Headless Compression Screw Variable Pitch Thread Feedback
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Solution Overview
Problem
Surgeons face challenges in determining the adequate advancement of compression screws due to lack of appropriate tactile feedback, as torsional resistance does not correlate with bone fragment compression, and existing designs are ineffective in providing sufficient compression and easy removal post-healing.
Innovation Solution
A headless compression screw with a first threaded portion having constant pitch threads and a second threaded portion with varying pitch threads, where the distance between threads decreases as distance from the end decreases, providing a correlation between torsional force and compression level, and facilitating easier removal after fracture healing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a compression screw with constant pitch threads is used, then the screw can be inserted deeply into the bone without a head, but the torsional resistance does not correlate with bone fragment compression, providing no tactile feedback to surgeons
Solution Approach 1:
The screw thread is segmented into two distinct portions: a first threaded portion with constant pitch threads for deep insertion, and a second threaded portion with variable pitch threads for providing tactile feedback. This segmentation allows each portion to fulfill its specific function independently, resolving the contradiction between insertion depth and tactile feedback.
Solution Approach 2:
Different portions of the screw thread are given different local qualities: the first threaded portion has constant pitch for smooth deep insertion, while the second threaded portion has variable pitch (decreasing thread spacing) to provide increasing torsional resistance that correlates with compression level, giving surgeons tactile feedback.
2Force
If a compression screw provides sufficient compression between bone fragments, then fracture reduction is achieved, but the screw becomes difficult to remove after healing
Solution Approach 1:
The screw thread design is dynamic in function: the variable pitch portion provides high compression force during the healing phase, then after healing when removal is needed, the headless design allows the screw to be backed out by reversing the threading action, making removal feasible despite the compression force previously applied.
3Loss of information
If the thread pitch is variable with decreasing spacing near the end, then torque correlates with compression level providing tactile feedback, but the screw structure becomes more complex
Solution Approach 1:
The thread structure is segmented into two portions with clearly defined functions. The first portion has simple constant pitch threads, while the second portion has variable pitch threads. This segmentation provides the necessary information feedback through torque correlation without requiring the entire screw structure to be complex.
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 screw provides clear tactile feedback to surgeons, ensuring proper fracture reduction and easy removal by correlating torque and compression levels, allowing for precise fracture reduction and efficient post-healing screw removal.
Implementation Method 1
a second threaded portion proximate the second end that surrounds the shaft and comprises second threads. The second threads can be spaced apart from one another at a variable pitch, such that distances between adjacent threads of the second threaded portion can decrease as distance from the second end decreases. This construction can aid in creating a correlation between the torsional force and the compression level of the two bone fragments.
Data Source
AI summary
Headless compression screws are described. The headless compression screws include first and second ends coupled by a shaft, a first threaded portion positioned proximate the first end that surrounds the shaft and includes s first threads spaced apart from one another at a constant pitch, and a second threaded portion proximate the second end that surrounds the shaft and includes second threads. The second threads are spaced apart from one another at a variable pitch, such that distances between adjacent threads of the second threaded portion decrease as distance from the second end decreases. Methods of reducing a fracture using headless compression screws are also described.