Posterior Cervical Clamp with Polyaxial Screw for Vertebral Fixation
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Solution Overview
Problem
Existing posterior cervical fixation devices for fusing adjacent vertebrae are difficult to contour, have rigid screw positions, lack space for autograft bone, and require screw removal for plate revision, with potential injury to spinal nerves during screw insertion.
Innovation Solution
A clamp-based anchoring device with a polyaxial screw that engages adjacent vertebrae via a trans-articular pathway, allowing for customizable fit and independent screw orientation, with an installation tool to facilitate precise placement and secure attachment without extending past the clamp to avoid neurovascular elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed plate with predetermined screw holes is used, then the device structure is simple, but the screw positions are rigid and difficult to contour
Solution Approach 1:
The device is divided into separate components: a clamp body with openings and an independent fastener. This segmentation allows the fastener to be positioned independently within the clamp openings, providing customizable screw positions without requiring a completely complex new structure. The clamp provides the basic fixation framework while the fastener can be oriented independently.
Solution Approach 2:
The fastener is designed with polyaxial capability, allowing it to rotate and orient itself independently within the clamp openings. This dynamic orientation capability enables the screw trajectory to be adjusted to match the anatomical geometry of the lateral masses, providing adaptability without requiring multiple pre-drilled holes in the clamp.
2Reliability
If lateral mass screws are inserted to achieve cervical fusion, then vertebral attachment is secure, but spinal nerves may be injured
Solution Approach 1:
The clamp is designed to engage specifically the lateral masses of adjacent vertebrae, which are bony structures that provide secure anchorage. By localizing the fixation to the lateral masses rather than using broader plate configurations, the design achieves reliable vertebral attachment while maintaining a more focused engagement zone that can be positioned away from neurovascular structures.
Solution Approach 2:
The clamp acts as an intermediary device between the screws and the vertebrae. The fastener engages the lateral masses of both vertebrae, and the clamp body provides a protective framework that can be positioned to avoid direct interference with spinal nerves and vessels. The clamp structure itself serves as a mediator that distributes mechanical loads while allowing careful positioning to avoid neurovascular elements.
3Ease of operation
If a plate with fixed hole distances is used, then manufacturing is simple, but successive screws cannot be compressed or distracted
Solution Approach 1:
The fastener is designed to rotate independently within the clamp openings, allowing its orientation and position to be adjusted dynamically. This independent rotation capability enables the screw to be positioned at various angles and depths, facilitating compression or distraction of successive screws without being constrained by fixed hole positions in the clamp. The polyaxial design provides operational flexibility that simple fixed-hole plates cannot achieve.
4Ease of repair
If the plate needs to be revised, then fixation can be adjusted, but screws must be removed
Solution Approach 1:
The separation of the clamp body from the fastener allows for selective revision. If revision is needed, only the fastener portion needs to be accessed and adjusted, while the clamp remains in place securing the vertebrae. This segmented design enables partial revision without requiring complete removal and reinstallation of the entire fixation system, reducing revision time and complexity.
Data Source
AI summary
An anchoring device for attaching an upper vertebra adjacent to a lower vertebra comprises a clamp having a first end and a second end opposite the first end, adapted to be positioned around upper and lower lateral masses of the adjacent vertebrae, and a fastener which in an installed position engages opposite ends of the clamp and which engages adjacent vertebrae thereby attaching the adjacent vertebrae together.