US 3038475 A
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June 12, 1962 D. EQORCUTT v 3,038,475
SURGICAL NEEDLES AND MANUFACTURE OF SAME Filed June 27, 1960 2 Sheets-Sheet 1 F15. 5 FIG. 4 F15. 5
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7 SURGICAL NEEDLES AND MANUFACTURE OF SAME Filed June 27, 1960 2 sheetssheet 2 Syuare end Alam 22 Center IDLING/I Dr/// and 751 Bend 0 560 18 Harden United States Patent Ufifice 3,038,475 Patented June 12, 1962 3,038,475 SURGICAL NEEDLES AND MANUFACTURE OF SAME Donald Eugene Orcutt, Danbury, Conn., assignor to American Cyanamid Company, New York, N.Y., a corporation of Maine Filed June 27, 1960, Ser. No. 38,794 2 Claims. (Cl. 128339) This invention relates to a surgical needle having a hollow ground edge and an electrolytic method for forming such needles.
Surgical needles may range from the very small sizes used for eye surgery up to the sizes used in obstetrical repair work. The shank diameter of such needles commonly varies in the range of from about 0.008 inch to 0.050 inch. In the past, it has been usually customary to form the needle point by swaging or grinding, or both, including sharpening to final sharpness while the needle is straight, after which the needle is bent to a required curve, frequently from three-eighths to one-half circle, and then hardened. The hardened needle is usually too brittle to bend, and the hardening operations tend to dull the edges on the needle.
It is desirable that surgical needles be extremely sharp and that the needles have such shape as causes a minimum of drag in tissues in which the needle is used.
The advantages of hollow grinding knives and razor blades, and the like, have been common knowledge for some time. The usual method of hollow grinding involves the use of a rotating grinding wheel having a diameter such that the desired curvature is imparted to the edge of the sharpened object by grinding the axis of the grinding wheel parallel to the cutting edge. For a surgical needle, the diameter of the grinding wheel for a triangular-shaped needle would have to be within the range of three to four times the diameter of the needle wire size. For hollow grinding of lens-shaped needles, the diameter of the grinding Wheel for conventional grinding would have to be considerably less than the wire diameter from which the needle is formed. (Needles with lens-shaped cross sections are described in United States Patent No. 2,841,150, Riall, Cutting Edge Suture Needle, July 1, 1958.) Either way, the diameters are impracticably small.
Theoretically, a rounded edge on a thin grinding wheel could be used in which the axis of the Wheel is perpendicular to the sharpened edge, but the maintenance of proper curvature and problems of resharpening, as well as the accuracy of the relationships involved in the grinding, again render such a method of grinding uneconomical.
It has now been found that needles can be swaged or pressed in dies to approximately a desired shape leaving a flash adjacent the part which is to become the cutting edge. Forming may be partly by grinding or entirely by swaging, pressing or rolling. A wire stock somewhat larger than the finished needle shank is used. After forming, the needles are bent to shape, and then hardened. The needles are then sharpened by electrolytically etching away part of the metal stock. By sharpening in the final shape, the chances of damage to the edges in processing are reduced, and the needles are sharpened in their final configuration, and in the hardened state.
In effect, the sharpening seems to reduce the thickness of the metal nearly uniformly on flat surfaces, curved surfaces and reverse curved surfaces, and edges, so that a dull edge is eaten away on the flat sides until the remaining edge is extremely sharp. The rate of etching is fastest near the cathode, so etching near the point can be selectively accelerated by placing the point nearest to the cathode.
By such an etching procedure, the sharpening occurs in the desired locations, and the degree of precision required in preliminary shaping is minimized.
Whereas such method of sharpening can be used for any desired shape of surgical needle, it is described in more detail in connection with a triangular-shaped, cross-section needle and a lens-shaped, cross-section needle, as more particularly shown in the accompanying drawings in which:
FIGURE 1 shows an edge view of a three-eighths curve lens-shaped needle.
FIGURE 2 is a face view of the outside curve of the needle of FIGURE 1.
FIGURE 3 is a cross section at cutting plane 3-3 of the needle of FIGURES 1 and 2.
FIGURE 4 is a cross section at cutting plane 4-4 of the needle of FIGURES l and 2.
FIGURE 5 is a cross section at cutting plane 5-5 of FIGURES 1 and 2.
FIGURE 6 is a cross section at cutting plane 6-6 of the needle of FIGURES 1 and 2, showing the cross sec tion of the needle after the anodic etch in solid lines and before the anodic etch in dotted lines.
FIGURE 7 is a cross section of an alternate construction of the needle taken at cutting plane 41-4 in which the needle has flattened areas for the surgeons forceps.
FIGURE 8 is a cross section of a modification of the needle at cutting plane S-5 in which the butt of the needle is also of elliptical cross section.
FIGURE 9 is a view of the point of the needle of triangular shape with flat sides as is conventional in the prior art.
FIGURE 10 is a similar View of a triangular needle according to the present invention having hollow ground edges.
FIGURE 11 is a view of a blank cut from wire preparatory to forming a curved, lens-shaped needle.
