Flexible Surgical Tool Notch Stiffness
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Solution Overview
Problem
Current minimally invasive neurosurgical instruments lack sufficient stiffness and range of motion to effectively manipulate tissue and bear loads in anatomically confined spaces, limiting their application in complex procedures.
Innovation Solution
A flexible elongate shaft assembly with contact-aided compliant notch topology, where notches mechanically interfere with themselves to increase stiffness and prevent buckling, allowing for controlled bending and load-bearing capabilities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If asymmetric notches with deep cuts (exceeding 80% of tube diameter) are used to achieve sharp bending radius and compact joint size, then the range of motion and compactness are improved, but the stiffness and load-bearing capacity are severely diminished
Solution Approach 1:
The patent employs asymmetric notch geometry where the cut depth varies along the notch length, creating a profile that is deeper at certain sections and shallower at others. This asymmetric configuration allows the notch to achieve sharp bending radii in specific directions while maintaining adequate material thickness and structural integrity in other regions, thereby preserving load-bearing capacity despite compact dimensions
Solution Approach 2:
The notch design implements local quality variations by modifying the cut depth and geometry at different locations along the notch. The deeper cuts are strategically placed where flexibility is needed, while shallower regions maintain structural strength. This localized differentiation allows the joint to be compact overall while retaining sufficient stiffness for tissue manipulation tasks
2Adaptability or versatility
If the notch is made compact with sharp bending radius to fit small surgical workspaces, then the adaptability to confined spaces is improved, but the ability to counteract forces from all directions and manipulate tissue is reduced
Solution Approach 1:
The patent extends the notch geometry into multiple spatial dimensions by creating three-dimensional notch profiles that wrap around the tube in complex patterns. This multi-dimensional configuration allows the notch to achieve compactness in one dimension (fitting small workspaces) while maintaining structural integrity and load-bearing capacity in other dimensions through strategically placed material reinforcements and varied cut depths
3Device complexity
If standard neuroendoscopic equipment is used to perform complex procedures, then the simplicity of the instrument is maintained, but the range of motion and reach are limited
Solution Approach 1:
The patent divides the instrument shaft into multiple segmented sections, each containing notches with specific geometries optimized for different functional requirements. This segmentation allows each section to contribute differently to the overall range of motion and stiffness characteristics, enabling complex maneuvers while maintaining a relatively simple overall instrument structure that can be actuated through basic cable or rod mechanisms
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 enhances the stiffness and range of motion of neurosurgical instruments, enabling them to support higher loads and maintain articulation without plastic deformation, thus expanding their applicability in confined anatomical spaces.
Implementation Method 1
a tube made from a super-elastic material (such as nitinol) has rectangular shaped cuts or notches cut into it. The remaining material at these notches act like flexible hinges that can be bent without permanent deformation
Implementation Method 2
the flexible outer strip section of the notch comes into contact with the inner section of the tube such that the notch mechanically interferes with itself and self-reinforces. This contact increases the stiffness of the notch and prevents buckling
Data Source
AI summary
A flexible elongate shaft assembly which includes an elongate flexible tube having at least one joint built into the elongate flexible tube, and the at least one joint comprised of at least one notch. Each notch includes a contact-aided compliant notch topology built into the elongate flexible shaft configured to cause each notch to mechanically interfere with itself and self-reinforce during bending of each notch resulting in an increase in stiffness of each notch to prevent buckling and plastic deformation of the elongate flexible shaft assembly, and assume a predetermined and designed bending shape of the elongate flexible shaft assembly. The flexible elongate shaft assembly is incorporated into a flexible articulate surgical tool that provides the needed stiffness in order to be able to manipulate tissue and bear loads in anatomically confined spaces. The surgical tool includes a clinician operated handle, the flexible elongated shaft assembly extending from the handle to a surgical tool with the flexible elongate tube having one or more joint sections located near the surgical tool. A flexible cable connects the handle to the surgical tool. The joint sections are configured so that when the clinician activates the surgical tool, a mechanical interference is generated in each of the notches and this mechanical interference not only increases stiffness throughout the articulation of the notch's range-of-motion but it also serves the dual purpose of controlling the bent “shape” of the flexible portion of the notch.