Circular Stapler Anvil Retainer Ribs Prevent Rotation
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Solution Overview
Problem
Circular stapling devices face misalignment issues between the anvil assembly's staple forming pockets and the shell assembly's staple receiving pockets due to spline misalignment, leading to staple malformation during firing.
Innovation Solution
The surgical stapling device incorporates an anvil retainer with first and second longitudinal ribs, where the first rib is received within a slot in the shell housing and the second rib is received within longitudinal channels of the anvil shaft, preventing rotation and ensuring proper alignment without the need for splines.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If splines are used to align the anvil assembly with the shell assembly, then alignment is provided, but misalignment occurs resulting in staple malformation
Solution Approach 1:
The patent removes the problematic spline alignment mechanism entirely and replaces it with a rib-and-slot guidance system. The anvil retainer includes longitudinal ribs that engage with corresponding slots in the shell assembly, eliminating the misalignment issues associated with splines while maintaining proper alignment between the anvil and cartridge assemblies
Solution Approach 2:
Instead of using internal splines within the anvil shaft that mate with splines in the shell housing, the invention inverts the approach by using external longitudinal ribs on the anvil retainer that engage with slots in the shell assembly. This inverted alignment mechanism provides more reliable positioning and prevents rotation
2Ease of operation
If the anvil retainer is inserted into the anvil shaft bore, then the anvil assembly is secured, but rotation may occur causing misalignment
Solution Approach 1:
The anvil retainer is designed with longitudinal ribs that preliminarily establish the correct alignment and prevent rotation before the anvil shaft is fully inserted into the shell assembly. This preliminary alignment action ensures that once assembled, the components remain properly positioned without requiring additional alignment steps
Solution Approach 2:
The longitudinal ribs on the anvil retainer create an asymmetric engagement geometry with the slots in the shell assembly. This asymmetric design prevents rotational movement by providing directional guidance, ensuring the anvil assembly can only be inserted in the correct orientation and remains fixed against rotation
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 design enhances the reliability of staple alignment, preventing staple malformation and improving the stapling process by maintaining precise positioning of the anvil and cartridge assemblies during tissue clamping and firing.
Implementation Method 1
The resilient legs flex outwardly to facilitate passage of the anvil retainer into the bore
Data Source
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AI summary
A circular stapling device (10, 100) includes structure to position an anvil assembly (20, 120) in proper alignment with a cartridge assembly (18, 118) prior to firing of the stapling device (10, 100). The stapling device (10, 100) includes an anvil assembly (20, 120), a cartridge assembly (18, 118) including a staple cartridge (18a, 125) and shell housing (36, 126), and an anvil retainer (30, 130) that has a proximal portion (84) including a first longitudinal rib (86) and a distal portion including at least one second longitudinal rib (88). The first longitudinal rib (86) is received within a slot (66) formed within the shell housing (36, 126) to prevent rotation of the anvil retainer (30, 130) in relation to the shell housing (36, 126). The at least one second longitudinal rib (88) is received within a longitudinal channel (70a) of the anvil assembly (20, 120) to prevent rotation of the anvil assembly (20, 120) in relation to the anvil retainer (30, 130). The presently disclosed structure obviates the need for splines (134, 136) and the disadvantages associated with the use of splines (134, 136).