Development of Powered Transtibial Prosthesis: Validation of Prototype of Passive Bi-Articular Exoskeleton

People with transtibial amputation face a challenge of natural gait because in the absence of bi-articular muscle action during push-off. Currently used uni-articular actuators are inadequate to fully simulate the function of ankle plantarflexors for aiding push off. Therefore, present study aimed to develop a biarticular prototype for powered trans-tibial prosthesis informed by the difference in gait biomechanics between the unaffected limb and the prosthetic limb in for individuals with transtibial amputation. A passive bi-articular exoskeleton was developed, incorporating actuators that simulate natural function of gastrocnemius muscle to provide torque to knee and ankle joints during walking. This powered device was tested on one healthy participant. The results indicated substantial reduction in gastrocnemius muscle activity during walking with orthosis compared to walking without orthosis. The gastrocnemius muscle demonstrated 76.32% reduction in average root mean square value on S-EMG (from 14.54 μV during barefoot walking to 3.44 μV with orthosis). Hamstring muscle activity decreased by 39.92%, while the quadriceps and tibialis anterior demonstrated 15.98% and 35.4% reduction respectively. Gluteus maximus demonstrated 27.72% lesser activity compared to barefoot walking. The preliminary results of the passive bi-articular exoskeleton demonstrated significant reduction in muscle activity of gastrocnemius and improved gait efficiency, suggesting that passive bi-articular exoskeleton can inform design of a powered transtibial prosthesis, which holds potential in minimizing the biomechanical differences between prosthetic limb and unaffected limb during level walking in people with transtibial amputation.