Flexible Drive Shaft Retainer for Tissue Resection
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Solution Overview
Problem
Existing minimally invasive surgical devices for tissue resection in anatomically constrained sites, such as the spine, face issues with mechanical failures like cutting head detachment and wobbling, leading to potential tissue damage and complications during procedures like laminectomy and spinal stenosis treatment.
Innovation Solution
A surgical device with a flexible drive shaft and a retainer mechanism that prevents cutting head detachment and wobbling, featuring a multi-layer wire cable for high torsional rigidity and low bending rigidity, and a safety mechanism to maintain the cutting head's alignment and attachment to the shaft body, even if the drive shaft breaks.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a flexible drive shaft is used to enable the cutting head to operate in narrow and curved anatomical spaces, then the device can access constrained sites, but the drive shaft may break under load causing cutting head detachment
Solution Approach 1:
The patent implements a retainer mechanism that acts as a safety backup before drive shaft failure can cause cutting head detachment. The retainer is pre-positioned to engage with the cutting head, creating a fail-safe system that cushions against the harmful effect of drive shaft breakage. This prior cushioning ensures that even if the flexible drive shaft fails under load, the cutting head remains secured and cannot detach or wobble uncontrollably.
2Productivity
If the cutting head is designed to rotate at high speeds and torques for effective tissue cutting, then cutting efficiency is improved, but the mechanical stress on the drive shaft increases leading to potential breakage
Solution Approach 1:
The retainer mechanism serves as a preventive safety measure that cushions against the consequences of high mechanical stress. By pre-positioning the retainer to engage with the cutting head, the system creates a backup support that will activate if the drive shaft breaks under the high torques and speeds required for effective tissue cutting. This allows the system to operate at high productivity levels while having a safety cushion in place.
3Reliability
If the drive shaft is made more rigid to prevent breakage, then reliability improves, but the device cannot flex to navigate curved anatomical paths
Solution Approach 1:
The patent divides the drive shaft into multiple segments or layers with different mechanical properties. The flexible drive shaft is constructed with a multi-layer wire cable structure where individual layers can slide relative to each other, allowing the shaft to flex and bend while maintaining overall structural integrity. This segmentation enables the drive shaft to navigate curved anatomical paths without breaking, while the retainer mechanism provides additional reliability backup.
4Reliability
If the cutting head is securely attached to the drive shaft to prevent detachment, then reliability improves, but the device complexity increases
Solution Approach 1:
The patent combines the retainer mechanism with the existing drive shaft and cutting head structure, merging multiple functions into a unified design. The retainer is integrated into the overall device architecture rather than being a separate, independent component, which reduces overall device complexity while still providing the necessary reliability backup to prevent cutting head detachment.
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 device ensures reliable tissue cutting and drilling with reduced risk of mechanical failure, minimizing damage to surrounding tissues and extending the device's service life by preventing cutting head detachment and wobbling, thus enhancing the safety and efficacy of procedures like laminotomy and spinal decompression.
Implementation Method 1
featuring a multi-layer wire cable for high torsional rigidity and low bending rigidity
Implementation Method 2
the retainer prevents lateral movement, relative to axis of the elongated shaft body, of the cutting head
Data Source
AI summary
A device for cutting tissue including (a) an elongated shaft body defining a drive lumen, (b) a cutting head extending from a distal end of the elongated shaft body and being rotatable via a drive shaft disposed within the drive lumen, and (c) a retainer for keeping the cutting head attached to the shaft body if the cutting head becomes detached from the drive shaft or if the drive shaft breaks. A flexible drive shaft including (i) a core configured for resisting helixing, and (ii) at least one outer layer configured for transferring torque. A method of producing a flexible drive shaft including providing a core configured for resisting helixing, and wrapping the core with at least one outer layer of wires configured for maintaining high torsional rigidity. Related apparatus and methods are also described.