Expandable Spinal Cage with Nested Actuation
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Solution Overview
Problem
Conventional spinal interbody cages have a fixed height, which limits their ability to minimize wound size and can cause compression of neighboring nerves and tissues during height adjustment, complicating surgery.
Innovation Solution
An expandable spinal interbody cage design featuring a screw arbor with opposite spiral threads and slide blocks with inner threads, allowing continuous height adjustment without protrusion beyond the upper and lower plates, reducing volume and surgical complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the height of the conventional spinal interbody cage is adjusted by having wedge members approach each other to force the upper plate apart from the lower plate, then the height adjustment function is achieved, but the actuation shaft protrudes from the longitudinal ends of the upper and lower plates, increasing the volume of the implanted object and causing compression to neighboring nerves or tissues
Solution Approach 1:
The actuation shaft is nested within the body of the spinal interbody cage, specifically positioned within a cavity formed by the upper and lower plates. This nesting arrangement allows the actuation shaft to remain contained within the cage boundaries during height adjustment, eliminating the protrusion problem while maintaining the height adjustment function. The shaft moves vertically within the cage body rather than extending beyond the plates.
Solution Approach 2:
The invention changes the dimensional arrangement by positioning the actuation shaft in the vertical dimension (within the cage body) rather than allowing it to extend in the horizontal dimension (beyond the plate ends). This dimensional reorganization allows height adjustment to occur without increasing the lateral volume occupied by the implant.
2Adaptability or versatility
If the actuation shaft protrudes from the longitudinal ends of the upper and lower plates during height adjustment, then height adjustment is possible, but the surgery becomes more complicated and neighboring nerves or tissues are compressed
Solution Approach 1:
By nesting the actuation shaft within the cage body, the invention eliminates the need for complex external manipulation during surgery. The shaft can be actuated through the top surface of the upper plate without protruding beyond the cage boundaries, simplifying the surgical procedure and reducing the risk of nerve or tissue compression.
Solution Approach 2:
The top surface of the upper plate serves as an intermediary access point for actuating the shaft. Instead of requiring the shaft to protrude from the sides, the surgeon can apply rotational force to the shaft through the top surface, making the surgery easier and safer.
3Adaptability or versatility
If the screw arbor and slide blocks are positioned to enable height adjustment, then the expandable function is achieved, but the structure increases the volume of the implanted object if components protrude
Solution Approach 1:
The slide blocks are positioned within the body of the cage, nested between the upper and lower plates. The screw arbor is also contained within the cage boundaries. This nesting arrangement allows the expandable height function to be achieved without increasing the overall volume of the implanted object, as all moving components remain contained within the cage's external 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
Enables stable and continuous height adjustment to match spinal heights, minimizing nerve compression and simplifying surgery by maintaining the screw arbor and slide blocks within the cage's boundaries, thus reducing surgical challenges.
Implementation Method 1
a screw arbor disposed between the upper plate and the lower plate and having a first section and a second section, those sections have an outer thread respectively, wherein the outer thread of the first section and the outer thread of the second section are of opposite spiral direction; and a first slide block and a second slide block, wherein the first and the second block are disposed between the upper plate and the lower plate and respectively have a through hole with inner thread, and the inner threads are of opposite spiral direction
Data Source
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AI summary
Disclosed herein is a spinal interbody cage, comprising an upper plate, a lower plate, a screw arbor and two slide blocks. The screw arbor includes a first section with an outer thread and a second section with an outer thread. The outer threads of the first and second sections have opposite directions. The upper plate respectively has a pair of upper plate slanted surfaces proximate to the first and second sections of the screw rod. The lower plate respectively has a pair of lower plate slanted surfaces proximate to the first and second sections. The screw rod is disposed in and cooperates with the inner threads of the slide blocks. The screw rod and slide blocks are arranged between the upper and lower plates. The slide blocks respectively have two slide block slanted surfaces, each abutting and cooperating with one of the upper and lower plate slanted surfaces so as to distance the upper plate from the lower plate when the slide blocks are distanced from each other by rotating the screw rod in one direction.