Facet Sled Guide for Accurate Cervical Screw Trajectory
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Solution Overview
Problem
Current posterior cervical fusion hardware requires significant soft tissue dissection and lacks accurate screw placement due to anatomical challenges, such as the vulnerability of the cervical spinal cord and presence of vertebral arteries, which prohibits the safe use of existing lumbar spine techniques.
Innovation Solution
A screw insertion technique using a facet sled as a guide within the facet joint under radiographic guidance, allowing for accurate cranial-caudal trajectory of screws, which can be adapted with tower systems for rod insertion, enabling precise screw placement during open or minimally invasive surgeries.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If existing lumbar spine techniques are applied to the cervical spine, then screw placement can be achieved, but the vulnerability of the cervical spinal cord and presence of vertebral arteries prohibit safe placement
Solution Approach 1:
The patent introduces a facet joint guide wire and facet joint reamer as intermediary tools that serve as mediators between the surgeon and the critical anatomical structures. The guide wire is first placed within the facet joint to establish a safe trajectory, and the reamer is used to create a channel along this pre-established path. This intermediary approach allows screw placement while avoiding direct manipulation of the vulnerable cervical spinal cord and vertebral arteries, thereby resolving the contradiction between achieving screw placement and minimizing harm to critical structures.
Solution Approach 2:
The patent applies preliminary action by first placing a guide wire within the facet joint and establishing the correct trajectory before actually inserting the screw. The guide wire serves as a preliminary guide that defines the safe path, and subsequent instrumentation (reamer, screw) follows this pre-established trajectory. This preliminary placement of the guide wire ensures that the screw will be inserted along a safe path that avoids the cervical spinal cord and vertebral arteries, thus resolving the safety concern while maintaining placement accuracy.
2Ease of operation
If significant soft tissue dissection is performed to place hardware, then screw placement can be achieved, but tissue disruption increases
Solution Approach 1:
The facet joint guide wire acts as an intermediary that enables screw placement through a more conservative approach. By establishing the trajectory through the facet joint rather than requiring extensive soft tissue dissection, the guide wire facilitates screw insertion with minimal tissue disruption. The guide wire serves as a mediator that allows the surgeon to access the facet joint and establish the correct path without needing to perform significant soft tissue dissection, thus resolving the contradiction between operational feasibility and tissue preservation.
3Measurement precision
If guide wires are placed to guide screw insertion, then screw placement accuracy improves, but the vulnerability of the cervical spinal cord prohibits safe placement
Solution Approach 1:
The patent uses the facet joint guide wire as an intermediary tool that is placed within the facet joint to establish a safe and accurate trajectory for screw insertion. The guide wire serves as a mediator between the surgeon and the critical anatomical structures (cervical spinal cord and vertebral arteries). By confining the guide wire placement to the facet joint and using it to define the trajectory, the system achieves both accuracy in screw placement and safety in avoiding the vulnerable cervical spinal cord, thus resolving the contradiction between trajectory accuracy and spinal cord protection.
Data Source
AI summary
A posterior cervical fusion surgery assembly and method. The assembly includes a sled adapted to be positioned in a facet joint and two receivers slidably mounted on the sled. The receivers are adapted to support surgical instruments such as a drill, a tap, and a screw. The sled assists in orienting the instruments at a desired angle with respect to the spine.