Stabilizing Knee Prosthesis With Coincident-Axis Box and Post
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Solution Overview
Problem
Existing knee replacement implants do not provide a high degree of constraint while preserving natural interaction between femoral and tibial components over a range of motion, and modifying constraint levels is costly and tedious.
Innovation Solution
A knee implant system with a femoral component and tibial component that includes a central box and post design, allowing for a constrained total stabilizing knee joint with a coincident axis of rotation over a range of motion, and an adaptable knee implant kit for easy modification between varying constraint levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a hinge-based constraint implant is used to provide high constraint, then stability is improved, but natural interaction between femoral and tibial components is lost
Solution Approach 1:
The box central surface includes a concave curved surface portion that provides localized constraint only when needed (in extreme flexion positions), while allowing natural motion in other positions. This local quality approach applies constraint selectively rather than continuously, resolving the contradiction between stability and natural interaction.
2Stability of the object's composition
If an existing cruciate retaining implant is modified to a more constrained implant, then constraint is improved, but cost and complexity increase
Solution Approach 1:
The implant system allows dynamic adjustment of constraint levels through interchangeable inserts (e.g., different tibial inserts with varying post configurations). This enables modification from cruciate retaining to more constrained designs without replacing the entire implant, reducing complexity and cost while maintaining the ability to adapt to changing clinical needs.
3Reliability
If a more constrained implant is designed to provide stability, then reliability is improved, but adaptability decreases
Solution Approach 1:
The implant is segmented into modular components including interchangeable tibial inserts with different post configurations (e.g., post with convex curved surface, post with flat surface). This segmentation allows the same femoral component to work with multiple tibial inserts, providing both high reliability through constrained design when needed and adaptability through component interchangeability.
Data Source
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AI summary
A knee joint prosthesis (100, 600, 700, 1000) includes a femoral component (102, 602, 702, 1002) and a tibial component (104, 604, 704, 1004, 1104). The femoral component includes a medial condylar articulation surface (107, 607, 707), a lateral condylar articulation surface (109, 609, 709) and a central box (106, 606, 706, 1006) therebetween, the central box being enclosed on a bone-facing side (108) of the femoral component and open on a tibial-facing side of the femoral component. The tibial component including a medial tibial articulation surface (134, 634, 734), a lateral tibial articulation surface (136, 636, 736) and a post (112, 612, 712, 1012, 1112) therebetween, the post being disposed within the central box of the femoral component. A concave curved surface portion (101, 601, 701) of the box travels along a convex curved surface portion (142, 642, 742, 1042, 1142) of the post over a range of motion of the tibial component relative to the femoral component such that an axis of rotation of the box of the femoral component and the post of the tibial component is coincident over the range of motion.