Arizona Patent of the Month – July 2021

Prosthetic feet are common medical devices, with attachment points either above or below the knee socket, depending on the amputation point. They are connected through a friction retention system which uses specialized socks or liners to maintain this. However, this system can be inefficient as the user’s limb will change volume and the friction force may be affected. Ability Dynamics, LLC has designed a vacuum based attachment system, which creates a more stable limb volume and improves both socket retention and limb health.

As a person walks, the prosthetic foot goes through a cycle, and the prosthetic creates an energy transfer to “put a spring in your step”. This gait cycle process flows from the heel-strike phase to mid-stance, to the toe-off phase. Following this, is a swing phase, where the leg lifts off the ground, swings forward, and begins the heel-strike phase again. The stance phase involves the movement of the user’s weight over the foot. This transfer of weight is the key point where a vacuum system is truly more efficient than a friction system. 

Their system uses a compressible member and chamber within it. The valve system that connects to the prosthetic socket of the user. As the user walks, the foot is designed to improve surface-to-foot contact through the gait cycle, which creates a smoother gait cycle and improves stability. The valve system has both a valve housing and an air return. An air chamber connects the valves and allows for air travel between them. As the user walks, the downward force forces the compressible member and chamber to force air out and up into the air passageway. As the foot is lifted and the downward force removed, the air flows back into the chamber. The system enhances the feel, fit, and function of the prosthetic foot.

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