Retractable Sheath Delivery System With Threaded Engagement
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Solution Overview
Problem
Current delivery systems for deploying prostheses in body lumens face challenges in consistently and reliably retracting the outer sheath to deploy self-expanding stent-grafts, leading to inefficiencies and potential inaccuracies in the deployment process.
Innovation Solution
A delivery system with a handle featuring an internal spring assembly that selectively engages and disengages with a threaded slide shaft, allowing for controlled axial rotation and translation to retract the outer sheath, ensuring precise deployment of the prosthesis by managing frictional forces and facilitating both initial and rapid deployment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the outer sheath is tightly compressed within the catheter for delivery, then the prosthesis can be delivered through the vasculature, but high levels of friction are imposed between the prosthesis and the outer sheath
Solution Approach 1:
The handle mechanism transitions between two dynamic states: engaged (threaded connection active) and disengaged (threaded connection inactive). This dynamic switching allows the system to adapt its mechanical properties during different phases of the procedure, resolving the contradiction between maintaining compression during delivery and enabling retraction during deployment.
Solution Approach 2:
The system changes the mechanical engagement parameter between the handle and slide shaft. When engaged, the threaded connection provides high mechanical advantage for controlled retraction; when disengaged, the connection is released to allow free movement. This parameter change resolves the friction contradiction by switching between high-force control mode and low-friction movement mode.
2Productivity
If a significant force is imparted to retract the outer sheath, then the prosthesis can be deployed, but consistent and reliable retraction becomes difficult to achieve
Solution Approach 1:
The threaded mechanism is pre-configured on both the slide shaft and handle before the procedure begins. This preliminary mechanical configuration ensures that when retraction is needed, the mechanical advantage is already in place, eliminating the need to overcome unpredictable friction forces during the critical retraction phase and ensuring reliable, consistent deployment.
Solution Approach 2:
The threaded connection acts as an intermediary mechanical element between the operator's rotational input and the linear retraction motion. This intermediary mechanism translates rotational force into controlled linear movement, providing consistent and reliable retraction regardless of variations in friction conditions between the prosthesis and outer sheath.
3Ease of manufacture
If the handle is designed with a simple structure, then ease of manufacture is improved, but the ability to provide controlled retraction force is reduced
Solution Approach 1:
The handle is segmented into distinct functional components: the handle body, the threaded engagement mechanism, and the connection interface with the outer sheath. This segmentation allows each component to be manufactured independently using standard machining processes, maintaining ease of manufacture while enabling the complex threaded retraction control function.
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 system enables consistent and reliable deployment of prostheses by managing frictional forces, allowing for accurate positioning and rapid completion of the procedure, minimizing time during which blood flow is occluded and reducing the risk of complications.
Implementation Method 1
the spring arm resiliently lifts the head away from the slide shaft
Implementation Method 2
the ring is disposed over and radially compresses at least portion of the head onto the slide shaft such that the threaded inner surface of the head is threadedly engaged with the threaded outer surface of the slide shaft
Implementation Method 3
The slide shaft has a threaded outer surface. The handle includes an internal spring assembly for selectively engaging and disengaging the handle with the threaded outer surface of the slide shaft
Implementation Method 4
A stent-graft may be tightly compressed within a catheter for delivery, imposing high levels of friction between the stent-graft and the outer sheath of the catheter
Data Source
Figure 1~1A
Figure 2
Figure 3
AI summary
A delivery system (100) for delivering a prosthesis includes a sheath (106), a slide shaft (128) having a threaded outer surface (130), and a handle (110). The handle includes an internal spring assembly (116) for selectively engaging and disengaging the handle with the threaded outer surface of the slide shaft. The internal spring assembly includes at least one spring arm (120), a head (122) coupled to the spring arm and having a circumferentially rounded threaded inner surface (124), and a ring (118) slidably disposed over the spring arm. When the ring is in a first longitudinal position, the threaded inner surface of the head is spaced apart from the threaded outer surface of the slide shaft. When the ring is in a second longitudinal position, the threaded inner surface of the head is threadedly engaged with the threaded outer surface of the slide shaft. The handle may include a resilient cover (1312) to provide the internal spring assembly with a biased or nominal operational position.