Expandable Screw Anchor for Spinal Fixation
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Solution Overview
Problem
Conventional screw fixation in spinal surgery often leads to screw loosening due to bone cavitation, necessitating revision surgery and increased physical and economic burdens on patients, especially in cases with severe osteoporosis.
Innovation Solution
A screw anchor assembly that includes a screw anchor with an accommodating part and locking step, allowing for increased contact area and pullout strength, facilitating reliable screw fixation and reducing the need for revision surgery by using an expanding member to secure the screw anchor to the spinal bone.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conventional screw is inserted into the bone for fixation, then the screw can be installed to provide initial stabilization, but bone cavitation occurs over time leading to screw loosening and failure of fixation
Solution Approach 1:
The fixation system is divided into two functional components: a screw for initial stabilization and a separate expandable anchor for long-term anchoring. The anchor is segmented into an outer surface that contacts bone and an inner accommodating portion that receives the screw, allowing each component to perform its specific function optimally.
Solution Approach 2:
The expandable anchor is inserted into the bone cavity before the screw is fully secured. This preliminary placement allows the anchor to be positioned and expanded to create optimal anchoring conditions before the final screw fixation, ensuring long-term reliability.
Solution Approach 3:
The anchor expands radially outward from the insertion channel to contact the bone wall, transitioning from a compact inserted state to an expanded anchored state. This dimensional change creates frictional engagement and mechanical interlocking with the bone, preventing screw loosening over time.
2Strength
If a larger screw is inserted to prevent loosening, then fixation strength may be improved, but the surgical complexity and patient burden increase
Solution Approach 1:
The expandable anchor serves as an intermediary component between the screw and the bone. Instead of enlarging the screw itself, the anchor provides the additional fixation strength through radial expansion and frictional engagement, simplifying the overall surgical procedure while maintaining strong fixation.
3Reliability
If additional expanding members are used to secure the screw anchor, then fixation power is increased, but the device complexity and number of components increase
Solution Approach 1:
The screw and expandable anchor are merged into a single integrated assembly where the screw passes through the anchor's accommodating portion. This combination allows the screw to serve dual purposes: providing initial stabilization and simultaneously expanding the anchor to enhance long-term fixation, reducing the need for separate expanding mechanisms.
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 anchor assembly provides enhanced fixation power and stability, reducing the likelihood of screw loosening and the need for revision surgery, while allowing for pedicle screw fixation regardless of screw length, thereby minimizing surgical burden and costs.
Implementation Method 1
the screw anchor is attached to an inside of a spinal bone by the expanding member inserted into the accommodating part and expanding the accommodating part
Data Source
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AI summary
A screw anchor assembly used in pedicle screw fixation is provided. The screw anchor assembly includes a screw (10) having screw threads (20) defined on a circumferential surface, and a screw anchor (30) having a first end and a second end, an accommodating part (50) defined by anchor screw threads (40) on an inner surface of the screw anchor and having one end to receive the screw, and a locking step (60) extended in a circumferential direction from the first end of the screw anchor. The accommodating part flexibly extends when the screw is screw-coupled to the screw anchor.