Headless Compression Screw Variable Thread Pitch
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Solution Overview
Problem
Surgeons face challenges in determining the complete reduction of fractures due to lack of appropriate tactile feedback when using compression screws, as the torsional resistance does not accurately correlate with bone fragment compression, and existing designs are inadequate for providing sufficient compression and easy removal post-healing.
Innovation Solution
A headless compression screw with a shaft comprising a first portion having a constant thread pitch and a second portion with a variable thread pitch that decreases, providing proportional torque and compression, allowing for better tactile feedback and easier removal by reducing bony growth around an unthreaded portion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If a compression screw with constant thread pitch is used, then the screw can be manufactured simply and inserted into bone, but the torsional resistance does not correlate to bone fragment compression and tactile feedback is insufficient
Solution Approach 1:
The screw thread is segmented into two distinct portions: a first portion with constant pitch for initial insertion, and a second portion with variable pitch for compression. This segmentation allows each portion to serve its specific function optimally while maintaining manufacturability.
Solution Approach 2:
The thread pitch transitions from constant to variable along the length of the screw, creating a dynamic structure that changes its mechanical properties during insertion. The variable pitch portion increases compression force as the screw advances, providing progressive tactile feedback to the surgeon.
2Length of moving object
If a headless compression screw is used for deep fracture insertion, then the screw can reach distal fractures, but the screw becomes difficult to remove after fracture healing
Solution Approach 1:
The screw is divided into functional segments including a headless portion for deep insertion and a threaded portion for controlled engagement. This segmentation enables the screw to achieve deep fracture reduction while maintaining removal capability through the threaded engagement mechanism.
3Force
If a compression screw provides sufficient compression between bone fragments, then fracture reduction is achieved, but the torque required makes the screw difficult to insert
Solution Approach 1:
The variable pitch thread creates a dynamic compression mechanism where the compression force increases progressively as the screw advances into the bone. The pitch gradually decreases from the first portion to the second portion, allowing initial easy insertion followed by progressive compression without requiring excessive initial torque.
Solution Approach 2:
The thread pitch parameter changes along the length of the screw, transitioning from constant to variable. This parameter change enables the screw to provide increasing compressive force while maintaining reasonable insertion torque through the progressive engagement mechanism.
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 headless compression screw offers improved tactile feedback for surgeons, ensuring accurate fracture reduction and easier screw removal by correlating torque with compressive force and minimizing bony growth, thus addressing the limitations of existing designs.
Implementation Method 1
The second portion can comprise a second thread extending across at least a portion of the second portion and can have a variable pitch that decreases from a first value proximate the second intermediate point to a second value proximate the driving end
Data Source
AI summary
Implementations described herein include headless compression screws and corresponding systems. The headless compression screw has a shaft extending along a longitudinal axis from an insertion end to a driving end. The shaft includes a first portion and a second portion. The first portion extends from proximate the insertion end to a first intermediate point and includes a first thread extending along at least a portion thereof that has a constant pitch. The second portion extends from proximate the driving end to a second intermediate point and includes a thread extending along at least a portion thereof that has a variable pitch that decreases from a first value proximate the second intermediate point to a second value proximate the driving end. Methods of reducing a fracture using headless compression screws are also described.