Dynamic Spinal Stabilization Using Elastic Rods
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Solution Overview
Problem
Current spinal fixation devices are not suitable for cases where immobilization is not intended, as they either fuse vertebrae or fail to maintain restored height and allow necessary motion, leading to nerve pinching and pain due to spinal degeneration.
Innovation Solution
A dynamic intervertebral stabilization system comprising pedicle screw assemblies connected by an elastic rod assembly that allows compression, extension, and limited motion while maintaining the positional relationship of vertebrae, using a threaded shaft and screw head with a receiver for the rod, and a polycarbonate urethane rod capable of stretching and flexing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If traditional rigid rod assemblies are used to connect pedicle screws, then structural stability is improved, but vertebral motion is restricted and fusion is promoted rather than allowing necessary motion
Solution Approach 1:
The rod assembly is designed with dynamic characteristics that allow it to accommodate physiological motion between vertebrae. The rod can flex and deform elastically in response to compression, extension, and bending forces, enabling the connected pedicle screws to move relative to each other while maintaining overall structural stability. This dynamic behavior prevents fusion and preserves natural spinal motion.
Solution Approach 2:
The rod assembly's material properties and geometric parameters are optimized to provide appropriate flexibility. By controlling the rod's cross-sectional area, moment of inertia, and material modulus, the design achieves a balance between maintaining structural integrity and allowing controlled vertebral motion during compression and extension cycles.
2Stability of the object's composition
If vertebrae are immobilized to promote fusion, then spinal stability is improved, but restored height is lost and nerve pinching occurs
Solution Approach 1:
The dynamic rod assembly allows the spine to maintain restored vertebral height by permitting controlled motion and compression/extension of the vertebrae. The rod flexes to accommodate height changes during physiological loading, preventing the pinching of nerves that would occur with rigid immobilization while still providing sufficient stability.
3Adaptability or versatility
If an elastic rod assembly is used to allow vertebral motion, then adaptability is improved, but structural stability deteriorates
Solution Approach 1:
The rod assembly's material properties and geometric parameters are optimized to provide appropriate flexibility. By controlling the rod's cross-sectional area, moment of inertia, and material modulus, the design achieves a balance between maintaining structural integrity and allowing controlled vertebral motion during compression and extension cycles.
Solution Approach 2:
The rod assembly may utilize composite material structures that combine rigid and flexible components, or materials with tailored mechanical properties that provide both strength and elasticity. This allows the rod to maintain structural stability while accommodating physiological motion and deformation.
4Stability of the object's composition
If tension between pedicle screws is increased to maintain positional relationship, then stability is improved, but motion capability is reduced
Solution Approach 1:
The rod assembly is designed with dynamic characteristics that allow it to accommodate physiological motion between vertebrae. The rod can flex and deform elastically in response to compression, extension, and bending forces, enabling the connected pedicle screws to move relative to each other while maintaining overall structural stability. This dynamic behavior prevents fusion and preserves natural spinal motion.
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 maintains the restored height of vertebrae, allows necessary motion, and adjusts tension between pedicle screws, preventing fusion and alleviating nerve pinching, thus addressing the limitations of existing spinal fixation technologies.
Implementation Method 1
the rod assembly preferably has some elasticity and can provide for some compression and extension over its length and distortion along its axis
Data Source
AI summary
A vertebral dynamic stabilization system is used to fix the positional relationship of adjacent vertebrae of the spine. The vertebrae′ stabilization system includes at least two pedicle screws(20), with an interconnecting rod (60) disposed therebetween, the pedicle screws each having a threaded shaft (24) to be screwed into a vertebra segment, and a screw head (30) adapted to securely receive the interconnecting rod. The system allows some compression and extension of the vertebrae relative to each other, while still maintaining the overall positional relationship within an appropriate range.