Artificial Ankle Joint with Segmented Arc Surfaces
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Solution Overview
Problem
Current artificial ankle joints have a lower ten-year survival rate due to increased stress, wearing, and loosening caused by inadequate coordination with bone and ligament structures, resulting in limited error tolerance and motion restrictions during surgery.
Innovation Solution
The design of an artificial joint with a first and second joint assembly featuring convex and concave arc surfaces that allow for relative sliding, inversion, eversion, internal, and external rotation, reducing stress and preventing loosening by incorporating a gap between the contacting surfaces, which can be adjusted during surgery to accommodate individual bone sizes and motion requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional artificial ankle joint design is used, then surgical precision can be maintained, but stress concentration and loosening occur due to inadequate coordination with bone and ligament structures
Solution Approach 1:
The contacting surface is divided into multiple independent convex arc surfaces (first, second, and third convex arc surfaces) on the first joint assembly that correspond to multiple concave arc surfaces on the second joint assembly. This segmentation allows different regions of the contacting surface to independently accommodate variations in bone and ligament structures, distributing stress across multiple contact points rather than concentrating it at a single interface, thereby reducing stress concentration and improving reliability.
Solution Approach 2:
Each convex arc surface on the first joint assembly is designed with specific curvature and orientation to match the local anatomical requirements of the corresponding concave arc surface on the second joint assembly. The different convex arc surfaces are configured with varying radii and angles to provide localized adaptation to different regions of the ankle joint, allowing optimal stress distribution in each specific area while maintaining overall coordination with surrounding bone and ligament structures.
2Adaptability or versatility
If motion allowance is increased in the artificial ankle joint design, then fault tolerance is improved, but coordination with bone and ligament structures becomes more challenging
Solution Approach 1:
The multiple convex arc surfaces and corresponding concave arc surfaces are configured to enable dynamic motion adaptation. The joint assembly can accommodate inversion, eversion, internal rotation, and external rotation movements through the relative motion between the convex and concave surfaces. This dynamic design allows the joint to adapt to varying motion requirements and fault conditions while maintaining precise coordination through the geometric relationship between the arc surfaces, effectively increasing motion allowance without compromising manufacturing precision.
3Reliability
If a gap is incorporated between contacting surfaces, then stress is reduced and loosening is prevented, but the complexity of the joint assembly increases
Solution Approach 1:
The gap between the convex arc surfaces and concave arc surfaces is designed with curved transitions rather than sharp angles or flat surfaces. The convex and concave surfaces are configured with complementary curvatures that guide the relative motion between joint assemblies. This curved geometry distributes stress smoothly across the contacting surfaces, preventing stress concentration at the gap edges, while the spherical curvature design maintains aesthetic appearance and simplifies manufacturing compared to alternative gap configurations.
Data Source
AI summary
An artificial joint includes a first joint assembly and a second joint assembly. The first joint assembly is adapted to be connected to a first bone and has a first contacting surface, wherein the first contacting surface includes a first convex arc surface, a second convex arc surface, and a third convex arc surface. The second joint assembly is adapted to be connected to a second bone and has a second contacting surface, wherein the second contacting surface is in contact with the first contacting surface and includes a first concave arc surface, a second concave arc surface, and a third concave arc surface, and the first concave arc surface, the second concave arc surface, and the third concave arc surface respectively correspond to the first convex arc surface, the second convex arc surface, and the third convex arc surface.