Biomechanical Evaluation of Surgical Plantar Fascia Release Effects

Abnormal foot structures are known to influence tension stresses carried by the plantar fascia. An excessive arched foot structure may lead to plantar fasciitis. When conservative treatment fails, surgical intervention called plantar fascia release is often used for reducing chronic heel pain. A finite element structural model for mechanical analysis of the human foot during standing was developed and applied to the investigation of plantar fascia release biomechanical effects. The model integrates a system of five planar structures in the foot rays directions. It includes linear and non-linear elements representing different foot tissue types as well as inter-linking elements. A detailed normal foot structure was obtained using the newly developed advanced MRI technique, called Open MRI. The model was validated by comparing its resulted ground reactions with foot-ground pressure measurements and its predicted displacements with radiological tests. Simulation of fascia release (partial or total) was performed by gradually removing parts of the plantar fascia in the model. Results show that fascia release cause large sagging of the arch. Tension stresses carried by the long plantar ligament increase significantly. As the plantar fascia contribution to foot load bearing capabilities is of major importance, its release should be obviously carefully considered, and the model may be used to help surgeons decide about the degree of release.