Inverse Shoulder Glenosphere Geometry for Roll-Slide Mobility
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing inverse shoulder prostheses limit patient movement due to their mechanical design, which only allows rotation but not translation, restricting mobility in the transverse plane.
Innovation Solution
The design incorporates a glenoid implant with a dome-shaped articulating surface and a humerus implant with a concave inlay, featuring a mismatch in radii to enable translational movement, allowing a combined roll-slide mechanism and improved range of motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a spherical glenosphere with identical concavity prosthesis cup is used, then the joint allows pure rotation, but the patient is limited in movement in the transverse plane
Solution Approach 1:
The patent transitions from a static pure rotation joint to a dynamic joint that adapts its movement characteristics. The glenosphere is designed with an asymmetric articulating surface that enables the joint to switch between rotational and translational movements based on the movement plane, providing dynamic adaptability to improve range of motion while maintaining mechanical simplicity
Solution Approach 2:
The invention changes the geometric parameters of the glenosphere articulating surface by introducing asymmetry between the first and second radii. This parameter modification allows the joint to accommodate both rotational movements (in the plane containing the larger radius) and translational movements (in the plane containing the smaller radius), thereby expanding the range of motion without significantly increasing device complexity
2Ease of operation
If a pure ball and socket joint is used, then the prosthesis is mechanically simple, but further movement is blocked in the transverse plane
Solution Approach 1:
The patent applies local quality by creating different geometric properties in different regions of the glenosphere. The articulating surface has a first radius in one plane and a second radius in another plane, with the second radius being smaller than the first. This local differentiation allows the joint to provide rotational stability in one plane while enabling translational freedom in another plane, thus improving mobility without compromising mechanical stability
Solution Approach 2:
The invention adds dimensional complexity to the joint movement by enabling movements in multiple degrees of freedom. The asymmetric radii design allows the joint to perform both rotation (around the center) and translation (offset from center) in the transverse plane, effectively adding another dimension of movement capability while maintaining the overall spherical joint structure
Data Source
AI summary
An inverse shoulder prosthesis includes a glenoid implant and a humerus implant. The glenoid implant has a glenoid body with a convex dome shaped articulating surface. The articulating surface extends along a center axis, has specific radii in sagittal and frontal planes, and is oriented towards the humerus. The humerus implant has a humeral body and a concave inlay. The concave inlay has a center axis oriented towards the glenoid of a shoulder and has a specific inner radius. The second radius of the glenoid implant is proportionately smaller than the inner radius of the inlay, ensuring a precise fit and function. This configuration allows for improved joint mechanics and stability.