Expandable Spinal Cage with Reverse Dovetail Expander
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Solution Overview
Problem
Existing expandable interbody cages for spinal fusion are either complex in their expansion mechanisms, unreliable once implanted, or suffer from expansion issues, making them inadequate for effective vertebral fixation.
Innovation Solution
A two-component spinal interbody cage with a reverse dovetail configuration that uses an expander with legs of varying heights to progressively expand the cage components, allowing for adjustable height increase and facilitating easy insertion between vertebrae through a trapezoidal design with angled sidewalls and spikes for enhanced stability and bone graft integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If an expandable interbody cage is designed with complex expansion mechanisms, then the cage can achieve expansion capability, but the device complexity increases and reliability decreases
Solution Approach 1:
The cage is divided into two separate components (upper and lower) that can be assembled together. The expander is a separate third component that inserts into the assembled cage. This segmentation allows the expansion function to be achieved through a simple mechanical interaction between components rather than a complex integrated mechanism.
Solution Approach 2:
The expander component is designed to insert into and nest within the assembled cage structure. The expander's legs fit within the cage body, and the dovetail configuration allows the expander to be received within the cage's end opening. This nesting approach simplifies the overall device by having components fit within each other rather than requiring complex external mechanisms.
2Adaptability or versatility
If the cage is designed to expand after implantation, then the height can be adjusted, but the reliability of the expansion mechanism decreases
Solution Approach 1:
Instead of designing the cage to expand outward through complex mechanisms, the invention uses a reverse dovetail configuration where the expander inserts into the cage and the angled sidewalls naturally guide and constrain the expansion motion. The geometric configuration of the dovetail interfaces provides inherent mechanical guidance and stability, improving reliability.
Solution Approach 2:
The dovetail configuration with angled sidewalls creates a self-guiding expansion mechanism. As the expander is inserted and pushed, the geometry of the interfaces automatically guides the legs along the lateral channels and provides mechanical constraints that ensure reliable expansion without requiring additional guidance mechanisms or complex control systems.
3Ease of operation
If the cage components have angled sidewalls for easy insertion, then the ease of operation improves, but the structural complexity increases
Solution Approach 1:
The cage components feature curved surfaces including an upwardly curved lower front surface and a downwardly curved upper front surface that meet to form an angled nose. These curved surfaces facilitate easy insertion by conforming to the natural insertion path and reducing resistance, while the overall geometric complexity is managed through the systematic use of these curves throughout the component design.
Data Source
AI summary
A spinal interbody implant includes a two-component cage and expander. The two-component cage, when assembled, accepts the expander through a reverse dovetail configuration between the assembled cage and the expander. The expander has a pair of legs that move within and along lateral channels formed by and between the two cage components for increasing the height of the two cage components relative to one another. The amount of expansion of the cage is determined by the height of the pair of expander legs. The cage accepts different expanders each having pairs of legs of different heights in order to provide different amounts of cage expansion and thus the interbody implant. The front of each expander leg is arch shaped for reception in the lateral channels of the assembled cage and to progressively expand the two cage components relative to one another as the expander is received by the assembled cage.