Expandable Spinal Fusion Cage Restoring Lordotic Curvature
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Solution Overview
Problem
Existing spinal implants fail to effectively restore and maintain the natural lordotic or kyphotic curvature of the spine after disc removal, often leading to spinal curvature deformities due to excessive vertebral bone removal during implantation.
Innovation Solution
An expandable spinal fusion cage that transitions from an initial to an expanded configuration via displacement of an expansion member between branch portions, allowing for distraction and restoration of spinal curvature, while minimizing bone removal and facilitating bone growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If spinal implants with substantially uniform height are used, then the implant structure is simple and easy to manufacture, but the natural lordotic or kyphotic curvature of the spine cannot be restored
Solution Approach 1:
The fusion cage incorporates expandable branch portions that can transition from a compressed insertion state to an expanded functional state. This dynamic structure allows the cage to adapt its shape and volume to restore the natural lordotic curvature while maintaining manufacturing simplicity in the compressed configuration.
Solution Approach 2:
The fusion cage is divided into a fixed base portion and multiple expandable branch portions. This segmentation allows the structure to be manufactured as a simple unit and then expanded locally in the surgical field to achieve the desired curvature restoration without complicating the manufacturing process.
2Reliability
If reaming is performed to form passages for spinal implants, then the implant can be securely inserted, but excessive removal of load bearing vertebral bone occurs leading to instability
Solution Approach 1:
The expandable fusion cage allows the surgeon to first insert a minimally invasive implant and then expand it to the final size and shape required for stable fixation. This dynamic approach reduces the amount of bone removal needed during insertion while still achieving secure implantation and curvature restoration.
Solution Approach 2:
The fusion cage is inserted in a compressed or partially expanded state, performing the preliminary action of establishing basic stability. The final expansion is then achieved in situ to restore curvature and maximize bone contact area without requiring excessive pre-reaming of the vertebral bodies.
3Ease of operation
If the spinal implant is inserted via threading or push-in technique, then the implant can be placed into the disc space, but the natural curvature of the spine is not maintained
Solution Approach 1:
The fusion cage combines easy insertion in a compressed state with the ability to expand to the final functional configuration. This dynamic design allows standard insertion techniques to be used while achieving curvature restoration through post-insertion expansion of the branch portions.
Solution Approach 2:
The segmented structure with fixed base and expandable branches allows the implant to be inserted as a unit with simple geometry, then have its shape modified locally through expansion to restore the natural spinal curvature without complicating the insertion procedure.
Data Source
AI summary
An expandable spinal implant comprising a cage body including at least two movable branches having first end portions that are interconnected to one another and second end portions that are movable relative to one another. The movable branches include a first shell portion having a first pair of longitudinal edges and defining a first hollow region therebetween, and a second shell portion having a second pair of longitudinal edges and defining a second hollow region therebetween, with the first and second hollow regions cooperating to define at least a portion of a hollow interior of the cage body. An expansion member co-acts with the first and second shell portions to transition the cage body to an expanded configuration as the expansion member is axially displaced along said first and second pairs of longitudinal edges. In one embodiment, at least one of the shell portions defines a plurality of retention elements positioned at select axial locations along a corresponding one of the longitudinal edges, with the expansion member engaged with one or more of the retention elements to retain the expansion member at a select axial position to maintain the implant in the expanded configuration.