FIGURE 12 is the same blank with the end center punched.
FIGURE 13 shows the same blank after the butt end is drilled and tapped.
FIGURE 14 shows the same blank after the point is rough ground.
FIGURE 15 shows the completion of the forming of the point.
FIGURE 16 shows the bending of the needle to shape.
FIGURE 17 shows the needle hardened.
FIGURE 18 shows the needle after the electrolytic etching and polishing treatment.
A needle sharpened in accordance with the present invention is shown in FIGURE 1. Conveniently, such a needle may be formed as shown in FIGURES 11 to 18, inclusive, in which a coil "of wire is cut into needle-forming blanks 21, which are of slightly greater length than is to be the length of the completed needle. It is preferred that at least the butt end 22 is square with the axis of the blank. The butt end is center punched to leave a center punch mark 23 to aid in centering a drill. The butt end is then drilled with a drill of suitable size and length after which the hole is threaded with a tap to form a tapped hole 24. The tapped hole is of such size as to receive a surgical suture and be clamped by squeezing against the suture. Different size sutures require different size tapped holes. The threading roughens the inside of the tapped hole to increase the friction between the suture and the needle. Other forms of roughening may be used.
The end of the needle which is to become the pointed end is then rough ground to form a rough grind point 25. The reduction in stock aids in the next forming operation. The rough ground point is then inserted and compressed between forming dies to form a formed or swaged point 26. The configuration of the formed point depends upon the desired shape for the final needle point. For the lens-shaped point shown in FIGURES 1 to 8, the point is formed to a symmetrical double curve in which the configuration is something like that of a biconvex lens, but in which the flash from forming 27 extends from where the tWo curves would otherwise meet. In effect, the final formed shape is something like that of rhombus in which the greater included angle is rounded off and in which the acute included angle has a reverse curvature to join the flash so that adjacent the flash is a reverse curve on each side. The rhombic configuration may be almost totally lost in the curvature so that a double ogee curve is formed. The exact curve is a matter of choice. The flash can conveniently have a thickness of about 0.002 inch, although the thickness of the flash may vary with the size of the needle, wear on the dies, and other considerations. As shown in FIG- URE 6 in the dotted line indicating the form before anodic etching, the flash may extend for a distance from its own thickness to several times its own thickness. After the swaging of the point, which may be conveniently accomplished in one or more pressing operations, the needle is bent to shape. The bent needle blank 28 is conveniently in the shape of an arc of a circle. For eye Work, surgeons frequently prefer five-sixteenths of a circle. For general Work, surgeons usually prefer between three-eighths and one-half circle. The bend in the needle is conveniently within these limits, but may be to any degree of curvature desired for a particular surgical procedure, or even left straight.
The needle blank is then hardened to form a hardened needle blank 29. The hardening operation may be in accordance With conventional practices, conveniently by a heating and quenching operation. Because the needle is not yet sharpened, the hardening operation can be conveniently accomplished with masses of the needles without concern for the dulling of edges or minor surface erosion.
After the hardening treatment, the needles are anodically treated to etch and polish. The etching and polishing are accomplished simultaneously. The needles are racked for the operation. Conveniently, a magnetic rack is used in which the needles are set with the points outwardly. The rack is immersed in the electrolyte. The magnet serves both to hold the needles and conduct electric current to the needles.
The electrolyte may be any of the etching electrolytes used for the anodic polishing of steel. The current density and electrolyte are selected to give a bright finish to the metal, using conventional density and concentrations.
Example 1 An electropolishing solution is prepared from Electro-glo mixed in a 3 to 1 ratio with 85 phosphoric acid. (Electro-glo is sold by Electro-glo Company, 1430 South Tallman Avenue, Chicago 8, Illinois.) For a group of 20 needles for a No. suture, a current density of 25 amperes at 20 volts for 6 minutes at room temperature gives good results with sharp needles and a high polish.
In another instance, a group of 50 -inch needles from 24 gauge wire were polished for 7 /2 minutes at 20 amperes. A group of 50 needles before polishing weighed 3.5 grams and after polishing weighed 2.89 grams. After etching, the needle has the finished configuration of the lens-shaped needle 32.
Example 2 A group of 50 needles from 0.024 inch wire bent to three-eighths of a circle, with drilled ends and which have been swaged and bent to shape, then hardened are immersed in an electrolyte containing by volume 300 parts of 85% H PO 60 parts of H 80 and 60 parts of water. The needles are polished for five minutes at 32 C. with a current of 25 amperes which required a potential of 15 volts. The needles showed good cutting action and a good polish.
Example 3 A group of the same size needles as in Example 2 were polished in an electrolyte consisting of: 1500 volumes H PO 100 volumes of water, and 400 volumes of ethylene glycol. The temperature, current and potential conditions for the same size batch of needles were the same as in Example 2.
