Date of Award

12-2012

Document Type

Thesis

Degree Name

Master of Science (MS)

Program

Biomedical Engineering and Imaging

Research Advisor

Denis J. DiAngelo, Ph.D.

Committee

Richard J. Kasser, Ph.D. Brian P. Kelly, Ph.D. Gladius Lewis, Ph.D.

Keywords

ankle complex, four bar linkage, instantaneous axis of rotation, testing platform

Abstract

The objective of this study was to improve upon existing testing platform limitations with respect to foot and ankle mechanics in the sagittal plane during dorsiflexion and plantar flexion. The intent was to develop a multi-loading protocol that simulated aspects of early stance phase of walking gait. This data were used to evaluate the influence an Achilles load has on the kinematic profile of the ankle complex. Also, resulting kinematic profile data can be used to evaluate ligament/tendon effects, ankle arthroplasty, and various surgical techniques.

A pair of cadaveric human feet, from the same donor, 50 years of age were dissected and potted for testing. A pure moment protocol was developed to determine the path of least resistance or lowest energy state to rotate the tibia about the ankle complex. This protocol utilized a 4-degree of freedom robot coupled with a two 6-axis load cells. Positional data was used to calculate the instantaneous axis of rotation (IAR) of the ankle complex. The data was then normalized with respect to the widest distance across the tibia.

Results from this work include a repeatability study of the robotic testing platform (RTP), validation of protocol, calculation of the IAR, and a study of the effect an Achilles load has on ankle kinematics. The repeatability study used a modified version of the protocol to reduce setup effects. A repeatability analysis was conducted comparing repeated test runs for dorsiflexion and plantar flexion (one way repeated measures ANOVA with a Bonferroni test) and found no significant difference between the data sets for (P<0.05). The IAR results with and without a passive Achilles load were significantly different (P>0.05), using same statistical approach.

Future work is to actively drive the Achilles load and add a push-off condition were the rotation is about the distal end of the first and second metatarsals. Along with that, the upper limit of the vGRF is to be increased to simulate the later part of the stance phase of gait where the Achilles load is larger.

DOI

10.21007/etd.cghs.2012.0299

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