Segmented Inner Tubular Member for Angled Surgical Instruments
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Solution Overview
Problem
Angled rotary tissue cutting instruments face issues with torque transmission and irrigation loss due to spirally wound shafts unwinding when rotated in reverse, leading to inefficiency and potential device failure in applications like neuro tumor resection and ENT micro-debrider devices.
Innovation Solution
The inner member of the surgical cutting instrument features a rigid proximal and distal portion with a flexible intermediate portion made of thermoplastic material, such as Pebax®, which maintains a fluid barrier and prevents irrigation loss, while a spiral cut pattern in a second tubular member provides flexibility and torque transmission, preventing unwinding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a single spirally wound strip is used to provide flexibility and torque transmission, then the shaft can conform to angled configurations, but the shaft unwinds when rotated in the opposite direction and cannot transmit torque efficiently in both directions
Solution Approach 1:
The shaft is divided into multiple discrete spiral elements (first spiral element, second spiral element, third spiral element) rather than a single continuous spiral wound strip. Each spiral element is independently formed and can rotate freely relative to adjacent elements, preventing the unwinding problem while maintaining flexibility and bidirectional torque transmission capability.
2Adaptability or versatility
If spiral cuts or coils are included in the flexible region to provide flexibility, then the shaft can rotate within the angled configuration, but gaps form that cause loss of irrigation fluid
Solution Approach 1:
An intermediate portion comprising a continuous tube without spiral cuts or coils is provided between the proximal and distal rigid portions. This intermediate tube acts as a mediator that maintains the fluid barrier and prevents irrigation loss while still allowing rotational movement through its flexible material composition, thus eliminating gaps that would cause fluid leakage.
3Productivity
If high rotational speed is used to improve cutting efficiency, then productivity increases, but the risk of irrigation loss and device clogging increases
Solution Approach 1:
The shaft is segmented into multiple independent spiral elements that can rotate freely relative to each other. This segmentation reduces rotational resistance and allows the shaft to handle high rotational speeds more effectively, maintaining irrigation integrity and preventing clogging even at high cutting speeds.
Solution Approach 2:
The intermediate continuous tube portion serves as a mediator that maintains the fluid barrier during high-speed rotation, preventing irrigation loss that would otherwise occur at high rotational speeds and potentially cause device clogging or failure.
Data Source
AI summary
An inner member rotatable in an angled outer tubular member of a rotary surgical cutting instrument includes first and second tubular members. The first tubular member includes a rigid proximal portion, a rigid distal portion, and a flexible intermediate portion. The proximal and distal portions are comprised of a first material and the intermediate portion is comprised of a second material. The second tubular member is coaxially disposed around the first tubular member along the intermediate portion. The second tubular member includes a proximal section, a distal section, and a central section. The central section is flexible and the proximal and distal sections are rigid. The second tubular member is comprised of a single material. The proximal section is fixedly coupled to the proximal portion and the distal section is fixedly coupled to the distal portion.