Ultrasonic Surgical Drill With Periodic Force Control
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Solution Overview
Problem
Traditional bone drilling methods, such as hand-powered and rotary devices, often damage surrounding soft tissue during spinal operations due to the hardness of bone, necessitating improved techniques for minimizing collateral damage.
Innovation Solution
An ultrasonic drill assembly with a probe connected to an electromechanical transducer generating ultrasonic vibrations, featuring a tapered distal head with force-concentrating formations and a translatory drive that periodically reduces the applied force, combined with a source of pressurized liquid for cooling and debris removal, to effectively drill into bone while minimizing tissue damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If traditional bone saws or rotary drills are used to cut hard bone, then cutting effectiveness is improved, but surrounding soft tissue is damaged
Solution Approach 1:
The patent applies ultrasonic vibration to the drill bit at frequencies typically between 20-100 kHz. This high-frequency vibration allows the drill to efficiently cut through hard bone tissue while the oscillating motion prevents continuous contact with soft tissue, thereby reducing collateral damage. The vibratory motion creates micro-fractures in the bone that propagate cleanly without the need for excessive mechanical force.
Solution Approach 2:
The ultrasonic drill operates in periodic cycles where the drill bit vibrates at ultrasonic frequencies, creating intervals of contact and separation with the bone tissue. This periodic action allows for efficient bone cutting during contact phases while minimizing soft tissue damage during separation phases. The cyclic nature of ultrasonic vibration enables controlled material removal with reduced harmful effects.
2Productivity
If significant pressure is applied to drill into hard bone, then drilling effectiveness is improved, but risk of nerve damage increases
Solution Approach 1:
The ultrasonic drill bit vibrates at high frequencies with small amplitudes, allowing effective bone cutting through cyclic loading rather than continuous high pressure. This vibratory mechanism reduces the need for sustained heavy pressure that could damage nerves, while still achieving effective drilling through cumulative mechanical work during each vibration cycle.
Solution Approach 2:
The patent changes the operational parameters from continuous high-pressure drilling to high-frequency low-amplitude vibration. This parameter transformation allows the drill to maintain effectiveness through increased frequency rather than increased force, thereby reducing the risk of nerve damage while achieving the same drilling productivity.
3Productivity
If continuous force is applied during ultrasonic drilling, then drilling speed is improved, but heat generation and tissue damage increase
Solution Approach 1:
The ultrasonic drill operates in periodic cycles with brief intervals between vibration bursts. These periodic action sequences allow for heat dissipation during non-vibration intervals while maintaining high drilling speed through cumulative cutting action. The cyclic operation prevents continuous heat generation that would occur with sustained high-power delivery.
Solution Approach 2:
The system incorporates cooling intervals before heat buildup becomes problematic. By periodically interrupting the ultrasonic vibration, the system allows heat to dissipate before applying the next burst of drilling energy, thereby cushioning against excessive temperature rise while maintaining overall drilling productivity.
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 ultrasonic drill assembly effectively drills into bone with reduced risk of damaging adjacent soft tissue by using ultrasonic vibrations and controlled force application, ensuring precise and safe bone penetration.
Implementation Method 1
an electromechanical transducer for generating mechanical vibration of an ultrasonic frequency
Implementation Method 2
a source of pressurized liquid communicating with the lumen or channel
Data Source
Figure 1
Figure 2A~3B
Figure 4~9D
AI summary
A medical drill assembly includes a probe connectable at a proximal end to an electromechanical transducer for generating mechanical vibration of an ultrasonic frequency. The probe has a shaft with a central lumen or channel, the shaft being formed at a distal end with a head having a tapered distal side. A source of pressurized liquid communicates with the lumen or channel of the probe, and a translatory or linear drive is operatively connected to the probe for applying a distally directed force to the probe. A controller is operatively connected to the translatory or linear drive for periodically at least reducing the magnitude of the distally directed force.