Expandable Rod Reducer for Minimally Invasive Spinal Fixation
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Solution Overview
Problem
Constructing posterior spinal fixation constructs under minimally invasive conditions is challenging due to difficulties in aligning and seating the fixation rod within the anchor housing, particularly when vertebrae are out of alignment, and existing rod reducers either require larger incisions or provide inadequate alignment with the housing.
Innovation Solution
A reduction instrument with expandable reduction legs that can be deployed through the guide assembly to provide two points of contact on the rod, ensuring proper seating and alignment, while maintaining a minimally invasive approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a rod reducer is passed over the outside of the guide to engage the rod, then the rod can be engaged, but the incision size must be increased to fit the reducer
Solution Approach 1:
The rod reducer is nested within the guide assembly, with the reducer passing through the guide rather than around it. This allows the reducer to access the rod through the existing guide pathway without requiring a larger incision, effectively nesting one instrument within another to solve the spatial constraint problem.
2Length of moving object
If a rod reducer is passed through the center of the guide, then the incision size is minimized, but the rod may not align fully with the housing due to single point contact
Solution Approach 1:
The rod reducer is designed with a laterally extending portion that creates a second dimension of contact with the rod. Instead of single-point contact through the guide center, the reducer extends sideways to engage the rod at multiple points, ensuring proper alignment while maintaining the minimally invasive approach through the original guide pathway.
3Ease of operation
If traditional open procedures are used to construct the fixation construct, then rod alignment is easier, but muscle stripping and incision length are increased
Solution Approach 1:
The guide assembly serves as an intermediary device that enables minimally invasive rod alignment. It provides a structured pathway and alignment references that facilitate proper rod positioning without requiring extensive muscle stripping or large incisions, thus mediating between the need for precise alignment and the desire for minimally invasive surgery.
Data Source
AI summary
This application describes surgical instruments and implants, including a rod reduction instrument, for building a posterior fixation construct across one or more segments of the spinal column. Extension guides are provided that attach to bone anchors implanted within the spine. The extension guides have a guide channel that align with a rod channel in the anchor to help direct the rod to the anchor. The rod reducer may be passed through the interior of the guide assemblies with a distal end arranged in a first position allowing the distal end to pass through the guide. Once through the guide the distal end may be expanded to provide dual contact on the rod at each end of the bone anchor rod channel.