Thumb Joint Prosthesis Attachment Member Locking Mechanism

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Solution Overview

Problem

Carpometacarpal thumb joint prostheses are not adequately configured to withstand the substantial bending and distraction forces applied to the second metacarpal bone attachment member and compression forces applied to the first metacarpal bone attachment member, leading to potential breakage or loosening of components.

Innovation Solution

The attachment member for the second metacarpal bone includes a screw-like part with a locking device featuring a locking pin that secures to a connecting member, while the attachment member for the first metacarpal bone may use a screw-like part or an unthreaded stem, with articulating elements to ensure stable engagement with the bone, allowing the prosthesis to resist forces effectively.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If a simple screw-like attachment member is used for the second metacarpal bone, then the device complexity is reduced, but the attachment member cannot withstand substantial bending and distraction forces

Engineering Contradiction:

Improveattachment member structureVSAvoidresistance to bending and distraction forces

Core Design Contradiction:

Device complexityVSStrength

Solution Approach 1:

The attachment member for the second metacarpal bone is divided into distinct functional segments: a screw-like part for bone engagement and a separate locking device with a locking pin for securing the connecting member. This segmentation allows each component to be optimized for its specific function while collectively providing the required strength without excessive complexity.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The locking pin is pre-configured with a head portion that engages with the connecting member before final assembly. This preliminary configuration ensures that the locking mechanism is properly positioned and prepared to withstand bending and distraction forces from the outset, preventing loosening under load.

Inventive Principle:

Principle #10Preliminary action

2Strength

If a locking device with locking pin is added to the attachment member for the second metacarpal bone, then the resistance to bending and distraction forces is improved, but the device complexity increases

Engineering Contradiction:

Improveresistance to bending and distraction forcesVSAvoidattachment member structure

Core Design Contradiction:

StrengthVSDevice complexity

Solution Approach 1:

The locking device is merged with the screw-like part as an integrated assembly, where the locking pin is directly associated with the screw structure. This merging reduces the number of separate components and simplifies the overall device complexity while maintaining the enhanced strength against bending and distraction forces.

Inventive Principle:

Principle #5Merging (Combining)

3Manufacturing precision

If the locking pin is made in one piece with the screw-like part, then the manufacturing precision is improved, but the ease of manufacture decreases

Engineering Contradiction:

Improvelocking pin alignmentVSAvoidproduction process

Core Design Contradiction:

Manufacturing precisionVSEase of manufacture

Solution Approach 1:

The manufacturing process is segmented into two stages: first, the screw-like part is manufactured with a precisely positioned hole; second, the locking pin is separately manufactured and then inserted into the pre-positioned hole. This segmentation maintains high manufacturing precision for alignment while improving ease of manufacture by allowing each component to be produced using optimized processes.

Inventive Principle:

Principle #1Segmentation

4Reliability

If a locking means is added to lock the locking pin to the connecting member, then the reliability is improved, but the device complexity increases

Engineering Contradiction:

Improvelocking mechanism stabilityVSAvoidlocking device structure

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The locking means is designed to automatically engage with the locking pin and connecting member without requiring additional actuators or complex mechanisms. The locking pin's head portion and the locking means work together in a self-contained manner, improving reliability through automatic engagement while minimizing the increase in device complexity.

Inventive Principle:

Principle #25Self-service

Data Source

PatentEP3079636B1Attachment member and connecting member for a carpometacarpal thumb joint prosthesis and carpometacarpal thumb joint prosthesis

Publication Date: 2020.09.09 SWEMAC INNOVATION

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AI summary

The invention relates to an attachment member (2) and a connecting member (16) for a carpometacarpal thumb joint prosthesis (1) as well as to said thumb joint prosthesis. The attachment member (2) comprises a screw-like part (4) for attachment by screwing into the second metacarpal bone and a locking device (8) for locking the screw-like part to the connecting member (16). The connecting member comprises an elongated, arcuate element (16) which at one end portion (16a) thereof is configured with a hole (14) for connection to the attachment member (2) for the second metacarpal bone and which at the opposite end portion (16b) thereof is configured with a hole (15) for connection to an attachment member (3) for the first metacarpal bone. The joint prosthesis (1) comprises said attachment member (2) for the second metacarpal bone, an attachment member (3) with a screw-like part (5) for attachment by screwing into the first metacarpal bone and with an articulating ball element (6) as well as a corresponding articulating socket element (7), and said connecting member (16).