Hinged Knee Prosthesis Yoke Assembly Stability
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Solution Overview
Problem
Existing knee joint prostheses face challenges in providing adequate stability, especially when anterior and posterior cruciate ligaments are damaged or deteriorated, and may require revision to account for bone loss and altered motion patterns.
Innovation Solution
A hinged knee joint prosthesis design featuring a femoral component, tibial component, bearing, and yoke assembly that limits rotation to a fixed angle, utilizing a biocompatible metal bearing support and a yoke that nests within a pocket to prevent lift-off, ensuring stability and secure attachment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional knee joint prosthesis is used, then the basic articulating motion is simulated, but adequate stability is not provided when ligaments are damaged or deteriorated
Solution Approach 1:
The prosthesis transitions from a static, fully fixed design to a dynamic system that allows controlled motion. The hinge mechanism permits rotation within a limited range (approximately 20 degrees) while maintaining stability through the bearing support structure that prevents excessive movement and lift-off.
Solution Approach 2:
The design changes the motion parameters by limiting rotation to a fixed angle rather than allowing full range of motion. The bearing support structure modifies the mechanical parameters by providing a rotation axis perpendicular to the axle axis, thereby controlling the kinematic behavior of the prosthesis.
2Ease of operation
If the yoke is allowed to rotate freely, then motion flexibility is improved, but hyperextension and instability occur
Solution Approach 1:
The bearing support structure preemptively prevents hyperextension by providing a mechanical stop at the desired rotation limit. The design incorporates a rotation limit feature that actively counteracts any tendency toward excessive rotation before instability can occur.
Solution Approach 2:
The bearing support acts as an intermediary element between the yoke and the femoral component, mediating the rotation motion. It allows controlled rotation while simultaneously preventing unwanted movements through its structural design that includes a rotation limit feature.
3Reliability
If the yoke is securely attached to prevent lift-off, then stability is improved, but rotation control becomes more complex
Solution Approach 1:
The bearing support structure combines multiple functions into a single integrated component: it provides the rotation axis, limits rotation to a fixed angle, and prevents lift-off of the yoke. This merging of functions simplifies the overall design while achieving multiple control objectives simultaneously.
Solution Approach 2:
The bearing support structure serves multiple purposes: it acts as a rotational hinge, a motion limiter, and a stabilizing element that prevents yoke lift-off. This multi-functional design eliminates the need for separate components for each function, thereby reducing overall device complexity.
Data Source
AI summary
A prosthesis for replacing a knee joint between a femur and a tibia can include a femoral component, a tibial component, a bearing and a yoke assembly. The yoke assembly can have a yoke disposed between the bearing and the femoral component and an axle having an axle axis. The axle can hingedly couple the yoke with the femoral component. Rotation of the femoral component about a rotation axis that is perpendicular to the axle axis causes concurrent rotation of the yoke about the rotation axis.