Proximal Radioulnar Joint Prosthesis with Ulnar Brace for Load Transmission
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Solution Overview
Problem
Current elbow joint prostheses, particularly for the proximal radioulnar joint, face issues with dislocation and inability to transmit axial loads when the radial head is damaged, especially if the annular ligament is also damaged, leading to limited mobility and weight-bearing capacity in the affected hand.
Innovation Solution
A proximal radioulnar joint prosthesis design that includes a ulnar brace member secured to the ulna with screws and a radial brace member with a stem rod press-fit into the radius bone, featuring a hemispherical ball for rotational and translational motion, which stabilizes the radius relative to the ulna and humerus, mimicking the natural joint interaction without excising the ulna and using cobalt chromium and ultra-high molecular weight polymer components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a standard radial head replacement prosthesis is inserted to replace the damaged radial head, then the radial head can be replaced, but the prosthesis may become dislocated from the proximal ulna and/or humerus and unable to transmit axial loads when the annular ligament is damaged
Solution Approach 1:
The prosthesis is divided into separate functional components: a radial head component for articulation, a radial stem for bone anchoring, and a ulnar brace member for stabilizing the ulna. This segmentation allows each component to independently perform its specific function, ensuring stable load transmission while accommodating ligament damage.
Solution Approach 2:
The ulnar brace member acts as an intermediary element that stabilizes the ulna bone and provides a secure attachment point for the radial head prosthesis. This intermediary structure compensates for the damaged annular ligament by mechanically reinforcing the joint, enabling reliable axial load transmission from the radius to the humerus.
2Ease of manufacture
If the annular ligament is damaged as part of the incident causing damage to the radial head, then the radial head can be replaced, but the prosthesis becomes dislocated and unable to transmit axial loads
Solution Approach 1:
The ulnar brace member is pre-formed with a specific geometry that allows it to be secured to the ulna bone before assembly with the radial head component. This preliminary preparation ensures that the stabilizing structure is in place before the radial head is inserted, preventing dislocation during the surgical procedure and ensuring long-term joint stability.
Solution Approach 2:
The prosthesis utilizes composite construction combining metallic components (radial head, radial stem, ulnar brace member) with polymer or bone cement materials for bone integration. This composite approach provides both the structural integrity needed for stability and the biological compatibility required for long-term durability, addressing both ease of manufacture and reliability concerns.
3Productivity
If the prosthesis is designed to transmit axial loads from the hand through the forearm to the humerus, then weight-bearing capability is restored, but the complexity of the prosthesis structure increases
Solution Approach 1:
The radial stem and ulnar brace member are designed as integrated components that work together as a single functional unit. The radial stem inserts into the radius bone while the ulnar brace member simultaneously stabilizes the ulna, merging two stabilization functions into one assembled structure. This merging reduces the number of separate components and simplifies the overall prosthesis structure while maintaining weight-bearing capability.
Data Source
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AI summary
A proximal radioulnar joint (lateral elbow) prosthesis (10) includes an ulnar brace member (12) to be secured to the outer surface of the ulna bone. The ulnar brace member defines a bearing surface (39) for supporting the radius. The prosthesis may also include a radial brace member (16) which cooperates with the ulnar brace member.