Translating Polyaxial Screw with Biasing Yoke for Cervical Spine Alignment
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spinal fixation systems require multiple steps and manual adjustments to align screw heads for rod placement, which can be time-consuming and prone to repositioning errors, especially after screw placement in cervical spine procedures.
Innovation Solution
A translating polyaxial bone screw assembly with a biasing element, such as a spring element, that applies tension between the rod-receiving yoke and the polyaxially supported bone screw, allowing for provisional positioning and alignment to facilitate easier contouring and placement of connecting rods.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple manual adjustment steps are used to align screw heads for rod placement, then alignment precision can be achieved, but surgical time and complexity increase
Solution Approach 1:
The biasing element is pre-installed within the yoke structure before screw placement. When the screw is inserted, the biasing element automatically engages and maintains the yoke in a retracted position, eliminating the need for subsequent manual adjustments to achieve proper alignment for rod placement.
Solution Approach 2:
The biasing element provides automatic self-alignment functionality. As the screw is threaded into the vertebra, the biasing element self-activates to hold the yoke in the correct position, and the system automatically maintains this alignment without requiring additional manual intervention or adjustment steps.
2Stability of the object's composition
If the yoke is held in a fixed position after screw placement, then alignment is maintained, but the ability to accommodate spinal curvature is reduced
Solution Approach 1:
The system transitions from a static fixed position to a dynamic controlled position. The biasing element creates a movable but restrained system where the yoke can be easily repositioned during initial alignment but then maintains stable alignment through the biasing force, accommodating both stability and adaptability needs.
Solution Approach 2:
The biasing element acts as an intermediary between the yoke and the screw. It provides a controlled interaction that allows the yoke to maintain alignment while still permitting the necessary degrees of freedom to accommodate spinal curvature variations through the polyaxial screw design.
3Adaptability or versatility
If the yoke is allowed to move freely relative to the screw, then adaptability to spinal curvature is improved, but maintaining alignment during rod placement becomes difficult
Solution Approach 1:
The biasing element changes the positional parameter of the yoke by applying a restraining force. This force parameter modification allows the yoke to accommodate spinal curvature through the polyaxial screw's inherent mobility while simultaneously maintaining stable alignment for rod placement by preventing excessive movement.
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
This solution streamlines the surgical process by maintaining screw head alignment, reducing the need for repositioning and simplifying rod contouring, thereby enhancing surgical efficiency and accuracy in spinal fixation.
Implementation Method 1
a biasing element, such as a spring element, that applies a tension force between the rod-receiving yoke and the polyaxially supported bone screw
Data Source
AI summary
A translating polyaxial bone screw assembly for anchoring a connecting rod to a spinal vertebra comprises a bone screw having a threaded shank and a head coupled to a yoke. The yoke has at one end a rod receiving channel for receiving a connecting rod and an opposite end that is coupled to the bone screw by a coupling assembly. The coupling assembly couples the yoke for polyaxial movement relative to the bone screw and for translational movement of the yoke in a direction transverse to the axis of the bone screw. The coupling assembly comprises a biasing element supported for joint movement with the yoke that provides a manually surmountable tension force between the yoke and bone screw head that is maintained during polyaxial and translational movement. A fastening element is supported by the yoke for securing the connecting rod between the fastening element and the coupling assembly.