Bone Fastener Curved Thread Profile for Jamming 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, damaging the threads and leading to ineffective fixation in orthopedic surgery.

Innovation Solution

A bone fastener with a thread head featuring curved peaks and flanks, designed to reduce tilting and jamming, where the peaks form arc segments and the flanks have different curvatures, improving engagement with the implant hole and preventing damage.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If conventional bone fastener threads are used, then the screwing-in operation can be performed, but the thread can tilt and jam within the threaded portion of the implant hole

Engineering Contradiction:

Improvescrewing-in operationVSAvoidthread engagement

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The thread peaks are designed with a curved shape instead of sharp angles, forming arc segments that better conform to the cylindrical implant hole. This curvature prevents tilting and jamming during screwing-in by distributing contact pressure more evenly along the thread engagement surface, thereby improving both ease of operation and reliability of thread engagement.

Inventive Principle:

Principle #14Spheroidality (Curvature)

2Strength

If conventional threaded heads are used, then fixation can be achieved, but the flanks and peaks of the threaded head and the threaded hole may get damaged

Engineering Contradiction:

Improvefixation strengthVSAvoidthread damage

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The curved thread peaks with arc segment geometry reduce stress concentration at the thread contacts. The rounded shape distributes mechanical loads more uniformly, preventing damage to both the threaded head flanks and the implant hole threads while maintaining strong fixation through improved contact surface area and load distribution.

Inventive Principle:

Principle #14Spheroidality (Curvature)

3Ease of operation

If conventional threads are used, then bone fixation can be performed, but splinters and tissue materials can contaminate the edges and grooves of the threads, causing jamming

Engineering Contradiction:

Improvescrewing-in operationVSAvoidthread contamination

Core Design Contradiction:

Ease of operationVSObject-generated harmful factors

Solution Approach 1:

The curved thread peaks eliminate sharp edges and grooves where bone splinters and tissue materials could accumulate. The smooth arc segment geometry prevents contamination by allowing debris to be pushed aside rather than trapped, thereby preventing jamming and maintaining ease of operation throughout the screwing-in process.

Inventive Principle:

Principle #14Spheroidality (Curvature)

Data Source

PatentEP2364657B1Bone fixation system with curved profile threads

Publication Date: 2012.05.09 STRYKER TRAUMA SA

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AI summary

A bone fastener (10) for use in orthopaedic surgery for fixing an implant (72) to bone has a threaded or unthreaded shaft (12) configured to engage bone and a head (14) having a thread (16) 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 (28) with a curved shape.