Constrained Mobile Bearing Hip Assembly
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Solution Overview
Problem
Current orthopaedic hip implants face challenges in preventing dislocation of the femoral head during rotation, as existing designs lack effective mechanical constraints to secure the femoral head within the acetabular component.
Innovation Solution
The acetabular hip implant features a multi-axis locking mechanism with semi-annular and semi-circular projections and grooves, allowing rotation about specific axes while preventing rotation about others, ensuring the femoral head is securely constrained within the acetabular shell and inserts, thereby preventing dislocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a traditional ball and socket joint is used, then the hip implant allows rotation and range of motion, but the femoral head may dislocate during rotation
Solution Approach 1:
The acetabular component is divided into multiple segments: the acetabular shell, first insert, second insert, and femoral head. Each segment contains specific features (protrusions, recesses, channels) that work together to constrain movement. The segmentation allows independent optimization of each component while maintaining overall stability and range of motion.
Solution Approach 2:
The features defined in each component are asymmetric in design. The first insert has a first feature that is different from the second feature of the acetabular shell. The second insert has asymmetric features relative to the first insert. This asymmetry creates directional constraints that allow rotation about specific axes while preventing dislocation in other directions.
2Reliability
If mechanical constraints are added to prevent dislocation, then the stability of the femoral head is improved, but the complexity of the implant structure increases
Solution Approach 1:
The acetabular component uses a nested structure where the first insert is received within the acetabular shell, the second insert is received within the first insert, and the femoral head is received within the second insert. This nesting approach allows multiple constraint mechanisms to be integrated within a compact multi-layered structure, improving stability without excessive complexity.
Solution Approach 2:
The solution moves from simple planar constraints to three-dimensional constraints by defining features in multiple inserts at different depths. The first feature in the acetabular shell interacts with the second feature in the first insert, which interacts with the third feature in the second insert, creating a multi-dimensional constraint system that provides stability through spatial distribution of constraint features.
Data Source
AI summary
An acetabular hip implant and method includes an acetabular shell component having a first feature and a first insert having a second feature that cooperates with the first feature of the acetabular shell component and further includes a third feature. The implant further includes a second insert having a fourth feature that cooperates with the third feature of the first insert and further includes a fifth feature. A femoral head component includes a sixth feature that cooperates with the fifth feature. Interaction between the first and second features, between the third and fourth features, and between the fifth and sixth features mechanically constrains the acetabular hip implant to prevent dislocation of the femoral head during rotation.