Sutures with reduced diameter at suture tip
United States Patent 3926194
A needle-suture combination is provided in which the suture has at its tip within a recess at the blunt end of the needle and extending to a segment adjacent the attachment of the suture to the needle, a cross-sectional area and a cross-sectional amount of suture material less than the cross-sectional area and the cross-sectional amount of suture material in the remainder of its length. In one embodiment, the invention provides a weakened segment which permits a surgeon to separate the needle from the suture by a sharp tug. In another embodiment the invention also permits the use of needles having substantially the same external diameter as the suture attached thereto so that the suture in the sewn tissue substantially plugs the needle hole.
US Patent References:
Method of making needle-and-suture assembly
Morton et al. - April 1928 - 1665216
SPANDEX SUTURE NEEDLE COMBINATION
Thompson - October 1970 - 3534740
LATERAL RELEASE SUTURE
Beroff et al. - March 1974 - 3799169
Controlled release suture
Duncan - April 1975 - 3875946
Method of making needle-and-suture assembly
Morton et al. - April 1928 - 1665216
SPANDEX SUTURE NEEDLE COMBINATION
Thompson - October 1970 - 3534740
LATERAL RELEASE SUTURE
Beroff et al. - March 1974 - 3799169
Controlled release suture
Duncan - April 1975 - 3875946
Inventors:
Greenberg, Jonathan Fred (New York, NY)
Quade, Robert T. (Bernardsville, NJ)
Quade, Robert T. (Bernardsville, NJ)
Application Number:
05/525327
Publication Date:
12/16/1975
Filing Date:
11/20/1974
View Patent Images:
Export Citation:
Assignee:
Ethicon, Inc. (Somerville, NJ)
Primary Class:
Other Classes:
223/102, 163/5
International Classes:
A61B17/06; A61B19/00; A61B17/06
Field of Search:
128/335.5,339 163/1,5 223/102
Primary Examiner:
Truluck, Dalton L.
Attorney, Agent or Firm:
Eberhardt, Wayne R.
Claims:
What is claimed is
1. A needle-suture combination comprising a needle having a sharp end and a blunt end and having a recess at said blunt end, a suture having one tip positioned within said recess, means retaining said tip of said suture within said recess to attach said suture to said needle, said tip within said recess and a segment thereof beyond said recess and adjacent the location of the attachment of the suture to said needle being reduced in cross-sectional area and in the amount of cross-sectional suture material as compared to the cross-sectional area and the amount of cross-sectional suture material in the remainder of the suture length.
2. A needle-suture combination of claim 1 wherein said suture comprises a monofilament.
3. A needle suture combination of claim 1 wherein said suture comprises a multifilament suture which is unified at said suture end and which has fewer fibers at said suture end than in the remainder of said suture.
4. A needle-suture combination of claim 3 wherein said suture end is unified by resin impregnation.
5. The needle suture combination of claim 1 wherein said suture comprises a synthetic polymeric material selected from the group consisting of nylon, polyester, and polypropylene.
6. The needle-suture combination of claim 5 wherein said suture comprises a polyester selected from the group consisting of polyethylene terephthalate and homopolymers and copolymers of glycolide and lactide.
7. The needle-suture combination of claim 1 wherein said suture comprises a material selected from the group consisting of collagen, silk, cotton, and linen.
8. A needle-suture combination of claim 7 wherein said collagenous material is catgut.
9. A needle-suture combination of claim 7 wherein said collagenous material is extruded collagen.
10. A needle-suture combination of claim 1 wherein said suture is rupturable adjacent its junction to the needle by a straight pull at a force between about 3 ounces and about 26 ounces.
11. The needle-suture combination of claim 1 wherein said recess is a drilled hole.
12. The needle-suture combination of claim 1 wherein said recess is a closed channel.
13. The needle-suture combination of claim 1 wherein said cross-sectional area (in square inches) at said reduced portion is equivalent to KP/DT in which P is the desired rupture load, ranging from 0.2 to 1.6 pounds, D is the suture density of the suture, T is the tensile strength of the suture material in pounds per square inch, and K is a constant.
