Surgical Stapler Locking Mechanism Prevents Tissue Shear
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Solution Overview
Problem
Existing surgical staplers face challenges in preventing the end effector from being articulated relative to the shaft assembly after tissue closure, which can apply shear forces to the soft tissue, and require significant force to extend the cutting member, leading to premature return and difficulty in precise tissue manipulation.
Innovation Solution
A surgical instrument with a locking mechanism that engages the shaft assembly and end effector to fix their relative position, preventing articulation after closure, and a firing drive with a flexible band and brake system to manage the cutting member's movement, reducing the force required for extension and preventing premature return.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the end effector is allowed to articulate relative to the shaft assembly after jaw closure, then the surgeon can reposition the end effector, but shear force is applied to the captured soft tissue
Solution Approach 1:
The locking mechanism transitions from an unlocked state (allowing articulation) to a locked state (preventing articulation) based on the closure trigger position. When the closure trigger is depressed to close the jaw members, the locking mechanism automatically engages to prevent subsequent articulation that would harm the tissue. This dynamic state change resolves the contradiction by allowing repositioning when needed while preventing harm when tissue is captured.
2Ease of operation
If a return spring is used to retract the cutting member, then the cutting member can be retracted automatically, but significant force is required to extend the spring during advancement
Solution Approach 1:
The return mechanism is segmented into multiple components: the return spring provides retraction force, while the cam surface and follower portion provide mechanical advantage during extension. The cam surface converts the surgeon's input force into efficient spring extension, reducing the perceived force requirement. This segmentation allows automatic retraction while managing the force requirement through mechanical assistance.
Solution Approach 2:
The cam surface acts as an intermediary between the surgeon's manual extension action and the return spring. Instead of directly extending the spring (which requires significant force), the surgeon operates the cam surface which then extends the spring through mechanical advantage. This intermediary mechanism reduces the force requirement while maintaining automatic retraction capability.
3Productivity
If the return spring applies continuous biasing force to the cutting member, then the cutting member returns automatically, but premature return occurs during multi-stroke operation
Solution Approach 1:
The locking mechanism applies a preliminary counteracting force to the return spring's biasing force when the cutting member is in the advanced position. The locking mechanism engages to prevent the spring from causing premature return during multi-stroke operation. This preliminary anti-action ensures reliability by counterbalancing the automatic return force until the appropriate time for retraction.
4Object-affected harmful factors
If the locking mechanism is designed to prevent articulation after closure, then tissue shear force is prevented, but the mechanism adds device complexity
Solution Approach 1:
The locking mechanism is merged with the existing closure trigger mechanism. The same closure trigger that closes the jaw members also activates the locking mechanism to prevent articulation. By combining these functions into a single integrated system rather than adding a separate locking device, the patent reduces overall complexity while still preventing tissue shear force.
Data Source
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AI summary
A surgical instrument including a closure system configured to move an anvil of an end effector between an open position, a partially closed position, and a closed position. The surgical instrument can further include a lock member configured to selectively engage and lock the closure system when the anvil is positioned in at least one of its partially closed and closed positions. In at least one embodiment, the surgical instrument can include a trigger configured to pivot the anvil, the lock member can include a follower portion, and the closure drive can include a lock spring configured to bias the follower portion against a cam surface of the trigger such that the follower portion can engage a notch in the cam surface when the anvil is pivoted into its partially closed position, or closed position, and prevent the anvil from being pivoted into its open position.