Prosthetic Augment Bulbous Surface Muscle Mechanics
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In shoulder arthroplasty, particularly in reverse shoulder replacement, the altered joint center of rotation affects muscle mechanics, leading to decreased effectiveness of the deltoid muscle in abduction, increased muscle fatigue, and potential complications like impingement and stress fractures, due to changes in muscle moment arms and wrapping angles.
Innovation Solution
A prosthetic augment with a bulbous surface designed to alter the muscle's wrapping angle and increase its moment arm, which is configured to engage the bone and contact the muscle, thereby modifying the muscle's line of action and enhancing its mechanical advantage, is used to improve muscle mechanics and stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If the joint center of rotation is medially shifted in reverse shoulder arthroplasty, then the deltoid abductor moment arm is increased and abduction capacity is enhanced, but the torque on the glenoid fixation surface is increased and deltoid moment arm length is excessive requiring greater force for arm elevation
Solution Approach 1:
The prosthetic augment applies local quality by creating a non-uniform thickness profile with a bulbous surface that concentrates structural support at specific locations. The greater thickness (7-50 mm) at the bulbous surface provides localized reinforcement to handle increased torques, while the smaller thickness (1-5 mm) in other areas maintains overall lightness and proper moment arm geometry.
Solution Approach 2:
The bulbous surface with constant or variable radius of curvature applies spheroidality by creating a rounded, curved interface between the prosthesis and surrounding tissues. This curved geometry distributes stresses more evenly across the glenoid fixation surface and creates optimal contact surfaces for muscle attachment, reducing peak stress concentrations while maintaining enhanced moment arm leverage.
2Reliability
If the joint center of rotation is lateralized to tension rotator cuff muscles and minimize impingement, then muscle tension and impingement are improved, but the deltoid abductor moment arm is decreased requiring greater force for arm elevation
Solution Approach 1:
The prosthetic augment applies dimensionality change by extending in the lateral direction with a non-uniform thickness profile. This lateral extension with varying thickness (from 1-5 mm to 7-50 mm) allows the prosthesis to reach lateral positions that tension the rotator cuff muscles while simultaneously creating the structural bulk needed to maintain adequate deltoid moment arm length through the bulbous surface geometry.
Solution Approach 2:
The prosthetic augment applies composite material principles by combining different thickness regions within a single component. The gradient from thin (1-5 mm) to thick (7-50 mm) sections creates a composite-like structure that optimizes both lateral reach for muscle tension and local bulk for moment arm maintenance, achieving multiple functional requirements in one integrated component.
3Ease of manufacture
If a uniform thickness prosthetic augment is used, then manufacturing is simplified, but muscle wrapping angle and moment arm optimization are compromised
Solution Approach 1:
The prosthetic augment applies local quality by having different thicknesses in different regions - a smaller thickness (1-5 mm) in some areas and a greater thickness (7-50 mm) at the bulbous surface. This non-uniform thickness profile is specifically designed to optimize the muscle wrapping angle and moment arm geometry, with the thicker bulbous region providing the necessary leverage while thinner regions reduce overall mass.
Solution Approach 2:
The bulbous surface with its constant or variable radius of curvature applies spheroidality to create an optimized wrapping geometry for the muscle. This curved, rounded surface profile maximizes the moment arm and wrapping angle compared to flat or uniform geometries, while the specific radius values are selected to balance manufacturing feasibility with biomechanical optimization.
Data Source
AI summary
Prosthetic augments to improve muscle mechanics are disclosed herein. A prosthetic augment of the present disclosure includes an augment member configured to engage a bone, the augment member having a first face adapted for contacting the bone; 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 bone, wherein a first thickness is defined between the first face and the second face at a first position on the augment member, wherein a second thickness is defined between the first face and the bulbous surface of the second face, and wherein the first thickness and the second thickness are not equivalent so as to result in the augment member having a non-uniform thickness.