Apto-Ankle: Passive, Compliant Ankle with Enhanced Energy Storage and Return in Gait

PROJECT SUMMARY The Apto-Ankle project will create a novel low-cost, lightweight, unpowered passive compliant ankle that addresses the weaknesses of currently marketed hydraulic passive ankles by combining +/-10° of plantar and dorsiflexion with a gait dependent toe lock to provide energy storage and return, all without use of microprocessors or powered components. Appropriate for DMERC K-2 and K-3 individuals with transtibial limb loss, it will help them more efficiently and comfortably ambulate in their community environment, providing the documented benefits of passive compliant ankles with a forefoot loading phase transition from energy dissipation in the ankle to energy storage in the dynamic energy storage and return foot. This approach addresses the weaknesses of existing passive compliant ankles without adding the power or complexity of microprocessor-controlled ankles. By mechanically controlling dynamics based on parameters derived from normal ambulation and without additional cognitive burden on users, this design provides a gait and environmentally appropriate transition during stance from compliant, energy dissipation to dynamic energy storage and return. The Apto-Ankle project has three primary aims: 1) design and construction of 3 prototype Apto-Ankles to test adjustable components that determine gait dependent behaviors, both on the bench and on users, 2) bench testing to assess ankle performance against design specifications and confirm safety and robustness prior to clinical evaluation and 3) evaluate the proof-of-concept ankle by appropriately fitting it to users and evaluating it in a gait lab. Primary assessment outcomes will include objective measurable gait parameters and subjective clinical survey feedback from users. Successful design and implementation of the Apto-Ankle will enable individuals with transtibial limb loss to more easily ambulate in their normal community environment, increase stability, and increase amount of and comfort with ambulation in their typical activities and surroundings. The commercial application of Apto-Ankle is a low-cost, K-2 and K-3, lightweight prosthetic ankle that encourages ambulation, independence, and quality of life for transtibial prosthesis users.