14. The needle-suture combination of claim 13 wherein said suture comprises a monofilament and said suture density is unity.
15. The needle-suture combination of claim 13 wherein said suture comprises a braided suture and said suture density is between about 0.70 and about 0.95 percent.
16. A needle-suture combination of claim 13 wherein the suture material is catgut, D is unity, and K is a constant having a value of about 1.3.
17. The needle-suture combination of claim 1 wherein the suture diameter beyond said tip of reduced cross-sectional area has a diameter at least 85 percent as great as the needle diameter but no greater than the needle diameter.
1. A needle-suture combination comprising a needle having a sharp end and a blunt end and having a recess at said blunt end, a suture having one tip positioned within said recess, means retaining said tip of said suture within said recess to attach said suture to said needle, said tip within said recess and a segment thereof beyond said recess and adjacent the location of the attachment of the suture to said needle being reduced in cross-sectional area and in the amount of cross-sectional suture material as compared to the cross-sectional area and the amount of cross-sectional suture material in the remainder of the suture length.
2. A needle-suture combination of claim 1 wherein said suture comprises a monofilament.
3. A needle suture combination of claim 1 wherein said suture comprises a multifilament suture which is unified at said suture end and which has fewer fibers at said suture end than in the remainder of said suture.
4. A needle-suture combination of claim 3 wherein said suture end is unified by resin impregnation.
5. The needle suture combination of claim 1 wherein said suture comprises a synthetic polymeric material selected from the group consisting of nylon, polyester, and polypropylene.
6. The needle-suture combination of claim 5 wherein said suture comprises a polyester selected from the group consisting of polyethylene terephthalate and homopolymers and copolymers of glycolide and lactide.
7. The needle-suture combination of claim 1 wherein said suture comprises a material selected from the group consisting of collagen, silk, cotton, and linen.
8. A needle-suture combination of claim 7 wherein said collagenous material is catgut.
9. A needle-suture combination of claim 7 wherein said collagenous material is extruded collagen.
10. A needle-suture combination of claim 1 wherein said suture is rupturable adjacent its junction to the needle by a straight pull at a force between about 3 ounces and about 26 ounces.
11. The needle-suture combination of claim 1 wherein said recess is a drilled hole.
12. The needle-suture combination of claim 1 wherein said recess is a closed channel.
13. The needle-suture combination of claim 1 wherein said cross-sectional area (in square inches) at said reduced portion is equivalent to KP/DT in which P is the desired rupture load, ranging from 0.2 to 1.6 pounds, D is the suture density of the suture, T is the tensile strength of the suture material in pounds per square inch, and K is a constant.
14. The needle-suture combination of claim 13 wherein said suture comprises a monofilament and said suture density is unity.
15. The needle-suture combination of claim 13 wherein said suture comprises a braided suture and said suture density is between about 0.70 and about 0.95 percent.
16. A needle-suture combination of claim 13 wherein the suture material is catgut, D is unity, and K is a constant having a value of about 1.3.
17. The needle-suture combination of claim 1 wherein the suture diameter beyond said tip of reduced cross-sectional area has a diameter at least 85 percent as great as the needle diameter but no greater than the needle diameter.
Description:
BACKGROUND OF THE INVENTION
This invention relates to needle-suture combinations and particularly to a combination of a surgical needle with a suture in which the force necessary to separate the needle from the suture is within an acceptable range for convenient removal of the needle from the suture by a sharp tug.
In many surgical procedures, surgeons use a technique which employs a non-needled suture and an eyed needle. The needle is threaded by the nurse and the surgeon takes one pass through the tissue using a needleholder. He slips the needle off the suture, returns the needle to the nurse, and is ready for another threaded needle from the nurse. An assistant follows behind and ties the suture.
Surgeons find that this technique is more simple than using a needled item and cutting the suture with a scissors after each pass. However, the time required for threading results in a significant waste of expensive operating room time.
