Expandable Screw Anchor for Vertebral Fixation
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Solution Overview
Problem
Conventional vertebral fixing apparatuses face issues with screw loosening due to the halo phenomenon, leading to decreased fixing force and increased risk of degeneration and reoperation, especially in aging populations with vertebral column diseases.
Innovation Solution
A screw fixing apparatus featuring a screw anchor made of plastic material with an expandable inner space, matching screw thread pitch, and protrusions on the outer surface to enhance friction and prevent separation from the bone, allowing for improved pull-out strength and compatibility with various screw sizes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a screw is inserted directly into the bone, then the surgical procedure is simple, but the fixing force decreases over time due to the halo phenomenon causing screw loosening
Solution Approach 1:
The screw is nested within the screw anchor, which is inserted into the bone first. The screw anchor acts as a housing that contains the screw, creating a nested structure where the screw (inner element) is secured within the anchor (outer element). This nested configuration allows the screw to be held firmly by the expandable anchor, preventing loosening due to the halo phenomenon while maintaining a relatively simple overall structure.
Solution Approach 2:
The screw anchor is inserted into the bone before the screw is inserted into the anchor. This preliminary action creates a pre-prepared receiving structure that will firmly hold the screw. The anchor is positioned and expanded in advance, establishing a secure foundation that prevents subsequent screw loosening, thereby improving long-term fixing reliability.
2Strength
If the inner space of the screw anchor is expanded to improve fixing force, then the screw anchor connects better to the bone, but the connection portions between holes may disconnect
Solution Approach 1:
The screw anchor transitions from a compressed state during insertion to an expanded state after insertion. The anchor is inserted in a compressed configuration to facilitate easy insertion, then expanded within the bone to achieve firm connection. This dynamic transformation allows the anchor to adapt its shape and size, improving fixing force while the controlled expansion process maintains structural integrity of the connection portions.
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 apparatus effectively enhances the fixing force of screws within the bone, reducing the likelihood of loosening and degeneration, and simplifies manufacturing and surgical application.
Implementation Method 1
when a screw is inserted into the screw anchor, an inner space of the screw anchor is expanded
Implementation Method 2
protrusions are provided on an outer surface of a screw anchor such that the coefficient of friction between the screw anchor and a bone surface is increased
Data Source
AI summary
A screw fixing apparatus includes a screw inserted into a human body, and a screw anchor having an insertion hole that receives the screw. The screw anchor is inserted into the human body and the screw is inserted into the human body.