Spinal Fixation Device with Expandable Blades for Osteoporotic Bone
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Solution Overview
Problem
The insertion of pedicle screws into the spinal column, especially in osteoporotic bone, is time-consuming and can damage the vertebrae, necessitating a fixation device that can be secured without causing damage and reducing the effort required compared to traditional pedicle screws.
Innovation Solution
A fixation device comprising a tapered cannula, a shaft with a threaded inner surface, and a post that transitions between closed and open positions, allowing blades to extend laterally and engage the osseous tissue, along with a method of securing the device by moving the post to change the blade position and using helical threads on the cannula to engage the tissue.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional pedicle screws are inserted into the spinal column, then fixation is achieved, but the insertion process is time-consuming and can damage the vertebrae
Solution Approach 1:
The fixation device is pre-loaded in a compressed state within the insertion instrument, with the expansion element held in a retracted position. This preliminary preparation allows the device to be deployed instantly upon insertion, eliminating the need for time-consuming post-insertion tightening or expansion operations. The expansion element is pre-positioned to expand后立即 engage with the bone, providing immediate fixation.
Solution Approach 2:
The device transitions rapidly from the insertion phase to the fixation phase through a single insertion motion. The expansion element is designed to expand immediately upon deployment, skipping intermediate adjustment steps. This rushing through of the insertion process minimizes the time the surgical site is exposed and reduces overall procedure time while maintaining secure fixation.
2Reliability
If traditional pedicle screws are inserted into osteoporotic bone, then fixation is achieved, but the vertebrae can be damaged
Solution Approach 1:
The expansion element transitions from a retracted state during insertion to an expanded state after deployment. This dynamic transformation allows the device to adapt to the bone structure: during insertion, the retracted expansion element minimizes contact and potential damage to osteoporotic bone, while after deployment, the expanded element provides distributed fixation forces that secure the device without requiring excessive insertion force that could damage the vertebrae.
Solution Approach 2:
The device changes its physical parameters (expansion ratio, contact surface area) after insertion. The expansion element increases its volume and surface area engaged with the bone, transforming from a compact insertion profile to an expanded fixation profile. This parameter change allows the device to achieve strong fixation in osteoporotic bone without requiring high insertion forces that could cause vertebral damage.
3Reliability
If multiple pedicle screws are inserted, then adequate fixation is achieved, but the time and effort required increases significantly
Solution Approach 1:
The expansion element is designed to self-expand upon deployment, utilizing the insertion motion itself to trigger the expansion mechanism. This self-service feature eliminates the need for additional manual manipulation or separate expansion steps, reducing the effort required for each screw insertion. The device performs its own expansion function automatically, making the overall process easier and faster.
4Reliability
If the fixation device uses expandable blades, then securement in low-density bone is improved, but the device complexity increases
Solution Approach 1:
The expansion element is nested within the body of the fixation device during insertion, with the retracted expansion element contained inside the insertion instrument. This nesting arrangement allows the complex expandable structure to be compacted into a simple insertion profile, reducing the apparent complexity during the insertion phase while maintaining the securement benefits of the expandable blades after deployment.
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 device minimizes time and effort for insertion, provides improved securement in low-density bone, and reduces the risk of damage, offering enhanced toggling strength and resistance to pull-out forces compared to traditional screws.
Implementation Method 1
The post includes a threaded outer surface threadingly engaged with the threaded inner surface of the shaft
Implementation Method 2
using helical threads on the cannula to engage the tissue
Data Source
AI summary
A fixation device includes a tapered cannula defining a bore therethrough, a shaft, and a post. The shaft includes a proximal portion disposed within the bore, and central and distal portions extending distally from the tapered cannula. The proximal portion includes a threaded inner surface defined therein. The shaft includes blades disposed within the central portion, the blades movable between a closed position in which the blades are disposed within the shaft and an open position in which the blades extend laterally through the shaft. The post includes a threaded outer surface threadingly engaged with the threaded inner surface of the shaft. The post is movable longitudinally within the shaft to transition the blades between the closed and open positions.