US 2841150 A
Description (OCR text may contain errors)
July 1, 1958 c. T. RIALL CUTTING EDGE SUTURE NEEDLE Filed May 6, 1957 FIG. 5
CHARLES T. RIALL BY FIG.6
wwwwm ATTORNEY United States Patent CUTTING EDGE SUTURE NEEDLE Charles T. Rial], Danbury, Conn., assignor to American Cfyg lnamid Company, New York, N. Y., a corporation 0 ame Application May 6, 1957, Serial No. 657,377
3 Claims. (Cl. 128-339) This invention relates to improvements in surgical needles. More specifically it relates to a surgical needle of curved shape the front part of which is duck-billed in appearance and which is sharp on each side and at the point but not at the top and bottom and the cross-sections of the point of which are essentially bounded by two intersecting arcs of circles.
In many surgical operations it is necessary that the surgeon have a needle over which he can exercise superb control. For instance, in operations on the human eye, it is necessary that the surgeon be able to sew thin membranes to each other without penetrating those membranes. At present the conventional shapes of surgical needles include circle and V2 circle needles which have either a taper point or a cutting-edge point. The taper needles are similar to the ordinary needles used for sewing cloth in that the needle has a sharp point and a circular cross-section behind that point so that the point of the needle is generally conical in configuration al though the angle of the cone changes. This needle may be bent in the arc of a circle. The other type of needle in common use is one which has a triangular cross-section with each of the three edges being sharp. These cutting-edge needles are particularly effective for cutting through tough tissues. Certain of the cutting-edge needles have an approximate equilateral triangular crosssection in which one face of the triangle is parallel to the axis of curvature of the needle and the third cutting edge faces inward towards the axis of curvature of the needle. Such a needle when used to suture tissues can cut-out because this third cutting edge of the needle point has penetrated the path of the needle is fixed and can no longer escape from control.
To avoid cutting too wide a slit and minimize tissue damage, the width of the needle, that is the separation of the armed edges, is kept to a minimum so that as narrow a slit as will permit the passage of the needle and the attached suture is cut in the tissue.
In use the needle is placed in the tissues by grasping the needle in the needle holder and exerting downward pressure until the point of the needle reaches the depth to which penetration is desired. By turning his wrist, the surgeon causes the needle to be retained at that level of the tissue and the cutting edges do not dig deeper or cut out. Further, since the force on the needle is in the forward direction, there is a minimum risk of cutting too much sideways. For eye surgery, for example, the tissue of the sclera runs in a horizontal plane and the present duck-billed needle does not cut in that plane but remains parallel to the eye tissue. In eye surgery this is most critical because if too shallow the stitch will not hold, and if too deep the eyeball leaks and an unsatisfactory surgical result is obtained.
An additional advantage is that because of the extremely flexible control of the needle, the surgeon can take a large number of small stitches and small bites of the tissue and thus in plastic surgery obtain a more satisfactory cosmetic result than can be obtained with conventional needles.
The full scope of this invention may be more readily understood from drawings showing certain embodiments thereof.
Figure 1 shows a view of the cutting edge suture needle taken as an edge view of the plane of curvature, and at right angles to the axis about which the needle is curved.
Figure 2 shows a view of the same needle at right angles to Figure l, as a normal view of the plane of curvature.
Figures 3 to 8, inclusive, are cross-section views through the needle at the respective cutting planes 3 to 8 as shown in Figure 2.
While the present novel needles may be formed by other means, it is convenient to start with steel wire, in
faces inwardly towards the axis of curvature and as the needle is forced through tissue a slight lifting motion will cause the needle to cut inwardly and the needle thus cuts out of the tissue.
The other type of cutting-edge needle is one in which the third cutting edge is reversed so that as the needle is used to suture tissue it can cut deeper as this third the slit through the tissue but can neither cut deeper nor cut out, thus giving more efiective control over the depth of cut. By having the cutting edge of the needle describe a bent-ellipse the cutting edge of this needle can be controlled like the leading edge of an airplane wing soft condition, of circular cross-section and form the needles by stamping operations, and grinding.
The new shape of cutting needles may be used with an eyed needle or with a single-use needle to which a suture is attached. Conventional methods of attachment include flanged needles in which the butt end of the needle is thinned and flanged around the suture, and drilled end needles in which the end of the needle is Y drilled, then swaged around the suture.
The needle conveniently but not necessarily has flat spots for a needle holder and is curved to form from about 60 to 180 of curvature, about an axis of curvature. A /8 circle needle is shown in the drawings. Conveniently but not necessarily the curve is approximately circular and uniform. The back end of the needle to which the suture is attached may be either part of the curve or tangent thereto. I
The forward part of the needle is flattened so that a cross-section is bounded by intersecting arcs of two cirin flight by controlling the angle of attaclr, and once the cles, each of the circles being in a plane containing the axis of curvature of the needle. The intersection of these two arcs forms the cutting edges. 1
The needle may be considered asconsisting of a point 11, the armed edge section 12, a transition section 13, a round section 14, at least part of which contains fiat areas 15, for the needle holder and a suture attaching section 16. The arcs are of principal interest in the armed edge section in which the arcs intersect to form the cutting edges 17.
