Knee Prosthesis Stop Device Prevents Dislocation
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Solution Overview
Problem
Existing knee joint endoprostheses are prone to dislocation due to insufficient ligament stability, requiring excessive distraction during implantation, which can further damage the joint capsule and stabilizing tissues.
Innovation Solution
A knee joint endoprosthesis design featuring a stop device that limits movement of pivot bearing elements relative to each other in both proximal and distal directions, ensuring the femoral and tibial components remain connected, with a second pivot bearing element allowing defined luxation and increased mobility, and a modular design for optimal fit and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rotatably mounted pin is used to connect femoral and tibial components, then the knee joint can achieve flexion/extension movement, but the knee joint is prone to dislocation due to insufficient ligament stability
Solution Approach 1:
The connection device is divided into multiple functional elements: a first pivot bearing element for flexion/extension movement, a second pivot bearing element for rotational movement, and a connecting device with distal and proximal stops. This segmentation allows each element to perform its specific function while collectively preventing dislocation.
Solution Approach 2:
The connecting device acts as an intermediary mechanism between the femoral and tibial components, providing controlled movement through the pivot bearing elements while preventing unwanted dislocation through the stop device. The stop device serves as a mediator that limits the range of motion to safe parameters.
2Ease of manufacture
If excessive distraction is applied during implantation to connect components, then the components can be coupled together, but the joint capsule and stabilizing soft tissue are further damaged
Solution Approach 1:
The connection device is designed with integrated stops and pivot bearing elements that guide the assembly process. The distal stop prevents over-distraction during implantation, while the proximal stop ensures proper positioning. This preliminary design of protective features eliminates the need for excessive distraction forces during surgery.
3Object-affected harmful factors
If the femoral and tibial components are made shorter to reduce distraction needs, then implantation damage is reduced, but the stability and load-bearing capacity may be compromised
Solution Approach 1:
The load-bearing function is extracted from the length of the components and transferred to the connection device with its integrated stop and pivot bearing elements. This allows the components to be shorter while maintaining stability through the mechanical guidance and limitation provided by the connection device.
Solution Approach 2:
The connection device combines multiple functional features (pivot bearing elements, stops, and connecting structures) into a composite mechanical system that provides both stability and movement control. This composite approach allows shorter components to achieve the same stability as longer components would provide through geometry alone.
4Reliability
If a stop device is added to limit pivot bearing element movement, then dislocation is prevented, but the device complexity increases
Solution Approach 1:
The stop device is merged with the existing connection device structure, combining the stop features with the pivot bearing elements and connecting structures. This integration ensures that the stop device does not add separate, independent complexity but rather enhances the existing mechanism with protective functionality.
Data Source
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AI summary
The prosthesis (10) has a meniscal component (16) movably supported between a tibial component (14) and a femoral component (12). A connecting device (18) connects the tibial component with the femoral component in an articulated manner. The connecting device defines a connection position in which the tibial component and the femoral component are undetachably connected with each other. A bearing sleeve (98) is made of a plastic such as Polyether ether ketone, and the meniscal component is made of polyethylene.