Dual-Mobility Reverse Shoulder Arthroplasty for Dislocation Stability

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Solution Overview

Problem

Existing shoulder prostheses, both anatomical and reverse shoulder arthroplasty, face challenges with instability and recurrent or chronic dislocations, particularly in cases of extensive soft tissue and/or bone deficiency, where revision surgeries fail to stabilize the shoulder joint.

Innovation Solution

A dual mobility reverse shoulder arthroplasty device featuring a scapular implant, a humeral implant, a fixed small spherical head, and a mobile larger head, configured with a snap fit assembly, providing a double ball joint configuration to enhance stability and mobility, allowing large abduction and rotation angles while preventing dislocation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a conventional reverse shoulder arthroplasty is used, then the shoulder joint can be stabilized in many cases, but it cannot resolve recurrent or persistent dislocation in cases of extensive soft tissue and/or bone deficiency

Engineering Contradiction:

Improveshoulder joint stabilityVSAvoidability to handle extensive soft tissue and bone deficiency

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The prosthesis is divided into two separate head components: a fixed spherical head attached to the scapular implant and a mobile head that can rotate relative to the spherical head. This segmentation allows the mobile head to adapt to varying soft tissue conditions and provide stability even when extensive soft tissue or bone is deficient, as each head can independently adjust to the available anatomical structures.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The mobile head is designed to rotate with respect to the fixed spherical head about an articulation axis, creating a dynamic dual-mobility system. This dynamic capability allows the prosthesis to adapt to recurrent or persistent dislocation by permitting controlled movement and rotation, enabling the joint to stabilize in positions that accommodate extensive soft tissue and bone deficiency.

Inventive Principle:

Principle #15Dynamics

2Reliability

If a conventional shoulder prosthesis is used, then it provides a solution for end-stage pathology, but it becomes potentially unstable with recurrent or chronic dislocations

Engineering Contradiction:

Improveshoulder joint stabilityVSAvoidprosthetic stability

Core Design Contradiction:

ReliabilityVSStability of the object's composition

Solution Approach 1:

The dual-mobility configuration with a mobile head rotating on a fixed spherical head creates a dynamic stabilization system. The mobile head can rotate about the articulation axis to accommodate dislocation events while maintaining overall joint stability, preventing recurrent or chronic dislocations by allowing controlled movement rather than rigid constraint.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The mobile head acts as an intermediary element between the fixed spherical head and the humeral implant. This intermediate component absorbs and redistributes forces, mediating the interaction between the scapular and humeral implants to maintain stability while accommodating movement and preventing dislocation.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Ease of operation

If a conventional shoulder prosthesis is used, then it treats end-stage pathology, but it cannot achieve large mobility angles without mechanical impingement at extremal positions

Engineering Contradiction:

Improvemobility angle rangeVSAvoidmechanical impingement

Core Design Contradiction:

Ease of operationVSObject-affected harmful factors

Solution Approach 1:

The mobile head rotating on the fixed spherical head creates a dual-mobility system that increases the total mobility angle range. The rotation of the mobile head about the articulation axis allows the joint to achieve greater abduction and rotation angles without the fixed geometric constraints of conventional single-mobility prostheses, thereby avoiding mechanical impingement at extremal positions.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentEP4640187A1Reverse shoulder arthroplasty with dual mobility

Publication Date: 2025.10.29 MEDICALEX

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AI summary

A dual mobility reverse shoulder arthroplasty device for repairing a shoulder articulation, the device comprising : - a scapular implant (1), configured to be attached to a scapula of a patient, - a humeral implant (2), configured to be attached to the humerus of the patient, - a spherical head (3), rigidly mounted on the scapular implant, - a mobile head (4), formed as an intermediate cup, mounted on the spherical head with a snap fit assembly manner, the mobile head being able to rotate with regard to the spherical head about an articulation axis, thereby forming a first inner ball joint assembly, the humeral implant comprising an outer cup (21) configured to bear on the mobile head, forming a second outer ball joint assembly, concentric with the first ball joint, thereby achieving large mobility angles of the humeral implant with respect to the scapular implant, and thereby avoiding mechanical impingement at extremal positions.