Resilient Multi-Axial Ankle Foot Prosthesis for Gait Stability
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Solution Overview
Problem
Existing prosthetic feet lack the ability to mimic the natural multiaxial movement and energy return of a human foot, leading to inadequate stability and comfort during various phases of gait, particularly at heel strike, mid-stance, and toe-off.
Innovation Solution
A prosthetic foot design featuring a resilient multi-axial ankle with a compressible and durable ankle member sandwiched between stiffer elements, incorporating a gap filled with resilient material and a unique structural configuration that allows for progressive stiffness and natural rollover, including a split heel and varying sole stiffness to guide the center of pressure effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a resilient ankle member is sandwiched between stiffer elements to allow multiaxial movement, then the natural-feeling toe-off and rollover are improved, but the stability at heel strike deteriorates
Solution Approach 1:
The prosthetic foot is divided into distinct functional zones: a resilient ankle member for toe-off movement, a rigid heel strike plate for stability, and a progressive stiffness sole. This segmentation allows each zone to independently optimize its function without compromising others.
Solution Approach 2:
Different regions of the prosthetic foot have different stiffness properties tailored to their specific functions: the heel strike area uses rigid materials for stability, the mid-sole uses progressively stiffer materials for controlled rollover, and the toe-off area uses resilient materials for natural movement.
2Use of energy by moving object
If spring inserts are added to the ankle block to increase rigidity, then the energy storage and return characteristics are improved, but the device complexity increases
Solution Approach 1:
The spring mechanism is integrated directly into the ankle block structure itself, eliminating the need for separate spring assemblies. The ankle block serves dual functions as both a structural connector and an energy storage element.
Solution Approach 2:
The ankle block uses composite construction combining rigid structural materials with resilient spring elements, creating a unified component that provides both structural integrity and energy storage capability.
3Adaptability or versatility
If the ankle member completely separates the lower and upper elements, then the multiaxial movement capability is improved, but the stress on securing members increases
Solution Approach 1:
Resilient material is placed in the gap between the adapter and upper element to act as a stress-absorbing intermediary. This material allows the elements to move independently while distributing loads and reducing peak stresses on securing members.
4Duration of action of moving object
If a gap is left between the adapter and upper element, then the progressive stiffness during rollover is improved, but the structural integrity deteriorates
Solution Approach 1:
Resilient material fills the gap between the adapter and upper element, serving as a mediator that maintains structural continuity while allowing progressive compression during rollover. This material bonds both surfaces together while providing controlled compliance.
Solution Approach 2:
The resilient material's compression characteristics are engineered to provide progressive stiffness: initially compliant to allow gap closure and smooth rollover, then progressively stiffer as compression increases to maintain structural integrity under full load.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The design provides enhanced stability at heel strike, progressive support during mid-stance, and natural-feeling toe-off, reducing stress on components and improving overall gait dynamics with smooth rollover and energy return.
Implementation Method 1
A gap exists between a lower front edge of the adapter and the upper surface of the upper element. The gap contains a resilient material.
Implementation Method 2
The ankle member is positioned between the lower and upper elements, and completely separates the lower element from the upper element such that the lower element does not contact the upper element.
Implementation Method 3
The spring inserts increase the rigidity of the foot and alter the energy storage and return characteristics thereof.
Data Source
AI summary
The present foot prosthesis includes various structural features that provide the foot with advantageous rollover properties. In certain embodiments, the foot guides rollover toward the medial side. For example, an asymmetrical upper element and a correspondingly shaped resilient ankle member support more of the wearer's weight on the lateral side as the foot rolls over. In another embodiment, stiffeners added to the resilient ankle member increase the stiffness on the lateral side relative to the medial side. In certain other embodiments, the foot provides progressively increasing support from mid stance through toe off. For example, a gap between the resilient ankle member and the lower element closes during the later portion of the wearer's gait. The closing gap increases a contact area between the resilient ankle member and the lower element, providing progressively increasing support. In another embodiment, the foot includes a gap between a lower front edge of an attachment adapter and the upper element. The gap may be filled with a resilient material.