Flexible Shaft Support Rod for Orthopedic Torque Transmission
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Solution Overview
Problem
Flexible shafts used for applying torque to difficult-to-reach bone sites along curved paths often become stiffened when a guide wire is inserted, leading to torque loss and issues like pig-tailing due to increased rigidity, especially when bending around tight radii.
Innovation Solution
A support rod is designed to be inserted within the flexible shaft, featuring a support portion that maintains rigidity in non-bending sections and a flex portion with an annular gap to allow bending, preventing coiling and ensuring torque transfer along curved paths by maintaining flexibility and support through a snug fit and reduced diameter design.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a guide wire is inserted into the flexible shaft to provide support, then the shaft gains structural support, but the shaft becomes overly stiffened and loses flexibility causing torque loss and pig-tailing
Solution Approach 1:
The support rod is designed with varying diameters along its length, creating different mechanical properties in different sections. The larger diameter portions provide support where needed, while the reduced diameter portions allow flexibility and bending, thus resolving the contradiction between structural support and flexibility.
Solution Approach 2:
The support rod is divided into multiple sections with different diameters rather than being a uniform structure. This segmentation allows the rod to provide support in specific regions while maintaining flexibility in other regions, preventing both torque loss and pig-tailing.
2Adaptability or versatility
If a thin flexible shaft is used to reach curved paths, then the shaft can navigate curved paths, but torque loss and pig-tailing occur due to insufficient stiffness
Solution Approach 1:
The support rod provides localized stiffness enhancement in the flexible shaft through its varying diameter design. The larger diameter sections are positioned to provide torque transmission support, while the reduced diameter sections allow the shaft to bend and navigate curved paths, thus preventing torque loss while maintaining navigability.
3Strength
If the support rod has a uniform diameter fitting the shaft, then maximum support is provided, but the shaft cannot bend and becomes too rigid
Solution Approach 1:
The support rod features non-uniform diameter with larger portions providing support and smaller portions allowing bending. This local variation in geometry enables the rod to provide structural support where needed while maintaining the shaft's ability to bend and navigate curved anatomical paths.
Solution Approach 2:
The support rod's varying diameter creates a dynamic structure that adapts to different mechanical requirements along the shaft length. The larger diameter sections resist bending to provide support, while the smaller diameter sections allow bending to enable navigation, making the system dynamically responsive to operational needs.
Data Source
AI summary
A support rod for a hollow, flexible torque transmitting shaft for treating a bone includes support and flex portions. When the rod is received at a desired position within the shaft, the support portion extends through a first non-bendable portion of the shaft. An outer diameter of the support portion substantially corresponds to an inner diameter of the shaft to support the first portion. When the support rod is received at the desired position, the flex portion extends through a second bendable portion of the shaft. The flex portion includes a holding portion having an outer diameter substantially corresponding to an inner diameter of the second portion and a gap portion having an outer diameter reduced relative to the outer diameter of the holding portion to form an annular gap between the gap portion and an inner surface of the holding portion.