Expandable Member Outer Sheath Abrasion Resistance
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Solution Overview
Problem
Medical devices with expandable members face issues such as abrasion, tearing, and puncturing due to rough surfaces during minimally-invasive procedures, and existing devices lack effective mechanisms for controlling the rotation and size reduction of these members for easy removal.
Innovation Solution
A medical device comprising an elongated member, an expandable member, and an outer sheath, where the expandable member is coupled to the elongated member and the outer sheath is disposed about the expandable member to provide discontinuous contact, allowing for improved resistance against abrasion and tearing, and a twisting apparatus with a ratchet wheel and pawl mechanism to control the rotation and size reduction of the expandable member.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the expandable member is made with thicker walls to resist abrasion and puncturing, then durability is improved, but the overall size increases making removal through the cannula difficult
Solution Approach 1:
The expandable member is placed inside an outer sheath that provides additional protection and structural support. The nested configuration allows the expandable member to have adequate wall thickness for durability while the outer sheath contains the overall package size to fit through the cannula during removal
2Ease of operation
If the expandable member is wrapped or folded to reduce size for removal, then ease of removal is improved, but the device lacks components to withstand the torsional stress
Solution Approach 1:
The outer sheath is configured to receive and protect the expandable member during wrapping and folding operations. The sheath provides a protective environment that allows the expandable member to be twisted and folded for size reduction while the sheath itself is designed to withstand the associated torsional stresses
Solution Approach 2:
The outer sheath acts as an intermediary between the expandable member and the external environment during removal. It provides a protective interface that allows controlled manipulation and folding of the expandable member while protecting it from excessive torsional stress that could cause damage
3Ease of manufacture
If the outer sheath is made from the same material as the expandable member, then manufacturing is simplified, but the discontinuous contact required for durability is compromised
Solution Approach 1:
The outer sheath is made from a different material than the expandable member, with each material selected for its specific properties. The outer sheath material is chosen to provide the necessary protection and structural support, while the expandable member material is optimized for its expansion and contraction functions. This local differentiation of material properties ensures both durability through discontinuous contact and functional performance
Data Source
AI summary
In some embodiments, an apparatus includes an elongated member, an expandable member coupled to the elongated member, and an outer sheath. The outer sheath, which can be constructed from a different material than the expandable member, is disposed about the expandable member such that an outer surface of the expandable member is in discontinuous contact with an inner surface of the outer sheath. The expandable member and the outer sheath are configured to cooperatively displace a bone structure when moving between a collapsed configuration and an expanded configuration.