Compression Fastener Thread Geometry for Multi-Axial Bone Fixation

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Solution Overview

Problem

Traditional fastener thread designs fail to provide sufficient fixation and load sharing under multi-axial and off-axis loading conditions in surgical procedures involving bone and other tissues.

Innovation Solution

The development of fastening devices with improved thread designs, featuring a shaft with a proximal and distal shaft portion, and helical threads with varying pitches and undercut surfaces angled towards the ends of the shaft, to enhance bone fixation and load distribution.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If traditional fastener thread designs are used, then the device complexity is low, but the bone fixation and load sharing capability under multi-axial and off-axis loading conditions is insufficient

Engineering Contradiction:

Improvebone fixation and load sharing capabilityVSAvoidthread design complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The thread design is segmented into multiple distinct portions: a first thread portion with a first pitch angle, a second thread portion with a second pitch angle, and a third thread portion with a third pitch angle. Each portion is optimized for specific loading conditions, allowing the fastener to handle multi-axial and off-axis forces more effectively while maintaining manageable complexity through modular design

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different sections of the thread are given different local properties through varying pitch angles. The first thread portion has a pitch angle optimized for axial loading, the second for radial loading, and the third for shear loading. This local differentiation allows each section to excel at specific functions, improving overall reliability without requiring complete redesign of the entire thread structure

Inventive Principle:

Principle #3Local quality

2Strength

If helical threads with varying pitches and undercut surfaces are implemented, then the load sharing and bone fixation are improved, but the manufacturing precision requirements increase

Engineering Contradiction:

Improveload sharing capabilityVSAvoidthread pitch and undercut surface precision

Core Design Contradiction:

StrengthVSManufacturing precision

Solution Approach 1:

The manufacturing process is segmented into distinct steps for creating each thread portion with its specific pitch angle. The first thread portion is manufactured with a first pitch angle, the second with a second pitch angle, and the third with a third pitch angle. This segmentation allows each portion to be manufactured and verified independently, reducing the cumulative precision errors that would arise from attempting to manufacture a continuously variable pitch thread

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The pitch angle parameter is changed discretely between thread portions rather than continuously. The first thread portion has a first pitch angle, the second has a second pitch angle, and the third has a third pitch angle. These discrete parameter changes are easier to manufacture and control with conventional machining equipment compared to continuous parameter variation, thereby reducing manufacturing precision requirements while still achieving improved load sharing capability

Inventive Principle:

Principle #35Parameter changes

3Adaptability or versatility

If multiple helical threads with different pitches are used, then the adaptability to multi-axial loading conditions is improved, but the device complexity increases

Engineering Contradiction:

Improveadaptability to multi-axial loadingVSAvoidnumber of thread portions

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

Multiple thread portions with different pitch angles are merged into a single integrated fastener body. The first thread portion, second thread portion, and third thread portion are all formed on the same shaft, creating a unified component that provides adaptability to multi-axial loading without requiring multiple separate fasteners or complex assembly procedures

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The fastener is designed with multi-functionality by incorporating thread portions optimized for different loading conditions within a single device. The first thread portion handles axial loading, the second handles radial loading, and the third handles shear loading, making the fastener universally applicable to various loading scenarios without requiring device selection based on specific loading conditions

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12226129B2Fastening devices, systems, and methods

Publication Date: 2025.02.18 RTG SCIENTIFIC LLC

AI summary

A compression fastener may include a shaft and a helical thread disposed about the shaft. The shaft may include a proximal end, a distal end, a proximal shaft portion, and a distal shaft portion. The helical thread may include at least one concave undercut surface and a plurality of pitches that may include at least one first pitch along the proximal shaft portion and at least one second pitch along the distal shaft portion. The at least one concave undercut surface may be angled towards one of the proximal end and the distal end of the shaft, and the at least one first pitch and the at least one second pitch may not be equal to each other.