Helical Wire Growth Plate Implant for Constant Force
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Solution Overview
Problem
Current implants for correcting unbalanced growth plate activity in pediatric angular limb deformities and length discrepancies are not passively safe, as the force they exert increases with bone growth, leading to potential implant breakage or growth arrest, and often result in a 'rebound effect' where growth accelerates after removal, negating the desired effect.
Innovation Solution
A device comprising a wire with two bone screws, where the wire unwinds to exert a constant force against the growth plate, allowing for controlled growth deceleration, featuring a helix that unwinds from one screw to the other, providing a predefined range of action and ensuring passive safety by gentle detachment without catastrophic failure.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Force
If plate and screw constructs are used for growth deceleration, then growth control is achieved, but the force increases with bone growth leading to implant breakage or growth arrest
Solution Approach 1:
The wire construct is designed to be dynamic rather than rigid, allowing it to adapt its force output as the bone grows. The wire gradually relaxes and changes configuration over time, maintaining a relatively constant deceleration force throughout the growth period rather than experiencing increasing forces that lead to failure.
Solution Approach 2:
The mechanical properties of the wire construct change over time as it undergoes gradual relaxation and configurational changes. The wire's effective length, tension, and geometric arrangement evolve dynamically, allowing the force parameters to remain within safe limits while continuing to provide growth deceleration.
2Force
If plate and screw constructs are used for growth deceleration, then growth control is achieved, but surgical intervention is required for removal due to force increase
Solution Approach 1:
The wire construct is designed to be self-removing through gradual relaxation and configurational changes. As the bone completes its growth and the treatment period ends, the wire naturally loosens and can be easily removed or even resorbed, eliminating the need for complex surgical intervention.
3Force
If growth deceleration is applied during treatment, then angular deformity is corrected, but rebound effect occurs after implant removal
Solution Approach 1:
The dynamic nature of the wire construct allows for gradual, continuous adjustment of the deceleration force throughout the treatment period. This progressive approach prevents sudden growth changes and reduces the likelihood of rebound effects after treatment completion, as the growth plate adapts gradually to the changing mechanical environment.
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 maintains a constant force independent of bone growth, preventing critical force buildup, allowing for larger extension (10-20 mm) and simultaneous bilateral use, addressing the issues of implant breakage and growth arrest while minimizing tissue irritation and rebound effects.
Implementation Method 1
a device consisting of a wire to be used in an assembly comprising such a device and two bone screws... the helix of the wire unwinds from the second bone screw exhibiting a, within limits, constant force
Data Source
AI summary
An assembly for correcting unbalanced growth plate activity including: (a) an implant formed of wire having (i) a longitudinal central section (2), (ii) a first end (3) configured as a first loop (4) in a form of a first helical coil (9) having a central axis (5) that is transverse to a longitudinal axis of the central section, and (iii) a second end (6) configured as a second loop (7) having a central axis (8) that is transverse to the longitudinal axis of the central section; (b) a first bone screw having a shaft section that is insertable through the first loop; and (c) a second bone screw having a shaft section that is insertable through the second loop. A kit for correcting unbalanced growth plate activity and to a method for correcting unbalanced growth plate activity are also disclosed.