Characterising the biomechanical properties of the plantar soft tissue under the conditions of simulated gait

Parker, D

Abstract

The plantar soft tissue at the heel and ball of the foot provide the interface between the body and the ground. This tissue is adapted to attenuate large amounts of energy during impact (heel strike) and to become rigid under continuous loading (standing). The heel pad tissue is composed of multiple specialised layers including a rigid bone (Calcaneus), a highly compliant fatty pad and a stiff rugged skin boundary. To assess this complex tissue STRIDE (Soft Tissue Response Imaging Device) has been developed. Using bespoke displacement driven profiles STRIDE is capable of simulating the vertical component of gait to compress the tissue, whilst collecting data to describe the response of the tissue via the combination of ultrasound imaging to detect vertical displacement and a miniature load cell to detect vertical load. From this data we are able to calculate tissue stress and strain and derive the characteristic mechanical properties of the tissue. A study of 38 individuals ranging in age from 18 to 85 was conducted to develop a baseline of tissue properties over age. The results show that the tissue has a highly rate dependent nature, reinforcing the need to conduct tests at rates relevant to the functional range of the tissue. Under gait conditions the elderly group displayed non-significant trends toward increased Energy loss (+45%), elastic modulus (+4%) and compressibility (+11%) whilst decreased trends were observed for viscosity (-20%) and the measured gradient of the stress strain curve throughout tissue compression. These differences suggest that the normal structural changes, which occur within the tissue as a result of aging, can cause disruption to the mechanical response of the tissue during compression. The mechanical properties derived will be used to inform the development of mechanisms (therapy/treatment) or interventions (orthotics/shoes) which may compensate for these changes.

Citation

Parker, D. Characterising the biomechanical properties of the plantar soft tissue under the conditions of simulated gait. (Thesis). The University of Salford

• Thesis Type: Thesis
• Deposit Date: Jul 22, 2013
• Publicly Available Date: Jul 22, 2013