The ankle sprain is the most commonly injured joint modality in the body, because the ankle bears more stress than any other joint in the body. The sprained ankle constitutes 38%–45% of all recreational injuries, and 33%-40% of patients reported lingering symptoms for 3-6 months after treatment. Several foot models exist that are being used to assist clinicians in understanding foot-ankle injury biomechanics; however, they all model ligaments as linear springs instead of visco elastic springs. To date, no study has investigated the viscoelastic effects of ligaments which belong to different morphometric families. Hence, the objective of my dissertation research was to develop a ligament structural model, which relies on linear estimates of ligament behavior by finding and predicting relationships between viscoelastic parameters and ligament morphometry through experimentally collected data.
A hierarchical cluster analysis was performed using imaging data from the NllI ViSible Human Project. Thirty-nine ligaments were visualized and measured for average crosssectional area and length. The cluster analysis found five distinct groups, providing a framework for conducting biomechanical tests on ligaments that belong to different morphometric profiles. Non-destructive biomechanical testing was then performed using an MTS materials testing system to obtain stress relaxation data of 109 ligaments acquired from fresh-frozen cadavers. Fonowing experimental testing, relaxation data was curve fit to a three-element Maxwen model and to a variation ofFung's QLV theory. Afterward, each ligament was measured for morphometry, using a novel quick-freeze technique~ and a second cluster analysis was perfonned on the new morphometric data.. Average relaxation response for each of the five clusters was used to predict the relaxation response of 10 previously tested ligaments. Eight of the 10 predictor ligaments fell within one standard deviation of the average of their respective clusters9 and all 10 predictor ligaments fell within 2 standard deviations. Viscoelastic relaxation was predicted from ligament morphometry. Future work involves implementing morphometric-derived relaxation data into a pre-existing computational foot-ankle model9 where this model has the potential to mimic the affect of severe ankle sprains on foot and ankle biomechanics.