Deflectable Surgical Tool Tip Using Nested Tube Push-Pull Bending
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Solution Overview
Problem
There is a need for small-diameter surgical tools with deflectable joints that provide dexterity for delicate and intricate surgical procedures, such as tissue dissection, resection, and suturing, which can be navigated through natural orifices or percutaneously, and are useful in procedures like colorectal resection, pituitary tumor resection, neurosurgery, and intracardiac surgery.
Innovation Solution
The implementation of an agonist-antagonist deflectable joint in small-diameter surgical tools using nested tubes with non-central, offset neutral axes, where axial translations cause push-pull action to bend the joint, achieved through asymmetric cutouts or notches to relocate neutral bending planes, allowing for a large range of motion and variable curvature actuation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If small-diameter surgical tools are used to navigate through natural orifices or percutaneously, then access to deep anatomical targets is improved, but dexterity and range of motion are reduced
Solution Approach 1:
The surgical tool is divided into multiple nested tubular segments that can deflect relative to each other at defined joint locations. This segmentation allows the tool to maintain a small overall diameter while achieving large range of motion through cumulative deflection of multiple segments, resolving the contradiction between small size and dexterity.
Solution Approach 2:
Multiple tubular members are nested within each other, with each tube capable of independent deflection. The nested configuration allows the tool to pass through tight anatomical passages in a compact state while deploying dexterity through sequential deflection of nested tubes at joint locations, addressing both small diameter requirements and operational dexterity.
2Strength
If rigid structures are used to maintain structural integrity, then strength is improved, but flexibility and range of motion are reduced
Solution Approach 1:
The tubular members feature localized regions of reduced stiffness (hinge regions) at specific locations rather than uniform flexibility throughout. These localized compliant regions allow deflection at joint locations while the remainder of the tube structure maintains sufficient rigidity for structural integrity and force transmission, resolving the contradiction between strength and flexibility.
Solution Approach 2:
The structure transitions from a static rigid form to a dynamic system where tubular members can change their relative configuration through deflection at joint locations. The ability to transition between straight and curved configurations allows the tool to maintain structural integrity when needed while achieving range of motion during operation.
3Ease of operation
If deflectable joints are added to increase dexterity, then range of motion is improved, but device complexity increases
Solution Approach 1:
Multiple functional elements are merged into the tubular structure itself - the tube walls provide both structural support and contain the hinge mechanism. The deflection mechanism is integrated within the tube walls rather than being a separate external mechanism, reducing overall device complexity while maintaining dexterity.
Solution Approach 2:
The tube walls are designed with varying thickness and material properties to create compliant hinge regions that provide deflection capability. This approach uses the tube structure itself as the flexible element rather than adding separate flexible components, simplifying the overall device design while achieving the required range of motion.
4Ease of operation
If asymmetric cutouts are made in tube walls to create deflection, then range of motion is improved, but structural strength is reduced
Solution Approach 1:
Asymmetric cutouts are created only in localized hinge regions of the tube walls rather than throughout the entire tube structure. This allows deflection capability to be introduced at specific locations while the majority of the tube wall retains its full thickness and strength, resolving the contradiction between deflection capability and overall structural strength.
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 surgical apparatus with a deflectable joint that offers high dexterity, low stiffness, and variable curvature actuation, enabling precise manipulation and navigation in complex surgical environments without elastic stability issues.
Implementation Method 1
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
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.