The high-speed liquid (water) jet has distinctive characteristics in surgical applications, such as tissue dissection without thermal damage and small blood vessel preservation, that make it advantageous over more conventional instruments. The continuous pressurized jet has been used since the first medical application of water jets to liver surgery in the 1980s, but exhibited drawbacks partly related to the excess water supply required and unsuitability for application to microsurgical instruments intended for deep, narrow lesions (endoscopic instrumentation and catheters) due to limitations in miniaturization of the device. To solve these issues, we initiated work on the pulsed micro-liquid jet. The idea of the pulsed micro-liquid jet originated from the observation of tissue damage by shock/bubble interactions during extracorporeal shock wave lithotripsy and evolved into experimental application for recanalization of cerebral embolisms in the 1990s. The original method of generating the liquid jet was based on air bubble formation and microexplosives as the shock wave source, and as such could not be applied clinically. The air bubble was replaced by a holmium:yttrium-aluminum-garnet (Ho:YAG) laser-induced bubble. Finally, the system was simplified and the liquid jet was generated via irradiation from the Ho:YAG laser within a liquid-filled tubular structure. A series of investigations revealed that this pulsed laser-induced liquid jet (LILJ) system has equivalent dissection and blood vessel preservation characteristics, but the amount of liquid usage has been reduced to less than 2 μ l per shot and can easily be incorporated into microsurgical, endoscopic, and catheter devices. As a first step in human clinical studies, we have applied the LILJ system for the treatment of skull base tumors through the transsphenoidal approach in 9 patients (7 pituitary adenomas and 2 chordomas), supratentorial glioma (all high grade glioma) in 8 patients, including one with fine perforating vessel involvement, and cerebrovascular disease (1 arteriovenous malformation and 2 intracerebral hemorrhages) in 3 patients. Precise dissection and mass reduction of the tumor were obtained in all tumor cases except for one chordoma with significant fibrosis. Small arteries down to 100 μ m were preserved, allowing subsequent microsurgical devascularization. Veins were also preserved occasionally. The arachnoid membrane and the tumor capsule were resistant to the LILJ except for one case with prolonged exposure. No complications related to use of the LILJ system were observed. No disturbance of the surgical field by splashing, aerosol, or dissemination of pathological tissue occurred with placement of the optimal suction system. The Ho:YAG LILJ system enhances the advantages of commercialized pressure-driven continuous liquid jet instrumentation in terms of small vessel preservation and accessibility in confined spaces for minimally invasive neurosurgery, and solves some of the drawbacks involved with excessive liquid use and size.
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