Variable-Length Spinal Rod with Ratchet Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current spinal implants for conditions like scoliosis, hyperkyphosis, and hyperlordosis lack advanced mechanisms for adjustable length and movement, limiting their adaptability and stability during surgical correction.
Innovation Solution
A spinal device with a variable-length member featuring a ratchet mechanism that can be lengthened or shortened, with multiple configuration settings (active, passive, and locked) and a force applicator to control the ratchet, allowing for connection to pedicle screws and bony elements, and incorporating polyaxial-joint attachment members for multiple degree-of-freedom movement.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fixed-length spinal rod is used, then the structure is simple and reliable, but the adaptability to different spinal deformities is limited
Solution Approach 1:
The spinal rod is transformed from a fixed-length static structure to a variable-length dynamic structure. The ratchet mechanism enables the rod to be lengthened or shortened during surgery, allowing adaptation to different spinal deformities while maintaining structural integrity through the locked position when length is fixed.
Solution Approach 2:
The rod system is divided into modular components including the variable-length member, ratchet mechanism, connectors, and attachment members. This segmentation allows the rod to be adjusted in length while maintaining connection to pedicle screws and other spinal rods, resolving the contradiction between adaptability and structural simplicity.
2Adaptability or versatility
If a ratchet mechanism is added to enable length adjustment, then the adaptability is improved, but the device complexity increases
Solution Approach 1:
The ratchet mechanism is designed to be self-locking, automatically preventing backward movement when the rod is lengthened. This self-service feature reduces the need for additional control mechanisms, enabling length adjustment without proportionally increasing overall device complexity.
Solution Approach 2:
The ratchet mechanism serves multiple functions: it enables length adjustment, provides a locked position for stability, and can be activated by various means including manual rotation, worm gear mechanisms, or electric motors. This multi-functionality justifies the added complexity by delivering multiple capabilities through a single integrated system.
3Adaptability or versatility
If the rod is made flexible to allow movement, then the movement freedom is improved, but the stability and load-bearing capacity deteriorate
Solution Approach 1:
The rod transitions from a purely rigid structure to a dynamically adjustable structure. When the ratchet mechanism is active, the rod can be lengthened or shortened while maintaining sufficient rigidity for load-bearing. When locked, the rod provides maximum stability. This dynamic behavior resolves the contradiction between movement freedom and strength.
Solution Approach 2:
Different portions of the rod system have different rigidity characteristics. The variable-length member can be flexible during adjustment, while the connectors and attachment members maintain high rigidity for load transmission. This local differentiation of mechanical properties allows the system to achieve both movement freedom and strength where needed.
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 adjustability and stability for spinal correction, allowing for precise alignment and movement, improving surgical outcomes by enabling customizable length adjustment and secure fixation to the spine.
Implementation Method 1
a ratchet mechanism which 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 rotation of the internal element can be done using a worm gear mechanism
Data Source
AI summary
A 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, characterized by a force applicator operative to adjust or advance the ratchet mechanism.