Humeral Component Posterior Offset for Shoulder Prosthesis Rotation
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Solution Overview
Problem
Reverse shoulder joint prostheses face challenges in achieving increased range of joint articulation and reducing the risk of impingement between the epiphyseal part and cortical tissue, which can lead to undesirable weakening of the patient's tissue.
Innovation Solution
A humeral component with an elongate stem part and an epiphyseal part having a concave bearing surface, where the epiphyseal axis is offset posteriorly relative to the stem axis, creating a lever arm for increased internal rotation and reducing impingement risk by allowing a larger epiphyseal part to be implanted without compromising cortical tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the epiphyseal part is made larger to improve joint articulation range, then the range of motion is increased, but the risk of impingement with cortical tissue increases
Solution Approach 1:
The patent applies dimensional offset by shifting the epiphyseal axis posteriorly relative to the stem axis, creating a spatial separation that resolves the conflict between larger epiphyseal part size and impingement risk. This posterior offset creates additional space in the anterior-posterior dimension, allowing the epiphyseal part to be larger without contacting cortical tissue during rotation.
Solution Approach 2:
The posterior offset acts as an intermediary spatial buffer between the epiphyseal part and the cortical tissue of the humerus. This offset creates a protective zone that prevents direct contact and impingement, allowing the epiphyseal part to achieve greater size for improved articulation range without compromising bone tissue.
2Object-affected harmful factors
If the epiphyseal axis is offset posteriorly to reduce impingement risk, then cortical tissue is protected, but the device complexity increases
Solution Approach 1:
The patent introduces posterior offset as a dimensional solution that protects cortical tissue without requiring complex protective mechanisms. By utilizing the anterior-posterior dimension for offset, the design achieves tissue protection through simple geometric relocation rather than complex active protection systems.
3Ease of operation
If modular stem and epiphyseal parts are used with angular offset to improve internal rotation, then the range of movement is increased, but the manufacturing precision requirements increase
Solution Approach 1:
The patent moves from solely relying on angular offset in the transverse plane to incorporating posterior offset in the anterior-posterior dimension. This dimensional addition provides an alternative mechanism for improving internal rotation that does not depend as heavily on precise angular alignment, thereby reducing manufacturing precision requirements while maintaining rotational improvement.
Data Source
AI summary
A humeral component of a reverse shoulder prosthesis includes a stem part configured for location within the intramedullary cavity of the humerus, the stem part having a stem axis, an epiphyseal part connected to the elongate stem part and having a concave bearing surface defining an epiphyseal axis, and wherein the epiphyseal axis is offset posteriorly relative to the stem axis.