Expandable interbody fusion cage with ribbons for graft retention
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Solution Overview
Problem
Existing interbody fusion cages face challenges in securely holding graft material in place during spinal fusion, leading to potential subsidence and recurrent pain due to inadequate mechanical stability and ease of insertion, particularly in minimally invasive procedures.
Innovation Solution
An interbody fusion cage with expandable support elements and ribbons or sutures that form a secure pocket for graft material, allowing easy access during insertion and maximizing retention, while being robust enough to withstand daily activities and similar to cortical bone in elasticity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional interbody fusion cages are used, then the procedure can be performed, but the graft material is not securely held in place leading to subsidence and recurrent pain
Solution Approach 1:
The cage is divided into two separable support elements that can be inserted independently through minimally invasive approaches. This segmentation allows each element to be positioned and secured separately, providing better control over graft material containment and reducing the risk of subsidence while maintaining reliability.
Solution Approach 2:
The support elements are designed to be dynamically adjustable after insertion, allowing the cage to be expanded or adjusted to optimize graft material retention. This dynamic capability ensures secure holding of the graft while adapting to anatomical variations, preventing subsidence and associated pain.
2Ease of operation
If minimally invasive insertion techniques are used, then patient trauma is reduced, but the cage must be small and compact making it difficult to securely hold graft material
Solution Approach 1:
The two support elements are designed to nest together in a compact configuration for minimally invasive insertion. After insertion, they separate and expand to form a stable structure with a pocket for graft material. This nesting approach enables small-profile insertion while maintaining large-volume graft containment capability.
Solution Approach 2:
The cage transitions from a compact inserted state to an expanded functional state after insertion. This dynamic transformation allows the cage to achieve sufficient size and mechanical stability for secure graft retention while maintaining ease of minimally invasive insertion in the compressed configuration.
3Strength
If the cage is made robust to withstand daily activities, then mechanical stability is improved, but the cage becomes difficult to insert through minimally invasive approaches
Solution Approach 1:
The robust cage structure is nested in a compact form for minimally invasive insertion. The two support elements are configured to fit together tightly during insertion, reducing the profile to pass through small incisions. Once positioned, they separate to form the full-strength structure capable of withstanding daily activities.
Solution Approach 2:
The cage exhibits dynamic structural transformation, transitioning from a flexible, compact insertion configuration to a rigid, load-bearing functional configuration. This allows the strong structure to be inserted easily while maintaining the strength needed for daily activities after implantation.
4Reliability
If the cage is designed to securely retain graft material, then fusion success is improved, but the cage structure becomes complex making insertion difficult
Solution Approach 1:
The complex graft retention function is achieved through segmentation into two support elements that create a pocket structure. This segmentation simplifies the overall design compared to a single complex cage, as each element can be individually inserted and positioned, reducing insertion difficulty while maintaining high fusion success rates.
Solution Approach 2:
The cage uses dynamic expansion after insertion to create the secure retention pocket. The support elements separate and expand to form the graft-containing structure, transforming from a simple inserted configuration to a complex functional configuration in situ. This reduces insertion complexity while maintaining effective graft retention for successful fusion.
Data Source
AI summary
An interbody fusion cage comprised of two support elements that separate after insertion into the interbody space to form a pocket into which graft material may be inserted. The expansion of the support elements deploys ribbons between the two support elements to further insulate the pocket into which the graft material is inserted, thereby holding it securely in place. Ribbons may be formed of a flexible material so that graft material can be inserted by a surgeon above or below them. Ribbons may also be deployed manually by the surgeon so as to allow insertion of graft material before the ribbon is deployed.