External Driver Growing Rod for Spinal Deformity Length Adjustment
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Solution Overview
Problem
Current growing rods for treating spinal deformities, such as scoliosis, require frequent surgical interventions to extend and maintain length with the patient's growth, 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, along with alternative embodiments using fluid pressure and a toggling switch for length adjustment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional growing rods are used, then spinal deformity treatment is achieved, but frequent surgical interventions are required to extend and maintain length
Solution Approach 1:
The growing rod incorporates a dynamic extension mechanism with a telescopic structure that allows the rod to be extended through manual manipulation. The rod includes an outer rod and an inner rod that can slide relative to each other, enabling length adjustment without frequent surgeries. The mechanism includes a ratchet and pawl system that allows controlled extension in one direction while preventing backward movement, providing dynamic adaptability to spinal growth.
Solution Approach 2:
The extension mechanism is designed to be self-operating through manual manipulation by the patient or caregiver. The external driver interface allows the user to rotate a drive shaft that mechanically extends the inner rod relative to the outer rod through gear engagement. This self-service capability eliminates the need for frequent surgical interventions by enabling patients to manage their own growth requirements.
2Ease of operation
If manual extension mechanism is added, then surgical intervention frequency is reduced, but device complexity increases
Solution Approach 1:
The extension mechanism is extracted as a separate modular assembly that can be independently operated. The external driver interface is positioned outside the spinal implant, allowing manual operation without complicating the internal spinal structure. The drive shaft and gear mechanism are contained within a housing that interfaces with the telescopic rod assembly, separating the operational complexity from the spinal support function.
Solution Approach 2:
An external driver serves as an intermediary between the user and the internal extension mechanism. The external driver interfaces with a drive shaft through a housing, translating manual rotation into linear extension of the inner rod. This intermediary layer simplifies the user interface while containing the mechanical complexity within a protected housing structure.
3Ease of operation
If gear rack mechanism is used, then linear movement is achieved, but manufacturing precision requirements increase
Solution Approach 1:
The patent replaces complex gear rack mechanisms with simpler mechanical engagement systems. Instead of requiring precision-machined gear racks, the design uses a drive shaft with external threads that engage with an internally threaded rod, or a ratchet and pawl mechanism that provides linear movement through rotational motion. These alternative mechanisms reduce manufacturing precision requirements while maintaining the ability to achieve controlled linear extension.
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 system reduces the complexity of extending and retracting the growing rod, minimizing the need for frequent surgeries and maintaining length effectively with the patient's growth, providing a less invasive and more efficient solution for spinal deformity treatment.
Implementation Method 1
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 2
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
Implementation Method 3
different types of gears and gear configurations are employed to extend the extendible rod relative to the base rod. The extendible rod is extended relative to the base rod by means of applying fluid pressure through a fluid intake coupled to a fluid connection body of the growing rod
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.