Polyaxial Bone Screw Connecting Device for Spinal Fixation
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Solution Overview
Problem
Existing bone screw systems face difficulties in driving and installing screws, and connectors tend to obscure the installation area, making it challenging for practitioners to attach a framework to the vertebrae.
Innovation Solution
A bone screw system with a connecting device that includes a proximal locking feature and a frictional or lateral locking mechanism to securely attach a pedicle screw to a connecting device, allowing for stable and adjustable angular orientation, and a set screw to secure a rod-shaped member, facilitating easier installation and stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If connectors are initially coupled to screws before installation, then the connection between screw and connector is secure, but the connectors flop around and obscure the installation area making framework attachment more difficult
Solution Approach 1:
The connecting device is divided into separate components: a connector body and a screw receiving portion that can be assembled together. This allows the screw to be secured to the vertebra first, then the connector to be attached to the screw, and finally the framework to be attached to the connector, eliminating the flopping issue while maintaining secure connections at each stage
Solution Approach 2:
The screw is installed into the vertebra and secured in a fixed position before the connector is attached to it. This preliminary fixation of the screw prevents the connector from flopping around during subsequent framework attachment operations
2Reliability
If connectors are rigidly fixed to screws, then the connection is stable, but the framework attachment becomes more difficult due to obscured area and lack of adjustability
Solution Approach 1:
The connecting device incorporates a polyaxial mechanism that allows the screw to be inserted at various angles relative to the connector body. The screw can be inserted at different angular orientations and then locked in place, providing both adaptability during insertion and stability once positioned
Solution Approach 2:
The device allows change in the angular parameter of screw insertion. The screw can be inserted at different angles (e.g., 0 degrees, 15 degrees, 30 degrees) relative to the connector body axis, and the device maintains secure fixation at each angular position through its locking mechanism
3Reliability
If the connecting device has multiple locking mechanisms, then the connection security is improved, but the device complexity increases
Solution Approach 1:
The device combines multiple functions into a single integrated structure: the connector body houses both the screw receiving portion with angular adjustment capability and the framework attachment portion. This merging reduces the number of separate components while maintaining secure connections for both the screw and framework
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 system enhances the ease of screw installation and framework attachment by providing a secure yet adjustable connection, reducing the complexity and difficulty for practitioners, and ensuring a stable connection between the pedicle screw and the vertebrae support structure.
Implementation Method 1
a frictional or lateral locking mechanism to securely attach a pedicle screw to a connecting device
Data Source
Figure 1A~1C
Figure 2A~2B
Figure 2C~3
AI summary
A bone screw system includes a bone screw and a connecting device for coupling the bone screw to an elongate rod-shaped member. The bone screw has proximal and bone-engaging portions disposed at opposing ends relative to a long axis of the screw. The proximal portion includes a proximal locking feature that extends away from the long axis in a radial direction that is perpendicular to the long axis. The connecting device includes first and second coupling portions at opposing ends relative to the long axis when the coupling device is assembled to the bone screw. The first coupling portion defines an opening for receiving the proximal portion of the bone screw. The second coupling portion is configured to receive the rod-shaped member. The connecting device also includes a restraining feature that frictionally resists rotational motion of the connecting device relative to the bone screw.