Hemispherical Liner Lip Undercut for Dual-Mobility Head Constraint
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Solution Overview
Problem
Existing orthopedic prosthesis solutions require additional components or structural modifications to prevent dislocation of the artificial femoral head, limiting versatility and freedom of movement.
Innovation Solution
A hemispherical-shaped liner with a lip projecting beyond the equatorial line and an extended portion to create an undercut edge, allowing for secure containment of a dual-mobility head without additional components, ensuring stable articulation and preventing dislocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional components or structural modifications are used to prevent dislocation of the artificial femoral head, then reliability is improved, but device complexity increases
Solution Approach 1:
The invention merges the dislocation prevention function into the liner itself by adding a lip structure that projects beyond the equatorial line. This eliminates the need for separate retainer rings or additional components, as the lip integrally provides the constraint function while maintaining structural simplicity.
Solution Approach 2:
The liner's lip structure self-constrains the artificial femoral head through its geometric configuration. The undercut edge created by the lip projecting beyond the equatorial line automatically prevents dislocation without requiring external active control mechanisms or additional components.
2Reliability
If the liner height is increased to prevent dislocation, then reliability is improved, but ease of operation deteriorates
Solution Approach 1:
Instead of increasing liner height in the vertical direction, the invention uses the lip structure that extends radially beyond the equatorial line. This dimensional approach creates an undercut edge that provides dislocation prevention through lateral constraint rather than vertical height, preserving insertion freedom.
Solution Approach 2:
The lip projects only partially beyond the equatorial line, extending just enough to create the undercut edge necessary for constraint. This partial extension provides sufficient dislocation prevention without excessive material or structural addition that would impede insertion.
3Reliability
If projections are added to the liner to constrain the artificial head, then reliability is improved, but adaptability deteriorates
Solution Approach 1:
The lip structure creates an asymmetric undercut edge that provides constraint in the dislocation direction while maintaining symmetry and freedom in the insertion direction. The asymmetric geometry of the lip projecting beyond the equatorial line selectively constrains movement without restricting insertion adaptability.
Data Source
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AI summary
The invention concerns an improved prosthesis component (1), for example an acetabular or glenoid cup (2) of an orthopedic prosthesis (12) or a liner constrained inside the cup (2) and intended to receive a spherical joint (4, 5) of an artificial femoral or humeral head (10), said component being substantially hemispherical- shaped with a base (6) defining the lower edge of the liner (1). Advantageously, according to the invention, the insert or liner (1) comprises a lip (8) projecting beyond the base (6); in other words, the lip (8) projects beyond the equatorial line of the hemispherical form of the liner (1) partially occupying the missing hemisphere of the hemispherical form to define an undercut edge, as well as an extended portion (20) of said lip (8) by at least one tract of said base (6) in order to receive and hold a dual-mobility head in the spherical segment (9) inside the component (1, 1').