Reverse Shoulder Prosthesis Adaptor Rotation
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Solution Overview
Problem
Reverse shoulder arthroplasty faces challenges in maintaining full internal and external rotation of the humerus due to impingement on bone or soft tissue and limited rotational surface area, which restricts the range of motion in patients undergoing joint replacement surgery.
Innovation Solution
The implementation of an implant assembly comprising a humeral component with an angularly oriented neck portion and an adaptor that allows rotational movement while preventing displacement, featuring a locking mechanism such as a tongue-and-groove joint and a keel-in-chamber structure to limit angular motion, enabling the humeral component to rotate freely while maintaining stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a reverse total shoulder arthroplasty is performed with standard components, then the joint replacement can be completed, but full internal and external rotation of the humerus is prevented due to impingement on bone or soft tissue and limited rotational surface area
Solution Approach 1:
The patent introduces an intermediary structure (the adaptor with bearing surfaces) between the humeral component and the glenosphere to mediate the rotational movement. This adaptor allows the humerus to rotate through a greater range by providing an intermediate articulation point that avoids direct impingement between the humeral head and surrounding bone or soft tissue structures.
Solution Approach 2:
The patent utilizes a different dimensional approach by creating a rotational axis that is offset from the traditional anatomical center. The bearing surfaces are configured to allow rotation in a plane that is generally parallel to the bearing surface, effectively changing the dimension of rotation and avoiding impingement in the traditional rotational path.
2Ease of operation
If the rotational surface area of the bearing surface is increased to allow full rotation, then the range of motion improves, but the device complexity increases
Solution Approach 1:
The patent segments the rotation function into two distinct interfaces: the first bearing surface between the adaptor and humeral component, and the second bearing surface between the adaptor and glenosphere. This segmentation allows each interface to be optimized for its specific function, with the adaptor acting as an independent rotational element that can rotate relative to both components.
Solution Approach 2:
The adaptor serves multiple functions simultaneously: it provides the first bearing surface for rotation relative to the humeral component, provides the second bearing surface for articulation with the glenosphere, and acts as a structural connector between the two components. This multi-functionality reduces the need for additional separate components.
3Ease of operation
If the adaptor is allowed to rotate freely relative to the humeral component, then full rotation is achieved, but displacement or decoupling of the adaptor may occur
Solution Approach 1:
The patent creates a dynamic system where the adaptor can rotate freely during the intended range of motion, but includes mechanical features (such as engagement surfaces or limiting structures) that become active only when displacement or decoupling is attempted. This allows the system to be both mobile within the functional range and stable against unwanted movements.
Solution Approach 2:
The patent changes the parameters of the bearing surfaces, such as their curvature, friction characteristics, or geometric configuration, to provide natural mechanical constraints that prevent displacement while allowing rotation. By carefully selecting these parameters, the system achieves both rotational freedom and positional stability without requiring complex locking mechanisms.
Data Source
AI summary
Implant assemblies for reverse shoulder arthroplasty are disclosed. In one embodiment, the implant assembly comprises a humeral component, an adaptor fixed to the neck of the humeral component, and a glenosphere bearing component coupled to the adaptor. The glenosphere bearing component comprises a first bearing surface that interfaces with an articulating surface of the adaptor to allow the adaptor to rotate relative to the adaptor and humeral component. The adaptor and the glenosphere bearing component form a locking mechanism that prevents the adaptor from decoupling from the glenosphere bearing component while allowing the adaptor to remain rotatable relative to the glenosphere bearing component after the implant assembly is implanted in the patient The second bearing surface is configured to interface with a glenosphere component to allow the glenosphere bearing component to articulate relative to the glenosphere component.