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Development of a subject-specific computational foot and ankle model and its application to the evaluation of total ankle replacements
Dissertation   Open access

Development of a subject-specific computational foot and ankle model and its application to the evaluation of total ankle replacements

María Ruiz Rincón
Doctor of Philosophy (Ph.D.), Drexel University
Jun 2022
DOI:
https://doi.org/10.17918/00001281
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Abstract

Foot--Mathematical models Ankle--Mathematical models Total Ankle Replacement Artificial Joints
Due to the complicated kinematics of the ankle joint, and the great morphological variation reported between individuals, a subject-specific computational foot and ankle model proved to be the best tool to study the behavior of 10 subjects under different dynamic conditions. The goal of this study was to use an already existing computational model that replicated the conditions of the ankle joint and develop new additions so that it would include the complete foot, as well as the leg just below the knee. The new additions were evaluated against experimental tests carried out on 10 cadaveric legs that were CT scanned under different positions and loading, in order to see if the computational model could match the results from the experimental data. Once the model was evaluated with a one-to-one subject comparison, the 10 computational models were then implanted two Total Ankle Replacements on their bone surfaces to compare the two designs and how they affect the feet's passive mechanics under different loadings. One of the implants is designed to have more constrained and stable features that will focus on the rotation of the ankle in one main direction. The other implant's design is semiconstrained so that the ankle can rotate in any direction. The implants were additionally set up in three misaligned configurations in order to look at the effect it has on the joint while weightbearing standing on a surface. Even though both designs proved they were able to reach the same amount of motion as the natural ankle joint, the constrained implant would reach certain rotations by losing congruity between its articulating surfaces, and having loads concentrated on small areas of contact. This would lead to much higher contact pressures than the ones found in the semi-constrained design.

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