Finite Element and Cadaveric Simulations of theMuscular Dysfunction of Weightbearing Foot

The tibialis posterior is a strong invertor and a weak plantarflexor of the foot which supports the longitudinal arch of the foot and creates a rigid lever for the foot to facilitate propulsion. Inflammation and dysfunction of the posterior tibial tendon is a common pathological condition of foot which is painful and disabling. Untreated posterior tibial tendon insufficiency will lead to severe inflammation and dysfunction of the tendon and flattening of the foot arch. In this study, a three-dimensional finite element model of the human foot and ankle, incorporating geometrical and material nonlinearity was employed to investigate the load distribution and spatial motion of the ankle-foot structures during simulated midstance. Cadaveric foot simulations were done to validate the finite element predictions in terms of strains of the plantar fascia, and major joint movements. Unloading the posterior tibial tendon was found to increase the arch deformations and strains of the plantar ligaments especially the spring ligament. The lack of foot arch support with plantar fascia release and posterior tibial tendon dysfunction may lead to attenuation of surrounding soft tissue structures and elongation of foot arch, resulting in a progressive acquired flatfoot deformity.

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