Expandable Spinal Fusion Implant for Post-Packing Bone Graft
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Solution Overview
Problem
Existing spinal fusion implants do not effectively reduce the risk of neural injury during implantation and often lack sufficient space for adequate bone graft material, hindering successful fusion outcomes.
Innovation Solution
An expandable spinal fusion implant designed to be inserted in a collapsed state and expanded to a desired height, featuring a translation mechanism that maintains endplates stationary, allowing for post-packing of bone graft material through a large cannula at the proximal end, and incorporating endplate safety retainers to prevent dislocation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the implant is designed with a large through aperture at the proximal end for post-packing bone graft material, then bone graft distribution is improved, but the device complexity increases due to the offset drive mechanism
Solution Approach 1:
The drive mechanism is intentionally positioned asymmetrically (offset from the width centerline) to accommodate a large through aperture at the proximal end. This asymmetric layout allows bone graft material to be packed through the aperture while the drive mechanism operates from the opposite side, resolving the conflict between providing adequate bone graft space and maintaining drive mechanism functionality.
2Object-affected harmful factors
If the expansion mechanism is translated to expand the endplates, then neural injury risk is reduced by minimizing tissue disruption, but the endplates must be fixed in the longitudinal direction which increases device complexity
Solution Approach 1:
An endplate retainer is introduced as an intermediary component that temporarily fixes the endplates in the longitudinal direction during expansion. This retainer acts as a mediator between the expansion mechanism and the endplates, allowing controlled translation for expansion while preventing unwanted movement, thereby reducing neural injury risk without requiring complex integrated fixation systems.
3Length of moving object
If the expansion mechanism is translated by advancing the drive mechanism, then endplate expansion is achieved, but the drive mechanism must be retained within the housing which limits the aperture size
Solution Approach 1:
The drive mechanism is positioned asymmetrically within the housing, offset from the width centerline, which allows one side of the housing to maintain a large through aperture for bone graft packing while the drive mechanism operates from the opposite side. This asymmetric arrangement resolves the conflict between accommodating the drive mechanism and providing a large aperture.
Data Source
AI summary
An expandable spinal fusion implant including first and second endplates coupled to an expansion member that sits within a housing. The expansion member is translated by a drive mechanism, whereby translation of the expansion member by the drive mechanism in a distal and proximal directions causes the distance between the endplates to increase and decrease, respectively.