Surgical Cutting Instrument Zero Clearance Mechanism
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Surgical cutting instruments, particularly those used in percutaneous and minimally invasive procedures, face difficulties in cleanly severing target tissue due to incomplete cutting or failure to sever, especially when dealing with viscous tissues like vitreous tissue in the eye, leading to inefficiencies and potential tissue lodging issues.
Innovation Solution
The surgical cutting instrument incorporates a sloped member within the cannula to guide the cutting head toward a zero clearance point with the cutting edge, enabling a scissor-like action for precise tissue severing, using features such as a ramp, indentation, or crease to ensure clean cuts without the cutting head exiting the cannula.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If a tube-within-a-tube cutting instrument is used with reciprocating cutter, then minimally invasive access is enabled, but clean severing of target tissue is compromised
Solution Approach 1:
The cutting head is made dynamically adjustable through a hinge mechanism that allows it to pivot between a retracted position and a forward position. This dynamic adjustment enables the cutting head to adapt its position relative to the cutting opening, achieving zero clearance for precise tissue severing while maintaining the minimally invasive tube-within-a-tube structure.
Solution Approach 2:
The hinge mechanism changes the positional parameter of the cutting head relative to the cutting opening. By pivoting the cutting head forward, the distance between the cutting edge and the cutting opening edge is reduced to zero clearance, transforming the cutting geometry to achieve clean tissue severing while preserving the minimally invasive access capability.
2Force
If running clearance is maintained throughout the entire stroke, then low friction reciprocation is achieved, but clean tissue severing is prevented
Solution Approach 1:
The hinge mechanism creates a localized zero clearance condition specifically at the cutting opening where tissue severing occurs, while maintaining running clearance in other portions of the stroke. This local quality change ensures low friction reciprocation during most of the stroke while achieving precise cutting at the critical location.
Solution Approach 2:
The cutting head dynamically adjusts its position through pivoting, maintaining running clearance during the approach and withdrawal phases of the stroke for low friction, while achieving zero clearance at the cutting opening during the cutting phase for precise tissue severing.
3Manufacturing precision
If cutting head pivots to zero clearance, then clean tissue severing is achieved, but sliding friction and motor load increase
Solution Approach 1:
The hinge mechanism applies zero clearance condition partially, only at the cutting opening where it is most needed for clean tissue severing, rather than maintaining zero clearance throughout the entire cutter length. This partial application minimizes the sliding friction and motor load while achieving the necessary cutting precision.
Solution Approach 2:
The design concentrates the zero clearance condition locally at the cutting opening rather than along the entire cutting head length. This localized approach achieves clean tissue severing at the critical cutting point while minimizing the contact area that generates sliding friction and motor load during reciprocation.
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
This design enhances cutting efficiency and precision, reducing the likelihood of incomplete cuts and tissue lodging, while maintaining the benefits of hinged and pre-bent cutting head features, although it may introduce sliding friction that could affect motor load and heat generation.
Implementation Method 1
a sloped member disposed in the cannula bore guides the cutting head toward the cutting edge as the cutting head advances toward the distal end of the cannula
Implementation Method 2
Vacuum is drawn through the inner tubular cutter to pull tissue severed by the cutter back through the instrument
Data Source
AI summary
A surgical cutting instrument for cutting tissue includes an outer cannula with a cutting opening and a cutting member within the cannula. The cutting member is connected to a source of reciprocation, and as the cutting member reciprocates the cutting member head is guided by a sloped member within the cannula to essentially a zero clearance position relative to a cutting edge of the cutting opening of the cannula. The instrument cleanly severs tissue extending through the cutting opening into the outer cannula.