The security of attachment of eyeless needles to absorbable surgical sutures or to non-absorbable surgical sutures is prescribed in the U.S. Pharmacopoeia, Vol. XVIII at Page 944 (also see U.S. Pharmacopoeia, Vol. XVII, Page 919). It has been the practice of suture manufacturers in the U.S. and abroad to securely attach the suture to the needle by swaging or with an adhesive so that the minimum pull-out standard recited in the U.S. Pharmacopoeia is met or exceeded.
To avoid the problems discussed above it has been found useful to use needle-suture combinations in which the needle and the suture are readily separable from each other by a sharp tug. Several methods have been devised for preparing needle-suture combinations in which the pull-out values, or the force required for separating the needle from the suture by a straight pull, is within a controlled range.
One approach to this problem is described in co-pending and co-assigned application Ser. No. 409,974, filed Oct. 26, 1973, now abandoned. This approach includes inserting into a drilled hole in the blunt end of the needle one end of a braided suture which has been sized with a resin and is smaller in apparent diameter than the remainder of the suture and then swaging the needle at its blunt end to provide a controlled degree of compression to the end of the suture within the hole. This approach is particularly directed to needle-suture combinations wherein the suture is of large size, i.e., size 4-0and larger (diameter greater than 7.0 mils), and produces average pull-out values of 3 to 26 ounces, indicating that it takes a straight pull of a magnitude within that range to separate the needle from the suture.
Another approach to the problem is described in co-pending and co-assigned application Ser. No. 446,174 filed by Robert Barclay Duncan on Feb. 27, 1974, now U.S. Pat. No. 3,875,946. In this approach sufficient tension is applied to the suture in a swaged needle-suture combination to move the suture relative to the needle recess and the tension is released when the force drops to the range desired for the pull-out value, the range varying for different sizes of suture. This approach is applicable to a broad range of suture sizes, including sizes as small as 8-0.
The present invention, in one aspect, provides another approach to the problem and provides for easy separation of needles from needle-suture combinations without requiring any major change in the manner of manufacture of the needle-suture combinations.
There has been another problem in needle-suture combinations, unrelated to and independent of the problem of providing controlled pull-out values, namely the problem in certain applications, of leakage in sewn tissues through needle holes made during surgical sewing.
In a typical needle-suture combination in which the suture is held within a recess of the blunt end of a needle, the suture is of about the same diameter as (or somewhat smaller than) the diameter of the recess and is thus smaller than the external diameter of the needle. In the surgical sewing of certain tissues, such as blood vessels or bladder walls, it is undesirable to have unfilled or partially unfilled needle holes in the tissue because such unfilled holes provide paths for undesired leakage. In the case of a bladder repair there can be leakage of urine which can be harmful in the abdominal cavity and in the case of blood vessel repair there can be leakage of blood onto surrounding body tissues.
This invention, in another aspect, provides a means to avoid leaving partially unfilled needle holes in surgically sewn tissue by providing a needle-suture combination in which the extended transverse dimensions of the needle and the suture are substantially equal.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a needle-suture combination comprising a needle having a sharp end and a blunt end and having a recess at said blunt end, a suture having one tip positioned within said recess, means retaining said tip of said suture within said recess to attach said suture to said needle, said tip within said recess and a segment thereof beyond said recess and adjacent the location of the attachment of the suture to said needle being reduced in cross-sectional area and in the amount of cross-sectional suture material, as compared to the cross-sectional area and the amount of cross-sectional suture material in the remainder of the suture length.
In the aspect of the invention in which it is desired to control the pull-out values for separating the needle from the suture, the invention provides a weakened suture segment adjacent the juncture of the needle and the suture, which suture segment has a rupture strength which is lower than the rupture strength in other portions of the suture and lower than the force necessary to pull the suture tip out of the needle recess. The rupture strength in the weakened segment may be controlled to a value which makes the needle separable from the suture by a sharp tug, and preferably to a value between about 3 and about 26 ounces.
In the aspect of the invention in which it is desired to minimize or eliminate any unfilled space in the needle holes made in tissue during surgical sewing, the outside dimensions of the needle and the suture may be controlled so that the diameter of the suture (except at its tip) is substantially as great as, or somewhat greater than the maximum lateral dimension of the needle.
