Bone Fixation Device One-Way Rod Translation Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current growing rod systems for scoliosis treatment require frequent surgical interventions to adjust their length as the spine grows, which is inconvenient and can interfere with normal growth in younger patients.
Innovation Solution
A bone fixation device with a locking mechanism that allows the rod to passively lengthen in response to bone growth without the need for post-installation adjustments, using a combination of split rings, springs, and cam mechanisms to facilitate one-way translation of the rod relative to the housing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If traditional growing rod systems are used, then the rod can be adjusted manually every six months, but this requires frequent surgical interventions and post-installation adjustment
Solution Approach 1:
The locking mechanism is designed to automatically accommodate rod lengthening through passive translation as the bone grows, without requiring manual intervention or surgical adjustments. The mechanism self-regulates the rod length adaptation process
Solution Approach 2:
The locking mechanism allows dynamic adjustment of the rod length through controlled translation in the growth direction while maintaining stability in the opposite direction. This enables the system to adapt automatically to bone growth
2Ease of operation
If manual adjustment procedures are used, then the rod length can be changed, but this interferes with normal growth in younger patients
Solution Approach 1:
The device performs the lengthening adjustment automatically through passive translation driven by bone growth forces, eliminating the need for manual surgical interventions that would interfere with normal growth processes
Solution Approach 2:
The locking mechanism is pre-configured to allow translation in the growth direction while preventing reverse movement, enabling automatic adaptation to future growth without requiring intervention
3Extent of automation
If active elements and telemetry systems are used, then the rod can lengthen without surgical procedures, but this increases device complexity and requires additional power sources
Solution Approach 1:
The patent replaces complex active systems with a simple passive mechanical locking mechanism that uses the natural forces of bone growth to drive rod lengthening through controlled translation, eliminating the need for power sources or active elements
Solution Approach 2:
The mechanical system uses the bone's own growth forces to drive the lengthening process automatically, without requiring external power sources or active control mechanisms
4Adaptability or versatility
If the rod is allowed to translate freely, then the bone can grow without interference, but this compromises structural stability
Solution Approach 1:
The locking mechanism is designed with asymmetric constraints that allow translation in the growth direction while preventing translation in the opposite direction, enabling adaptive lengthening while maintaining structural stability
Solution Approach 2:
The mechanism provides dynamic stability by allowing controlled movement in the growth direction while maintaining rigid constraints in the opposite direction, adapting to growth while preserving structural integrity
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
Enables the bone fixation device to accommodate spinal growth without requiring surgical adjustments, maintaining structural stability and allowing for passive lengthening of the rod, reducing the frequency of interventions and minimizing interference with normal bone growth.
Implementation Method 1
a spring element applying a force to the split ring in the direction of the smaller diameter where the rod is positioned within the split ring
Implementation Method 2
a cam that is rotationally biased in one direction and has a surface that is configured and dimensioned to inhibit translation of the rod relative to the housing in one direction and allowing for translation of the rod relative to the housing in an opposite direction
Data Source
AI summary
A bone fixation device adapted to be coupled to bone anchors that allows movement of rods to permit a screw-rod construct to lengthen in response to bone growth without necessitating post surgical installation adjustment of the device. The bone fixation device includes a locking mechanism that is operably associated with a housing to allow relative movement of a rod and a housing in a first direction and inhibiting relative movement of the rod and the housing in a second direction.