Modeling and simulation of transfemoral amputee gait

Abstract

Contemporary prosthetic solutions vary widely, from purely passive devices to microprocessor-controlled powered devices. Controlling the prosthesis requires extensive training sessions for the user, and still relies on some manual operations by the user to ensure proper mode transitions. The trial-and-error nature of such training is burdensome for both the user and clinical team, thus limiting the potential of this technology to be clinically adopted. In this thesis, the full-body musculoskeletal model of the transfemoral amputee that inputs subject-specific anatomy, biomechanics, and muscle electrophysiology to simulate the human movement of the user was successfully delivered as a potential solution. The developed model was then used to control the prosthesis by allowing a different prosthesis control strategy that can mimic the control mechanism of the C-Leg prosthesis to be applied. In this approach, a torque was applied to the knee prosthesis of the simulated amputees to assess the effect of the muscle performance and the ability to develop a control pattern to artificially produce the desired movement. The currently existing neuromuscular model (23-degree-of freedom, 92 muscles model) of the human upper and lower body was adapted to include an amputee's leg with a prosthesis. The modified model was validated by acquiring 3D motion analysis data and Electromyography (EMG) from 15 able-bodied limbed individuals and two transfemoral amputees during a variety of locomotor activities. The simulated joint kinematics closely tracked experimental quantities with coordination error of less than 2 degrees for hip position and less than 1 degree for knee position during all gait speeds. In Computed Muscle Control (CMC) results, the timing of muscle contractions predicted by CMC was similar to those exhibited by EMG signals measured during the experiment for both able bodied and amputee participants (showed a good agreement between the measured EMG and both muscle activity and muscle force for both able bodied and amputee participants). The approach of the added knee moment had a positive effect on some of the lower body joint while no effect on others. Therefore, it is necessary to apply different scenarios of the approach to allow for variable amounts of added knee moment and quantify how the lower body joint and muscles respond under these variable values. Moreover, it would be beneficial to expand the approach to include the mechanics of the prosthesis ankle joint.