Steerable Catheter Assembly with Offset Revolute Joints
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Solution Overview
Problem
Steerable catheters face challenges in maintaining control over the distal end during procedures in tortuous body lumens, as existing designs can be overly flexible, leading to unintended position changes under slight external forces, disrupting procedures like mitral valve repair.
Innovation Solution
A catheter with a steerable assembly featuring revolute joints that allow bending in specific planes, connected by intermediate elements and pullwires secured in detents, limiting bending freedom to one degree and preventing accidental shape changes, ensuring stability and precise positioning.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the steerable assembly is made highly flexible to navigate tortuous body lumens, then the catheter can reach distant targets, but the distal end becomes unstable and changes position under slight external forces
Solution Approach 1:
The steerable assembly is divided into multiple discrete segments (first segment with first and second elements, second segment with third and fourth elements) connected by revolute joints. Each segment can bend independently in controlled planes, providing both flexibility for navigation and stability when positioned, as the segmented structure resists unintended movements better than a continuously flexible tube.
Solution Approach 2:
The patent changes the flexibility parameter along the length of the catheter. The steerable assembly has controlled flexibility through revolute joints that permit bending only in specific planes, while the remainder of the catheter body maintains different flexibility characteristics. This parameter variation allows the distal end to be flexible enough for navigation yet stable enough for precise positioning.
2Ease of operation
If the steerable assembly allows bending in multiple directions for freedom of movement, then the physician can steer the catheter tip in any direction, but control precision is lost and the catheter cannot maintain a stable pre-shaped configuration
Solution Approach 1:
The revolute joints are configured with asymmetric bending constraints - each joint permits rotation only in a specific single plane, not in all directions. The first revolute joint allows bending in a first single plane, while the second revolute joint allows bending in a second single plane offset by an angle. This asymmetric constraint provides controlled steering capability while maintaining precision and stability in the intended bending directions.
Solution Approach 2:
The steerable assembly provides dynamic control through revolute joints that can be actively positioned using pullwires. The joints transition from a fixed straight configuration to bent configurations in specific planes based on operational needs. This dynamic adjustability allows the catheter to achieve precise positioned in tortuous paths while maintaining stability once positioned.
3Ease of operation
If opposing pullwires are freely extended up the bore of the tube to provide steering capability, then the distal tip can be pulled from one side to the other, but the tube lacks sufficient structural support to maintain small radius of curvature bends
Solution Approach 1:
The tube is segmented into discrete elements (first element, second element, third element, fourth element) connected by revolute joints. This segmentation allows the structure to bend into sharp configurations with small radius of curvature at the joints while the individual elements maintain their structural integrity and provide necessary support.
Solution Approach 2:
The revolute joints act as intermediaries between the pullwires and the tube elements. These joints provide the mechanical interface that translates pullwire tension into controlled bending moments, enabling the tube to achieve sharp bends without requiring the entire tube structure to be flexible throughout its length.
Data Source
AI summary
A catheter configured for intraluminal delivery to a location in the body of a patient, the catheter comprising a steerable assembly comprising a first segment connected to a second segment; the first segment comprises first and second cylindrical elements connected to each other by a first revolute joint in a first single plane; the second segment comprises third and fourth cylindrical elements connected to each other by a second revolute joint in a second single plane, wherein the first single plane and the second single plane are offset by an angle from each other.