Development and Evaluation of a Novel Robotic Gait Simulator

Biomechanical research on living subjects is limited to what can be measured without causing pain or permanent damage to volunteers. Utilizing cadaveric, or post-mortem human surrogate (PMHS), models can allow for invasive measurements that could augment our understanding of the biomechanics of the foot and ankle complex. Dynamic gait simulators, which replicate tibia kinematics and the dynamic muscle forces that occur during gait on PMHS, have the potential to produce repeatable and biofidelic foot and ankle mechanics to permit such investigations. Therefore, the goals of this thesis were to 1) develop a novel robotic gait simulator, 2) to use the simulator to capture repeatable foot bone kinematics, 3) to assess how well the captured foot bone kinematics can predict realistic foot bone kinematics, and 4) to assess how much variation in response can occur when using the same inputs across different anthropometries. A simulator that utilizes a 6-degree of freedom serial robotic arm to prescribe tibia kinematics and an array of nine linear tendon actuators to control muscle forces, was developed to recreate biomechanically accurate gait in a PMHS model and address these goals. Then, through experiments on five PMHS, bony kinematics for nine different foot/ankle joints were recorded, The correlation and analysis (CORA) method was used to make quantitative comparisons of bony kinematics across multiple tests on the same subject (repeatability), between PMHS and volunteers (biofidelity) and across subjects (subject-specific effects). Output bone kinematics from repeated trials were found to be repeatable within a subject, to vary between subjects despite having similar generalized inputs, and to generally represent volunteer bone kinematics data. Utilizing this system as a foundation, future studies could investigate biomechanical changes resulting from orthopaedic implants, the effects of muscular deficiencies or diseases, and determine how active musculature affects the risks of traumatic injury.