Expandable Interbody Device Dual-Stage Wedge Linkage Mechanism
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Solution Overview
Problem
Conventional interbody devices used in spinal surgery lack the ability to achieve significant expansion, limiting their stability and fixation capabilities between vertebrae, as they rely solely on wedge mechanisms that restrict maximum height expansion.
Innovation Solution
An expandable interbody device with a dual-stage mechanism, utilizing wedge and linkage blocks controlled by a drive screw, where the threads are timed to engage and disengage at specific stages to allow for initial expansion by wedge blocks and further expansion by linkage blocks, enabling greater height increase than conventional devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If a conventional wedge mechanism is used for expansion, then the device structure is simple, but the maximum height expansion is limited
Solution Approach 1:
The expansion mechanism is divided into two independent stages: a first wedge mechanism for initial expansion and a second linkage mechanism for further expansion. This segmentation allows each mechanism to be optimized for its specific function while achieving greater overall expansion than a single mechanism could provide.
Solution Approach 2:
The device transitions from a static single-mechanism design to a dynamic multi-stage system where the drive screw sequentially engages different mechanisms. The system adapts its expansion method based on the current expansion state, using the wedge mechanism first and then the linkage mechanism for additional expansion.
2Length of moving object
If a dual-stage mechanism with wedge and linkage blocks is used, then the height expansion is significantly increased, but the device complexity increases
Solution Approach 1:
The drive screw serves multiple functions: it acts as the actuating mechanism for the wedge blocks in the first stage and then engages the linkage blocks in the second stage. This multi-functionality reduces the need for separate actuating mechanisms for each expansion stage, thereby limiting the increase in overall device complexity.
Solution Approach 2:
The second linkage mechanism is positioned within the same structural envelope as the first wedge mechanism, with both mechanisms sharing the same drive screw and structural space. This nesting approach allows dual functionality without proportionally increasing the device's external dimensions or structural complexity.
3Ease of operation
If the drive screw threads are timed to engage only wedge blocks in the first stage, then the expansion sequence is controlled, but the manufacturing precision requirements increase
Solution Approach 1:
The drive screw is designed with pre-calculated thread geometry that automatically sequences the engagement of wedge and linkage blocks. The thread profile is manufactured to inherently control the expansion sequence, eliminating the need for complex control systems or post-manufacturing adjustments, thereby reducing operational complexity despite increased manufacturing precision requirements.
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 dual-stage mechanism allows for increased expansion, potentially doubling the initial height of the device, providing enhanced stability and fixation between vertebrae, while maintaining resistance to compressive loads through ratchet mechanisms and spring-loaded teeth.
Implementation Method 1
controlled by rotation of a drive screw. The threads of the drive screw are timed such that only the wedge blocks are engaged by the drive screw in a first stage
Implementation Method 2
Angled grooves of the wedge blocks engage with angled bosses on the endplates of the expandable interbody device, which causes the device to expand
Implementation Method 3
maintaining resistance to compressive loads through ratchet mechanisms and spring-loaded teeth
Implementation Method 4
maintaining resistance to compressive loads through ratchet mechanisms and spring-loaded teeth
Data Source
AI summary
An example expandable interbody device can include a structural body having an upper endplate and a lower endplate, where the endplates are shaped to nest tightly in a closed position. The device can include at least one wedge block and at least one linkage block arranged between the upper and lower endplates of the structural body. The device can include a drive screw threaded through the at least one wedge block and the at least one linkage block. The drive screw can be configured to rotate and drive the at least one wedge block to expand the upper and lower endplates of the structural body from the closed position to an intermediate position. Additionally, the drive screw can be further configured to rotate and drive the at least one linkage block to expand the upper and lower endplates of the structural body from the intermediate position to an open position.