Bend Limiting Access Sheath for Ureteral Procedures

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Solution Overview

Problem

Existing access sheaths for ureteral procedures are prone to kinking and elongation, which reduces their effectiveness and can cause trauma to patients due to excessive flexibility, and their kink-resistant variants often compromise the working channel or cause anatomical damage with increased outer diameters.

Innovation Solution

An access sheath with a tubular frame that incorporates a bend limiting feature, using slots to restrict bend angle and radius, allowing flexibility up to a specific point before becoming rigid, along with a guidewire retention feature and lubricious coatings to enhance navigation and insertion.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Area of moving object

If the access sheath wall is made thin to maximize working channel, then the working channel is maximized, but the sheath becomes susceptible to kinking and ovalization

Engineering Contradiction:

Improveworking channel areaVSAvoidresistance to kinking and ovalization

Core Design Contradiction:

Area of moving objectVSReliability

Solution Approach 1:

The access sheath combines a thin-walled polymer tube with an embedded flexible wire reinforcement structure. This composite construction allows the sheath to maintain a thin overall wall thickness for maximized working channel while the wire reinforcement provides structural support to prevent kinking and ovalization. The wire is positioned within the polymer wall to create a composite structure that exhibits both flexibility and structural integrity.

Inventive Principle:

Principle #40Composite materials

2Reliability

If wire reinforcement is added to prevent kinking, then resistance to kinking is improved, but the wall thickness increases reducing the working channel

Engineering Contradiction:

Improveresistance to kinkingVSAvoidworking channel area

Core Design Contradiction:

ReliabilityVSArea of moving object

Solution Approach 1:

The access sheath uses a thin-walled polymer tube as the primary structure, which is then reinforced with a flexible wire embedded within the wall. This approach maintains the thin overall profile of the sheath while providing kink resistance. The wire reinforcement is integrated within the polymer wall rather than adding external layers, preserving the working channel dimensions.

Inventive Principle:

Principle #30Flexible shells and thin films

3Strength

If the access sheath outer diameter is increased to provide structural support, then structural stability is improved, but anatomical trauma increases

Engineering Contradiction:

Improvestructural stabilityVSAvoidanatomical trauma

Core Design Contradiction:

StrengthVSObject-affected harmful factors

Solution Approach 1:

The access sheath employs a composite construction with a thin-walled polymer tube reinforced by an embedded flexible wire. This composite structure provides the necessary structural stability and resistance to deformation while maintaining a small outer diameter. The wire reinforcement internally supports the thin wall, allowing the sheath to remain slender and minimize anatomical trauma while still providing structural integrity during manipulation.

Inventive Principle:

Principle #40Composite materials

4Adaptability or versatility

If the access sheath is made highly flexible to follow anatomy, then anatomical accommodation is improved, but pushability and force transmission deteriorate

Engineering Contradiction:

Improveanatomical accommodationVSAvoidlongitudinal force transmission

Core Design Contradiction:

Adaptability or versatilityVSForce

Solution Approach 1:

The access sheath combines a flexible thin-walled polymer tube with an embedded wire reinforcement structure. The polymer provides flexibility to accommodate anatomical curves and tortuosity, while the embedded wire maintains longitudinal stiffness for effective pushability and force transmission. This composite construction allows the sheath to bend smoothly along anatomical pathways while still transmitting pushing forces effectively from the operator to the distal tip.

Inventive Principle:

Principle #40Composite materials

Solution Approach 2:

The wire reinforcement is constructed as a series of segmented or braided elements rather than a solid continuous wire. This segmentation allows the reinforcement to flex and conform to anatomical curves while maintaining longitudinal structural support. The segmented structure provides flexibility in the radial direction (allowing bending) while preserving stiffness in the longitudinal direction (allowing force transmission).

Inventive Principle:

Principle #1Segmentation

Data Source

PatentUS9782566B1Bend limiting access sheath

Publication Date: 2017.10.10 ANNEX MEDICAL INC

AI summary

The present invention is an access sheath comprising a tube or sheath with a passageway primarily for endoscopic procedures accessing the ureter through the bladder. The sheath has a bend limiting feature to limit the bend angle or bend radius. The sheath exhibits flexibility up to this limit at which point it becomes rigid. Excessive force is required to bend the sheath beyond the bend limit and would result in the kinking of the tubular frame.