Tuberosity Augment Geometry for Reverse Shoulder Joint Mechanics

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Solution Overview

Problem

Prosthetic designs for shoulder arthroplasty alter muscle function and joint mechanics, particularly reducing the moment arm and wrapping of the deltoid muscle, leading to impaired shoulder stability and function in cases of proximal humeral bone loss.

Innovation Solution

The use of humeral trays with tuberosity augments that recreate the shape and contour of the lateral tuberosity, featuring a bulbous surface to alter muscle wrapping and increase the moment arm, length-tension relationship, and line of action, thereby improving muscle mechanics and joint stability.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional prosthetic designs are used in shoulder arthroplasty, then the surgical procedure can be completed, but the muscle moment arm is reduced and muscle wrapping is impaired, leading to degraded shoulder function and stability

Engineering Contradiction:

Improveshoulder joint stabilityVSAvoidmuscle moment arm

Core Design Contradiction:

ReliabilityVSLength of moving object

Solution Approach 1:

The augment member features a bulbous surface with constant or variable radius of curvature that recreates the lateral tuberosity shape. This curved geometry restores the muscle wrapping path and increases the moment arm by providing a rounded contour that the deltoid muscle can wrap around, thereby improving shoulder function and stability

Inventive Principle:

Principle #14Spheroidality (Curvature)

Solution Approach 2:

The augment member is designed with specific local geometries including the bulbous surface portion and flat surface portion, each with distinct curvature characteristics. The bulbous surface specifically addresses the moment arm reduction by providing a rounded contour, while the flat surface provides a different local geometry to optimize muscle attachment and wrapping in specific regions

Inventive Principle:

Principle #3Local quality

2Reliability

If conventional prosthetic designs are used in shoulder arthroplasty, then the surgical procedure can be completed, but muscle wrapping around the lateral tuberosity is reduced, leading to impaired shoulder function

Engineering Contradiction:

Improveshoulder joint functionVSAvoidmuscle wrapping

Core Design Contradiction:

ReliabilityVSDuration of action of moving object

Solution Approach 1:

The bulbous surface with its curved geometry extends the path along which the muscle can wrap around the augment member, thereby increasing the duration of muscle action and improving shoulder function

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Object-affected harmful factors

If conventional prosthetic designs are used in shoulder arthroplasty, then the surgical procedure can be completed, but the lateral tuberosity shape is not reconstructed, leading to increased probability of deltoid scarring

Engineering Contradiction:

Improvedeltoid scarring probabilityVSAvoidlateral tuberosity shape

Core Design Contradiction:

Object-affected harmful factorsVSShape

Solution Approach 1:

The augment member is designed to copy and recreate the natural lateral tuberosity shape and contour. By replicating the anatomical geometry of the tuberosity, the device provides a smooth surface that reduces friction and prevents deltoid muscle scarring while restoring the natural shoulder anatomy

Inventive Principle:

Principle #26Copying

4Ease of manufacture

If a bulbous surface with constant radius of curvature is used, then the manufacturing is simplified, but the adaptability to accommodate anatomical variance of the lateral tuberosity is reduced

Engineering Contradiction:

Improveaugment member manufacturingVSAvoidanatomical variance accommodation

Core Design Contradiction:

Ease of manufactureVSAdaptability or versatility

Solution Approach 1:

The augment member design allows for parameter changes in the radius of curvature, offering both constant and variable radius options. This enables the device to be manufactured with different geometric parameters to accommodate varying anatomical conditions while maintaining manufacturing feasibility

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS12478479B2Humeral trays with tuberosity augments sufficiently designed to improve joint mechanics

Publication Date: 2025.11.25 ADVITA ORTHO LLC

AI summary

Disclosed is a prosthetic augment designed to reconstruct a lateral tuberosity shape of a humerus in a subject having proximal bone loss that includes a humeral adapter tray configured to connect a humeral liner of a reverse shoulder prosthesis to a humeral stem of the reverse shoulder prosthesis and an augment member having a first face adapted for contacting the humeral stem of the reverse shoulder prosthesis and a second face adapted for contacting an underside of a muscle, wherein at least a portion of the second face includes a bulbous surface adapted to alter a wrapping angle of the muscle around the lateral tuberosity, and wherein the second face has a radius of curvature selected from one of a constant radius of curvature or a variable radius of curvature.