Dynamic Knife Assembly Speed Control for Excess Tissue Cutting
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Solution Overview
Problem
Conventional powered circular stapling devices face issues with incomplete cuts due to excessive tissue being captured, leading to premature reaching of the cut force limit before the annular knife fully traverses the cutting stroke.
Innovation Solution
The device adjusts the knife assembly's velocity and increases the cut force limit when the predetermined force is detected, allowing the knife to complete the cutting stroke by reducing speed and increasing force incrementally until the tissue is fully cut.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the knife pusher advances at a constant speed until a specified cut force limit is detected, then the cutting process is simple and quick, but the cut force limit is reached prior to the annular knife completely cutting through the tissue when excessive tissue is captured, resulting in an incomplete cut
Solution Approach 1:
The knife pusher advancement speed is made dynamic rather than constant. The system transitions from a fixed velocity approach to a variable velocity approach where the speed adjusts based on real-time force feedback. When the strain gage detects the predetermined force limit, the controller automatically reduces the advancement speed to allow the annular knife to complete its cutting stroke, ensuring reliable cut completion while maintaining efficiency.
Solution Approach 2:
The system implements feedback control by continuously monitoring the force applied to the knife pusher assembly via a strain gage. The controller receives real-time force data and adjusts the knife pusher advancement velocity accordingly. This closed-loop feedback mechanism ensures that when excessive tissue resistance is detected, the system responds by reducing speed to prevent incomplete cuts, while maintaining high productivity when tissue conditions are normal.
2Productivity
If the knife pusher advances at a high speed to maintain productivity, then the stapling procedure is efficient, but excessive tissue pressure causes the cut force limit to be reached prematurely, preventing complete tissue cutting
Solution Approach 1:
The system dynamically adjusts the knife pusher advancement velocity based on real-time tissue conditions. During normal cutting conditions, the system maintains high advancement speed for efficiency. When the strain gage detects the predetermined force limit indicating excessive tissue capture, the controller automatically reduces the advancement speed to precision mode, allowing the annular knife to complete its cutting stroke without premature force limit termination.
Solution Approach 2:
The system changes the operational parameter (advancement velocity) based on detected tissue conditions. The controller monitors the force parameter and adjusts the velocity parameter accordingly. When excessive tissue pressure is detected, the system transitions from high-velocity cutting mode to low-velocity precision cutting mode, ensuring complete cut precision while maintaining overall procedural efficiency.
3Device complexity
If the cut force limit is set at a fixed value (e.g., 275 lbf) to simplify control, then the control system is straightforward, but the system cannot accommodate varying tissue conditions, leading to incomplete cuts when excessive tissue is present
Solution Approach 1:
The control system transitions from a static, fixed force limit approach to a dynamic, adaptive control approach. The controller continuously monitors the actual force applied during cutting and compares it against the predetermined force limit. When the force limit is approached, the system dynamically adjusts the knife pusher advancement velocity to accommodate varying tissue conditions, maintaining adaptability while keeping the control logic relatively simple.
Solution Approach 2:
The system implements feedback control that monitors actual cutting force in real-time. The strain gage provides continuous force data to the controller, which adjusts the knife pusher advancement velocity based on this feedback. This feedback mechanism enables the system to adapt to varying tissue conditions without requiring complex predetermined parameters for every possible tissue scenario, balancing control simplicity with adaptability.
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 approach ensures complete tissue cutting by accommodating excess tissue, preventing component damage and ensuring a successful stapling procedure.
Implementation Method 1
a strain gage supported inside the handle assembly or adapter assembly
Data Source
AI summary
A method of operating a surgical stapler includes advancing a knife assembly at a first velocity until a predetermined force is detected, advancing the knife assembly at a second velocity when the predetermined force is detected, the second velocity being less than the first velocity, and continuing to advance the knife assembly at the second velocity until the knife assembly travels a cutting stroke distance.