Expandable Sheath Retrieving Irregular Implants
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Solution Overview
Problem
Minimally invasive medical procedures face challenges with sheaths that have thin walls, leading to insufficient strength and difficulty in retrieving objects with irregular shapes or configurations due to high stiffness and rigidity, which can result in kinking, bending, or snagging, especially when objects with unique geometries are pulled into the sheath.
Innovation Solution
A sheath system with a radially expandable distal portion and slits that form flaps, allowing for increased inner diameter and accommodating objects of larger profiles, along with a joint for deflection and stress reduction, facilitating the retrieval of irregularly shaped objects while minimizing the risk of snagging and tearing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Length of moving object
If the sheath wall is made thin to minimize outer diameter and maximize inner diameter, then the sheath provides less disruption to the circulatory pathway and smaller wound size, but the sheath lacks sufficient strength and may kink, bend or fold when objects are pulled into it
Solution Approach 1:
The distal portion of the sheath is designed to be radially expandable, transitioning from a collapsed state during insertion to an expanded state during object retrieval. This dynamic structure allows the sheath to adapt its diameter based on operational requirements, maintaining a small profile for insertion while providing sufficient strength and capacity when needed.
Solution Approach 2:
The sheath material and structure are designed to change physical parameters, specifically radial expansion, in response to operational conditions. The distal portion can expand radially to accommodate objects of larger profiles, changing the effective inner diameter and structural capacity while maintaining the original thin-walled design for minimally invasive insertion.
2Strength
If the sheath material has high stiffness or rigidity to provide sufficient strength, then the sheath maintains structural integrity, but the withdrawal of objects becomes more difficult and the sheath may tear or fold inward
Solution Approach 1:
The sheath transitions from a rigid, stiff state during insertion to a more compliant, expandable state during object retrieval. The radially expandable distal portion can adapt its stiffness locally, providing structural integrity when needed while allowing flexibility to accommodate object withdrawal without tearing or folding.
Solution Approach 2:
Different portions of the sheath have different mechanical properties. The proximal portion maintains high stiffness for structural integrity during insertion, while the distal portion is designed with radial expandability to provide localized flexibility and accommodation during object retrieval, preventing tearing and folding at the distal edge.
3Area of stationary object
If the inner diameter of the sheath is maximized to accommodate objects, then objects can pass through more easily, but the outer diameter increases and causes more disruption to the circulatory pathway
Solution Approach 1:
The sheath inner diameter is dynamic rather than fixed. The distal portion can expand radially to provide a larger effective inner diameter for object accommodation, while the proximal portion maintains a smaller, fixed diameter for minimally invasive insertion. This dynamic adaptation allows the sheath to maximize inner diameter only when and where needed.
Solution Approach 2:
The sheath utilizes radial expansion in the third dimension to increase inner capacity without increasing the longitudinal or insertion profile diameter. By expanding radially at the distal portion, the sheath can accommodate objects of larger profiles while maintaining a small insertion diameter, effectively decoupling the relationship between inner and outer diameters.
Data Source
AI summary
The present invention provides a device for delivering and/or recovering an object, such as a patent foramen ovale (PFO) occluder. According to one embodiment of the invention, a device contains an outer sleeve and an inner sheath. The inner sheath has a proximal portion and a distal portion; the distal portion of the inner sheath is disposed inside the lumen of the outer sleeve. The distal portion of the inner sheath can expand radially to facilitate retrieval of an object. The distal portion of the inner sheath has a larger diametrical configuration than the proximal portion of the inner sheath. The distal portion of the inner sheath may be in the shape of a cone or similar shape. The distal portion of the inner sheath further includes slits that form flaps which collapse inward and overlap each other as the distal portion is in its unexpanded configuration.