Deflectable Surgical Tip Using Nested Tubes for Small-Lumen Dexterity
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Solution Overview
Problem
There is a need for small-diameter surgical tools with deflectable joints that provide dexterity for delicate surgical procedures, such as tissue dissection, resection, and suturing, which can be navigated through natural orifices or small lumens, and are capable of actuating at various positions along the tool length.
Innovation Solution
The implementation of an agonist-antagonist deflectable joint in small-diameter surgical tools using nested tubes with offset neutral axes, where axial translations cause push-pull action, allowing the joint to bend through asymmetric cutouts or notches, providing a range of motion and variable curvature actuation modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If small-diameter surgical tools are used to navigate through natural orifices or small lumens, then access to target locations is improved, but dexterity and range of motion are limited
Solution Approach 1:
The surgical tool is divided into multiple nested tubular segments that can move independently relative to each other. Each tube can translate axially and rotate, allowing the distal tip to achieve complex spatial orientations despite the tool's small overall diameter. This segmentation enables the tool to navigate through tortuous anatomy while maintaining dexterity at the tip.
Solution Approach 2:
Multiple tubes are nested within each other in a concentric arrangement, with each tube having its own degree of freedom. The inner tubes can move independently within the outer tubes, creating a telescopic structure that provides multiple degrees of freedom at the distal tip while keeping the proximal profile compact and small-diameter.
2Strength
If rigid structures are used to maintain structural integrity, then strength is improved, but flexibility and ability to deflect are reduced
Solution Approach 1:
The structure transitions from a static rigid form to a dynamic system where tubes can move relative to each other. The nested tubes are connected through joints that allow controlled translation and rotation, enabling the structure to adapt its shape while maintaining structural integrity through the strength of individual tube segments.
Solution Approach 2:
The tubular structures utilize thin-walled construction that provides sufficient axial strength while allowing bending and deflection. The tubes can elastically deform to follow curved paths through anatomy, and the nested arrangement allows inner tubes to follow the curvature of outer tubes while maintaining their own degrees of freedom.
3Adaptability or versatility
If actuators and control mechanisms are integrated into the tool, then dexterity is improved, but device complexity increases
Solution Approach 1:
The nested tube structure is self-actuating through push-pull mechanisms where translation of one tube relative to another automatically produces the desired deflection. The agonist-antagonist pair of tubes works together where one tube's movement causes the joint to bend in one direction, and the other tube's movement bends it in the opposite direction, eliminating the need for separate actuators at the distal tip.
Solution Approach 2:
Complex distal actuators are replaced with a simpler proximal actuation system. By translating tubes at the proximal end, the desired distal deflection is achieved through the mechanical coupling of the nested structure, reducing the need for complex motors, sensors, and control electronics at the fragile distal tip.
4Adaptability or versatility
If multiple degrees of freedom are provided at the distal tip, then workspace and dexterity are improved, but overall stiffness and stability are reduced
Solution Approach 1:
The tool is segmented into multiple rigid tube sections connected by flexible joints. Each segment maintains its own structural stiffness, while the joints between segments provide the necessary degrees of freedom. This allows the distal tip to access complex geometries while the proximal segments remain stable and rigid for precise instrument manipulation.
Solution Approach 2:
The nested tube structure creates a composite system where the combination of multiple tubes provides both flexibility and stiffness. The outer tubes provide structural stability while inner tubes provide additional degrees of freedom, creating a hierarchically structured system that is stiff where needed and flexible where required.
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 offers a large range of motion, low overall stiffness, and variable curvature actuation, enhancing dexterity and workspace, without elastic stability issues, and allows for the integration of surgical instruments without the need for actuator wires within the lumen.
Implementation Method 1
Axial translations of the tubes relative to each other causes the push-pull, agonist-antagonist action between the tubes, which causes the deflectable joint to bend
Data Source
AI summary
A small diameter surgical tool implements an agonist-antagonist deflectable joint. The deflectable joint is an actuatable bendable structure that uses push-pull, agonist-antagonist action of a pair of nested tubes to actuate the joint. The tubes are designed to have non-central, offset neutral axes, and they are fixed together at locations distal to the deflectable joint, such as at their distal ends. Axial translations of the tubes relative to each other causes a push-pull, agonist-antagonist action between the tubes, which causes the deflectable joint to bend. In one implementation, a deflectable joint can be created in nested tubes by configuring radial portions of the tube sidewalls extending along the joint to have an axial region of reduced stiffness. As a result, axial agonist-antagonist motion between the tubes can cause bending of the deflectable joint.