Variable Stiffness Surgical Instrument for Flexible Navigation
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Solution Overview
Problem
Current percutaneous surgical procedures, such as pericardiocentesis and intracerebral hemorrhage evacuation, face challenges with buckling resistance and limited dexterity due to the use of rigid instruments, which can cause tissue damage and limited access, while existing flexible robots have not been adequately tested for these applications.
Innovation Solution
Development of flexible surgical devices featuring a shape memory alloy (SMA) spring with variable stiffness for safe needle insertion and dexterous manipulation, combined with a heating tube for controlled temperature adjustment, and a pre-curved body with a flexible tip for nonlinear insertion paths and enhanced dexterity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If rigid instruments are used for percutaneous surgical procedures, then buckling resistance is improved, but tissue damage increases and dexterity is limited
Solution Approach 1:
The surgical instrument employs a variable stiffness mechanism that allows the shaft to dynamically adjust its rigidity. During insertion, the shaft maintains high stiffness to resist buckling, while during manipulation, it transitions to a flexible state to follow tissue contours and avoid damage. This dynamic property resolution enables the instrument to exhibit both rigid and flexible characteristics as needed.
Solution Approach 2:
The instrument's stiffness parameter is changed from fixed to variable through the use of a shape memory alloy spring mechanism. By controlling the phase transformation temperature of the shape memory alloy, the stiffness of the shaft can be adjusted between high and low states, allowing the instrument to adapt its mechanical properties to different operational requirements and minimize tissue damage.
2Strength
If rigid instruments are used for percutaneous surgical procedures, then buckling resistance is improved, but dexterity is limited
Solution Approach 1:
The variable stiffness mechanism enables the instrument shaft to transition between rigid and flexible states dynamically. During the insertion phase, the shaft remains rigid to maintain structural integrity and resist buckling forces. Once positioned, the shaft becomes flexible to allow the distal tip to be steered and manipulated with high dexterity, enabling complex navigation through tortuous anatomical pathways.
Solution Approach 2:
The instrument is divided into distinct functional segments: a proximal rigid section for structural support and buckling resistance, and a distal flexible section for dexterous manipulation. This segmentation allows each part to perform its specialized function optimally while working together as an integrated system.
3Ease of operation
If flexible instruments are used for percutaneous surgical procedures, then dexterity is improved, but buckling resistance deteriorates
Solution Approach 1:
The instrument employs a variable stiffness mechanism that allows dynamic adjustment of the shaft's rigidity. During insertion, the shaft transitions to a high-stiffness state to resist buckling, while during manipulation, it transitions to a low-stiffness state to enable flexible navigation and dexterous operation. This dynamic property change resolves the contradiction between flexibility and buckling resistance.
4Device complexity
If straight insertion paths are used, then procedural simplicity is improved, but access to targets behind critical structures is limited
Solution Approach 1:
The variable stiffness mechanism enables the instrument to transition from a straight, rigid insertion path to a flexible, curved manipulation path. The shaft maintains rigidity during initial insertion to follow a simple trajectory, then becomes flexible to allow the distal tip to navigate around critical structures and reach previously inaccessible targets, thereby enhancing adaptability without significantly increasing procedural complexity.
Solution Approach 2:
The instrument is designed to transition from a straight configuration during insertion to a curved configuration during manipulation. The flexible distal section can be steered to follow curved anatomical pathways, allowing access to targets located behind critical structures while maintaining a relatively simple overall procedural approach.
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 devices minimize tissue damage during insertion, enable precise targeting and dexterous manipulation, and facilitate safe and effective procedures like pericardiocentesis, intracerebral hemorrhage evacuation, and third ventriculostomy, with the ability to bend and steer away from critical structures, thereby reducing complications and improving clinical outcomes.
Implementation Method 1
The first percutaneous device features a flexible wrist made of a shape memory alloy (SMA) spring which can vary its stiffness through temperature variation
Implementation Method 2
The SMA spring can be heated and thus stiffened to allow needle insertion. Further provided is a heating tube made of nichrome wire and PTFE tube as controlled heat source for the SMA spring
Data Source
AI summary
The subject invention pertains to percutaneous surgical device with variable stiffness for percutaneous procedures, including but not limited to pericardiocentesis, and flexible neurosurgical devices for procedures, including but not limited to intracerebral hemorrhage evacuation and third ventriculostomy and brain tumor biopsy, and methods of making and using them.