Catheter Steering Handle Cam Mechanism for Bi-directional Tip Control
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Solution Overview
Problem
Catheter navigation through biological lumens is challenging due to their circuitous nature, requiring precise tip deflection control, which varies by operator, leading to extended surgical times and potential patient injury. Existing steering mechanisms lack adaptability to individual tactile preferences and often require high forces for deflection, causing discomfort or over-deflection.
Innovation Solution
A catheter handle with a thumb knob arrangement that increases axial displacement of pull wires per rotation, enabling bi-directional steering with quasi-linear wire intake and release, and a cam assembly with dual pin sets to manage pull wire tension, accommodating varying operator preferences and reducing force requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standardized force-to-deflection relationship is used in the catheter handle, then the manufacturing precision is improved, but the adaptability to different operator tactile preferences deteriorates
Solution Approach 1:
The catheter handle incorporates an adjustable frictional engagement mechanism that allows operators to dynamically modify the force-to-deflection characteristics according to their individual tactile preferences. The frictional engagement between the thumb wheel and pulley system can be varied to provide different levels of resistance, enabling each operator to optimize the steering control to their comfort and skill level.
2Measurement precision
If high force is required to deflect the catheter tip, then the control precision is improved, but the ease of operation deteriorates due to operator discomfort
Solution Approach 1:
A pulley system serves as an intermediary mechanism between the operator's input force and the catheter tip deflection. The pulley system with frictional engagement provides mechanical advantage and allows for fine control of the pull wire tension, enabling precise tip deflection with reduced operator effort. The frictional engagement acts as a mediator that smooths the force transmission and reduces peak forces required.
3Device complexity
If a single pull wire steering mechanism is used, then the device complexity is reduced, but the adaptability for bi-directional steering deteriorates
Solution Approach 1:
The steering mechanism is segmented into multiple functional components: a rotatable cam with dual pin sets, where each pin set controls one direction of deflection. This segmentation allows the single pull wire system to achieve bi-directional steering capability by independently controlling the engagement and disengagement of each pin set with the catheter shaft, effectively creating two steering functions from one wire system.
4Device complexity
If the catheter tip must be rotated 180 degrees to deflect in the opposite direction, then the steering mechanism simplicity is maintained, but the productivity deteriorates due to extended surgical time
Solution Approach 1:
The catheter shaft incorporates a dynamic cam mechanism that allows the pull wire to engage different segments of the cam profile depending on the desired deflection direction. By rotating the cam to appropriate angular positions, the system can deflect the tip in either direction without requiring a 180-degree rotation of the entire catheter assembly, significantly reducing the time and maneuvers required during navigation.
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 solution provides a more intuitive and comfortable control of catheter tip deflection, reducing the force needed for navigation and accommodating individual tactile preferences, thereby improving surgical efficiency and reducing the risk of injury.
Implementation Method 1
A cam assembly with dual pin sets to manage pull wire tension
Implementation Method 2
pull wire tension
Implementation Method 3
thumb knob arrangement that increases axial displacement of pull wires per rotation
Data Source
AI summary
A steering handle for a catheter. The steering handle includes a thumb knob arrangement for driving a cam assembly that in turn actuates a pull wire or pull wires. In some embodiments, the cam assembly includes a set of dual pins that actuate the pull wire in a quasi-linear relationship between cam rotation and axial displacement of the wire. In certain embodiments, the second set of dual pins imparts a reverse action on a second pull wire, also in quasi-linear fashion. That is, when one wire is released by the cam assembly, the other wire is taken in by the cam assembly. In various embodiments, the quasi-linear action can cause release of more pull wire than is taken in, thereby helping prevent the released pull wire to act as an unwanted counter force to the actuated pull wire.