The invention is particularly applicable to monofilament sutures, although it is also applicable to multifilament sutures, e.g., covered, twisted and braided sutures, provided that the suture tips are first unified by resin impregnation, fusing or other technique. By "unified" it is meant that the treated portion of the suture is transformed from a collection of loose, individual filaments to a single, coherent stucture. Such unification is commonly employed in the art to prevent brooming of cut ends and to facilitate needle attachment. Reducing the diameter of the tip of a multifilament suture which is not first unified will produce an undesirable "brooming" effect in which loose ends of individual fibers of the suture stick out where they have been severed adjacent the reduced diameter tip.
As stated above, U.S. application Ser. No. 409,974 teaches swaging in a drilled needle one end of a braided suture which is unified by impregnating with a resin and is smaller in apparent diameter than the remainder of the suture. The teachings of Ser. No. 409,974 relative to the resin impregnation of sutures to obtain a unified structure is hereby incorporated by reference. The smaller diameter suture end in Ser. No. 409,974 is obtained by impregnating the suture tip with a resin while the suture is under tension. The unified suture end thus produced has an apparent diameter somewhat smaller than the remainder of the suture because the fibers of the tip are compacted relative to the remainder of the suture, but there are the same number of fibers in the smaller diameter tip as in any other portion of the suture.
In contrast, in the embodiment of the present invention utilizing a braided or other multifilament suture, the amount of diameter reduction or actual cross-sectional area reduction at the suture tip is at least 10 percent of the cross-sectional of the area of the remainder of the suture and there is at least 10 percent less suture material in the cross-section of the smaller diameter suture end than in the remainder of the suture.
To reduce the diameter, or cross-sectional area of a suture end for the preparation of the needle-suture combination of this invention, the suture end may be ground down to the desired diameter and to the desired length of the cutaway portion. The grinding is carried out by known techniques and in known equipment, such as in a jeweler's lathe or in a grinding machine such as that described in British Pat. No. 1,180,276 of American Cyanamid Company.
Another method of producing a suture end of the desired reduced diameter which is applicable for monofilament sutures is to produce a continuous monofilament with spaced segments of reduced diameter, each such segment being cut to provide two reduced diameter suture ends. A continuous filament of this type may be prepared by providing pulsation during the extrusion of the monofilament, or periodic partial slowdown of the rate of polymer feed to the extrusion orifices.
The sutures suitable for use in the preparation of the reduced suture tip needle-suture combination of this invention include monofilament and multifilament sutures having a unified tip. Suitable suture materials include natural materials such as collagen (including catgut and extruded collagen), silk, cotton and linen, and synthetic polymers, such as nylon, polypropylene and polyesters, such as polyethylene terephthalate, and homopolymers and copolymers of lactide and glycolide.
When the suture tips are reduced in area for providing easy separability of the needle from the suture in accordance with one aspect of this invention, it has been found that the remaining strength of the suture is less than would be expected if the strength and cross-sectional areas were directly proportional. For example, the rupture strength of 2-0 catgut suture reduced to size 5-0 at the tip segment is only about 1/1.3 times the rupture strength that would be expected based on the relative areas of the original suture cross section and the cross section of the reduced portion of the suture tip.
With multifilament sutures, the entire cross-sectional area of the suture is not made up of suture material since there is, of necessity, some free space between the suture strands. The proportion of the total cross-sectional area of a suture which is occupied by the suture strands is called "suture density". The suture densities of multifilament structures are calculated from the volume of the sample of the suture and the volume of the fiber therein in accordance with the formula: ##EQU1## in which S is the volume of the suture, F is the volume of the fiber, and D is the suture density.
For convenience, it is best to determine volumes in samples at fixed lengths of 9.000 meters, or 9 × 10 5 centimeters. This is convenient because fiber denier is defined as weight in grams per 9,000 meters. At this length, the volume of the suture in cubic centimeters is: ##EQU2## where d is the diameter of the suture in centimeters. The volume in cubic centimeters of the individual fibers, F, at the same length would be: ##EQU3## or ##EQU4## where r is the density of the suture material in grams per cubic centimeter.
