KNIVES SURGICAL — one of types of the cutting medical tools intended for division of fabrics. The knives called by scalpels (Latin of scalpellum a knife are most widespread in surgery). Their versions are the bistoury (fr. bistouri) — the tool having the edge similar to a scalpel, but developing in the handle as at a penknife, a lancet (Latin of lancea a spear) — a folding two-edged knife. The bistoury and lancets at the beginning of 20 century were a part of sets and bags of the surgeon and were used for bloodletting and opening of small abscesses. N x. appeared long before our era, however only in the middle of 20 century there was a theory of cutting of fabrics an edge, thanking a cut effective ways of their division with the smallest energy consumption and with preservation of high resistance and sharpness of the tool were developed.
N x. consists of an edge, a neck (a transitional part) and handles (fig). It can be made of one material or from different, i.e. to be compound, and also can have a removable edge. The edge for ensuring the high cutting properties shall be made of high-quality tool steel with carbon content from 0,8 to 1,2% (U8A, U10A and U12A brand) or the alloyed stainless steel containing up to 13 — 14% of chrome (e.g., brand 10X13M) or molybdenum and tungsten. Edges undergo so-called heat treatment (tempering) for obtaining high hardness (to 62 units according to Rockwell — a scale C), wear resistances and jokes.
In a form of an edge distinguish bellied and sharp-pointed knives. Bellied N. x. have more roundish trimming blade and are applied to cuts of skin and fabrics of considerable length.
Sharp-pointed surgical knives are applied preferential to cuts of fabrics on small depth and to punctures.
The cutting element H. x. the edge executed in the form of a wedge with a certain corner of a point (sharpening) is, size to-rogo depends on N.'s purpose x. during the cutting of fabrics. The corner of a point — a corner β (fig., a), the more sharply a knife is less and the quicker it loses sharpness (is rebated). The edges used for cutting of soft tissues have a small corner β — from 12 to 25 ° (at ophthalmic scalpels — 20 °, at all-surgical — 25 °), for cutting of cartilages it is more — from 30 to 35 °, for cutting of bone tissues it reaches 40 °.
The cutting properties of a knife depend also on microgeometry of an edge (fig., b). The parties of a wedge, being crossed, form a trimming blade with microroughnesses, edges has the form of a ribbon width in several microns. These microroughnesses (up to 5 microns) provide effect of a saw, i.e. easier section of fabrics during the drawing of a knife. Width of a trimming blade and height of microroughnesses are normalized by technical specifications ranging from 2 to 5 microns. The effect of simplification of cutting of fabrics is observed also at reduction of a tilt angle of an edge in relation to the cut material and delay of speed of drawing of a knife. The trimming blade can be rectilinear (e.g., at an amputating knife) or curvilinear, up to the closed circle (eye trepan).
For the prevention of corrosion of N. x., made of carbon steel, cover with a layer of nickel, chrome, however the trimming blade remains unprotected and is subject at storage of instruments of the greatest corrosion. N x., made of stainless steel, are exposed to electropolish.
The knife blade shall be well polished. The handle is manufactured with a mat surface or apply on it notches thanks to what the knife does not slip out a hand, especially in a rubber glove.
Testing of the cutting properties H. x. depending on their appointment make by the cutting of suede, skin, paper tense on a barabanchik for a yaroba of sharpness of medical tools. As a result of testing of edge of a section shall be equal, edges shall not be rebated. The main requirements to knives surgical are determined by GOST 21 270 — 77.
In the USSR the St. 100 names H. are issued x. taking into account requirements of the general and special surgery. Nek-ry types of knives and scalpels and area of their main medical use are given in the table.
Nek-ry N. are not given in the table x., obsolete: the excision knife of sharp-pointed type of Bergmann, a direct knife of Lisfrank, an excision knife with a direct trimming blade of Nelaton which was earlier applied to a section of cartilages, sheaves and other dense fabrics; double-edged amputating knifes; the transplant knife of Tir-sha which was earlier applied to cutting of skin transplants; scalpel of a straight line, etc.
Thin operative measures under a microscope led to creation of knives for microsurgery (see) — small knives with the rectangular handle manufactured of titanium and with a tiny edge of various form 1 — 1,5 mm wide and 2,0 — 3,0 mm long, edges of safety razors are also applied to these purposes.
Sterilization (see) knives it is more preferable to carry out in sukhovozdushny sterilizers at t ° 160 — 180 ° within respectively 60 — 45 min.; at wet sterilization (e.g., in a steam sterilizer) knives are quicker rebated owing to emergence of the corrosion centers on a trimming blade (in the available microroughnesses).
N x. periodically sharpen by means of installations for electrolytic sharpening of medical tools, machines for sharpening of surgical instruments and scalpels, and also the elementary devices — oselok and belts for editing of tools.
Store P. x. in the dry place, edges should be protected from damages. During the transportation and warehousing for the prevention of corrosion they are previously degreased and preserved protective lubricants or packed into tight plastic bags with addition of inhibitors (see. Surgical tools ).
Table. Some types of knives and scalpels and area of their main medical use
Bibliography: Nabatov Yu. F. Medical tools, equipment and equipment, page 101, M., 1977; P. E's List distance. and Nabatov Yu. F. Medical merchandizing, page 188, M., 1974; Reznik H. E. The theory of cutting by an edge and bases of calculation of the cutting devices, M., 1975; Horse-radishes A. P. Surgical instruments and medical metal and rubber goods, L., 1955.
Yu. F. Kabatov.