Ceramic Cup Insert Back-Side Collision for Hip Prosthesis
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Solution Overview
Problem
Current hip joint prostheses face issues with premature failure due to uneven stress distribution and contact between the socket insert and hip socket, leading to inadequate clamping force and potential lifting of the socket insert, especially under load, which can result in malfunction and failure.
Innovation Solution
The design features a gap between the socket insert and hip socket that decreases with load, ensuring controlled surface contact beneath the clamping cone, reducing tensile stresses and increasing the breaking load by coordinating radial contours for tangential transitions and identical geometric elements from the cone end to the pole.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If a gap is provided between the socket insert and hip socket in the back-side region, then the clamping force increases unhindered with increasing load, but the components may experience point contact under asymmetrical loads leading to premature failure
Solution Approach 1:
The invention applies different geometric characteristics to different regions of the components. The back-side region features identical radial contours with tangential transitions, while the equatorial region maintains the clamping connection geometry. This local differentiation ensures surface contact in the back-side region without compromising the clamping force mechanism.
Solution Approach 2:
The invention employs curved surfaces with identical radial contours in the back-side region of both the socket insert and hip socket. These curved surfaces are designed to mate tangentially, ensuring that contact occurs over a surface area rather than at discrete points, thereby distributing stresses evenly and preventing premature failure.
2Force
If contact occurs between the socket insert and hip socket in the back-side region, then the clamping force is relieved and remains at the lowest level, but the socket insert may be lifted from the hip socket under tensile forces
Solution Approach 1:
The curved surfaces with identical radial contours in the back-side region are designed to contact tangentially when the socket insert is properly clamped. This geometric design ensures that contact occurs only when adequate clamping force is present, preventing premature contact that would relieve clamping force, and simultaneously preventing lifting by distributing loads evenly across the contact surface.
Solution Approach 2:
The invention changes the geometric parameters of the back-side region by implementing identical radial contours with tangential transitions. This parameter modification ensures that the gap closes in a controlled manner under load, allowing contact to occur at the appropriate moment when clamping force has been established, thereby maintaining both force transmission and coupling stability.
3Stress or pressure
If point contact occurs between the socket insert and hip socket, then localized stress increases lead to overload and premature failure, but surface contact cannot be ensured with present geometries
Solution Approach 1:
The invention applies specific geometric characteristics (identical radial contours with tangential transitions) only to the back-side region of the components. This localized geometric design ensures that even with normal manufacturing tolerances, the contact in this region occurs over a surface area rather than at points, distributing stresses evenly without requiring excessive manufacturing precision.
Data Source
AI summary
The invention relates to an acetabular cup (4) and a cup insert (3) for a hip joint prosthesis (12), wherein the cup insert (3) is coupled to the acetabular cup by means of a clamping cone (5) of a conical clamping device in the equatorial region (7) of the two components (3, 4) and, in the unloaded state of the cup insert (3), a gap (8) is provided between the two components (3, 4) below the clamping cone (5) to the pole (6), said gap being delimited by the radial contours of the two components (3, 4). In order to reduce the tensile stresses in the cup insert, the radial contours of the two components (3, 4) have identical geometric elements in the same order, starling front the lower cone end (9) to the pole (6), and tangential or substantially tangential transitions exist between the geometric elements.