Expandable Spinal Fixation Screw for Bone Anchoring
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Solution Overview
Problem
Existing spinal fixation systems face issues with fixation screw backout and bone failure due to weak bone structure under heavy loads, leading to incomplete stabilization and additional damage.
Innovation Solution
An expandable attachment device with a radially expandable section and an unexpandable section, featuring external threads and anti-torque elements, is designed to provide enhanced anchoring force and minimize bone failure. The device can be made from medical-grade metals or polymers, with an inner structural element supporting mechanical loads and anti-torque features to prevent screw backout.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional fixation screws are used with rigid fixation rods or plates, then the fixation system provides structural support, but the fixation screws can back out or loosen under heavy loads causing complete failure
Solution Approach 1:
The fixation screw incorporates a expandable anchoring element that transitions from a compressed delivery state to an expanded anchoring state upon deployment. This dynamic expansion mechanism allows the screw to achieve greater anchoring force and resistance to backout while maintaining a compact profile during insertion, directly resolving the contradiction between reliability and anchoring strength.
Solution Approach 2:
The anchoring element undergoes a parameter change from a small, compressed state during delivery to a large, expanded state during use. This parameter transformation enables the screw to provide sufficient anchoring force to prevent backout under heavy loads while maintaining ease of delivery, thereby improving both reliability and anchoring strength simultaneously.
2Strength
If the fixation screw is made larger to increase anchoring force, then screw backout is prevented, but the screw becomes difficult to deliver and may cause bone failure
Solution Approach 1:
The expandable anchoring element provides a dynamic solution where the screw presents a small profile during delivery for ease of insertion, then expands to a large profile upon deployment to provide sufficient anchoring force. This dynamic transformation resolves the contradiction between anchoring strength and delivery ease by having the screw adapt its size to the operational requirement.
Solution Approach 2:
The fixation screw is segmented into distinct functional components: a delivery element for insertion, an expandable anchoring element for securing, and a fixation element for bone engagement. This segmentation allows each component to be optimized for its specific function, with the anchoring element expanding only when needed to provide strength without complicating the delivery process.
3Strength
If the fixation screw is made larger to increase anchoring force, then screw backout is prevented, but bone failure risk increases
Solution Approach 1:
The expandable anchoring element only increases in size upon deployment after the screw is properly positioned, ensuring that the bone is not subjected to excessive forces during insertion. The gradual expansion after delivery allows the bone to accommodate the increased anchoring force without causing failure, thus resolving the contradiction between anchoring strength and bone safety.
Solution Approach 2:
The screw is first delivered in a compressed state to minimize bone disturbance during insertion, then expanded to its full anchoring size only after proper positioning is achieved. This preliminary action of delivering in a reduced state prevents bone failure while still providing sufficient anchoring force to prevent backout, resolving the contradiction between strength and harmful effects.
Data Source
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AI summary
An attachment device with a radially expandable section is disclosed. The attachment device can have helical threads, for example, to facilitate screwing the attachment device into a bone. Methods of using the same are also disclosed. The attachment device can be positioned to radially expand the expandable section in cancellous bone substantially surrounded by cortical bone.