Ultrasonic Blade Static Casing Heat Management
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Solution Overview
Problem
Traditional surgical saws and ultrasonic bone cutting devices generate excessive heat and produce uneven cuts, leading to tissue damage and impaired healing, especially when cutting large bone sections like the femur, due to inadequate cooling and blade design.
Innovation Solution
An ultrasonic surgical device with a static casing that sheaths the ultrasonic horn, separated by a lubrication film, and features fluid channels for cooling and therapeutic agent delivery, along with a flexible joint to reduce heat transfer and vibrational energy, allowing for deeper penetration without damaging adjacent tissues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional surgical saws use rapid blade motion to cut bone, then cutting efficiency is improved, but excessive heat is generated causing tissue damage
Solution Approach 1:
The patent employs ultrasonic vibration at high frequency (20-100 kHz) to cut bone tissue. The ultrasonic blade vibrates rapidly in a longitudinal direction, creating micro-fractures in the bone through fatigue loading rather than traditional mechanical cutting. This vibrational mechanism achieves efficient bone cutting while generating significantly less heat compared to traditional oscillating or reciprocating saws, as the ultrasonic vibrations are damped before converting to harmful thermal energy.
Solution Approach 2:
The patent incorporates an integrated irrigation system with fluid channels that deliver cooling fluid directly to the blade-bone interface. The hydraulic flow removes generated heat through convection and prevents thermal damage to surrounding tissues. The fluid channels are designed to maintain patency despite surgical debris, ensuring continuous cooling during the cutting process.
2Productivity
If traditional bone saws use serrated blades to cut bone, then cutting capability is improved, but soft tissues are torn causing blood loss and nerve damage
Solution Approach 1:
The ultrasonic blade vibrates at high frequency with a continuous or fine-toothed edge rather than large serrations. The vibrational cutting mechanism creates micro-fractures in bone through cyclic loading, allowing the blade to cut through bone efficiently without catching and tearing soft tissues. The rapid vibration frequency prevents soft tissue from being dragged or torn, as the blade moves too quickly to engage significantly with softer materials.
3Temperature
If irrigation channels are provided along the blade edge to cool the interface, then heat management is improved, but the blade edge becomes discontinuous reducing cutting efficiency
Solution Approach 1:
The irrigation system uses multiple discrete fluid channels positioned along the blade rather than a single continuous channel. These segmented channels can be strategically placed to deliver cooling fluid to critical heat-generating areas without compromising the structural integrity or continuity of the blade edge. The segmented approach allows optimization of both cooling effectiveness and cutting performance.
Solution Approach 2:
The fluid channels are integrated within the blade structure itself, with channels nested inside the blade body that deliver fluid to outlets at or near the cutting edge. This nested configuration allows the cooling system to be embedded within the cutting tool without adding external components that would interfere with cutting efficiency or blade continuity.
4Productivity
If larger blade size is used to cut large bone sections, then cutting capability is improved, but heat transfer to adjacent tissues increases causing damage
Solution Approach 1:
The ultrasonic blade uses high-frequency vibration (20-100 kHz) to cut large bone sections efficiently. The vibrational mechanism generates less heat overall compared to traditional mechanical cutting, and the heat that is generated is quickly dissipated through the integrated irrigation system. This allows cutting of large bones like femur or tibia without excessive heat transfer to surrounding soft tissues, even when larger blade sizes are used.
Solution Approach 2:
The integrated irrigation system delivers cooling fluid directly to the blade-bone interface through channels within the blade structure. This hydraulic cooling system efficiently removes heat at the source, preventing thermal energy from transferring to adjacent tissues. The fluid flow rate and distribution are optimized to match the heat generation during cutting of large bone sections.
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 effectively reduces heat transfer and tissue damage, enabling precise and efficient cutting of large bone sections while maintaining a stable temperature, thus promoting better healing outcomes.
Implementation Method 1
The sheathing slot is separated from the ultrasonic horn by at least one lubrication film
Implementation Method 2
at least one ultrasonic horn...generate and propagate ultrasonic vibrations along the ultrasonic horn toward the cutting end
Implementation Method 3
features fluid channels for cooling
Data Source
AI summary
An ultrasonic surgical device capable of cutting biological tissues such as bone and cartilage. The ultrasonic surgical device includes a static casing, which sheaths an ultrasonic horn, and a lubrication film, which separates the ultrasonic horn and the static casing. The static casing, which may also incorporate a plurality of fluid channels to allow passage of fluids along its length and eventual distribution of such fluids at the cutting end and biological tissue interface, inhibits the transfer of heat generated along the ultrasonic horn. The cutting end and the static casing are separated by a flexible joint, which serves to inhibit the transfer of vibrational energy, and consequently heat, from the cutting end to the static casing. As such, the static casing remains stable and can be used both to manipulate the surgical device with greater haptic control and facilitate effective penetration of larger cross-sections of biological tissue.