Cannulated Surgical Knife Offset Blade for Extended Incisions
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Solution Overview
Problem
Current knife handles designed for use through cannulae in robotic and minimally invasive surgeries do not accommodate the need for larger incisions, leading to tissue damage and lack of precision in incision placement.
Innovation Solution
A surgical knife with an elongated handle portion and a reduced portion connected by a transition portion, allowing the blade to shift laterally upon exiting the cannula, creating an incision longer than the cannula diameter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a scalpel blade is placed through a cannula, then precise placement of incisions is achieved, but the incision size is insufficient to accommodate round instruments
Solution Approach 1:
The blade is positioned offset from the longitudinal axis of the handle, allowing it to extend beyond the cannula diameter in a lateral dimension. This dimensional offset enables the cutting edge to create an incision longer than the cannula diameter while the handle remains constrained within the cannula for precise placement.
Solution Approach 2:
The handle with reduced portion fits within the cannula like a nested structure, while the blade extends beyond the cannula boundary. This nesting allows the knife to be guided through the cannula for precision while the blade creates a larger incision than the cannula diameter would normally permit.
2Length of moving object
If a larger scalpel is employed outside of a working cannula, then a larger incision can be created, but precision in sizing and placement of incisions is lost
Solution Approach 1:
The handle with reduced portion fits within the cannula like a nested structure, while the blade extends beyond the cannula boundary. This nesting allows the knife to be guided through the cannula for precision while the blade creates a larger incision than the cannula diameter would normally permit.
3Length of moving object
If the blade width is increased to create a longer incision, then the incision can accommodate round instruments, but the handle dimension exceeds the cannula diameter
Solution Approach 1:
The knife is divided into distinct segments: a handle portion for insertion through the cannula, a reduced portion that transitions from the handle, and a blade portion that extends beyond the cannula. This segmentation allows each part to serve its specific function while maintaining overall compatibility with the cannula system.
Solution Approach 2:
Different portions of the knife have different dimensions optimized for their specific functions. The handle has a dimension suitable for cannula insertion, while the blade has a larger width for creating the required incision length. This local differentiation of dimensions resolves the contradiction between handle fit and blade function.
Data Source
AI summary
A surgical knife for introduction through a cannula includes a handle portion with an angled transition to a reduced portion. A blade connected to the reduced portion has a width perpendicular to the longitudinal axis that is equal to or greater than-half the effective handle dimension. The blade is connected to the handle so that the outer transverse edge of the blade is outwardly offset from the outer surface of the handle. The blade width is preferably 80% of the effective dimension of the handle. The blade includes a cutting edge that extends across the width of the blade. In use, the knife can be extended through a cannula to make a first incision, retracted and rotated 180°, and then make another incision colinear with the first incision to create a single incision having a length greater than the width of the cannula.