Ratcheted Spinal Rod With Polyaxial Joints for Controlled Alignment
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Solution Overview
Problem
Current surgical treatments for scoliosis, involving long fusion rods affixed to the spine, often fail to perfectly correct spinal deformity and are not a desired clinical solution due to frequent failures.
Innovation Solution
A ratcheted spinal device with a variable-length member and a ratchet mechanism that can be lengthened or shortened using a ratchet mechanism, connected to pedicle screws or bony elements, and configured to extend, contract, or lock in place, allowing controlled spinal correction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If long fusion rods are used to force the deformed spine into a healthier position, then spinal alignment is corrected, but the deformation is rarely perfectly corrected and the long fusion for life is not a desired clinical situation
Solution Approach 1:
The spinal rod incorporates a ratchet mechanism that allows it to dynamically adjust its length after implantation. The rod can be extended or shortened in controlled increments by advancing or retracting the telescoping section, enabling post-surgical adaptation to achieve optimal spinal alignment that may not be attainable with fixed-length rods alone.
Solution Approach 2:
The spinal rod is divided into multiple sections: a fixed-length section, a telescoping variable-length section with ratchet mechanism, and connection elements. This segmentation allows independent adjustment of the variable section while maintaining structural integrity of the entire rod system, providing both stability and adjustability.
2Adaptability or versatility
If a variable-length member with ratchet mechanism is used to allow length adjustment, then adaptability is improved, but device complexity increases
Solution Approach 1:
The ratchet mechanism uses a simple pawl-and-tooth design rather than complex motorized or electronic adjustment systems. The pawl engages with ratchet teeth to prevent rotation in one direction while allowing controlled rotation in the other direction, providing reliable adjustment functionality with minimal mechanical complexity.
Solution Approach 2:
The ratchet mechanism is designed to be self-locking, automatically maintaining the adjusted length without requiring continuous active control or power sources. Once the rod is adjusted to the desired length and the locking element engages, the mechanism maintains that position passively, eliminating the need for complex control systems.
3Reliability
If the ratchet mechanism is designed to prevent rotation in one direction, then reliability of length maintenance is improved, but the ability to adjust length in both directions is reduced
Solution Approach 1:
The adjustment mechanism allows periodic bidirectional adjustment during the post-surgical recovery period. The rod can be extended or shortened in controlled increments by rotating the adjustment element, which moves the telescoping section. Once adjustment is complete, the ratchet mechanism locks the position to prevent any further rotation, providing both adjustability and stability.
Solution Approach 2:
The system transitions from a dynamic adjustable state to a static locked state. During the adjustment phase, the ratchet mechanism allows controlled rotation in both directions for extending and shortening. After the desired length is achieved, the locking element engages to prevent rotation in both directions, providing reliable length maintenance.
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 precise and controlled adjustment of spinal alignment, reducing trauma and improving the effectiveness of spinal correction procedures.
Implementation Method 1
a ratchet mechanism that has an operative configuration that allows a change in length of the variable-length member in one direction and prevents a change in length of the variable-length member in an opposite direction
Implementation Method 2
the variable-length member includes polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of the attachment members about more than one pivoting axis
Implementation Method 3
the rotation of the internal element can be done using a worm gear mechanism. The worm gear can be activated by a shaft, through a percutaneous procedure
Data Source
AI summary
A ratcheted spinal device including a variable-length member including a ratchet mechanism that has an operative configuration that allows a change in length of the variable-length member in one direction and prevents a change in length of the variable-length member in an opposite direction, wherein the variable-length member includes polyaxial-joint attachment members for attachment to bone, which permit pivoting movement of the attachment members about more than one pivoting axis.