by Vladimir ROZANOV, Dr. Sc. (Biol.), Cand. Sc. (Phys. & Math.), Deputy Director of the Scientific and Information-Methodological Center Bazis of the RF Ministry of Education and Science, Deputy Director of the Scientific Center of Hydrophysical Studies, Physics Department of the Lomonosov Moscow State University (MGU); Igor MATVEICHUK, Dr. Sc. (Biol.), Head of the Research and Educational-Methodological Center of Biomedical Technologies of the All-Russia Research Institute of Medicinal and Aromatic Herbs; Academician Valery BYKOV, RAMS and RAAS (Moscow); Nikolai SYSOYEV, Dr. Sc. (Phys. & Math.), Dean of the Physics Department at MGU

The effect of water jet on human organism has been used for long and successfully by physicians in their medical practice. Some researchers believe that hydrotherapeutic methods were brought to Europe from Egypt by the Ancient Greek philosopher Pythagoras of Samos (570-490 B.C.). Later the famous physician Hippocrates (circa 460 B.C.--between 377 and 356 B.C.) developed this theory and described in detail its substance in his treatise well known in the medical scientific circles (5th cent. B.C.) "On Air, Waters and Localities" ("De aere, aquis et locis"), in which he substantiated methods of physiotherapeutic water effect on man. In the 2nd-1st cent. B.C. the Roman physician Asclepiad (Aesculapius) acted as a follower and continuer of this theory and widely used hydrotherapeutic procedures (in particular, sponge-down and shower baths) in treatment of his patients.

WATER JET EFFECT IN PHYSIOTHERAPY

The methods of physiotherapeutic procedures in the form of jet effect on human organism originate from the first Italian showers of the 14th century. In modern physiotherapy there are dozens of shower-baths different in technology and purpose such as jet (well known as Charcot's douche), dispersive, needle, rising or perineal, raining, circular*, Scottish, underwater massagedouche, etc., which form four main classification groups: descending, ascending, jet and circular. Besides, whatever specific douche is used, it always produces mechanical and thermal effect at the same time on human organism. In addition, the former is determined by static and dynamic pressure of a jet (or jets) on the body surface. The value of the static pressure of a water jet changes depending on a douche type over a wide range from 0.5 to 4 atm.

In general at the initial moment a local mechanical effect of water jets causes a short constriction of the lumen of blood vessels in tissues and then their strong continuous distension. Under the effect of changing local stresses, the tone of vascular and muscular tissues increases, muscle strength as well as its electric and mechanical excitability improve, and the gas composition of blood changes essentially. As a result of such jet

* Circular douche is one of its varieties of medium pressure. For this purpose a special facility is used which consists of a system of vertical pipes located circlewise and forming above and below an incomplete circle. There are small holes in the inner surface of pipes through which water is supplied to the patient. Taking such a douche, the person is exposed to numerous horizontal water streamlets directed to his body under pressure. They produce a stimulating effect on peripheral receptors and tone up the central nervous system.--Ed.

massage we get high arterial tension and better oxygen assimilation due to attaining not frequent but deeper respiration. There is an extensive list of indications for application of douches but there are also contraindications, which should be known to all patients with high blood pressure, heart trouble and patients suffering from atherocardiosclerosis (one of the types of in cardiac muscle change.--Ed.) and stenocardia.

Another sphere of medical application of jet currents of fluids includes intramuscular, intravenous and percutaneous injections of pharmaceuticals under pressure created by syringes of different design or hyposprays.

One more area of using jet effects is treatment of septic wounds by the jet under low pressures. It provides reduction of microbial contamination in a wound to 10¹ per 1g of tissue. Such effect is achieved due to a pulsating jet (pulsation frequency from 60 to 1,000 per minute) under pressure about 3 atm. Fluid consumption can reach 700 ml/min.

One should also keep in mind such important application of water jet as necessary daily hygienic procedures both in everyday life and at hospital (for example, during preparation of a surgeon and a patient for an operation).

WATER JET AS A "CUTTING INSTRUMENT"

It should be stressed that in all above-mentioned cases specialists use jet effects under pressure not exceeding several atmospheres. But if we increase it to several hundreds or thousands of atmospheres, liquid jet becomes an efficient cutting instrument, "water knife or scalpel", and the edge of such "knife" will never become blunt. In

other words, it can cut practically any material such as steel and granite, titanium and concrete, rubber and paper, glass and textolite!* The first studies devoted to problems of hydrodynamic cutting of different materials date from 1956 and belong to Soviet scientists though patents for hydraulic cutting equipment were issued initially to American companies.

However, it is important to note that commercial applications of hydrodynamic technologies are rather various. They include cutting of sheet metal and non-metallic materials for shipbuilding, aviation, automobile and atomic industries, disposal of munitions and military equipment, cleaning of ship hulls, figured cutting of variegated marble for mosaic floors, manufacture of complex parts from materials whose mechanical processing is rather complicated (kevlar, paronite)** and also from different honeycomb structures, repair works on product pipelines, preparation of fish for fillet, figured cutting of cakes, etc.

