Fixed-Bearing Knee Prosthesis Rail Constraint System
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Solution Overview
Problem
Fixed-bearing knee prostheses face challenges in securely attaching the tibial bearing to the tibial tray without allowing rotational or lateral movement, which can lead to instability and potential dislodgment during joint articulation.
Innovation Solution
A fixed-bearing knee prosthesis design featuring a tibial tray with a peripheral rail and retaining rail system, where the bearing is snap-fit secured with tabs and undercuts, ensuring a tight fit and preventing movement in anterior/posterior and medial/lateral directions, and reducing rotational micromotion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a simple bearing attachment method is used, then ease of manufacture is improved, but reliability deteriorates due to rotational or lateral movement and potential dislodgment
Solution Approach 1:
The bearing is nested within the tibial tray structure, with the peripheral rail extending upwardly from the tray platform to receive and constrain the bearing. The bearing sits within the confines formed by the peripheral rail and retaining rail, creating a nested configuration that secures the bearing while maintaining a relatively simple overall structure.
Solution Approach 2:
The attachment mechanism utilizes multiple dimensional constraints: the peripheral rail provides lateral and anterior/posterior constraints, while the retaining rail extending posteriorly adds a third dimensional constraint. This multi-dimensional approach prevents rotational and lateral movement without requiring complex multi-component fastening systems.
2Reliability
If a secure attachment mechanism with peripheral rail and retaining rail is used, then reliability is improved by preventing movement and dislodgment, but device complexity increases
Solution Approach 1:
The peripheral rail and retaining rail are merged into a single integrated structure that extends from the tibial tray. Rather than using separate fastening components, the rails are combined into one continuous element that provides multiple constraints simultaneously, reducing the number of parts while maintaining attachment stability.
Solution Approach 2:
The peripheral rail serves multiple functions: it provides lateral constraint, anterior/posterior constraint, and rotational constraint through its upward extension and configuration. The retaining rail similarly provides multi-directional constraint while also serving as part of the overall structural framework, reducing the need for additional specialized components.
Data Source
AI summary
A fixed-bearing prosthesis includes a femoral component having a medial condyle surface and a lateral condyle surface. The knee prosthesis also includes a bearing having a medial bearing surface configured to articulate with the medial condyle surface of the femoral component, and a lateral bearing surface configured to articulate with the lateral condyle surface of the femoral component. A tibial tray is secured to the bearing. The tibial tray has a platform with an elongated stem extending downwardly from a lower surface thereof. A peripheral rail extends along at least an anterior section of the perimeter of the tray's platform. The peripheral rail extends upwardly from an upper surface of the platform. A retaining rail extends upwardly from the upper surface of the platform and posteriorly away from the peripheral rail.