Expandable Spinal Cage With Lordosis Locking and Graft Compression
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Solution Overview
Problem
Current spinal fixation devices provide suboptimal rigidity, occupy space, limit bone graft volume, and fail to directly compress the bone graft between vertebral endplates, thereby reducing the chances of achieving biological fusion, especially in elderly patients with less dense bone.
Innovation Solution
A spinal fixation system with an expandable disc replacement body and adjustable locking mechanism, allowing for controlled angulation and direct compression of the bone graft between vertebrae, facilitated by an angle adjustment instrument and locking mechanisms to secure the desired lordosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a mono-block screw-cage device is used, then the device provides structural rigidity, but it occupies space and reduces the bone graft chamber volume
Solution Approach 1:
The device is divided into separate components: a lordotic cage body for bone graft placement and separate lordosis correction mechanisms (wedges or shims) that can be positioned in the lateral aspects. This segmentation allows the central bone graft chamber to maintain full volume while structural rigidity is provided by the combined cage and correction mechanisms.
2Stability of the object's composition
If a mono-block screw-cage device is impacted into position, then the device provides initial stability, but it cannot directly compress the bone graft between vertebral endplates
Solution Approach 1:
The device transitions from a static impacted structure to a dynamic system where lordosis correction can be adjusted after implantation. The separate correction mechanisms allow progressive compression forces to be applied to the bone graft as the lordotic angle is corrected, enhancing direct compression without compromising initial stability during implantation.
3Adaptability or versatility
If internally contained lordosis adjustment mechanisms are used, then the device allows in-situ lordosis correction, but it occupies the central space needed for bone graft placement
Solution Approach 1:
The lordosis correction mechanism is relocated from the central vertical dimension to the lateral dimensions of the cage. Wedges or shims are positioned in the lateral aspects of the cage body, allowing lordosis adjustment without encroaching on the central bone graft chamber volume.
4Strength
If conventional mono-block devices are used in elderly patients with less dense bone, then the devices provide fixation, but they provide suboptimal rigidity and fail to achieve desired lordotic angles
Solution Approach 1:
The device allows preliminary implantation of the cage body with bone graft, followed by subsequent lordosis correction using separate correction mechanisms. This staged approach allows the bone to be prepared and grafted first, then the precise lordotic angle to be adjusted afterward, achieving both secure fixation in osteoporotic bone and precise angular positioning.
Data Source
AI summary
A spinal fixation system includes an expandable disc replacement body and an angle-setting disc replacement holder; The expandable disc replacement body includes a first wall, a second wall, and a hinge connecting the first wall and the second wall. An insertion instrument may be used to implant the expandable disc replacement body into a subject. The disc replacement holder is positioned between the first wall and the second wall, and an angle and/or height between the first wall and the second wall can be varied by adjustment of the disc replacement holder and locked into place using locking mechanisms.