Spinal Growing Rod Manual Extension Mechanism
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Solution Overview
Problem
Current growing rods for treating spinal deformities, such as scoliosis, require frequent surgical interventions to extend as the patient grows, which is complex and inconvenient.
Innovation Solution
A growing rod system with a base rod and an extendible rod connected via a distraction unit, featuring a gear rack mechanism and a rotatable drive interface accessible externally, allowing manual extension and retraction without a power source, and a latching mechanism to prevent unintended retraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If traditional growing rods are used, then the rod can be implanted to treat spinal deformities, but frequent surgical interventions are required to extend the rod as the patient grows
Solution Approach 1:
The growing rod system allows the patient to extend the rod themselves through a manual crank mechanism accessible through the skin, eliminating the need for frequent surgical interventions. The patient can perform the extension action independently, making the system self-servicing rather than requiring external medical intervention for each adjustment.
Solution Approach 2:
The patent replaces the complex surgical extension mechanism with a simple manual crank system that can be operated through the skin. This mechanical substitution transforms a surgically-intensive system into a user-friendly manual operation system, reducing device complexity while extending functionality duration.
2Adaptability or versatility
If the growing rod is made extendible to accommodate patient growth, then the rod can grow with the patient, but the mechanism for extending and retracting becomes complex
Solution Approach 1:
The extendible rod is nested within the base rod, with the extendible rod containing the gear rack and the distraction unit housed within the base rod structure. This nesting arrangement allows the rod to adapt to patient growth while maintaining a compact, integrated design that reduces overall device complexity.
Solution Approach 2:
The gear rack and pinion mechanism serve as intermediaries between the manual crank operation and the linear extension of the rod. This intermediary mechanical system translates rotational crank motion into linear rod extension, providing a simple and effective solution for adaptability without requiring complex control systems.
3Ease of operation
If the growing rod allows manual extension, then surgical interventions are reduced, but the risk of unintended retraction increases
Solution Approach 1:
The ratchet mechanism is designed to prevent reverse motion (unintended retraction) by allowing motion in only the extension direction. This preliminary anti-action is built into the mechanism structure, where the ratchet teeth engage to block any backward movement, ensuring reliability while maintaining ease of manual extension.
Solution Approach 2:
The locking mechanism automatically engages through the ratchet and pawl design, providing self-locking functionality without requiring additional active components or power sources. This self-service locking feature maintains reliability while keeping the system simple and easy to operate.
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
This design reduces the complexity of extending and retracting the growing rod, minimizing the need for frequent surgeries and maintaining stability under patient movement, allowing for extended growth periods before replacement.
Implementation Method 1
rotation of the rotatable drive interface causes linear movement of the extendible rod through the gear rack
Implementation Method 2
a drive gear mechanism housed within the housing and coupled to the rotatable drive interface and the gear rack such that rotation of the rotatable drive interface causes linear movement of the extendible rod through the gear rack
Implementation Method 3
A latching mechanism housed within the housing is configured to latch onto the drive gear mechanism to prevent the rotatable drive interface from being able to rotate in a second direction
Data Source
AI summary
An implantable growing rod assembly adapted to be secured along a length of a spine for treating deformities of the spine. The assembly includes a housing, a fixed rod extending along a longitudinal axis away from the housing, and an expansion rod extendible from the housing along the longitudinal axis. A driver assembly is fixed to the housing and adapted to translate the expansion rod along the longitudinal axis.