Surgical Stapler Knife Velocity Control for Excess Tissue Cuts
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Solution Overview
Problem
Conventional powered circular stapling devices face issues with incomplete cuts due to excessive tissue being trapped, leading to premature reaching of the cut force limit before the annular knife fully traverses the cutting stroke.
Innovation Solution
The method involves adjusting the knife assembly's velocity and increasing the cut force limit when a predetermined force is detected, reducing the speed to allow tissue relaxation and ensuring complete cutting by traversing the entire stroke distance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the knife pusher is advanced 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 present, 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 predetermined force is detected, the system automatically reduces the advancement speed to allow complete cutting through excessive tissue, thereby resolving the contradiction between cutting speed and cut completeness.
Solution Approach 2:
The system incorporates feedback control where the strain gage continuously monitors the force applied during knife pusher advancement. Based on this feedback, the control system adjusts the knife pusher velocity. When the predetermined force threshold is reached, the system reduces speed to ensure complete cutting, preventing premature termination of the cutting stroke while maintaining overall efficiency.
2Productivity
If the knife pusher is advanced at a high speed to improve productivity, then the stapling procedure is faster, but excessive tissue causes the cut force limit to be reached prematurely, resulting in incomplete cuts and potential component damage
Solution Approach 1:
The system dynamically adjusts the knife pusher advancement speed based on tissue conditions. High speed is maintained during normal cutting, but when excessive tissue is detected through force feedback, the system automatically reduces speed to prevent component damage. This dynamic adjustment allows the system to maintain high productivity during normal operations while protecting components when abnormal conditions occur.
Solution Approach 2:
The system prepares for potential component damage by continuously monitoring force levels and having a reduced velocity mode ready. When the predetermined force is detected, the system immediately reduces speed to cushion against excessive forces that could damage components. This preemptive protective mechanism prevents damage before it occurs while maintaining overall procedural efficiency.
3Reliability
If the cut force limit is increased to accommodate excessive tissue, then complete cutting can be achieved, but the risk of component damage increases and the device requires more force than originally designed
Solution Approach 1:
Instead of increasing the cut force limit statically, the system dynamically adjusts the advancement speed based on real-time force feedback. When excessive tissue is detected, the system reduces velocity to allow the existing cut force limit to be sufficient for complete cutting. This approach maintains component strength requirements while achieving complete cuts through intelligent speed modulation rather than force increase.
Solution Approach 2:
The system changes the operational parameters by adjusting the knife pusher advancement speed rather than changing the cut force limit threshold. By modulating velocity based on tissue conditions, the system achieves complete cutting through excessive tissue without requiring increased force capacity. This parameter change approach preserves component design strengths while adapting to varying tissue loads.
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, reducing the risk of component damage and improving the stapling device's efficiency and reliability.
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.