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Mechanical lithotripsy

- Jun 25, 2018 -

Mechanical lithotripsy editing

ML has a long history and can be traced back to ancient Egypt. According to records, the method used was to fix a piece of diamond or hard stone on the end of a hollow reed rod with glue or asphalt, and then insert the rod into the patient's bladder and allow the patient to walk around and gradually move the stone by the action of diamonds or stones. Crushed. However, this method can only treat soft “trimstone” (magnesium ammonium phosphate stones), and it is incapable of treating hard stones such as calcium oxalate monohydrate. In 1782, Indian doctor Martin designed a metal tweezers that can be inserted into the urethra. He successfully cured his bladder stones with this forceps. In 1824, the French doctor Civiale invented a triple forceps. He can grasp the bladder stones with his tactile sensation, pressurize it with special screws, and finally smash the stones. However, until the 19th century, open surgery (mainly for bladder stones) was prevalent in continental Europe, and internal lithotripsy was less commonly used because of its low success rate. In 1879, the advent of cystoscopy was a milestone in the history of IL development. Since then it has changed the blind operation of doctors and greatly improved the success rate and safety of lithotripsy. Since then, people have designed a variety of mechanical lithotripters and lithotripters, some of which are still in use today. There are two main types of gravel pliers: the clamp type and the punch type. The latter was first designed and applied by Mauermayer and Hartung in 1976. It can rush stones out at the same time as gravel and keep the operative field clear. ML is easy and safe to use. It can break stones with various components less than 3cm in diameter. It is now mainly used for the treatment of bladder stones. In rare cases, it can also be used for the treatment of kidney stones. Special attention should be paid to avoid pinching the kidney tissue, otherwise it will be difficult Controlled bleeding.

Electrohydraulic lithotripsy

(electrohydrauticlithotripsy, EHL)

EHL was originally invented in 1955 by former Soviet engineer Yutkin. After more than 10 years of improvement, a clinical bladder lithotripsy device called Urat-1 was introduced. Its basic principle is the same as what is used now: there is an insulating layer between two electrodes of different voltages, when the two electrodes are When the voltage difference between the electrodes exceeds the maximum resistance of the insulating layer, sparks are generated between the electrodes to form a plasma. The plasma is an ion and electron vacuole that rapidly expands to a certain degree and then disintegrates rapidly to form liquid shock waves and micro-jets that break up the stones. With high-speed photography and sound detection technology, it can be found that with each discharge, plasma bubbles oscillate around the EHL probe tip, and three shock waves are generated at the same time. The first shock wave is formed by plasma expansion; the second and third are due to cavitation bubble disintegration. When the tip of the probe is about 1 mm from the surface of the stone, the shock wave generated is the strongest and the effect of the gravel is best. If the distance is >3 mm, the energy of the cavitation bubble will be converted into sound energy more, and the efficiency of the gravel will be reduced. These observations are consistent with the actual clinical conditions.

Due to material limitations in the early days, the discharge time was very long (5 to 10 ms), and the resulting shock wave easily damaged the probe and the tissue. With the development of electronics and materials science, now the discharge time of the hydrolithite is generally 1 ~ 5μs, the working voltage is 1 ~ 8kV, and the output energy is 50 ~ 1300mJ. The thickness of the probe is also reduced from F10 of Urat-1 to F1.6. EHL has no selectivity for stones, and the probe can be bent. It can be used to treat various parts of the urinary system, but there are certain complications such as ureteral perforation. The study confirmed that, in addition to direct mechanical injury, tissue damage was mainly related to the formation and disintegration of cavitation bubbles, and the degree was directly proportional to the output energy, and no evidence of thermal damage was found. In order to reduce the tissue damage, foreigners have recently added a metal shield at the end of the probe so that the surrounding tissue can be prevented from direct exposure to the plasma and a certain effect is achieved.


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