Hydraulic Expandable Spinal Rod for Scoliosis Growth
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Solution Overview
Problem
Existing expandable spinal rods for treating scoliosis, such as magnetic and mechanically distractible rods, face limitations including restricted growth accommodation, invasive multiple surgeries, and susceptibility to medical imaging issues, necessitating an improved device for pediatric patients with growing spines.
Innovation Solution
A hydraulic expandable spinal rod system comprising a static rod and a piston rod with a hydraulic pressure chamber, injection port, and locking mechanism, allowing for axial movement and expansion without the need for multiple invasive surgeries, utilizing hydraulic fluid to lengthen the rod and accommodate spinal growth.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If fixed-length spinal rods are used to correct spinal curvature, then the initial correction is achieved, but the rod prevents further spinal growth in pediatric patients
Solution Approach 1:
The spinal rod transitions from a static fixed-length structure to a dynamic expandable structure. The rod includes internal components (piston rod, hydraulic cylinder, seals) that allow it to change length over time. The system can be adjusted from an initial compressed state to an expanded state, enabling it to adapt to spinal growth while maintaining correction forces.
Solution Approach 2:
The rod employs a nested structure where the piston rod is inserted within the hydraulic cylinder, and the expandable portion is contained within the main rod body. This nested arrangement allows the rod to compactly store its expansion mechanism while providing the capability for length adjustment, enabling both initial correction and future growth accommodation.
2Length of moving object
If magnetic motors are used to distract rod portions for lengthening, then some expansion is achieved, but distraction forces are limited by motor strength and MRI compatibility is lost
Solution Approach 1:
The invention replaces magnetic motor mechanisms with a hydraulic distraction system. Hydraulic fluid is pumped into the cylinder to generate distraction forces that separate the rod portions. This hydraulic approach provides stronger and more controllable distraction forces compared to small magnetic motors, and the materials used (titanium, cobalt-chromium, stainless steel) are MRI-compatible.
Solution Approach 2:
The patent substitutes magnetic field-based actuation with a hydraulic mechanical system. Instead of using magnetic motors that generate force through electromagnetic fields, the system uses hydraulic pressure transmitted through fluid to generate mechanical distraction forces. This substitution maintains mechanical reliability while ensuring MRI compatibility.
3Length of moving object
If mechanically distractible rods are used with manual distraction instruments, then rod lengthening is possible, but multiple invasive surgeries are required
Solution Approach 1:
The rod system incorporates self-contained lengthening capabilities that can be activated through minimally invasive procedures. The hydraulic system includes an injection port that allows fluid to be introduced through a small needle puncture rather than requiring open surgical access. This enables the rod to perform its own lengthening function with minimal external intervention, reducing the need for multiple invasive surgeries.
Solution Approach 2:
The invention introduces a minimally invasive intermediary access method using needle punctures and injection ports rather than requiring open surgical access. The hydraulic fluid serves as a mediator that can be introduced through the small puncture to activate the lengthening mechanism, bridging the gap between the external world and the internal rod mechanism without requiring invasive surgical exposure.
4Adaptability or versatility
If expandable rod portions are used to accommodate growth, then spinal growth can continue, but the mechanism becomes more complex with additional components
Solution Approach 1:
The expandable components are nested within each other - the piston rod within the hydraulic cylinder, and both within the main rod body. This nested arrangement allows multiple functional components to be contained within a compact space, providing growth accommodation capability without significantly increasing the overall device footprint or apparent complexity.
Solution Approach 2:
The hydraulic cylinder and piston rod assembly serves multiple functions: it provides the expansion mechanism for growth accommodation, acts as a structural component of the rod, and includes sealing mechanisms to maintain hydraulic pressure. By making these components multi-functional, the design reduces the need for separate dedicated components for each function, thereby managing complexity.
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 hydraulic expandable spinal rod system effectively corrects spinal deformities by allowing controlled and minimally invasive lengthening, accommodating spinal growth, and is compatible with medical imaging techniques, reducing surgical trauma and frequency.
Implementation Method 1
the second rod portion is inserted within the internal cavity of the first rod portion and is axially movable relative to the first rod portion within the internal cavity in an expansion direction. The rod is sealingly engaged to the internal wall surface and thereby defines a hydraulic pressure chamber
Data Source
Figure 1A~1B
Figure 2A~2B
Figure 3
AI summary
Hydraulically expandable spinal rods and methods of use thereof are disclosed. The spinal rod may include a piston rod, a static rod, and a hydraulic pressure chamber for accepting hydraulic fluid and causing the piston rod to move in an expansion direction relative to the static rod. Upon connection of the piston and static rods to a patient's spinal column, the hydraulic spinal rod may be expanded to aid in correction of an underlying spinal deformity.