Dynamic Spinal Rod With Tight Casing For Load Sharing
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Solution Overview
Problem
Current dynamic spinal systems face challenges in effectively mimicking the natural load-bearing and motion characteristics of the spine, particularly in supporting full ranges of flexion, extension, and lateral bending, while providing adequate fixation and load sharing with anterior portions of the vertebrae.
Innovation Solution
A dynamic spinal rod system comprising a shank coupled with pedicle screws and a slideable stay, with a casing that stretches tightly between the shank and the stay to provide structural connection, allowing for non-linear load distribution and deformation to mimic natural spinal motion, and a method of injecting a damping material to manage contracting movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a rigid fixation system is used to stabilize spinal joints, then stability and fixation strength are improved, but natural spinal motion and load-bearing characteristics are lost
Solution Approach 1:
The spinal rod incorporates a dynamic element that allows relative motion between rod segments, enabling the implant to adapt to natural spinal movements while maintaining stabilization. The dynamic component permits controlled translation and rotation, mimicking physiological spinal mechanics rather than imposing rigid fixation.
Solution Approach 2:
The system utilizes materials and structural designs that change mechanical properties under different loading conditions. The rod exhibits non-linear load distribution characteristics, where stiffness and flexibility vary depending on the magnitude and direction of applied forces, allowing it to maintain stability at high loads while permitting motion at physiological load levels.
2Strength
If pedicle screws are used for fixation, then anchoring strength is improved, but the system fails to share loads with anterior portions of the spine in a physiologically appropriate manner
Solution Approach 1:
The dynamic spinal rod acts as an intermediary between the pedicle screws and the anterior spinal structures. It transfers and distributes loads non-linearly, allowing the posterior fixation system to share loads with anterior portions of the spine in a manner that mimics natural load-bearing patterns rather than concentrating all forces at the screw-bone interface.
3Adaptability or versatility
If a dynamic system is designed to mimic natural spinal motion, then physiological accuracy is improved, but providing adequate fixation and supporting full ranges of motion becomes challenging
Solution Approach 1:
The dynamic rod employs non-linear mechanical properties where the relationship between applied force and resulting motion is not proportional. This allows the system to provide rigid support when needed for fixation stability while permitting greater motion ranges under physiological loading conditions, effectively changing mechanical parameters based on load magnitude.
Solution Approach 2:
The spinal rod utilizes composite material construction combining elements with different mechanical properties. This allows the implant to exhibit both rigid and flexible characteristics in different regions or under different conditions, providing adequate fixation strength while maintaining the ability to mimic natural spinal motion patterns.
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 supports a wide range of anatomical loads and mimics natural spinal motion, providing stable fixation and load sharing with anterior vertebrae, enhancing the physiological accuracy and durability of spinal implants.
Implementation Method 1
the casing being sized to stretch tightly between the shank and the stay and provide a structural connection between the shank and the stay when the stay is near the second end of the shank
Implementation Method 2
injecting a material between the shank and the stay to dampen contracting movement of the dynamic spinal rod
Data Source
AI summary
Embodiments of the invention include a system and method for stabilizing a segment of a spinal column with a dynamic spinal rod having a shank, a stay, and a casing sized to stretch tightly between components of the dynamic spinal rod and provide a structural connection between the components.