Variable Angle Bone Fixation Device Burr Prevention

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Solution Overview

Problem

Existing variable angle bone fixation systems often produce burrs when screw heads are locked in plate holes, especially in systems larger than 3.5 mm and at angulated positions, which can damage the bone plate or bone screw.

Innovation Solution

A bone fixation system with a screw head and shaft designed for variable angle rotation, featuring a bore with angled sides and a securing element that allows for joint-like rotation, along with a threaded plate hole with dulled edges to prevent burr formation, and a nut for secure fixation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If variable angle screws are used to permit user-selected angle insertion, then adaptability is improved, but burr generation increases causing damage to the bone plate or bone screw

Engineering Contradiction:

Improvevariable angle insertion capabilityVSAvoidburr generation and damage

Core Design Contradiction:

Adaptability or versatilityVSObject-affected harmful factors

Solution Approach 1:

The patent modifies the thread geometry of the screw head to convert the harmful burr-generating interaction into a beneficial locking mechanism. The modified threads are designed to engage with dulled edges of the plate hole, transforming the previously harmful sharp edge interaction into a controlled engagement that prevents burr formation while maintaining variable angle capability

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent applies different geometric properties to different parts of the screw head threads. Specifically, certain portions of the threads have modified geometry with adjusted pitch, angle, or profile to interact differently with the plate hole edges depending on the insertion angle, allowing optimal performance at various angles without generating burrs

Inventive Principle:

Principle #3Local quality

2Stability of the object's composition

If screw head is locked in plate hole at angulated position, then fixation stability is improved, but burr generation increases damaging the components

Engineering Contradiction:

Improvefixation stabilityVSAvoidburr generation

Core Design Contradiction:

Stability of the object's compositionVSObject-generated harmful factors

Solution Approach 1:

The locking mechanism is redesigned so that the same engagement that provides stability at angulated positions is modified to prevent burr generation. The modified thread geometry and dulled plate hole edges work together to create a stable lock without the harmful sharp edge interaction that previously caused burrs

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

3Strength

If threaded plate hole with sharp edges is used for locking, then locking strength is improved, but burr generation occurs from the sharp edges acting as a die

Engineering Contradiction:

Improvelocking strengthVSAvoidburr generation

Core Design Contradiction:

StrengthVSObject-generated harmful factors

Solution Approach 1:

The sharp edges of the plate hole threads are intentionally dulled or modified to eliminate the die effect that causes burrs. The modified edge geometry is designed to work with the modified screw head threads to maintain locking strength through a different engagement mechanism that does not involve the harmful sharp edge interaction

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The plate hole edges are selectively modified in specific zones where they interact with the screw head threads. The dulled edges are positioned to engage with corresponding modified thread portions, creating a localized interaction that maintains strength while preventing burr formation

Inventive Principle:

Principle #3Local quality

Data Source

PatentUS10765461B2Variable angle bone fixation device

Publication Date: 2020.09.08 DEPUY SYNTHES PROD INC

AI summary

A bone fixation system including a bone fixation element including a head portion having a bore passing therethrough from a first side surface to a second side surface, wherein the bore is perpendicular to a longitudinal axis of the bone fixation element, a securing element positioned within the bore, and a bone plate extending along a plate axis and having a threaded plate hole extending therethrough from a first surface to a second surface configured to contact a bone in an operative configuration.