Modular Elbow Prosthesis Retaining Mechanism
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Solution Overview
Problem
Conventional linked and unlinked elbow prostheses face challenges in assembly accuracy and cost due to the need for precise hole drilling and limited joint space, and unlinked designs have difficulties with pin removal for bearing replacement.
Innovation Solution
A modular elbow prosthesis with a stem structure and articulating components featuring C-shaped body portions and retaining mechanisms, including extension portions and anti-rotation patterns, that interlock to inhibit translation and rotation, allowing for secure assembly and potential conversion between unlinked and linked configurations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional linked elbow prosthesis uses a retaining pin requiring precise hole drilling, then assembly accuracy is improved, but manufacturing cost and surgical time increase
Solution Approach 1:
The prosthesis is divided into separate modular components (humeral stem, ulnar stem, bearing component) that can be assembled without requiring precise pre-drilled holes. The retaining pin is eliminated in favor of a simpler insertion-based assembly method where components are placed into receptacles and secured with a single pin through pre-formed holes that do not require precise alignment.
Solution Approach 2:
The humeral and ulnar stems are prepared with receptacles and alignment features before surgery. The bearing component is pre-formed with a recess that receives the retaining pin. This preliminary preparation eliminates the need for precise intraoperative hole drilling and alignment, reducing surgical complexity and cost.
2Manufacturing precision
If conventional linked elbow prosthesis uses a retaining pin through the humerus, then assembly accuracy is improved, but device complexity increases
Solution Approach 1:
The prosthesis components are segmented with dedicated receptacles and alignment features. The humeral stem has a receptacle for the bearing component, and the ulnar stem has a receptacle for the bearing component. This segmentation allows each component to be assembled independently with simple pin insertion rather than complex multi-step alignment procedures.
Solution Approach 2:
The complex retaining pin assembly mechanism is extracted and replaced with a simpler pin insertion system. The retaining pin is removed from the yoke structure and replaced with a simple pin that passes through pre-formed holes in the bearing component to secure it to the stem. This extraction simplifies the overall assembly process while maintaining alignment accuracy.
3Ease of operation
If unlinked elbow prosthesis uses a transverse retaining pin, then ease of assembly is improved, but ease of repair deteriorates
Solution Approach 1:
The bearing component is segmented as a separate, removable module from the stems. The retaining pin is positioned to allow easy removal of the bearing component from either side, enabling straightforward replacement if needed. The modular design with dedicated receptacles allows the bearing to be independently accessed and replaced without disturbing the stem structures.
Solution Approach 2:
Instead of having the pin fixed in position making removal difficult, the pin arrangement is inverted to allow easy access from multiple directions. The retaining pin is positioned and oriented to enable simple removal of the bearing component, and the design allows the pin to be inserted from either side of the joint, providing flexibility for repair procedures.
4Manufacturing precision
If conventional prosthesis requires large hole drilling through the humerus, then assembly accuracy is improved, but loss of substance increases
Solution Approach 1:
The prosthesis components are segmented with receptacles that are formed as integral parts of the stems rather than requiring separate large holes. The bearing component has a recess that is part of its structure, eliminating the need for large bone removal. This segmentation allows for precision alignment through the receptacle geometry without sacrificing bone substance.
Solution Approach 2:
Local receptacles and alignment features are created at specific locations on the stems and bearing components rather than requiring large general bone removal. The precision alignment is achieved through the local geometry of the receptacles and the fitting of the retaining pin, minimizing the overall bone substance that needs to be removed while maintaining the required alignment precision.
Data Source
AI summary
An elbow prosthesis according to the present teachings can include a stem structure and an articulating component. The stem structure can be operable to be positioned in a bone of a joint. The stem structure can include a stem portion that is operable to be positioned in the bone and a C-shaped body portion having a first retaining mechanism formed thereon. The articulating component can have a second retaining mechanism formed thereon. One of the first and second retaining mechanisms can comprise an extension portion and a first anti-rotation portion. The other retaining mechanism can comprise a receiving portion and a second anti-rotation portion. The articulating component can be advanced from an insertion position to an assembled position, such that the first and second mechanisms cooperatively interlock to inhibit translation and rotation of the articulating component relative to the C-shaped body portion of the stem structure.