Expandable Spinal Implant with Screw-Driven Linkage
Solution Overview
Problem
Existing spinal interbody implants face challenges in providing a large footprint while minimizing surgical invasiveness, often compromising on design complexity, manufacturability, patient safety, and material choice, with uncontrolled expansion mechanisms leading to instability and difficulty in retraction.
Innovation Solution
A spinal implant with a U-shaped base and link arms that expand in a controlled and predictable manner, using a threaded screw mechanism to translate link arms and maintain the displaceable element parallel to the base, allowing for a large expansion ratio and stable support, while enabling easy insertion and retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a large fixed dimension spacer is used to provide adequate footprint and support, then the implant can adequately support adjacent vertebrae and provide stability, but the surgical procedure becomes more invasive and recovery time increases
Solution Approach 1:
The implant transitions from a static fixed dimension spacer to a dynamic expandable structure. The device is inserted in a collapsed low-profile state to minimize surgical invasiveness, then expanded in-situ to achieve a large footprint area for adequate vertebral support and stability.
Solution Approach 2:
The implant employs a nested configuration where the displaceable element is contained within the base element during insertion. The expandable structure allows the implant to be inserted in a compact collapsed state and then deployed to its full expanded size within the intervertebral space.
2Object-affected harmful factors
If expandable implants are used to provide large footprint with minimally invasive insertion, then surgical invasiveness is reduced, but design complexity increases and may impact manufacturability and reliability
Solution Approach 1:
The implant is divided into distinct functional segments: a base element with first and second ends, and a displaceable element with corresponding segments. This segmentation allows independent optimization of each component and simplifies the expansion mechanism by using discrete movable parts rather than a monolithic complex structure.
Solution Approach 2:
The displaceable element is extracted as a separate movable component from the base element. This separation allows the displaceable element to be independently actuated through the link arm mechanism, simplifying the overall design compared to integrated expandable structures.
3Object-affected harmful factors
If expandable implants are used to reduce surgical invasiveness, then smaller insertion size is achieved, but control over expansion path and position may be lost leading to dislodgment
Solution Approach 1:
The link arm mechanism provides mechanical feedback control during expansion. As the displaceable element expands, the link arms translate in response to the changing geometry, automatically maintaining proper alignment and preventing lateral displacement or rockling motion throughout the expansion process.
Solution Approach 2:
The link arms are positioned asymmetrically relative to the centerline of the implant, with specific distances from the centerline defined. This asymmetric configuration creates geometric constraints that guide the expansion path and prevent lateral displacement, ensuring stable controlled expansion.
4Volume of moving object
If link arms converge toward the center during expansion, then expansion is achieved, but the enclosure for biological filler material becomes inadequately small
Solution Approach 1:
The link arms are constrained to move in a direction substantially parallel to the longitudinal axis of the implant rather than converging toward the center. This dimensional change in the expansion path maintains a large enclosed volume for biological filler material while still achieving the desired expansion of the implant footprint.
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 implant achieves a wide footprint with controlled expansion, providing structural stability and ease of biological filler insertion, suitable for a range of disc heights, and allowing for minimally invasive procedures with reduced risk of dislodgment.
Implementation Method 1
using a threaded screw mechanism to translate link arms
Data Source
AI summary
An expandable spinal interbody implant having a base member and a displaceable member connected by a screw driven linkage mechanism. The implant may include mechanisms for controlling the implant throughout its full range of expansion and retraction to prevent formation of the implant into undesired profiles in the intervertebral space. The displaceable element may be overlapped with the base in a fully expanded state. Alternatively, the displaceable element may exist fully outside of the base. The displaceable element may be hinged and bent in conjunction with the linkage based implant expansion.