The angle of intersection of these arcs is preferably between about 30 and 80. A cutting edge angle of about 60" is particulary advantageous. less than about 30 the edges are so thinas to lack proper support, and turn too'easilyf If the angle is more than about 80, the edge is too blunt to cut as well as is desired.
The cutting edges may be sharpened as by honing so that the arc is somewhat flattened at the cutting edge, and similarly rather than being a perfect arc, the curvature'may be approximate that of an are. This section does not have to be an exact arc, to possess the advantages of an arc of .a circle, and in production it is diflicult to form surfaces perfectly by stamping. Hence approximate arcs are frequently produced.
The tapered armed edge section is conveniently rough formed by stamping between dies. The final shaping is conveniently performed by a grinding operation which gives sharp edges, and readily removes the flash from the stamping operation.
In use, one of the problems with surgical needles is the tendency for the needle to snap or bend at a point forward of the position at which the needle holder grips the needle. The loading forward from the point of the needle holder grip is that of a cantilever beam. From the standpoint of stress analysis, the loading of this cantilever beam is somewhat between that of a concentrated load at the free end and that of uniform loading along the length. The greatest individual load is frequently on the point of the needle as it penetrates tissue. However, the needle may also have a more or less uniform loading along its length due to a twist on the needle holder to cause the needle to cut more shallowly or more deeply as it penetrates, friction and cutting loads. The taper of the armed edgepart of the needle is preferably between that required for uniform stress distribution considering the load on the needle as a concentrated load at the point, and that required for uniform stress distribution considering the load on the needle as uniformly distributed along the length of the needle. Accordingly, the controlling design for the taper is between these limits and conveniently is approximately half-way between these two limiting tapers.
The resistance to bending of a beam of similar crosssectionfin which the width is proportional to the depth, varies as the fourth power of the depth. For the configuration in question in which the upper and lower boundaries of the cross-section are segments of circles of increasing radius, the moment of inertia about an axis connecting the armed edges is the integral of y dA where the x axis is considered as the line connecting the armed edges, and y is perpendicular thereto in the plane of the cross-section. The bending moment, M, is represented by the equation:
where c is the maximum depth and s is the unit stress, and the dimensions of the units are consistent.
For an end loaded cantilever beam the moment, M, at any point is equal to L2 where L is the load at the end of the beam and z is the distance of the section in questionfrom that load. Thus, for any given section of the needle c is proportional to the maximum depth of the'beam so that in combining these equations and lumping the If the angle is,
4 constants Lz==Kx For a given load, the width of a needle at any cross-section is proportional to the cube root of the distance of that section from the end of the needle. Hence, over the armed edge portion of the needle, the following table shows the relationship between the value of x at a given point and the relative distance of that cross-section from the end of the needle:
For a uniformly distributed load,
from the end of the needle, x is the width of the needle, and L is the total load on the needle, uniformly distrib- 0 uted over its length.
H ooomexzo Preferably the needle is tapered back to a point such that the periphery of the tapered portion of the needle is at least about equal to the periphery of the round portion of the needle, for example, the periphery of the wire from which the needle is formed. This periphery is necessary so that a slit is cut in the tissues big enough for the needle to go through. For this periphery the width between the cutting edges is slightly greater than the wire diameter. 1 The maximum width must be such that the cross-section is less than the cross'section of the wire from which the needle is formed. For a 60 cutting angle the width of the needle between the armed edges can be approximately twice the wire diameter with out exceeding the area of the wire. Usually slightly less than this is preferred. For example, a maximum width of between about 1.2 and 1.5 times the wire diameter is usually preferred.
The cutting edges should be sharp back almost to the widest section of the needle. Preferably the edges are duller just at the widest part so that the tissue penetrated drags slightly on this part of the needle, so that the drag is equal to the force required for the original penetration and cutting. Thus the total force required on the needle for penetration, cutting, and drag resistance is comparatively uniform during the entire passage of the needle, which gives the surgeon better control over the needle.
Back of the armed edge section is a transition section 13 connecting the armed edge section 12 with the round wire. section 14. As shown in the drawings, Figure 6, the transition section may be formed by using the same radii for arcs as is used for the large end of the armed edge section, but separating these arcs until the normal circular cross-section of the wire is obtained. In other words the wire may be squeezed by dies having the arc of the large end of the armed edge section which compresses the wire at the inner and outer faces between the round section and the armed edge section thus forming the transition section 13. Other faired transitions may be used as, for example, the angle at the cutting edge may be gradually increased, while uniformly tapering the cross-section from that of the back end of the armed edge section to that of the round section. Other smooth transitions may be used which are convenient from the standpoint of forming operations.