The suture density of multifilament structures may range from about 0.50 to nearly unity depending on the compactness of the structure. The suture density of braided sutures for example, generally runs from about 0.70 to about 0.95, and most usually from about 0.80 to about 0.92.
The load at which a reduced tip suture will rupture may be estimated from the equation: ##EQU5## wherein P is the rupture load, in pounds;
T is the tensile strength of the suture material, in pounds per square inch;
A is the area, in square inches, of the reduced diameter portion of the suture;
D is the suture density of the suture, being unity in the case of a monofilament; and
K is a constant factor, empirically determined and representing the degree of weakening at the reduced tip portion of the suture over and above the weakening to be expected from its reduced area.
The reduced tip area required to obtain a desired level of rupture strength at a tip portion of a suture may be calculated from another form of the same equation: ##EQU6## in which A,K,P,D, and T are as defined above.
It is usually desired that the suture be rupturable at its reduced tip portion by a force of from about 3 ounces to about 26 ounces, or from about 0.2 to about 1.6 pounds; and these limits may be inserted in the above equation as the limiting values for P. Selecting an average P value of 0.8 provides leeway for differences in individual sutures and for differences in the grinding of their tips and assures rupture strengths within the desired range for most of the reduced tip sutures. The value of K is experimentally determined for each suture material by comparing the actual breaking strength of a reduced diameter suture to the strength calculated on the basis of the tensile strength of the material and the diameter of the reduced tip. For example, a sample of chromic catgut is known to have a tensile strength of 65,000 psi. A size 5-0 catgut would accordingly be expected to have a breaking strength of 1.85 pounds. When the tip of a 2-0 catgut is reduced to size 5--0, however, the breaking strength is determined to be 1.4 pounds, and a value for K is computed as 1.85/1.4 or 1.3. Values of K for other suture materials are readily determined in a like manner.
BRIEF DESCRIPTION OF THE INVENTION
The invention will become more readily apparent upon consideration of the following detailed description when taken in connection with the accompanying drawings wherein:
FIG. 1 is an enlarged elevation, partly in cross-section of the blunt end of a needle and the reduced diameter end of a suture before the suture end is inserted into the recess in the blunt end of the needle;
FIG. 2 is an enlarged elevation, partly in cross-section of the suture-needle combination of this invention after the suture end of FIG. 1 has been inserted into the recess in the blunt end of the needle and the blunt end has been swaged;
FIG. 3 is an enlarged elevation similar to FIG. 2 but showing rupture of the suture near its juncture to the needle after application of tension thereto;
FIG. 4 is a transverse cross-section of the suture at plane 4--4 of FIG. 1; and
FIG. 5 is a fragmentary elevation of a continuous filament with reduced diameter from which sutures with reduced diameter ends can be cut.
DETAILED DESCRIPTION
As may be seen in FIGS. 1 to 3, needle 11 has a cylindrical hole 12 in its blunt end 13 which may be formed by drilling or closed channel. Suture 14, for most of its length, has about the same diameter as needle 11, but at suture end 16, the diameter is reduced to fit into hole 12. The length of suture end 16 is preferably somewhat greater than the depth of hole 12 so that there is a segment of suture end 16 extending beyond the juncture of the needle and the suture when the suture end is fully inserted into the hole.
The application of cold pressure to the blunt end of the needle after insertion of the suture end into the hole produces swaged portion 17 at the blunt end of the needle and compresses the suture within the hole to reduce its transverse dimension within the hole somewhat, as shown in FIGS. 2 and 3.
The application of tension to the needle suture combination after it has been used during a surgical procedure results in rupture of the suture in the segment of reduced diameter adjacent the needle-suture juncture, as shown in FIG. 3. The cross-sectional area 18 of the suture at the needle end is smaller than the cross-sectional area in the remainder of the suture, as shown in FIG. 4.
