Offset Anvil Spline Asymmetry for Circular Stapler Alignment
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Solution Overview
Problem
Circular stapling devices often experience malformation of staples due to spline crashing, which damages the alignment structures and prevents proper alignment of the anvil and shell assemblies, leading to improper staple formation.
Innovation Solution
The design incorporates anvil splines with offset tapered surfaces, where the first tapered surface has a larger surface area than the second, allowing for asymmetry that directs the anvil splines into guide channels when crashing occurs, ensuring proper alignment and minimizing staple malformation by applying a greater force to the larger surface area, thus rotating the anvil assembly out of the crashed position.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If symmetric tapered splines are used for alignment, then the alignment structure is simple and easy to manufacture, but the splines may crash head-on causing damage and preventing proper alignment
Solution Approach 1:
The anvil spline is designed with asymmetric tapered surfaces where the first tapered surface has a larger surface area than the second tapered surface. This asymmetry causes the apex to be offset from the longitudinal axis, ensuring that during engagement the splines guide each other into proper alignment rather than crashing head-on. The larger surface area on the first tapered surface provides a broader engagement area that directs the splines into the guide channel formed by adjacent shell splines.
2Device complexity
If the apex is centered on the longitudinal axis, then the spline structure is symmetric and simple, but head-on engagement causes spline damage and misalignment
Solution Approach 1:
The apex of the anvil spline is offset from the longitudinal axis, creating asymmetric tapered surfaces. This offset design ensures that during the engagement process, the splines do not meet head-on at the center but rather engage at an offset position, allowing one spline to guide the other into proper alignment within the guide channel, thereby preventing damage and ensuring manufacturing precision.
3Device complexity
If equal surface areas are provided on both tapered surfaces, then the spline design is symmetric and simple, but proper alignment direction cannot be provided during engagement
Solution Approach 1:
The first tapered surface is designed with a larger surface area than the second tapered surface, creating an asymmetric configuration. This asymmetry provides a directional guidance mechanism during engagement, where the larger surface area directs the anvil spline into the guide channel formed by adjacent shell splines, ensuring proper alignment and ease of operation during the stapling process.
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 solution effectively prevents spline damage and ensures reliable alignment of the anvil and shell assemblies, reducing staple malformation and maintaining the integrity of the stapling process.
Implementation Method 1
applying a greater force to the larger surface area, thus rotating the anvil assembly out of the crashed position
Data Source
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AI summary
A surgical stapling device includes an anvil assembly and a shell assembly. The anvil and shell assemblies each include splines that define guide channels. Each of the anvil splines defines a distally positioned triangular tip that is defined by an apex and first and second right cam surfaces. The cam surfaces of the anvil splines are configured to engage one of the shell splines to cam or rotate the anvil assembly into alignment with the shell assembly as the anvil assembly is moved in relation to the shell assembly to a clamped position. The apex of each of the anvil splines is offset from a longitudinal axis of the anvil spline such that the first and second cam surfaces of the anvil splines define a short edge and a long edge and have surfaces that have different surface areas. By providing anvil splines that have cam surfaces with different surface areas, a greater force is applied to the cam surface having a greater surface area when the apexes of the anvil and shell splines "crash". As such, when spline crashing occurs, the anvil splines are pushed in one direction to rotate the anvil assembly in relation to the shell assembly to direct the anvil splines into the guide channels defined by the shell splines to properly align the shell assembly with the anvil assembly.