Circular Stapler Independent Actuation Mechanism
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Solution Overview
Problem
Circular stapling instruments require simultaneous actuation of staple formation and tissue cutting, limiting staple formation height to the knife travel distance and necessitating sufficient force for both functions, which can be inefficient and restrictive.
Innovation Solution
A circular stapler with a cartridge assembly that allows independent actuation of the staple forming and cutting mechanisms, enabling separate strokes for staple formation and tissue cutting, with the pusher assembly advancing a first distance and retracting a second distance greater than the first, allowing for independent movement of the knife assembly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If simultaneous actuation of staple forming mechanism and knife advancement is used, then the device structure is simplified, but the force required exceeds available actuation force and staple formation height is limited to knife travel distance
Solution Approach 1:
The actuation process is segmented into two independent strokes: a first stroke for staple formation and a second stroke for tissue cutting. This segmentation allows each function to be performed with optimized force requirements, eliminating the need for the actuation force to simultaneously overcome both staple formation resistance and knife advancement resistance.
Solution Approach 2:
The knife assembly is designed with dynamic engagement characteristics, being selectively fixed relative to the pusher assembly. During the first stroke, the knife remains engaged with the knife pusher to advance with the pusher for staple formation. During the second stroke, the knife is disengaged and advances independently to cut tissue, allowing flexible adaptation of force requirements for each phase.
2Device complexity
If simultaneous actuation of staple forming mechanism and knife advancement is used, then the actuation mechanism is simplified, but the staple formation height is limited to the knife travel distance
Solution Approach 1:
The cutting function is separated into a distinct second stroke that occurs after staple formation. This allows the knife to travel a greater distance independent of the pusher assembly's stroke, enabling staple formation height to exceed the knife travel distance during the first stroke while the knife performs its cutting function in the subsequent second stroke.
Solution Approach 2:
The selective fixing mechanism allows the knife assembly to transition between being fixed to the pusher assembly during staple formation and being free to move independently during tissue cutting. This dynamic configuration enables the knife to achieve greater travel distance for cutting without constraining the staple formation height.
3Force
If independent actuation of staple forming and cutting is implemented, then force requirement is reduced and staple formation quality is improved, but the device complexity increases
Solution Approach 1:
The knife assembly and knife pusher assembly are merged through a selective fixing mechanism that allows them to move together during the first stroke (staple formation) and separately during the second stroke (tissue cutting). This merging approach enables independent actuation benefits while maintaining structural integration, avoiding the need for completely separate mechanisms.
Solution Approach 2:
The selective fixing mechanism provides dynamic connectivity between the knife assembly and pusher assembly, allowing the system to transition between coupled and decoupled states. This dynamic feature enables independent force optimization for each function without requiring permanently separate actuation systems, thus limiting the increase in device complexity.
Data Source
AI summary
A circular stapling instrument including a stapling forming assembly that is actuated independently from actuation of the cutting assembly is provided. The instrument includes a handle assembly, an elongate body extending from the handle assembly, a cartridge assembly mounted on a distal end of the elongate body. The cartridge assembly includes a pusher assembly and a knife assembly. The knife assembly is selectively fixed relative to the pusher assembly.