Expandable Ring Intervertebral Fusion Device Fixation
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Solution Overview
Problem
Current interbody fusion techniques require bulky and complex fixation hardware, which increases procedure time and cost, and can cause tissue irritation and vessel erosion, while also limiting the ability to implant additional hardware at adjacent locations.
Innovation Solution
An expandable tube with lockable rings is inserted into the disc space, expanded to distract and lock the rings, then collapsed and removed, leaving the rings to support the disc space and facilitate fusion without the need for supplemental fixation hardware.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If supplemental fixation hardware is used, then fixation strength is improved, but device complexity and procedure time increase
Solution Approach 1:
The fusion cage integrates the fixation function directly into its structure by extending the cage body beyond the disc space to contact the vertebral endplates. This merging of fixation and fusion functions eliminates the need for separate fixation hardware, reducing device complexity while maintaining fixation strength.
Solution Approach 2:
The fusion cage serves multiple functions simultaneously: it provides structural support for bone fusion, acts as fixation hardware through its extended profile contacting the endplates, and maintains disc height. This multi-functionality eliminates the need for additional specialized components.
2Strength
If fixation hardware extends out of the disc space, then fixation strength is improved, but tissue irritation and vessel erosion occur
Solution Approach 1:
The fixation function is localized to the posterior aspect of the cage where it contacts the vertebral endplates, while the anterior portion remains within the disc space. This localized approach provides fixation strength only where needed without causing widespread tissue irritation or vessel erosion.
3Reliability
If secondary locking feature is added, then fixation reliability is improved, but device bulkiness and procedure time increase
Solution Approach 1:
The locking function is merged into the primary cage structure through integrated locking arms that are part of the cage body itself, rather than separate locking components. This integration provides reliable fixation without adding bulkiness or complexity.
4Strength
If fixation hardware is implanted, then fixation strength is improved, but ability to implant additional hardware at adjacent locations is limited
Solution Approach 1:
The fixation function is segmented into discrete contact points at the posterior aspect of the cage where it interfaces with the vertebral endplates. This segmentation allows the cage to provide fixation at specific locations while leaving adjacent areas accessible for additional hardware implantation if needed.
Data Source
AI summary
An expandable tube having a substantially semicircular unexpanded shape is inserted into the disc space after the disc material has been removed therefrom. A plurality of expandable lockable rings are passed over this tube in their unexpanded states and positioned along the anterior edge of the endplates. The tube is then expanded, thereby forcing the rings to expand. The rings hold their final expanded configuration via a one-way locking mechanism. Once sufficient distraction is achieved and the rings locked, the tube is collapsed and removed, thereby leaving the expanded, locked rings behind to support the disc space.