Reverse Shoulder Prosthesis Medial Rotation Shift
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Solution Overview
Problem
Shoulder replacement surgeries face challenges in achieving stability and functionality, particularly in cases where the rotator cuff is less functional, as existing prostheses may not adequately compensate for muscle deficiencies and provide sufficient range of motion and stability.
Innovation Solution
A shoulder prosthesis design featuring a ball-and-socket coupling with a disc-shaped base portion that allows three rotational degrees of freedom, shifting the center of rotation medially and distally, coupled with a Z-shaped adaptor for patient-specific adaptation, to engage the deltoid muscle effectively and enhance stability and functionality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a reverse prosthesis is used to compensate for rotator cuff deficiency, then the deltoid muscle can compensate for rotator cuff deficiency, but the device complexity increases due to reversing the socket and head configuration
Solution Approach 1:
The patent applies the inversion principle by reversing the traditional ball-and-socket configuration to create a reverse prosthesis. The socket is positioned on the humeral side and the ball on the glenoid side, which changes the mechanical advantage to allow the deltoid muscle to compensate for rotator cuff deficiency. This inversion resolves the technical contradiction by achieving functionality through structural reversal.
2Ease of operation
If the center of rotation is shifted medially and distally in a reverse prosthesis, then the deltoid muscle can be engaged effectively throughout the range of motion, but the stability of the joint articulation is reduced
Solution Approach 1:
The patent applies dimensionality change by shifting the center of rotation from its traditional position to a more medial and distal location. This spatial repositioning in multiple dimensions (medial-lateral and proximal-distal axes) allows the deltoid muscle to maintain effective leverage throughout the range of motion while the prosthesis design compensates for the reduced joint stability through the reverse configuration.
3Reliability
If a total shoulder replacement is performed, then the functionality of the shoulder joint is restored, but the rotator cuff functionality must be good for the prosthesis to work effectively
Solution Approach 1:
The patent applies inversion by creating a reverse prosthesis that inverts the traditional ball-and-socket arrangement. This allows the prosthesis to function effectively even when the rotator cuff is deficient, as the deltoid muscle becomes the primary driver of motion. The inversion principle enables the same prosthesis design to adapt to patients with varying rotator cuff functionality.
Data Source
AI summary
The present application concerns a shoulder prosthesis assembly. The shoulder prosthesis assembly comprises a humeral stem including a first articulating coupling means, a base portion of a substantially disc shaped geometry including a second articulating coupling means. Said first articulating coupling means and said second articulating coupling means connect the stem to the base portion. The ratio between the circumference of the disc shaped base portion and the peripheral thickness of the disc shaped base portion is at least 18:1.