Double-Layer Helical Bone Fixation Cable

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Solution Overview

Problem

Existing medical linear members for bone fixation lack sufficient strength while maintaining the necessary stretchability and flexibility, particularly when dealing with thick bones like the thighbone or hipbone, which requires strong fastening forces.

Innovation Solution

A double-layer linear member with an inner and outer helical body structure, where the outer helical body has a longer pitch and larger number of wires, and gap portions between the wires to prevent friction, providing enhanced strength and flexibility, and using titanium shape-memory alloy wires for resilience.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a fastening tool such as a cable is used to fix a fractured bone, then the bone can be fixed inside the body, but the bone may be damaged if the fastening force is excessively strong or fixation is insufficient

Engineering Contradiction:

Improvefixation reliabilityVSAvoidbone damage from excessive fastening force

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The cable's physical properties are changed by controlling the wire diameter within a specific range (0.12mm to 0.20mm) and adjusting the helical structure parameters (pitch, number of turns) to achieve optimal fastening force that prevents both bone damage and fixation failure

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The cable is constructed as a composite structure with multiple wires (7-19 wires) bundled together in a helical configuration, combining the strength of multiple thin wires to achieve both high fastening reliability and reduced risk of bone damage compared to single thick wires

Inventive Principle:

Principle #40Composite materials

2Object-affected harmful factors

If the linear member is designed with smooth outer shape to prevent bone damage, then it is applicable to children's bones and elderly people's bones, but it may be insufficient in strength when fixing thick bones like thighbone or hipbone

Engineering Contradiction:

Improvebone damage preventionVSAvoidfastening strength for thick bones

Core Design Contradiction:

Object-affected harmful factorsVSStrength

Solution Approach 1:

The cable has different structural characteristics at different scales: the overall smooth outer surface prevents bone damage, while the internal helical structure of multiple wires provides high fastening strength for thick bones like thighbone and hipbone

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

Multiple wires are nested in a helical configuration within each other, creating a compact structure that maintains a smooth outer surface while packing sufficient material volume to provide high fastening strength for thick bones

Inventive Principle:

Principle #7Nested doll (Nesting)

3Strength

If the linear member has high strength to fix thick bones with strong fastening force, then sufficient fixation is achieved, but stretchability and flexibility are reduced

Engineering Contradiction:

Improvefastening strengthVSAvoidstretchability and flexibility

Core Design Contradiction:

StrengthVSAdaptability or versatility

Solution Approach 1:

The helical structure of the cable allows dynamic deformation - the wires can slide and rotate relative to each other, enabling the cable to stretch and flex while maintaining its overall integrity and fastening strength

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The cable is divided into multiple individual wires (7-19 wires) that can move independently within the helical structure, providing both strength through the collective structure and flexibility through individual wire movement

Inventive Principle:

Principle #1Segmentation

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

The double-layer structure with titanium wires ensures stable fixation with strong fastening force, preventing bone damage from excessive force while maintaining flexibility for easy handling and absorption of strong forces, effectively addressing the strength and flexibility limitations of previous designs.

Implementation Method 1

uses resilience that is a restoring force of a linear member for medical use stretched in a long-axis direction and contracted in a diametrical direction as a fastening force

Methodology Applied

Scientific EffectElasticity: Elasticity

Implementation Method 2

using titanium shape-memory alloy wires for resilience

Methodology Applied

Scientific EffectShape memory alloy: Shape Memory Alloy

Implementation Method 3

gap portions are provided between the respective wires, thereby preventing friction between the wires

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9913673B2Linear member for medical use for bone union

Publication Date: 2018.03.13 SYNTEC CORP

AI summary

A linear member for medical use having stretchability and flexibility while maintaining sufficient strength includes: an inner helical body including a plurality of helically wound wires, the inner helical body including a space portion inside, gap portions being provided in an axial direction between each wire; and an outer helical body provided outside of the inner helical body including a plurality of wires helically wound in such a manner as to form a layer along an axis of the helical body and a helical direction of the outer helical body is opposite to that of the inner helical body with gap portions being provided between each of the wires, the outer helical body being disposed to provide a multilayer structure.