The round section 14 is conveniently the unaltered wire from which the needles are manufactured. Although the same shape needles may be made from other starting material, it is particularly convenient to manufacture the needles from smooth round wire. Preferably an annealed soft steel wire is used so that the forming operations may be more easily accomplished.
The round section may vary in length, depending upon the arc of curvature of the needles. If the needle is a half circle or longer, the round section is conveniently of a greater length than when the needle is formed in a quarter circle. The section with the flat areas 15 for the needle holder may extend up to the cutting edge section and be faired into the cutting edge section so that no fully round section is needed, but usually such a long holding section is not necessary, though in no way deleterious.
Back of the round section is a section of the needle which has flat areas for the needle holder 15. This section may be formed by either grinding the round wire slightly or by flattening the wire between forming dies. Whereas only one flat may be used, two flats are preferred to give an area which may be gripped by a needle holder to give positive control of the needle. When the needle is gripped on the flat sections, there is much less tendency for the needle to twist or roll in the needle holder and accordingly the surgeon has better control and more positive control over his needle. The length of the flat section is not critical but conveniently is fairly long so that the surgeon has considerable choice in the location of the bite of the needle holder.
Back of this flat section is the suture attaching means. Shown in Figures 1 and 2 is a conventional flange. A portion of the needle is stamped into a U-shaped channel having ridges or striations 18 on the inside thereof. This flange is crimped or swaged around the suture when the suture is attached.
In the manufacture of the needles, it is convenient to form the point and the armed edge section by first a stamping operation from straight wire. The flattening operation in the flat areas 15 may be conducted at the same or at a later time. With soft annealed wire a single stamping operation can shape this portion of the needle. The flange may be formed at the same time or by a subsequent stamping operation. Conveniently the flange is at an angle to the plane of curvature of the needle and is formed with a separate stamping operation.
While straight, the point and armed edges are sharpened. Final honing and polishing of the needle may be accomplished at this time. The bending of the needle to the final curved shape may be either before or after the tempering of the needle. If the needle is hardened in an inert atmosphere, the needle may be bent to final shape and then hardened. On the other hand, it is sometimes convenient to harden the needle in the straight form because this permits a final polishing operation before the needle is curved, and polishing is frequently more conveniently accomplished in the straight condition. In the final sharpening operations, slightly flat spots are frequently formed adjacent the cutting edges, and at the very point may in efiect give four nearly planar areas which intersect to form a diamond shape point, with a very short upper and lower ridge, which may be fairly sharp, but at an obtuse angle, which smoothly blends into the arcuate top and bottom curves. If the needles are tempered, they may be curved after the tempering operation.
The temper is drawn from the flange and if not previously accomplished, the remaining wire is cut off at the flange after the annealing. Conveniently a portion of wire is left extending beyond the flange as a handle during operations up to and including the final annealed operation of the flange and the cutting otfof the handle from the flange is the final manufacturing operation.
Instead of a flanged end the suture attaching means may be a drilled end. For this type of needle the end of the wire is drilled and striated or threaded internally. The suture is inserted in the drilled hole and crimped or swaged about the suture to retain the suture. Eyed needles may be used with the novel shape of front ends, although the eyeless construction is much preferable.
The method of attaching the suture and the final finishing operations such as polishing, bufling, and/or plating may be accomplished in accordance with conventional procedures.
While the shape of the needle is conveniently described in terms of the theoretically preferred embodiment, manufacturing variations usually cause minor modifications from the theoretical form. In the needles as manufactured, such minor variations are within the scope of the appended claims.
1. A surgical needle comprising a point, an armed edge portion, a cross-section of which is essentially bounded by arcs of circles which intersect to form armed edges having an included angle of between 30 and and which tapers from the point towards the rear of the needle, a smoothly faired transition portion, a round portion and at the back end, suture attaching means.
2. The needle of claim 1 in which at least a part of the round portion has flattened areas for a needle holder.
3. A surgical needle comprising a point, an armed edge portion which portion has a cross-section bounded by the arcs of circles which arcs intersect to form the armed edges and which armed edges have a cutting angle between about 30 and 80, and which increasing to a faired section which smoothly connects the armed edge portion to a round portion, the width of the needle in the armed edge portion at any section being proportional to between the 3 3 and the V3 power of the distance back from the point, the rear of the armed edge portion having a periphery not less than the periphery of the round portion and a cross-sectional area not greater than the cross-sectional area of the round portion; back of the round section a portion having flat areas for a needle holder, and back of the flattened portion, means for attaching a suture to the needle.
References Cited in the file of this patent UNITED STATES PATENTS 373,372 LaForest-King Nov. 15, 1887 2,336,689 Karle Dec. 14, 1943 2,581,564 Villegas Jan. 8, 1952 2,811,157 Kurtz et al. Oct. 29, 1957 FOREIGN PATENTS 445,656 Great Britain Apr. 16, I936