Self-Deploying Wire Loops for Vascular Grasping
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Solution Overview
Problem
Current medical devices are inadequate for grasping and repositioning objects within the vascular system, such as stents, embolization coils, and guide wires, due to lack of control and frequent escape of the grasping loop during retraction.
Innovation Solution
A medical grasping device with a flexible, kink-resistant outer sheath and an elongate control member featuring self-deploying wire loops made from superelastic alloys, which can be actuated to securely grasp and retract objects, including a proximal control assembly for precise manipulation and an atraumatic distal tip for safe use within the vascular system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a loop-shaped distal segment is pulled proximally into the catheter to grasp a foreign body, then the foreign body is held during withdrawal, but the loop quickly flips between angled and axial orientations resulting in less assured control and common escape of the item
Solution Approach 1:
The loop is designed to dynamically change its configuration from an axial folded state during delivery to a transverse deployed state for grasping. The loop maintains a substantially transverse orientation to the longitudinal axis during the grasping operation, preventing the flipping motion that causes item escape. This dynamic design allows the loop to adapt its shape while maintaining controlled orientation.
Solution Approach 2:
The loop's orientation parameter is controlled to remain substantially transverse to the longitudinal axis during deployment and grasping, rather than allowing it to flip between axial and angled orientations. This parameter control ensures stable grasping and prevents item escape during retraction.
2Extent of automation
If the loop is made from superelastic Nitinol alloy to automatically form loops when emerging from the sheath, then the loops self-deploy into an extended configuration, but the loop flips between orientations during retraction causing item escape
Solution Approach 1:
The superelastic Nitinol alloy enables the loop to dynamically transition from a compressed axial state within the catheter to an extended transverse state upon deployment. The material's superelastic properties allow the loop to maintain its transverse orientation during retraction, preventing the flipping motion while still providing automatic deployment.
Solution Approach 2:
The loop's physical state changes from a folded axial configuration during delivery to an extended transverse configuration during grasping. The superelastic material enables this parameter change while maintaining controlled orientation, combining automatic deployment with reliable grasping control.
3Shape
If the device is designed with a low profile to conform to vascular anatomy, then the device can be navigated through vessels, but the grasping mechanism must be compact
Solution Approach 1:
The loop is nested within the catheter in a compact axial configuration during delivery, allowing the device to maintain a low profile for navigation through vessels. Upon deployment, the loop extends transversely from the catheter tip to provide full grasping capability. This nested design enables both low-profile delivery and effective grasping operation.
Solution Approach 2:
The grasping mechanism transitions from a compact folded state during delivery to an extended transverse state during grasping. This dynamic transformation allows the device to maintain low profile during navigation while providing full grasping capability when needed, resolving the contradiction between compactness and operational effectiveness.
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 device provides controlled and assured grasping and repositioning of objects within the vascular system, minimizing the risk of object escape and allowing for safe retrieval or repositioning with significant tensile force and low profile conformity to vascular anatomy.
Implementation Method 1
The grasping member comprises a plurality of pre-formed wire loops which self-deploy transversely upon emerging from the distal end of the outer sheath... said grasping member comprises a plurality of wire loops that each are formed from a superelastic alloy
Implementation Method 2
said elongate control member is a flexible cannula providing a lumen extending therethrough into which a guide wire is receivable and movable with respect thereto
Data Source
AI summary
A medical grasping device (1 ) has an elongate control member (9) with a grasping member ( 17) proximal to its distal tip. An outer sheath (3) with a passageway therethrough surrounds the elongate control member and is relatively movable with respect to the control member. A control assembly (2) disposed at a proximal end of said outer sheath has a fixed handle (5) and a sliding handle (7) and the proximal end of the elongate control member is fixed to the sliding handle to move the control member. The grasping member (17) has a plurality of pre¬ formed wire loops (50, 52, 54, 56) which self-deploy transversely upon emerging from said distal end of said outer sheath. Each wire loop is fastened to substantially opposite sides of the elongate control member so that each of said wire loops is substantially semi-circular upon full deployment and the respective ends (27, 29)of each wire loop extend substantially in opposite directions from the elongate control member.