Modular Humeral Prosthesis Angular Indexing
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Solution Overview
Problem
Existing modular humeral prostheses for inverted shoulder prostheses face challenges in securely orienting and locking the epiphyseal head relative to the anatomical rod, leading to potential dislodgment and over-tensioning of the deltoid muscle, while also requiring a large number of prostheses to accommodate varying patient anatomies and retroversion angles.
Innovation Solution
A modular humeral prosthesis with an anatomical rod and separable epiphyseal head that uses angular indexing and rotational blocking mechanisms, such as notches and a lug system, along with a coaxial screw for secure orientation and locking, ensuring the epiphyseal head remains within the humerus to avoid deltoid tension and facilitate easy extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a modular humeral prosthesis with separable epiphyseal head is used, then the epiphyseal head can be orientated angularly relative to the anatomical rod, but the prosthesis becomes more complex and requires additional locking mechanisms
Solution Approach 1:
The prosthesis is divided into separate modular components: an anatomical rod and a separable epiphyseal head. This segmentation allows the epiphyseal head to be angularly orientated relative to the rod while maintaining a manageable level of complexity through standardized connection interfaces.
Solution Approach 2:
The connection between the epiphyseal head and anatomical rod incorporates rotational blocking means that allow controlled angular orientation during assembly, then lock into fixed positions. This dynamic-to-static transition provides adaptability during implantation followed by stable locking in the operating position.
2Ease of operation
If the epiphyseal head is positioned to optimize internal rotation, then the range of motion is improved, but the prosthesis may become dislodged over time without locking mechanisms
Solution Approach 1:
The rotational blocking means enable the epiphyseal head to be positioned at optimal angles for internal rotation during surgery, then locked into fixed rotational positions. This allows the prosthesis to provide full range of motion capability while preventing dislodgment through mechanical locking.
Solution Approach 2:
The rotational blocking means include indexing features that provide tactile and visual feedback to the surgeon during assembly, allowing precise positioning and confirmation of the correct angular orientation before locking, thereby ensuring both optimal rotation and stability.
3Ease of repair
If an anatomical rod with separable epiphyseal head is used, then the prosthesis can be extracted easily, but the epiphyseal head may extend above the humerus causing deltoid muscle over-tensioning
Solution Approach 1:
The epiphyseal head is designed with specific dimensional characteristics that allow it to be positioned within the humeral epiphysis boundary. The rotational blocking means and indexing features enable precise angular positioning that optimizes the head's position relative to the humerus, preventing over-tensioning of the deltoid muscle while maintaining extractability.
Data Source
AI summary
The invention relates to a modular humeral prosthesis for an inverse shoulder prosthesis, comprising an anatomical shaft (1) and a separable epiphyseal head (2) which may be angularly orientated by rotation about the longitudinal axis (XX) of the anatomical shaft. The anatomical shaft and the epiphyseal head comprise complementary angular indexing means (11, 28) for relative rotational fixation.