Multi-segment foot modelling to enable an understanding of altered gait in diabetes

• Main Author: Jaitman, Abigail
• Published: University of Warwick 2016
• Subjects: 616.4; QP Physiology
• Online Access: https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.714938

Diabetes is a multisystemic disease that affects the whole human body, in particular, the musculoskeletal system. Muscles, tendons, ligaments and bone marrow are its main victims, the foot being the most common target. Changes in its anatomy can occur rapidly, and therefore an early diagnosis is imperative in order to provide the appropriate medical care, thus avoiding amputation which is a high factor of morbidity. In order to understand the biomechanical implications of the disease, it is necessary to develop new and improved models that allow the study of the foot during gait. The difficulties arising in foot modelling are inherent in its complex composition, thus most models simplify the foot geometry, structure, materials and kinetic analysis. This thesis presents a new approach towards foot modelling, combining readily available non-invasive methodologies to develop multi-segment foot models. This research helps in the in-depth understanding of the effects of changes in structure and shape of the foot brought about by diabetes and in the evaluation of the effects of interventions and long-term rehabilitation. Intermediate results are presented in order to establish the reliability of the proposed methods, developing first a new method for simultaneous plantar pressure and gait study. New approaches to muscle-tendon length and moment arm measurement are tested and validated, following an analysis of different pennation angle assumptions for force production assessment. Both extrinsic and intrinsic muscles are included in the model using the Hill muscle model. Stiffness and damping parameters are estimated on a per-subject basis. In order to model the soft tissue, which is of particular interest in diabetic patients, a model consisting of a system of parallel spring and damper, is proposed. Parameters are presented for 15 subjects with the purpose of characterising the properties of the soft tissue under the calcaneus (heel pad), metatarsal heads and hallux. A further analysis is provided by simulating different diabetic foot injuries and comparing their effect in joint range of movement and moment and soft tissue. Combined, these studies produce a complete subject-specific musculoskeletal and soft tissue model that enhances our understanding of both normal and altered gait.