The range of its unique technological features includes: absence of open flame and spark formation, low mechanical stresses in impact areas and consequently low heating, insignificant structural changes of the processed material, stress locality and minor losses, varying jet structure, environment-friendly technology, remote operation potential and also any type of cutting including small radii of curvature. All this opens up new vistas for use of jet methods in biomedical technologies. The results of scientific and practical efforts of the last 30 years, in particular, creation of a hydro-jet scalpel, convincingly testify to this fact.

HYDRO-JET SCALPEL

The specific feature of the latter as a cutting instrument lies in the fact that separation of tissues is effected by a high-energy fluid or abrasive fluid (of high hardness.--Ed.) jet. Today there exist original designs of a hydro-jet scalpel providing its efficient use in ophthalmology, brain and abdominal surgery***, in operations on parenchymatous organs and in separation of the bone.

* Textolite is an electrical insulation structural material used for production of friction bearings, pinions and other parts, and also in electric and radio engineering.--Ed.

** Kevlar has a great strength (fivefold stronger than steel, ultimate strength σ_o = 3,620 M Pa). It was first produced by Stephanie Kwolek team in 1964, and its production process was developed in 1965. Paronite is a stable material (rubber compound with asbestos fiber) retaining its elasticity under low temperatures.--Ed.

***Abdominal surgery is a field of medical knowledge, whose purpose is a surgical treatment of diseases and traumas of abdominal cavity organs and walls.--Ed.

Using a water jet effect in osteoarthrology (teaching on bones and synostoses.--Ed.) is of special interest as there are unique opportunities for introduction of noninvasive (safe) physico-mechanical methods into medical practice as compared with the used mechanical methods based on application of bone saws, scissors, drills and chisels (for hollowing out of holes). It provides conditions for development of a new line in practical medicine--hydrodynamic surgery, and serves as a basis for development and introduction into practice of innovative biomedical technologies.

The experience accumulated in the development and application of hydrodynamic medical technologies allowed working out of a number of necessary requirements imposed on properties of the used fluids, materials and abrasive (high-strength) additives. Methods of a cutting jet formation depend also on specifics of a current task such as a type of actual operations and characteristics of biological tissues liable to physicomechanical impact.

The conducted studies prove that various biological tissues have essential differences in mechanical properties, and for their hydrodynamic separation, power efforts different in value are needed. For example, efficient hydrodynamic incision of soft biological tissues is achieved due to the use of a fluid jet without use of abrasive additives. These characteristics are considered in the development of requirements and are reflected on structural peculiarities of hydro-surgical instruments being created.

To the point, it is well known from literature that the method at hand was first introduced by American researchers Dimitrios N. Papachristou and Richard Barters, who in 1982 published a paper devoted to resection (extraction of a body organ or its part.--Ed.) of liver by a water jet. But it is less known that works of our countryman and famous modern ophthalmosurgeon Nikolai Temirov, Dr. Sc. (Med.), devoted to "hydromonitoring eye microsurgery" left behind works of these authors at least for two years!

Meanwhile, the pilot studies in hydrodynamic surgery were notable for absolute simplicity of choosing devices for creation of necessary pressure of working fluid and formation of a cutting fluid jet. For example, for creation of pressure in the fluid, Temirov in his first experiments on "hydromonitoring" eye microsurgery used a vessel consisting of two hemispheres with an inner membrane with fluid on its one side and gas supplied under pressure on the other side. Low values of the attained pressure at minimal

fluid consumption were sufficient for work on eye tissues, studies of the process specifics and working conditions. Let's point out: a set of changeable tips was developed with regard for operation specifics.

Papachristou and Barters chose an easy way in development of special engineering and equipment. For creation of working pressure in their hydro-jet scalpel they used a garden pump. They managed to prove the main point: for the first time to show that application of a fluid jet leads to local "washout" of parenchyma, effective isolation of blood vessels and biliary ducts with their visualization and a good access to further intersection by using routine methods. In this case blood losses are minimal and only due to bleeding from capillaries destroyed by the water jet are identified. They used transparent screens for protection from possible splashes. The working fluid and microparticles of the washed parenchyma were removed by suction upon completion of the operation. Later on such suction became a compulsory part of the equipment for hydrodynamic surgery.

The new method was tested in the experiment with 45 lobectomies (from Latin lobectomia, where lobus is a part and ektomia is extraction, i.e. extraction of a part of a body organ.--Ed.) of dogs' liver and then introduced at the hospital (4 resections). In all cases blood losses were minimal under atraumatic (safe) isolation and identification of main vascular structures and biliary ducts. Special studies were carried out to show that a water jet really did not harm the most important intrahepatic structures discharged from parenchyma. Partial liver intersections were made for 6 dogs in such a way that each separated part was connected to other parts of the organ only through main blood vessels and biliary ducts. The laparotomy* carried out three months later proved that thus isolated part was not destroyed while

* Laparotomy is a surgical maneuver, incision of an abdominal wall to get access to the abdominal cavity organs, incision of a human body in the area of stomach.--Ed.

proliferation* of hepatocytes brought to a complete disappearance of a passage created earlier by a water jet.

