Modular Spinal Fixation Screw Linear Engagement
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Solution Overview
Problem
Existing low profile spinal stabilization systems require torque for final fastening, which can be cumbersome and may not provide precise or reproducible linear engagement and disengagement.
Innovation Solution
A modular low profile spinal fixation screw with a connector formed from a clamp and a collet, where the collet incorporates a living hinge and scallops for easy attachment to a bone screw, allowing for rapid linear engagement and elimination of torque fastening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a set screw is used to lock the rod to the connector and bone screw, then the connection strength is improved, but the ease of operation deteriorates due to the need for torque application and complex fastening procedure
Solution Approach 1:
The connector is divided into distinct functional components: a collet for gripping the bone screw and a clamp for securing the rod. This segmentation allows each component to perform its specific function independently, eliminating the need for torque-based fastening while maintaining strong connections.
Solution Approach 2:
The patent replaces the traditional torque-based set screw mechanism with a linear engagement system using a collet and clamp. Instead of requiring rotational force to tighten a set screw, the system uses axial movement of the clamp to compress the collet onto the bone screw, substituting a complex mechanical fastening system with a simpler linear engagement mechanism.
2Reliability
If torque fastening is used to secure the rod to the connector, then the reliability of the connection is improved, but the productivity deteriorates due to the time-consuming nature of applying and verifying torque
Solution Approach 1:
The collet and clamp system is designed to self-lock through linear compression. As the clamp moves axially to compress the collet onto the bone screw, the friction and mechanical interference create a self-sustaining locked position that maintains connection reliability without requiring external torque verification or additional fastening steps.
Solution Approach 2:
The patent extracts the torque application step from the fastening process entirely. By removing the set screw and torque-based locking mechanism, the system eliminates the time-consuming steps of applying, verifying, and documenting torque values, thereby significantly improving installation speed while maintaining connection reliability through the collet's friction-based grip.
3Device complexity
If a traditional connector with set screw is used, then the device complexity is reduced, but the manufacturing precision deteriorates due to the difficulty of achieving precise and reproducible linear engagement
Solution Approach 1:
The collet is pre-formed with specific geometric features including scallops and a tapered bore that guide the bone screw into precise alignment during insertion. These pre-configured geometric elements ensure reproducible linear engagement without requiring complex adjustment mechanisms or high-precision assembly procedures, as the precision is built into the component geometry itself.
Solution Approach 2:
The bone screw features a spherical head that interfaces with the collet's tapered bore. This spherical geometry provides self-centering and automatic alignment during insertion, ensuring precise linear engagement. The curvature of the spherical interface compensates for minor misalignments and ensures consistent positioning, achieving manufacturing precision through geometric design rather than complex mechanical adjustments.
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 enables precise and reproducible linear engagement and disengagement of the spinal connecting rod to the anchored bone screw, eliminating the need for torque and enhancing the stability and ease of use in spinal fixation.
Implementation Method 1
The collet incorporates the use of a living hinge which facilitates both attachment of the connector to a bone screw
Implementation Method 2
The clamp compresses the collet which holds the hold rod member to the bone screws in a pre-selected position by linear movement of the clamp
Implementation Method 3
The collet further includes scallops that facilitates the insertion of the spherical end of the bone screw into the collet
Data Source
AI summary
A modular spinal fixation screw capable of rapid linear engagement of a bone screw and a rod member. The fixation screw is coupled to a connector formed from a clamp and a collet. The collet incorporates the use of a T-shaped living hinge which facilitates both attachment of the connector to a bone screw and lessens the resistance of the collet for locking to the bone screw and rod member. The collet further includes scallops that facilitates the insertion of the spherical end of the bone screw into the collet. The clamp can be moved from a first unlocked position used for installation to a locked position securing the rod member to a pedicle bone. The clamp compresses the collet which holds the hold rod member to the bone screws in a pre-selected position by linear movement of the clamp.