Steerable Catheter Sheath Pull Wire Twisting Prevention

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Solution Overview

Problem

Traditional deflectable catheter sheaths face challenges in returning to a straight position for easy removal and can experience wire twisting, leading to undesirable forces that compromise their functionality.

Innovation Solution

A surgical apparatus with a steering mechanism featuring a pull wire retraction assembly and telescoping tube system, which includes a worm gear and rotatable drive nut, allows for controlled deflection and straight guidance of the pull wire, preventing tangling and ensuring proper force translation to the distal end of the sheath.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If the distal end portion of the sheath is deflected to navigate torturous vessels, then the ability to reach target locations is improved, but the difficulty of returning to a straight position for removal increases

Engineering Contradiction:

Improveability to navigate torturous vesselsVSAvoidease of removal from target location

Core Design Contradiction:

Adaptability or versatilityVSEase of operation

Solution Approach 1:

The pull wire system enables dynamic control of the sheath's distal end, allowing it to transition between deflected and straight configurations. The pull wire can be selectively tensioned to deflect the distal end for navigating torturous vessels, then relaxed to allow the distal end to return to a straight position for easy removal, making the sheath adaptability dynamic rather than fixed

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The system changes the geometric parameter of the sheath (its curvature/deflection angle) by applying or releasing tension on the pull wire. When the pull wire is tensioned, the sheath deflects to navigate vessels; when released, the sheath returns to straight for removal. This parameter change enables the sheath to switch between different operational states

Inventive Principle:

Principle #35Parameter changes

2Ease of operation

If the pull wire is connected to the distal end of the sheath for steering control, then the steering capability is improved, but the wire becomes twisted or creates undesirable forces on the proximal end

Engineering Contradiction:

Improvesteering capabilityVSAvoidwire degradation and sheath functionality

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The telescoping tube system acts as an intermediary between the pull wire and the handle assembly. The pull wire passes through the telescoping tube, which guides and constrains the wire's movement, preventing it from twisting or creating undesirable forces on the proximal end of the sheath while still transmitting the steering forces effectively

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The pull wire is extracted from directly connecting to the proximal end of the sheath and instead passes through a guided path defined by the telescoping tube. This separation of the wire's routing path from the sheath's deflection point prevents the wire from becoming twisted or creating harmful forces at the proximal end

Inventive Principle:

Principle #2Taking out (Extraction)

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

The solution enables precise control over the deflection and retraction of the sheath, preventing wire twisting and maintaining the pull wire's straightness, thus enhancing the usability and longevity of the device by reducing stress on the sheath and wire.

Implementation Method 1

The pull wire retraction assembly can include a worm gear mounted for reciprocal longitudinal movement within the interior cavity of the handle assembly relative to the handle assembly. The steering mechanism can include a rotatable drive nut meshed with the worm gear for effectuating the reciprocal longitudinal movement thereof.

Methodology Applied

Scientific EffectWorm gear mechanism: Worm Drive

Implementation Method 2

a telescoping tube system for straightly guiding the pull wire as the pull wire retraction assembly moves within the interior cavity of the handle assembly through movement of the pull wire retraction assembly

Methodology Applied

Scientific EffectMechanical guidance:

Implementation Method 3

a pull wire retraction assembly within the interior cavity of the handle assembly and configured to selectively retract a pull wire to deflect the distal end portion of the sheath

Methodology Applied

Scientific EffectWire retraction mechanism:

Data Source

PatentUS9572957B2Steerable medical devices and steering assemblies

Publication Date: 2017.02.21 OSCOR INC

AI summary

A surgical apparatus includes an elongated handle assembly having opposed proximal and distal end portions and an interior cavity. An elongated sheath extends from the proximal end of the handle assembly, through the interior cavity of the handle assembly and out from the distal end portion of the handle assembly. The sheath includes an interior lumen extending therethrough and a distal end portion of the sheath is deflectable. The surgical apparatus includes a steering mechanism operatively associated with the handle assembly for controlling deflection of the deflectable distal end portion of the sheath. The steering mechanism includes a pull wire retraction assembly configured to selectively retract a pull wire to deflect the distal end portion of the sheath and a telescoping tube system for straightly guiding the pull wire as the pull wire retraction assembly moves within the interior cavity of the handle assembly.