Strain estimations of the plantar fascia and other ligaments of the foot: Implications for plantar fasciitis

Abstract

<p>Plantar fasciitis is thought to occur due to excessive strain of the plantar fascia. There are numerous anatomical, biomechanical, and environmental factors that affect plantar fascia strain. Therefore, the first purpose of this dissertation was to investigate several biomechanical and environmental factors thought to increase plantar fascia strain. Fifteen healthy participants walked on a treadmill at two speeds, three inclines, and two shoe stiffness levels. A four-segment musculoskeletal model of the foot was used to analyze the data, and a significant effect of speed was found. Furthermore, the relationship between metatarsophalangeal (MTP) joint dorsiflexion and arch collapse was investigated, and the amount that each contributed to total plantar fascia strain was calculated. It was found that the increase in plantar fascia strain caused by MTP joint dorsiflexion is counteracted by the increase in arch height that occurs with MTP joint dorsiflexion, which is due to the function of the windlass mechanism. The second purpose was to validate a six-segment musculoskeletal model of the foot that estimates strains of several ligaments thought to assist the plantar fascia in arch support. Seven fresh-frozen cadaver specimens were dissected and ligament strains were directly measured using a manual digitizer. The directly-measured strains were compared to the model-estimated ligament strains as a way to validate the use of the model for future studies. The third purpose was to use the six-segment musculoskeletal model to determine the effects of a taping procedure on plantar fascia strain. Fifteen individuals with plantar fasciitis walked overground under two barefoot conditions: an untaped condition and a low-Dye taped condition. The low-Dye taped condition decreased the amount of arch collapse exhibited by the participants, and although the tape did not reduce peak plantar fascia strains during walking, it significantly reduced plantar fascia strains during midstance. We suggest that the taping method is effective due to its ability to reduce cumulative strain across the entire stance phase rather than peak strain. The final purpose was to use the musculoskeletal model to determine the effects of the low-Dye taped condition on several ligaments thought to assist the plantar fascia in arch support. Significant reductions of strain in the spring ligament and long plantar ligament affirm the role of these ligaments to provide support to the medial longitudinal arch.</p>