Conical End Cap for Intramedullary Nail Self-Alignment

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Solution Overview

Problem

The trailing end of bone implants often sticks out of the bone, causing pain and irritation due to sharp edges, and can hinder removal as bone tissue grows over the edges, making extraction difficult after healing.

Innovation Solution

An end cap with a threaded conical portion and a head, featuring a constant pitch thread and varying cone angles, designed to facilitate easy alignment and insertion into the trailing end of the implant, reducing pain and preventing bone growth into the implant.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If the trailing end of the bone implant is left exposed, then the implant can be easily inserted, but the sharp edges cause pain and irritation to surrounding soft tissue

Engineering Contradiction:

Improveease of insertionVSAvoidpain and irritation

Core Design Contradiction:

Ease of manufactureVSObject-affected harmful factors

Solution Approach 1:

The harmful trailing end of the implant is extracted and replaced with a separate end cap component. The end cap is inserted into the trailing end of the implant, removing the sharp edges that cause pain and irritation while maintaining the implant's structural integrity and insertion ease.

Inventive Principle:

Principle #2Taking out (Extraction)

2Object-affected harmful factors

If the trailing end of the bone implant is covered with an end cap, then pain and irritation are reduced, but the insertion process becomes more difficult due to misalignment issues

Engineering Contradiction:

Improvepain and irritationVSAvoidease of insertion

Core Design Contradiction:

Object-affected harmful factorsVSEase of operation

Solution Approach 1:

The front end of the end cap is designed with a conical shape featuring a rounded tip instead of sharp edges. This curved geometry allows the end cap to smoothly engage with the inner thread of the implant during insertion, automatically aligning itself and facilitating easy insertion while eliminating the harmful sharp edges that cause pain and irritation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Ease of manufacture

If the trailing end of the bone implant is left exposed, then insertion is easy, but bone tissue grows over the edges making extraction difficult

Engineering Contradiction:

Improveease of insertionVSAvoidease of extraction

Core Design Contradiction:

Ease of manufactureVSEase of repair

Solution Approach 1:

The end cap is designed with a smooth, rounded tip that prevents bone tissue from growing over the edges. By replacing the exposed trailing end with this smooth cap, both insertion ease and future extraction ease are maintained, as bone cannot anchor to the smooth surface.

Inventive Principle:

Principle #2Taking out (Extraction)

4Adaptability or versatility

If a small screw is used as an end cap, then it can be inserted into the trailing end of the implant, but it easily tilts during insertion due to blind alignment

Engineering Contradiction:

Improvefit into implantVSAvoidalignment during insertion

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The conical shape with rounded tip acts as a self-aligning feature. During insertion, the rounded tip naturally guides the end cap into the correct axial alignment with the implant's inner thread, preventing tilting even when the insertion is performed blindly without visual feedback on the implant's orientation.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS10799270B2Conical end cap for intramedullary nail

Publication Date: 2020.10.13 STRYKER EUROPEAN OPERATIONS HOLDINGS LLC

AI summary

An end cap is provided comprising a head with a tool engagement portion and a shaft with a tip, wherein the shaft comprises a threaded conical portion starting from the tip and extending in a direction to the head. The thread may be provided with a constant pitch, i.e. with a constant distance between the turns of the thread.