In FIG. 5, monofilament 21 comprises a series of segments 22 having the full desired suture diameter and a series of short segments 23 of reduced diameter and cross-sectional area. Segments 22 are twice the desired suture length because they will be cut in half to make two sutures. Segments 23 will also be cut, as shown at 24 so that each short segment provides two suture ends of reduced diameter.
EXAMPLES 1 to 8
Samples of size 2-0 catgut sutures, having an outer diameter of 0.016 inches were ground at one end to the diameter of a 5-0 suture (0.006 inches). The ground down suture ends were inserted into channels in needles normally used for 5-0 sutures and swaged. For comparison purposes the opposite ends of some of the sutures (which were of normal diameter) were inserted into channels in needles normally used for 2-0 sutures and swaged. The samples were tested for needle separation values by pullout or breaking and the results were as follows:
Sample No. Reduced Diameter End Original Diameter End ______________________________________ 1 17 oz. 482 gm. 61/2 lb. 2.95 kg. 2 23 oz. 652 81/4 lb. 3.74 3 24 oz. 680 6 lb. 2.72 4 27 oz. 765 5 lb. 2.27 5 20 oz. 567 -- 6 21 oz. 595 -- 7 21 oz. 595 -- 8 28 oz. 794 -- Average 23 oz. 652 gm. 61/2 lb. 2.95 kg. ______________________________________
EXAMPLES 9 to 12
Samples of size 3-0 catgut sutures, having an outer diameter of 0.012 inches were ground at one end to the diameter of a 5-0 suture (0.006 inches). The ground down suture ends were inserted into channels in needles normally used for 5-0 sutures and swaged. For comparison purposes the opposite ends of some of the sutures (which were of normal diameter) were inserted into channels in needles used for 3-0 sutures and swaged. The samples were tested for needle separation values and the results were as follows:
Example No. Reduced Diameter End Original Diameter End ______________________________________ 9 24 oz. 680 gm. 5 lb. 2.27 kg. 10 27 oz. 765 4 lb. 1.81 11 31 oz. 679 5 lb. 2.27 12 19 oz. 539 -- Average 25 oz. 709 gm. 42/3 lb. 2.12 kg. ______________________________________
In those instances in which the invention is utilized to minimize leakage around the suture through sewn tissues, the suture tip is ground down to a diameter which will permit its insertion into a needle of approximately the same diameter as the remainder of the suture. In conventional commercial production, the suture diameter is always considerably less than the needle diameter. For example, a needle having a diameter of 0.026 inches may be used with sutures ranging in size from 5-0 (0.004 inches) to 2-0 (0.016 inches). Thus, even the largest suture available for this particular needle has only about 62 percent of the diameter of the needle.
In accordance with one aspect of the present invention, the tip of a catgut suture (0.016 inch diameter) may be ground down to the size of a 5-0 suture and then inserted into a needle having a diameter of 0.017 so that the suture diameter is about 94 percent that of the needle diameter. In this instance, the suture substantially fills the needle hole made in the sewn tissue and eliminates, or substantially eliminates a leakage therethrough.
In the practice of this embodiment of the invention suture tips are ground down sufficiently to permit the suture to be inserted into a needle whose diameter is such that the suture diameter is at least about 85 percent of the needle diameter. It is preferred that the suture diameter be no greater than the needle diameter because otherwise the suture would have to enlarge its own hole, resulting in the necessity to apply more tension during sewing than would otherwise be required and in increased danger of tearing delicate tissues.
The invention has been described with respect to preferred embodiments but other embodiments and modifications will be apparent to those skilled in the art.
This invention relates to needle-suture combinations and particularly to a combination of a surgical needle with a suture in which the force necessary to separate the needle from the suture is within an acceptable range for convenient removal of the needle from the suture by a sharp tug.
In many surgical procedures, surgeons use a technique which employs a non-needled suture and an eyed needle. The needle is threaded by the nurse and the surgeon takes one pass through the tissue using a needleholder. He slips the needle off the suture, returns the needle to the nurse, and is ready for another threaded needle from the nurse. An assistant follows behind and ties the suture.
