Dynamic Posterior Stabilization Device with Viscoelastic Shock Absorber
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Solution Overview
Problem
Existing posterior vertebral stabilization devices either rigidify vertebrae, leading to excessive stress on connecting elements, or provide insufficient mobility and stress absorption, particularly in tension/compression and flexion, while failing to conform to anatomical lordosis.
Innovation Solution
A dynamic stabilization device combining rigid and viscoelastic means, featuring a mobile piston rod, a viscoelastic shock-absorbing pad, and a fixed rod forming an angle to apply elastic return force, absorbing compression and flexion forces while maintaining mobility compatible with anatomical lordosis.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If rigid fixation systems are used to stabilize vertebrae, then mechanical stress absorption is improved, but mobility of the intervertebral segment is lost and excessive stress is placed on connecting elements
Solution Approach 1:
The device transitions from rigid fixation to dynamic stabilization by incorporating a mobile piston rod that can move within the cap, allowing the system to adapt to mechanical stresses while maintaining stability. The piston rod's mobility enables the device to absorb stresses in tension/compression and flexion without compromising the stabilization function.
Solution Approach 2:
The device changes the rigidity parameter dynamically through the viscoelastic shock-absorbing pad that compresses under load. This pad provides rigidity when needed for stress absorption but allows mobility when stresses are reduced, creating an intermediate state between rigid fixation and complete mobility.
2Adaptability or versatility
If semirigid systems with artificial ligaments are used, then intermediate rigidity is achieved, but the systems work only in tension and are not elastic in compression mode
Solution Approach 1:
The device combines rigid elements (piston rod, cap, fixed rod) with viscoelastic material (shock-absorbing pad) to create a composite system that provides both structural integrity and elastic deformation capability. This composite structure enables the device to function effectively in both tension and compression modes, overcoming the limitation of artificial ligament systems.
Solution Approach 2:
The viscoelastic shock-absorbing pad acts as an intermediary element between the rigid piston rod and the fixed rod. This intermediary provides the necessary elasticity and compression resistance, enabling the device to handle multi-directional stresses while maintaining intermediate rigidity.
3Strength
If polyurethane cylinder systems are used, then compression strength is improved, but the cylinder cannot comply with anatomical lordosis and mobility is restricted
Solution Approach 1:
The mobile piston rod can rotate and move within the cap, allowing the device to dynamically adapt to the anatomical lordosis angle. This dynamic capability enables the rigid polyurethane cylinder to comply with the natural curvature of the spine while maintaining compression strength, unlike fixed rigid systems.
Solution Approach 2:
The device segments the rigid structure into a mobile piston rod portion and a fixed rod portion, allowing different segments to perform different functions. The mobile segment can orient itself to match anatomical lordosis while the fixed segment provides compression strength, resolving the conflict between rigidity and adaptability.
4Stability of the object's composition
If metal rod systems are used, then structural rigidity is achieved, but mobility closer to rigid rod than to normal anatomical position is obtained
Solution Approach 1:
The viscoelastic shock-absorbing pad changes the rigidity parameter dynamically, allowing the device to provide structural rigidity when compression forces are applied but to permit mobility toward anatomical position when forces are reduced. This parameter change enables the system to balance stability with natural movement.
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 device provides enhanced mobility and stress absorption, reducing wear and tear, and ensuring a longer service life by distributing stresses evenly and applying a return force that aligns with spinal biomechanics, thus addressing the limitations of prior art.
Implementation Method 1
a viscoelastic shock-absorbing pad (23) comprising a convex face (230)
Implementation Method 2
a combination of rigid means and of viscoelastic means allowing the device (2) to form an angle γ in the neutral position between its two attachment elements to the pedicular screws and to apply a permanent elastic return force around this position while absorbing the compression and flexion forces applied to the pedicular screws
Data Source
AI summary
The a device is provided for dynamic posterior stabilization. The device combines includes a mobile piston rod with a piston head at an end thereof; a viscoelastic shock-absorbing unit having a convex surface; a fixed rod defining an angle relative to an axis of a casing and the fixed rod including, at an end thereof, a concave surface; a viscoelastic ring; and wherein the viscoelastic components are contained within the casing.