PERSPECTIVES FOR NEW METHODS

The further numerous studies in different countries of Europe, Asia and America affirmed the truth of using the new methods of surgical effect of a cutting water jet not only in ophthalmology and abdominal surgery but also in traumatology, purulent and plastic surgery, urology and other areas.

Hydro-jet scalpel proved to be effective also in otolaryngology (in radical surgery on nasal cavities when a high degree of purulent substance removal is achieved without damage to periosteum and consequent relapses). The positive experience of its application is also described during treatment of septic wounds and trophic ulcers, which was accompanied by a substantial reduction of treatment terms by 3-4 weeks as compared with average indicators. Moreover, the effect of a cutting jet appeared to be so sparing that in many cases operations did not require even local anesthesia, and formation of a scar tissue was recorded by physicians in a lesser degree.

HYDRODYNAMIC CUTTING OF BONE TISSUE

Our studies have proved that the hydrodynamic method is effective also for separation of such hard material as a bone tissue! We have established that in case of correct formation of a jet it is possible to cut a bone in different directions and make required parts of necessary forms and sizes with a plane and smooth surface and without chips and microcracks. It can be observed not only visually but also due to objective registration methods (such as optical, acoustic and electronic microscopy and profilometry**).

* Proliferation (from Latin proles--offspring, progeny, and fero--carry) means growth of the tissue of the organism by means of cell propagation through division. This term was first introduced into medicine by the German physician Rudolf Ludwig Karl Virchow at the end of the 19th century to define cell neoplasms by their propagation through division to distinguish this mechanism from others by changing cell volume, for example, edema or apoptosis.--Ed.

** Profilometry is a diagnostic method using semiconductor infrared laser with a wavelength of less than one micrometer. It allows modulation of laser beam intensity. Frequency fluctuations can be easily changed. At present it is widely used in stomatology. It is not only easy-to-use but also saves the dentist's time for treatment. Such diagnostics can help reveal a disease, prescribe the most correct and effective course of treatment and also follow further results. For example, profilometry can be used to trace a healing process.--Ed.

In particular, in the course of histological studies of bone and chondral specimens it was established on sampling of the material from respective fragments after hydrodynamic cutting: at the cut surface cellular structures of the bone and cartilage practically preserved their morphological peculiarities. In bone cells there are well-defined undestroyed nuclei, cartilage cells remain undamaged and retain their location in prolate cellular capsules.

It should be stressed that the hydrodynamic technology differs essentially from other methods of separating hard biological tissues, whose effect results often in heavy mechanical and thermal damage of superlayers. Usually they reveal chips and cuttings, which often happens in case of using saws with a wide tooth setting. Thus, the formed surface will be uneven. Researchers note damages of cellular elements of the bone during histological studies of the edge sections of the bone and chips. In the course of separation of chondral fragments their cellular elements break, and the characteristic structure cannot be determined. But in the case of hydrodynamic separation of a bone tissue even during studies of a cut surface by an electronic microscope scientists do not see pronounced defects of the tissue structure.

It is also important that by changing a jet pressure and its traveling speed with relation to a bone fragment being cut we can adjust the depth of cut. However, the level of efficiency of hydrodynamic cutting depends directly also on intrinsic properties of bone or chondral tissues subjected to jet impact. It can be used, in particular, in studies of biomaterials technology and at conducting forensic examinations. The latter arouse particular interest of specialists due to the everexpanding hydraulic cutting technologies in the most different industrial and even household applications, which is sometimes accompanied by occurrence of occupational traumatism.

Jet cutting can be of interest also to paleontologists in studies of fossil bone fragments, which often have increased brittleness. A hydrodynamic jet separates steadily and accurately this unique material and thus provides a detailed study of its internal structure.

And another thing. In conditions of a tissue bank* hydrodynamic technologies make it possible to take a quite new step in manufacture of bone implants. Fragments being cut can be immediately given the required form with necessary quality of their surfaces without resort to additional machining. At present the appro-

* Tissue bank is a high-tech production whose main objective is procurement, conservation and storage of biological tissues.--Ed.

priate technologies are already developed and patented. They are based on findings of the many-year integrated studies conducted under the program "Advanced Biomedical Technologies of Hydrodynamic Processing of Tissue".

Now the similar studies are carried out under a scientific program prepared in 2013 by the Physics Department of the Moscow State University, the All-Russia Research Institute of Medicinal and Aromatic Herbs (VILAR) and the Scientific Information Center Bazis in Moscow and implemented at their joint research laboratory of biomedical technologies created on the basis of VILAR. The main trend of these studies includes development, formation and introduction into practice of tissue banks of advanced biomedical technologies of hydrodynamic processing of bone tissues and development of special-purpose equipment for manufacture of high-quality bone implants.

Illustrations supplied by Vladimir ROZANOV