Elbow Prosthesis Segmented Pivoting Mechanism
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Solution Overview
Problem
Current elbow prostheses face challenges in minimizing movement of supporting components and fasteners during articulation, which can lead to instability and wear, particularly under anatomical loads.
Innovation Solution
The design incorporates a humeral and ulnar component with a pivoting mechanism using a pin and fasteners that secure the components, along with elastomeric bearings and surface treatments to reduce wear and stabilize the prosthesis, allowing for anatomical articulation while minimizing movement and wear.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a hinge mechanism is used to enable pivoting movement between humeral and ulnar components, then articulation is restored, but movement of supporting components and fasteners occurs leading to instability and wear
Solution Approach 1:
The prosthesis is divided into distinct segments: articulating components (humeral and ulnar) that move, and supporting components (dorsal and volar supports with fasteners) that remain stationary. This segmentation allows articulation to occur at designated surfaces while preventing movement of the supporting structure, resolving the contradiction between ease of operation and reliability.
Solution Approach 2:
Articulating surfaces act as intermediaries between the moving humeral and ulnar components. These surfaces accommodate the pivoting motion while the supporting components remain fixed, enabling articulation without transmitting movement to the fasteners and supports, thus maintaining both ease of operation and reliability.
2Ease of operation
If a hinge mechanism is used to enable pivoting movement, then articulation is restored, but wear increases due to movement of supporting components and fasteners
Solution Approach 1:
The prosthesis separates wearing surfaces from supporting structures. Articulating surfaces are designed to accommodate motion and absorb wear, while supporting components (fasteners, supports) remain stationary and do not experience wear, thereby extending the overall duration of action and longevity of the implant.
Solution Approach 2:
The articulating surfaces serve as intermediaries that bear the wear from articulation movements. By positioning these surfaces between the moving components and the supporting structure, the design protects the fasteners and supports from wear, ensuring long-term durability and longevity of the prosthesis.
3Strength
If traditional fastening methods are used to secure components, then secure attachment is achieved, but micro-motion occurs leading to loosening over time
Solution Approach 1:
The supporting components (dorsal and volar supports with fasteners) are designed to be self-stabilizing through their geometry and engagement with the bone and articulating components. The supports create a stable framework that prevents micro-motion without requiring additional active retention mechanisms, ensuring both strong initial attachment and long-term resistance to loosening.
Solution Approach 2:
Instead of relying on fasteners alone to prevent micro-motion, the design inverts the approach by using the supporting components to create a stable framework that prevents movement before it occurs. The geometry of the supports and their engagement with the bone provide inherent stability that eliminates the need for excessive fastener tension, preventing micro-motion and loosening over time.
Data Source
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AI summary
An elbow prosthesis (100) that includes a humeral component (102) having a yoke (122), an ulnar component (104) having a head, a humeral bearing positionable in a base of the humeral component, an ulnar bearing assembly (108,110) configured to engage with the head, and a pin (116) extendable through the bearing assembly and the head. The pin can is extendable into first and second ears of the yoke to enable pivotable movement of the ulnar component relative to the humeral component. The elbow prosthesis includes a first fastener (112) insertable through the first ear of the yoke and configured to engage with the pin, and a second fastener (114) insertable through the second ear of the yoke and configured to engage with the pin.