Expandable Interbody Spacer for Vertebral Load Distribution
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Solution Overview
Problem
Conventional intervertebral spacers face a tradeoff between maximizing surface area for load distribution and preserving space for bone graft, leading to potential subsidence and limited surgical access, which compromises safety and effectiveness in spine surgery.
Innovation Solution
A unitary intervertebral fusion cage with elastically deformable fingers connected by a common base, allowing the cage to collapse for insertion and expand for wider support, facilitating easier access and distribution of graft material while maintaining structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the surface area of the spacer is maximized to distribute loads on adjacent vertebral body endplates, then load distribution is improved, but the space available for blood and bone graft material is reduced
Solution Approach 1:
The spacer transitions from a collapsed configuration during insertion to an expanded configuration after placement. The expandable structure allows the device to occupy minimal space during delivery through the access tube, then expand to provide maximum surface area for load distribution and adequate volume for graft material containment, effectively resolving the contradiction between surface area and internal volume.
Solution Approach 2:
The spacer is designed to nest within itself or within the access delivery tube in a collapsed state, allowing it to pass through narrow surgical pathways. Once deployed, it expands outward to provide the necessary structural support and graft containment space, enabling both compact delivery and expanded functionality.
2Volume of stationary object
If the wall thickness of the cage is minimized to allow for inserted or packed graft or bone growth factor materials, then graft capacity is improved, but the cage becomes prone to subsidence
Solution Approach 1:
The cage structure transitions from a compact collapsed state to an expanded load-bearing state. In the expanded configuration, the structural walls provide sufficient thickness and strength to prevent subsidence, while the expandable design ensures that adequate space is created and maintained for graft material insertion and containment.
Solution Approach 2:
The cage is divided into multiple expandable segments or struts that can be compressed together for insertion and then separated upon expansion. This segmentation allows the structure to achieve both compact delivery dimensions and expanded structural integrity with adequate wall thickness for graft containment.
3Area of stationary object
If the spacer is made very wide to provide adequate support surface area, then load distribution is improved, but the margin of safety during surgical approach is minimized
Solution Approach 1:
The spacer is delivered in a collapsed configuration that minimizes its width and profile, allowing safe passage through narrow surgical access trajectories and avoiding soft tissue structures. After placement in the intervertebral space, the spacer expands to provide the necessary wide support surface area for load distribution, effectively separating the delivery phase from the support phase dimensions.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The expanded cage provides a larger surface area for vertebral endplate contact, enhances graft distribution, and allows for safer surgical approaches by accommodating bends and avoiding soft tissue structures, thereby improving fusion and healing outcomes.
Implementation Method 1
at least three elastically deformable fingers extending distally from the base in a plane
Data Source
AI summary
An interbody spacer comprising a series of stacked walls connected by a common base, wherein the spacer collapses when pressed into an access delivery tube. During insertion, the walls can flex as a unit, like bending a deck of cards, to traverse bends in the access tube. Upon distally exiting the portal of the access delivery tube, the walls track apart (like spreading fingers) to create a wide base of support for the vertebral body endplate. A graft delivery device that uses a conveyor belt-type approach to deliver bone graft from the device to a location in a patient. In some embodiments, the conveyor-belt is manually actuated.