Coaxial Screw Gear Sleeve Expansion for Disc Space Height Control
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Solution Overview
Problem
Existing intervertebral fusion devices face challenges in achieving sufficient distraction and fusion while maintaining the normal height of the disc space, often requiring multiple devices and increasing operation time and risk due to issues like device migration and nerve injury.
Innovation Solution
The use of a coaxial screw gear sleeve mechanism with a threaded post and corresponding sleeve, driven by a geared exterior surface, allows for controlled distraction and fusion by rotating the sleeve relative to the post, expanding the device to maintain disc space height.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single intervertebral fusion device is used to maintain disc space height, then device complexity is reduced, but it becomes difficult to achieve both sufficient distraction and precise height control
Solution Approach 1:
The device incorporates a telescoping mechanism with a distractible cage and extendable rod that allows dynamic adjustment of the device height after implantation. This enables the device to transition from a static structure to a dynamically adjustable one, providing both sufficient distraction capability and precise height control through the coaxial screw gear sleeve mechanism.
Solution Approach 2:
The device employs a nested structure where the rod is positioned within the cage, and the coaxial screw gear mechanism integrates multiple components (screw, gear, sleeve) in a compact nested arrangement. This nesting allows the device to achieve complex functions (distraction + height control) within a single integrated unit rather than requiring multiple separate devices.
2Reliability
If multiple devices are used to achieve sufficient distraction and fusion, then distraction effectiveness is improved, but operation time increases and risk of nerve injury increases
Solution Approach 1:
The invention merges the functions of multiple devices (cage and rod, or multiple cages) into a single integrated telescoping device. The distractible cage combined with the extendable rod provides the distraction capability that previously required multiple devices, thereby reducing operation time and minimizing the risk of nerve injury associated with implanting multiple separate components.
3Object-affected harmful factors
If the device is made small enough for minimal nerve retraction, then nerve injury risk is reduced, but the device height becomes insufficient to maintain normal disc space
Solution Approach 1:
The device is designed with a telescoping mechanism that allows it to start in a compact form factor for safe implantation with minimal nerve retraction, then be extended in situ to achieve the necessary height for maintaining normal disc space. This dynamic transformation resolves the contradiction between initial small size and final sufficient height.
Solution Approach 2:
The device is implanted in a collapsed or partially extended state to minimize nerve retraction and surgical risk, then subsequently extended to its full height capability. This preliminary action approach allows the surgeon to benefit from the reduced risk of implanting a small device while later achieving the necessary height for disc space maintenance.
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 mechanism provides controlled and efficient distraction and fusion, minimizing device migration and nerve injury risks, with high resolution height control and reduced operational time, while maintaining structural integrity under dynamic loads.
Implementation Method 1
a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post
Implementation Method 2
a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing the device to distract
Data Source
AI summary
Medical devices in accordance with various embodiments of the present invention employ one or more coaxial screw gear sleeve mechanisms. In various embodiments, coaxial screw gear sleeve mechanisms include a post with a threaded exterior surface and a corresponding sleeve configured to surround the post, the corresponding sleeve having a threaded interior surface configured to interface with the threaded exterior surface of the post and a geared exterior surface. A drive mechanism can be configured to interface with the geared exterior surface of the sleeve, causing the device to expand.