Spinal Stabilization Rigid-Flexible Coupling via Nested Bore
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Solution Overview
Problem
Combining rigid and dynamic stabilization systems in spinal stabilization poses challenges, particularly in maintaining the coupling of a flexible element with a rigid element after the flexible element's stiffness decreases post-implantation, which affects the stability and mobility of the spine.
Innovation Solution
A spinal stabilization system that securely couples a rigid element with a flexible element using various methods such as braiding, ultrasonic welding, and compression-fit collars, ensuring the connection remains stable even after the flexible element relaxes over time, utilizing anchor members like pedicle screws and spacers to distribute loads and maintain immobilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible element is coupled to a rigid element in a spinal stabilization system, then dynamic stabilization and mobility are improved, but the coupling reliability deteriorates after the flexible element's stiffness decreases post-implantation
Solution Approach 1:
The flexible element is inserted through an axial bore of the rigid element, with the rigid element's flange providing external containment. This nested configuration ensures the flexible element remains coupled to the rigid element even as its stiffness decreases, maintaining both dynamic stabilization and coupling reliability
Solution Approach 2:
The axial bore and flange structure of the rigid element serve as an intermediary mechanism that secures the flexible element. This intermediary structure maintains the coupling relationship between the rigid and flexible elements throughout the post-implantation period, preventing detachment despite changes in flexible element properties
2Stability of the object's composition
If rigid stabilization is used to immobilize the spine, then spinal stability is improved, but mobility and stress on nearby vertebrae worsen
Solution Approach 1:
The system merges rigid stabilization (providing spinal stability through the rigid element and anchor members) with dynamic stabilization (providing mobility through the flexible element). This combination allows the spine to remain stable while maintaining natural movement capabilities and distributing stress across both element types
Solution Approach 2:
The stabilization system uses a composite construct combining rigid and flexible elements with different mechanical properties. The rigid element provides structural stability while the flexible element allows movement, creating a composite system that delivers both stability and mobility simultaneously
3Ease of operation
If the flexible element's stiffness decreases after implantation, then range of motion is improved, but coupling with the rigid element deteriorates
Solution Approach 1:
The flexible element is nested within the axial bore of the rigid element, with the flange providing external containment. This nested design maintains coupling stability regardless of changes in the flexible element's stiffness, allowing range of motion to increase while preventing coupling failure
Solution Approach 2:
Instead of trying to prevent the flexible element's stiffness from decreasing, the design inverts the approach by creating a containment structure (axial bore with flange) that maintains coupling regardless of stiffness changes. This allows the natural relaxation process to occur while preserving coupling integrity
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 system effectively provides both rigid and dynamic stabilization, maintaining spinal stability and mobility by ensuring the flexible element remains securely coupled to the rigid element, reducing stress on nearby vertebrae and allowing for enhanced range of motion without compromising immobilization.
Implementation Method 1
the axial bore is shaped to retain an end portion of the flexible element therein
Data Source
Figure 1~2
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Figure 6~6A
AI summary
The present invention relates to a spinal stabilization system, comprising: first and second anchor members configured to be secured to first and second vertebrae within a patient's body, respectively, the second anchor member including a pedi-cle screw body, a housing having opposed first and second tabs extending upwardly therefrom, and a set screw, the first and second tabs and the housing each having internal threads; a flexible element secured to the first anchor member and having an end portion; a rigid element secured to the second anchor member and having an end portion with an end surface, an axial bore extending from the end surface, an outer surface, and an opening on the outer surface extending into the axial bore, the axial bore receiving the end portion of the flexible element; and a fastener extending through the opening in the outer surface of the rigid element to retain the flexible element in the axial bore; wherein the set screw engages the internal threads of the first and second tabs and the housing and drives the fastener into the axial bore.