PA morphology into the foot model can improve the accuracy of the path and length estimates of the PA. The developed anatomically detailed PA model might serve as a useful tool to clarify the PA function, mechanical effects, and pathogenetic mechanisms underlying foot disorders such as plantar fasciitis.