Multi-planar Taper Lock Screw for Spinal Rod Alignment
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Solution Overview
Problem
Conventional spinal fixation devices lack the ability to easily connect and disconnect spinal rods to vertebrae not aligned on the same plane without additional torque or locking pieces, and they do not provide a screw head configuration that facilitates easy locking and unlocking with a complementary tool.
Innovation Solution
A multi-planar taper lock screw with a proximal flange and a dual-layered housing system, featuring a spherically configured pivotable screw head and a slidable outer housing, allowing for easy connection and disconnection of spinal rods to vertebrae without additional torque and enabling locking and unlocking with a complementary tool.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If conventional spinal fixation devices are used to connect spinal rods to vertebrae not aligned on the same plane, then the structural stability is maintained, but the ease of operation for locking and unlocking is deteriorated
Solution Approach 1:
The device is divided into distinct functional segments: a screw body for bone engagement, a rod-receiving portion for rod attachment, and a locking mechanism with movable component. This segmentation allows each part to perform its specific function efficiently, enabling easy locking and unlocking operations while maintaining structural stability for multi-planar vertebrae connection.
Solution Approach 2:
The locking mechanism incorporates a movable component that can transition between locked and unlocked states. This dynamic element enables the surgeon to easily lock and unlock the spinal rod to the screw by simply moving the component, without requiring additional torque or complex procedures, thereby improving ease of operation.
2Reliability
If additional torque is applied to lock conventional devices, then the locking reliability is improved, but the harm to the patient increases
Solution Approach 1:
The locking mechanism is designed to self-lock through the movement of its component, eliminating the need for additional torque application. When the movable component is positioned to engage the rod-receiving portion, it automatically secures the spinal rod to the screw with reliable locking action, avoiding harmful torque transmission to the patient's bone structure.
3Reliability
If conventional devices require additional locking pieces, then the structural stability is improved, but the device complexity increases
Solution Approach 1:
The locking function is merged into the screw structure itself through the integrated locking mechanism with the movable component. This eliminates the need for separate locking pieces or set screws, reducing the number of components while maintaining structural stability for connecting spinal rods to multi-planar vertebrae.
Solution Approach 2:
The screw design incorporates multiple functions within a single device: bone anchoring through the screw body, rod attachment through the rod-receiving portion, and locking/unlocking through the movable component. This multi-functionality eliminates the need for additional locking pieces, simplifying the overall device while ensuring structural stability.
4Ease of operation
If screw head configuration is not optimized, then the manufacturing simplicity is maintained, but the ease of operation for tool engagement is deteriorated
Solution Approach 1:
The screw head configuration features an asymmetric design with a specifically shaped recess that complements the gripping tool. This asymmetric geometry provides optimal tool engagement for locking and unlocking operations, while the recess shape is designed to be manufacturable using standard machining processes, balancing ease of operation with manufacturing simplicity.
Data Source
Figure 1
Figure 2
Figure 3A~3B
AI summary
A multi-planar taper lock screw configured to have a slidable outer housing over an inner housing containing a spherically configured, pivotable screw head and a removable spinal rod wherein the outer housing can be selectively positioned to fully lock the screw head and the spinal rod in position within the inner housing or can be selectively positioned to lock only the screw head in position while permitting a sliding and rotating motion of the spinal rod about its long axis within the inner housing.