Tissue Cutting Cannula With Semi-Solid Seal and Stop Control
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Solution Overview
Problem
Existing tissue cutting devices for neurosurgical procedures face issues such as clogging due to fluid and air artifacts in the annular space between cannulae, leading to degraded performance, and fail to control the inner cutting cannula's stop position, causing tissue samples to be trapped.
Innovation Solution
A tissue cutting device with a semi-solid seal at the annular space between the inner and outer cannulae to prevent air and fluid artifacts, and an inner cannula stop position control to ensure precise positioning of the inner cannula, allowing for higher reciprocation rates and effective aspiration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If aspiration is used to remove tissue samples along the inner cannula lumen, then tissue removal effectiveness is improved, but fluids and air artifacts clog the annular space between inner and outer cannula, degrading performance
Solution Approach 1:
The device divides the cannula system into inner and outer cannulae with a defined annular space, separating the aspiration path (inner lumen) from the sealing region (annular space). This segmentation allows aspiration to occur through the inner lumen while the annular space remains dedicated to sealing, preventing fluid and air artifact intrusion into the cutting region.
Solution Approach 2:
A seal member is introduced as an intermediary element positioned in the annular space between the inner and outer cannulae. This seal member prevents fluids and air artifacts generated during aspiration from entering the annular space and interfering with the cutting operation, thereby maintaining system reliability while preserving aspiration effectiveness.
2Productivity
If the inner cutting cannula reciprocates within the outer cannula, then tissue cutting capability is improved, but the rest position of the inner cannula is uncontrolled, causing tissue samples to be trapped
Solution Approach 1:
The device incorporates a stop mechanism that pre-establishes a defined rest position for the inner cannula. Before each reciprocating cutting cycle, the inner cannula is positioned at a predetermined location relative to the outer cannula, ensuring that tissue samples are properly oriented and preventing trapping during the return stroke.
Solution Approach 2:
The stop mechanism provides positional feedback by mechanically limiting the inner cannula's travel range. This feedback ensures the inner cannula consistently returns to the same precise rest position, enabling controlled stopping and preventing tissue sample trapping between the cannulae while maintaining effective tissue cutting capability.
3Productivity
If higher reciprocation rates are used to increase cutting speed, then productivity is improved, but performance degrades due to clogging and uncontrolled stop positions
Solution Approach 1:
By segmenting the cannula system into distinct functional zones (inner lumen for aspiration, annular space for sealing), the device enables higher reciprocation rates without clogging. The seal member confined to the annular space prevents fluid interference with the cutting action, allowing faster operation while maintaining reliability.
Solution Approach 2:
The seal member acts as an intermediary that isolates the high-speed reciprocating cutting action from the aspiration flow. This separation allows the inner cannula to reciprocate at higher rates for increased productivity while the seal prevents performance degradation from fluid and air artifact intrusion.
Solution Approach 3:
The stop mechanism pre-positions the inner cannula at defined rest points, ensuring consistent starting positions for each high-speed cutting cycle. This preliminary positioning prevents tissue trapping even at elevated reciprocation rates, maintaining both productivity and performance stability.
Data Source
AI summary
A tissue cutting device is disclosed and described. The device includes a handpiece disposed along a first central longitudinal axis and an outer cannula in which a reciprocating inner cannula is disposed. The inner and outer cannulas are disposed along a second longitudinal axis that is axially spaced from the first central longitudinal axis. The device may also include an inner cannula stop position control for selectively controlling the position of the inner cannula when it is at rest.