Bone Fastener Curved Thread Profile for Jam Prevention

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Solution Overview

Problem

Conventional bone fasteners often jam during screwing-in due to thread tilting and contamination with bone splinters or tissue materials, leading to damage of threads and implant holes.

Innovation Solution

A bone fastener with a thread head featuring curved peaks and flanks, designed to engage implants without jamming, where the peaks form arc segments and the flanks have different curvatures, improving engagement and reducing tilting and contamination risks.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of manufacture

If conventional bone fastener threads are used, then the fastener can be manufactured with standard thread designs, but the thread can tilt and jam during screwing-in operation

Engineering Contradiction:

Improvestandard thread designVSAvoidthread engagement

Core Design Contradiction:

Ease of manufactureVSReliability

Solution Approach 1:

The patent applies curvature to the thread peaks by rounding them with a radius of curvature between 0.05 mm and 3.0 mm. This rounded peak design prevents the thread from tilting and jamming during screwing-in operation while maintaining reliable engagement with the implant hole, resolving the contradiction between manufacturability and thread engagement reliability.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Device complexity

If conventional thread peaks are used, then the thread structure is simple, but bone splinters and tissue materials can contaminate the edges and grooves causing jamming

Engineering Contradiction:

Improvethread structureVSAvoidcontamination

Core Design Contradiction:

Device complexityVSObject-affected harmful factors

Solution Approach 1:

The rounded thread peaks with curvature radius between 0.05 mm and 3.0 mm eliminate sharp edges and grooves where bone splinters and tissue materials could accumulate. This curved geometry prevents contamination-related jamming while maintaining a relatively simple thread structure.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Ease of manufacture

If conventional thread flanks are used, then the thread can be manufactured with standard profiles, but the flanks and peaks can get damaged during screwing-in

Engineering Contradiction:

Improvestandard thread profileVSAvoidthread durability

Core Design Contradiction:

Ease of manufactureVSStrength

Solution Approach 1:

The rounded thread peaks prevent stress concentration at sharp edges, reducing the risk of flank and peak damage during screwing-in operation. The curved profile maintains manufacturability while significantly improving thread durability and resistance to damage.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentUS9339315B2Bone fixation system with curved profile threads

Publication Date: 2016.05.17 STRYKER EUROPEAN OPERATIONS HOLDINGS LLC

AI summary

A bone fastener for use in orthopedic surgery for fixing an implant to bone has a threaded or unthreaded shaft configured to engage bone and a head having a thread on an outer surface to engage the implant. The thread on the head of the fastener has a profile in cross section that includes peaks with a curved shape.