Inverted Joint Prosthesis Design for Radial Head Stability
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Solution Overview
Problem
Prior joint prostheses for the articulation of bones, particularly the radial head, suffer from stiffness, misalignment issues, and ligament wear due to their design, leading to reduced mobility and potential dislocation, as well as injury to the anular ligament.
Innovation Solution
The design is inverted with a projecting engagement member on the articular head element and a cavity on the first bone engaging element, shifting the center of rotation closer to the first bone, allowing for better movement compensation and preserving ligament structures, featuring a stem component with a receptacle component and a telescopic mechanism for intraoperative adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the cavity is provided on the radial head component and the projecting engagement member is provided on the stem component, then the prosthesis structure is simplified, but the prosthesis becomes stiff and prohibits further movement when deflection occurs
Solution Approach 1:
The patent inverts the conventional design by placing the projecting engagement member on the articular head element (replacing the cavity) and the cavity on the first bone engaging element (replacing the projecting member). This inversion allows the articular head element to rotate freely within the cavity, enabling movement compensation while maintaining structural simplicity.
2Ease of manufacture
If the stem component is anchored within the radius bone with a slight misalignment, then the prosthesis can be implanted, but the distal centre of the radial head component cannot compensate the misalignment and dislocation may occur
Solution Approach 1:
The patent introduces dynamic movement capability by allowing the articular head element to rotate freely within the cavity on the first bone engaging element. This dynamic design enables the distal centre to compensate for implantation misalignments through rotational movement, maintaining articulation stability even when the stem is anchored with slight deviations from optimal positioning.
3Stability of the object's composition
If the anular ligament supports the prosthesis, then the prosthesis is positioned stably, but recurrent stretching of the ligament causes wear and early relaxation of the prosthesis
Solution Approach 1:
The patent inverts the movement mechanism so that the articular head element rotates within the cavity rather than the cavity rotating within the head element. This inversion shifts the center of rotation and reduces the leverage effect on the anular ligament, minimizing recurrent stretching and wear while maintaining stable prosthesis positioning.
4Stability of the object's composition
If the anular ligament runs around the radial head, then the radial head is supported, but the ligament may be injured through being crushed or clamped when the radial head component performs movements
Solution Approach 1:
The patent inverts the rotation mechanism, placing the cavity on the first bone engaging element and the projecting engagement member on the articular head element. This inversion changes the movement dynamics and reduces the risk of the anular ligament being crushed or clamped during radial head component movements, while still providing adequate support.
Data Source
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AI summary
A joint prosthesis for the articulation of a first bone with respect to a second bone of a human patient, comprising a first bone engaging element (18) being configured to be arranged and supported on the end of said first bone that faces said second bone, and an articular head element (16) having an adjoining portion (25) adapted to cooperate with the end of the second bone that faces said first bone, is characterized in that said articular head element (16) includes at its end that faces said first bone a projecting engagement member (17) and that said first bone engaging element (18) includes a cavity (28) for receiving said projecting engagement member (17).