Example 4 A group of 50 of the same size needles were polished in 85% by weight orthophosphoric acid, the remaining 15% being Water. The voltage was adjusted to between 7 and 15 volts for different groups of needles to maintain a current of 25 amperes. Good results were obtained at temperatures from 32 C. to 72 C. with the higher temperatures requiring the lower voltages. Temperatures lower than 32 C. give satisfactory polishing, but due to the heating effects of the current, cooling is required to keep the temperature down for such condi tions. It is usually more convenient to operate at the temperature the electrolyte assumes in the room, includ ing the raise due to the heating by the current of the electrolyte.
Example 5 A group of 50 needles were polished for five minutes at 25 amperes current at temperatures of from 32 C. to C. in a mixture of parts by volume of 85% phosphoric acid, 40 parts by volume of polyethylene gly= col, and 40 parts by volume of water. The voltage varied from 10 to 15 volts, the lower potentials being used at higher temperatures. The needles gave good cutting action and a fair polish was obtained.
Other etching solutions and current densities can be used in accordance with conventional practice in the elec tropolishing art.
The amount of metal removed and the shape of the swaged blank are correlated. In effect, the rate of anodic etching appears to be largely independent of the amount of curvature of the surface so that the etch ing and polishing remove about the same thickness at all areas, and as the flash is etched away the remainder assumes a sharp edge. The etching is continued until the sharpness on the edge is as desired. For most purposes, it is desirable that the edge be razor sharp and have an included angle at the edge of around 30. An edge with an angle of less than 30 becomes more apt to bend, and one with an angle of greater than 60 does not cut as readily. For tender tissues, an angle of as low as 20 gives very easy penetration. For tougher tissues, an edge angle of 40 or 50 has advantages, in that the edge is stiffer, although penetration may be more difiicult.
The term hollow ground is used to describe the reverse curvature adjacent the cutting edge because the shape of the edge resembles that conventionally obtained in hollow grinding, although the size is too small for any conventional grinding process to give the desired shape.
The hollow grinding is such that a tangent from the point to the body of the needle misses a good portion of the periphery of the needle and, as a result, there is less drag on the needle as it penetrates tissue.
Normally, for a lens-shaped needle, the edges are armed from 20% to 60% of the length of the needle, although this figure may vary with the surgeons choice. Between the armed edges and the butt of the needle, as shown at FIGURE 7, there may be a flat forceps surface 30 for the surgeon to grip the needle forceps and prevent the needle twisting at the time of use.
A triangular shape point is preferred for some surgical procedures. The needle may have a sharp edge either cutting in towards the inside of the curve, or out- 'wardly. A needle, with the apex of the triangle on the outside of the curvature, is shown in FIGURE 10. A conventional flat side shape is shown in FIGURE 9, representing the prior art. The triangular hollow ground point 31 shown in FIGURE is formed by swaging to an approximate shape, and etching anodically to final shape. The depth of the hollow of the hollow grind, as well as the exact shape, can vary widely, depending on the surgeons choice. One such curve, with about 30 cutting angles, and a circular arc between the cutting edges, is shown in FIGURE 10.
The needle may be of stainless steel, or may be plated with gold, nickel, nickel phosphide, or other surface coating of choice. Anodic polishing imparts considerable corrosion resistance so that the needles are somewhat resistant to corrosion without plating. Other curves and modifications within the scope of the appended claims may be used.
The needles, or other items, sharpened by anodic etching have a sharper edge than is normally attained by use of standard grinding procedures. The anodic etching gives a smoother finish to the metal than can be obtained by conventional polishing. The anodic etching tends to remove noncrystalline metal and leave a sharp metal edge free from striations or saw-tooth like efiect which can be observed under a microscope on a conventional needle. The hollow grinding additionally reduces the drag on the needle. Needles produced by the pres ent process penetrate tissues more readily than needles obtained by conventional sharpening procedures. A test of sharpness is conveniently obtained by measuring the force required for penetration in a hockey puck. A hockey puck is a rather strenuous test, but needles sharpened by the present process give equal penetration with approximately 40% less loading than do conventionally sharpened needles. Another good method of comparison is to compare the force required to cause the needle to penetrate A cowhide belting leather. A triangular hollow ground anodically etched obstetrical needle penetrates much more readily than a needle of the same size with flat sides sharpened by conventional methods as exemplified by commercially available needles.
1. A symmetrical surgical needle comprising: a point, an armed edge portion having a general double-convex lens cross-section shape with a reverse curve adjacent the intersection between curved surfaces to give a concave curvature adjacent and extending to the cutting edges, and having an included angle at the cutting edge between about 20 and and suture attaching means.
2. A symmetrical surgical needle comprising: a point, an armed edge portion having generally double-convex lens cross-section shape with a reverse curve adjacent the intersection between two convex faces to give a concave curvature adjacent and extending to the cutting edges, and having an included angle at the cutting edge between about 20 and 50, and an unarmed portion having flat needle forceps surfaces and suture attaching means, the entire needle being bent to a curve between about and /2 of a circle.
References Cited in the file of this patent UNITED STATES PATENTS 20,409 Cottrill June 1858 2,581,564 Villegas Jan. 8, 1952 2,758,648 Dodds Aug. 14, 1956 2,773,024 Gurry Dec. 4, 1956 2,841,150 Riall July 1, 1958