Wrist Prosthesis U-Shaped Body Transverse Fixation

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Existing wrist prostheses face complications due to conventional fixation methods that lead to loosening and breakage under distracting forces, requiring significant bone resection and complicating follow-up procedures, especially in patients with rheumatoid arthritis or osteoarthritis.

Innovation Solution

A method using a prosthesis with proximal and distal assemblies featuring a U-shaped body that cooperates with carpal bones, allowing for controlled movement without substantial bone resection, using fasteners transverse to the radius to secure the prosthesis and fuse carpal bones, thereby reducing the risk of loosening and fractures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If conventional fixation methods with screws or prongs are used to secure the distal assembly, then the prosthesis can be fixed to the carpus and metacarpus, but the screws and prongs loosen or the bones break under distracting forces

Engineering Contradiction:

Improvefixation stabilityVSAvoidbone integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

Instead of fixing the distal assembly to the carpus with screws (conventional method), the invention inverts the fixation approach by securing the proximal assembly to the radius and using the U-shaped body to rest against the carpal bones without penetrating screws into the carpus. This reversal eliminates screw loosening and bone breakage while maintaining fixation stability through the transverse orientation and distributed load across multiple carpal bones

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention changes the dimensional orientation of fixation from longitudinal (screws parallel to radius length) to transverse (fasteners perpendicular to radius length). The U-shaped body extends transversely across the carpal bones, distributing forces in a different dimension and avoiding the distracting forces that cause conventional longitudinal fixation to fail

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Ease of manufacture

If a large carpal bone resection is performed to accommodate the prosthesis, then the distal assembly can be inserted and fixed, but the stable volume of carpal bones is significantly reduced

Engineering Contradiction:

Improveprosthesis installationVSAvoidstable bone volume

Core Design Contradiction:

Ease of manufactureVSVolume of stationary object

Solution Approach 1:

The invention extracts only the necessary cartilage from the carpal bones to allow the U-shaped body to rest against the bone surfaces, rather than removing large portions of the bones themselves. This minimal extraction approach enables prosthesis installation while preserving the stable volume of carpal bones for future procedures

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The prosthesis is designed with a U-shaped body that is pre-configured to accommodate the natural contours of the carpal bones. This preliminary design allows the prosthesis to be placed without significant bone resection, as the U-shape is prepared in advance to fit the existing bone structure

Inventive Principle:

Principle #10Preliminary action

3Reliability

If conventional longitudinal fixation is used with screws parallel to the radius, then the distal assembly can be secured, but the screws are subject to distracting forces causing loosening and breakage

Engineering Contradiction:

Improvefixation securityVSAvoiddistracting forces

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The invention inverts the fixation orientation from longitudinal (parallel to radius) to transverse (perpendicular to radius). The fasteners are inserted transversely through the proximal assembly and radius, which changes the direction of force distribution and eliminates the distracting forces that act on longitudinally oriented screws

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

By changing the fixation dimension from longitudinal to transverse, the invention redistributes the mechanical loads across a different orientation. The U-shaped body's transverse configuration allows forces to be distributed across multiple carpal bones rather than concentrating stress along the radius length, reducing the harmful distracting forces

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS9468533B2Method of reconstructing a patient's wrist

Publication Date: 2016.10.18 TRIMED INC

AI summary

A method of reconstructing a patient's wrist. A prosthesis is provided having proximal and distal assemblies. The distal assembly has a body with a U-shaped portion. The proximal and distal assemblies have surfaces that cooperate to guide movement between the proximal and distal assemblies. The proximal assembly is fixed to the patient's radius. The hand is prepared for placement of the distal assembly by removing cartilage against a plurality of carpal bones without significantly altering the configuration of stable volume of at least one of the patient's carpal bones in the first carpal row. The U-shaped portion of the body is placed against a plurality of bones in the first carpal row. Separate locations on the body are secured to a plurality of carpal bones.