The effect of prosthetic shape and stiffness on the biomechanics of people with lower limb amputation

Lower limb loss is a growing problem worldwide and is predicted to get worse. For example,  approximately 1% of the U.S. population are predicted to have limb loss by 2050, based on approximately 10% of the current population being at risk of amputation. People with lower limb amputation can regain their independence having lost biological structures crucial for human movement by utilising prosthetic devices. While mechanical and passive devices exist, lower limb amputees are often prescribed passive devices ranging from completely rigid representations (offering the best aesthetic replacement) to more expensive carbon-fibre based flexible options (offering greater independence and mobility). Despite individual movement patterns being heavily influenced prosthesis design and function, current practice for manufacturers is to prescribe uniformly shaped prostheses with the stiffness determined by categorising individuals based on height, weight, and physical activity. At present, the influence of prosthetic shape and stiffness on the biomechanics of lower limb amputees has been limited to lab-based experimental approaches. The limitation of controlling dependent variables in repeat-measure experimental approaches has led more advanced theoretical approaches being adopted to understand the cause and effect of dependent variables on the kinematics and kinetics of task-specific movement patterns. For example, forward-dynamics computer simulation models have been developed to investigate the limiting factors for a wide variety of maximal-effort sporting movements.  

This project aims to develop and apply a forward-dynamics simulation model to investigate the effect of prosthetic shape and stiffness on the biomechanics of lower limb amputees. Firstly, gold-standard motion analysis data will be collected of lower limb amputees completing different movement patterns, which will be used to investigate the modelling complexity required to represent the prosthetic and body. Secondly, individual-specific parameters of each participant will be determined and used to evaluate the ability of the simulation model to recreate the recorded movement patterns of lower limb amputees. Finally, the evaluated model will be optimised to investigate the effect of prosthetic size, shape, and stiffness on the biomechanics of lower limb amputee’s movement patterns. For example, how does prosthetic shape impact joint kinematics, what is the effect of prosthetic stiffness on whole body kinetics, or how do different individual, environmental or task constraints alter lower limb amputee’s movement patterns). These findings could impact health and well-being though aiding design to lower movement asymmetries and prescribing individual-specific protheses, as well as improving sport performance and legality via understanding the advantages prostheses provide in sport.