Knee Prosthesis Patellar Tracking via Fixed Helical Bearing
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Solution Overview
Problem
Current knee prostheses often fail to accurately replicate the natural position of the patella groove, leading to lateral patella maltracking, pain, and morbidity, and require complex mobile bearing designs that increase costs and surgical challenges.
Innovation Solution
A knee prosthesis design featuring a femoral component with medial and lateral condyles and an intercondylar groove, along with a tibial component with congruent and incongruent bearing surfaces that allow for antero-posterior movement, eliminating the need for a mobile bearing component by using a fixed bearing surface that is part-helical in shape to ensure correct patellar tracking and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the patella groove is laterally displaced and angulated to match natural knee anatomy, then correct patellar tracking is achieved, but the area of articulation for the lateral femoral condyle is reduced
Solution Approach 1:
The bearing surface is designed with different geometries in different regions: a first bearing surface region with a radius of curvature matching the femoral condyle for optimal articulation, and a second bearing surface region with different curvature characteristics. This local differentiation allows the groove to be positioned for correct patellar tracking while maintaining adequate articulation area through the tailored surface geometry.
2Reliability
If a mobile bearing component is used to accommodate femoral-tibial rotation, then correct patellar tracking is achieved, but device complexity and surgical implantation difficulty increase
Solution Approach 1:
The invention merges the functions of the bearing surface and the rotational accommodation mechanism into a single integrated tibial component. The bearing surface itself, through its specific geometry and curvature characteristics, accommodates femoral-tibial rotation without requiring a separate mobile bearing component, thereby simplifying the overall device structure while maintaining correct patellar tracking.
3Stability of the object's composition
If the bearing surface is highly congruent with the femoral condyle, then stability is improved, but antero-posterior movement is restricted
Solution Approach 1:
The bearing surface is designed with different congruency characteristics in different regions: a first region with high congruency to the femoral condyle that provides stability, and a second region with different geometric characteristics that allows controlled antero-posterior movement. This local differentiation enables the bearing surface to simultaneously provide stability and accommodate physiological movement ranges.
Data Source
AI summary
A knee prosthesis comprises a femoral component for securement to a femur, the femoral component defining medial and lateral J-shaped condyles and an intercondylar groove; and a fixed bearing tibial component for securement to a tibia, the tibial component having respective bearing surfaces which are fixed with respect to both a tibial engaging component and a stabilising peg for securing the tibial component to a tibia, the respective bearing surfaces being shaped to engage with said condyles both when the knee, in use, is extended and also over a range of flexion.