Spinal Screw Movable Tip Bi-Cortical Fixation
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Solution Overview
Problem
Current spinal screws face challenges in achieving bi-cortical bone purchase without risking penetration of the anterior wall of the vertebra, leading to instability, especially in sub-optimal bone quality.
Innovation Solution
A spinal screw with a movable or sliding tip that can be extended after placement, featuring a biasing device and anti-rotation elements, including a blunt or flat distal tip to prevent anterior wall penetration, and a mechanism for achieving bi-cortical fixation without risking penetration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a spinal screw is placed to achieve bi-cortical bone purchase, then screw stability is improved, but the risk of penetrating the anterior wall of the vertebra increases
Solution Approach 1:
The distal tip is designed as a movable member that can slide distally within the lumen of the shaft after screw insertion. This dynamic structure allows the tip to advance forward and engage the anterior cortical bone to achieve bi-cortical fixation, while the blunt or flat tip geometry prevents penetration through the anterior wall, thus resolving the contradiction between achieving stable fixation and avoiding harmful penetration.
2Ease of operation
If the distal tip is made sharp to facilitate insertion, then insertion ease is improved, but the risk of anterior wall penetration increases
Solution Approach 1:
The distal tip is designed with a blunt or flat geometry rather than a sharp point, specifically to prevent penetration of the anterior vertebral wall. The tip includes anti-rotation elements and is configured to slide within the shaft lumen, allowing it to engage bone cortex without penetrating through the anterior wall, thus maintaining safety while achieving functional engagement.
3Strength
If the screw length is increased to achieve bi-cortical fixation, then screw stability is improved, but the complexity of the device increases
Solution Approach 1:
The screw is segmented into a shaft with lumen and a separate movable distal tip. The tip can slide within the shaft lumen to adjust its position and achieve bi-cortical fixation. This segmentation allows the screw to achieve stable fixation without requiring a longer fixed-length screw, thereby reducing device complexity while maintaining the stability benefit of bi-cortical engagement.
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 solution allows for safe and stable bi-cortical bone purchase, enhancing screw stability and reducing the risk of anterior wall penetration, thereby improving surgical outcomes.
Implementation Method 1
a biasing device configured to provide an urging force on the distal movable member
Data Source
Figure 1A~1B
Figure 2~3
Figure 4
AI summary
A spinal screw includes a shaft formed with a lumen and including a head, and a distal movable member including a distal tip and arranged to move in a distal portion of the lumen. A distal movable member (18) includes a proximal surface (24) arranged to abut against a stopper (26) formed in the shaft (12).