Dynamic Stabilization Rod With Damper Slider Mechanism
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Solution Overview
Problem
Existing spinal stabilization devices often eliminate motion by using rigid rods and screws, which can lead to severe back pain and limited mobility, and require difficult decisions about screw types during implantation.
Innovation Solution
A dynamic spinal stabilization implant that uses pedicle screws with a rod system featuring a damper and slider mechanism, allowing for axial and bending motion, and utilizing materials with varying stiffness to regulate movement, eliminating the need for locking screws and approximating natural spinal motion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If rigid rods and screws are used to stabilize the spine, then spinal stability is improved, but natural spinal motion is eliminated
Solution Approach 1:
The rod system transitions from a static rigid structure to a dynamic system with dampers that allow controlled motion. The dampers enable the rod to adapt its stiffness characteristics based on loading conditions, permitting natural spinal motion while maintaining stability when needed.
Solution Approach 2:
The damper components change the effective stiffness parameter of the rod system dynamically. Under low loads, the dampers allow greater motion; under high loads, they provide increased resistance. This parameter change resolves the contradiction by making the rod neither completely rigid nor completely flexible.
2Strength
If locking screws are used to attach rigid rods, then rod-screw connection strength is improved, but implantation complexity increases
Solution Approach 1:
The non-locking screw design allows the rod to self-retain through friction and geometry without requiring additional locking mechanisms. The system serves itself by using the rod's own characteristics to maintain the connection, eliminating the need for complex locking procedures during implantation.
Solution Approach 2:
The connection transitions from a locked rigid state to a friction-based retained state. The rod and screw interface uses friction and geometric interference to maintain connection without mechanical locking, simplifying the implantation process while maintaining adequate strength.
3Ease of operation
If non-locking screws are used to attach rods, then implantation ease is improved, but connection reliability deteriorates
Solution Approach 1:
The rod system uses composite construction with different materials (e.g., PEEK and metal) that provide both ease of implantation and reliable connection. The composite structure allows for friction-based retention with non-locking screws while maintaining sufficient connection strength through material properties and geometric design.
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 implant provides dynamic stabilization, allowing for both axial and bending motion, simplifying the implantation process and closely mimicking natural spinal function, while reducing the need for complex screw decisions and minimizing pain and mobility limitations.
Implementation Method 1
The damper is formed of a material having compressive properties that limit movement of the slider portion along the first rod portion by: a. providing resistance to movement of the slider portion in the axial direction
Implementation Method 2
increasing the frictional resistance of the damper along the first rod portion as a result of radial deformation
Data Source
AI summary
A spinal stabilization rod includes a first rod portion having a proximal end and a distal end and having a first cross-sectional area. The second rod portion extends from the distal end of the first rod portion and has a second minimum cross-sectional area smaller than the first cross-sectional area. The second rod portion is formed of a first material and a different second material, with the first material being more resistant in shear than the second material. The implant also includes a slider portion disposed about and movable relative to the second rod portion.