Reverse Shoulder Prosthesis Adaptor for Rotational Freedom
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Solution Overview
Problem
Reverse shoulder arthroplasty faces challenges in maintaining full internal and external rotation of the humerus due to non-anatomic positioning, impingement on bone or soft tissue, and limited rotational surface area, which restricts the range of motion and stability of the joint.
Innovation Solution
An implant assembly comprising a humeral component with a stem and angularly oriented neck portion, coupled with an adaptor that allows rotational movement within a specific plane through a locking mechanism, such as a tongue-and-groove joint, and includes a keel-in-chamber structure or curved ring to limit excessive rotation, enabling improved mobility and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If reverse shoulder arthroplasty is performed with standard components, then the joint can be replaced, but the range of motion is limited due to non-anatomic positioning and impingement
Solution Approach 1:
The implant system is divided into separate modular components: a humeral component with specific geometry, a glenosphere component, and a coupling mechanism. This segmentation allows each component to be optimized independently for its function while enabling flexible assembly to achieve the desired non-constrained motion profile.
Solution Approach 2:
The design transitions from traditional spherical rotation to a more complex motion that utilizes multiple dimensions of movement. The coupling mechanism between the humeral component and glenosphere allows rotation about an axis that is not constrained to a single plane, enabling motion in multiple dimensions simultaneously.
2Reliability
If reverse shoulder arthroplasty is performed, then the joint can be replaced, but stability is compromised due to limited rotational surface area
Solution Approach 1:
The glenosphere component utilizes a spherical geometry that provides uniform contact and load distribution across the entire surface area. This spherical design maximizes the effective rotational surface area while maintaining stability, as the curved surface allows for smooth rotation without discrete contact points that would limit motion.
Solution Approach 2:
The coupling mechanism incorporates features that provide counterbalancing forces to maintain stability during rotation. The geometric relationship between the humeral component and glenosphere creates a self-stabilizing system where the center of rotation and load path are optimized to prevent dislocation while allowing full range of motion.
3Ease of operation
If reverse shoulder arthroplasty is performed with bone or soft tissue impingement, then the implant can be placed, but rotation is restricted
Solution Approach 1:
The coupling mechanism acts as an intermediary between the humeral component and glenosphere, mediating the interaction and allowing rotation even when external factors like bone or soft tissue impingement are present. This intermediary connection protects the rotational interface from external constraints while maintaining the integrity of the implant assembly.
Solution Approach 2:
The design incorporates dynamic elements that allow the implant to adapt its motion characteristics in response to external constraints. The coupling mechanism can accommodate variations in rotation path and range while maintaining stable articulation, enabling the system to overcome static obstacles like impingement through dynamic adjustment of the motion profile.
Data Source
AI summary
Embodiments of an implant assembly for reverse shoulder arthroplasty is disclosed. In one embodiment, the implant assembly comprises a humeral component and an adaptor coupled to the humeral component. The humeral component comprises a stem portion and a neck portion. The stem portion is configured for fixation to a humerus, and the neck portion is angularly oriented relative to the stem portion. The adaptor comprises a first bearing surface and a second bearing surface opposite the first bearing surface. The first bearing surface interfaces with an articulating surface of the neck portion to allow the adaptor to rotate relative to the humeral component in a plane that is generally parallel to the articulating of the neck portion. The second bearing surface is configured to interface with a glenosphere component to allow the glenosphere component to articulate relative to the adaptor.