Surgeons find that this technique is more simple than using a needled item and cutting the suture with a scissors after each pass. However, the time required for threading results in a significant waste of expensive operating room time.
The security of attachment of eyeless needles to absorbable surgical sutures or to non-absorbable surgical sutures is prescribed in the U.S. Pharmacopoeia, Vol. XVIII at Page 944 (also see U.S. Pharmacopoeia, Vol. XVII, Page 919). It has been the practice of suture manufacturers in the U.S. and abroad to securely attach the suture to the needle by swaging or with an adhesive so that the minimum pull-out standard recited in the U.S. Pharmacopoeia is met or exceeded.
To avoid the problems discussed above it has been found useful to use needle-suture combinations in which the needle and the suture are readily separable from each other by a sharp tug. Several methods have been devised for preparing needle-suture combinations in which the pull-out values, or the force required for separating the needle from the suture by a straight pull, is within a controlled range.
One approach to this problem is described in co-pending and co-assigned application Ser. No. 409,974, filed Oct. 26, 1973, now abandoned. This approach includes inserting into a drilled hole in the blunt end of the needle one end of a braided suture which has been sized with a resin and is smaller in apparent diameter than the remainder of the suture and then swaging the needle at its blunt end to provide a controlled degree of compression to the end of the suture within the hole. This approach is particularly directed to needle-suture combinations wherein the suture is of large size, i.e., size 4-0and larger (diameter greater than 7.0 mils), and produces average pull-out values of 3 to 26 ounces, indicating that it takes a straight pull of a magnitude within that range to separate the needle from the suture.
Another approach to the problem is described in co-pending and co-assigned application Ser. No. 446,174 filed by Robert Barclay Duncan on Feb. 27, 1974, now U.S. Pat. No. 3,875,946. In this approach sufficient tension is applied to the suture in a swaged needle-suture combination to move the suture relative to the needle recess and the tension is released when the force drops to the range desired for the pull-out value, the range varying for different sizes of suture. This approach is applicable to a broad range of suture sizes, including sizes as small as 8-0.
The present invention, in one aspect, provides another approach to the problem and provides for easy separation of needles from needle-suture combinations without requiring any major change in the manner of manufacture of the needle-suture combinations.
There has been another problem in needle-suture combinations, unrelated to and independent of the problem of providing controlled pull-out values, namely the problem in certain applications, of leakage in sewn tissues through needle holes made during surgical sewing.
In a typical needle-suture combination in which the suture is held within a recess of the blunt end of a needle, the suture is of about the same diameter as (or somewhat smaller than) the diameter of the recess and is thus smaller than the external diameter of the needle. In the surgical sewing of certain tissues, such as blood vessels or bladder walls, it is undesirable to have unfilled or partially unfilled needle holes in the tissue because such unfilled holes provide paths for undesired leakage. In the case of a bladder repair there can be leakage of urine which can be harmful in the abdominal cavity and in the case of blood vessel repair there can be leakage of blood onto surrounding body tissues.
This invention, in another aspect, provides a means to avoid leaving partially unfilled needle holes in surgically sewn tissue by providing a needle-suture combination in which the extended transverse dimensions of the needle and the suture are substantially equal.
BRIEF SUMMARY OF THE INVENTION
In accordance with the present invention there is provided a needle-suture combination comprising a needle having a sharp end and a blunt end and having a recess at said blunt end, a suture having one tip positioned within said recess, means retaining said tip of said suture within said recess to attach said suture to said needle, said tip within said recess and a segment thereof beyond said recess and adjacent the location of the attachment of the suture to said needle being reduced in cross-sectional area and in the amount of cross-sectional suture material, as compared to the cross-sectional area and the amount of cross-sectional suture material in the remainder of the suture length.
In the aspect of the invention in which it is desired to control the pull-out values for separating the needle from the suture, the invention provides a weakened suture segment adjacent the juncture of the needle and the suture, which suture segment has a rupture strength which is lower than the rupture strength in other portions of the suture and lower than the force necessary to pull the suture tip out of the needle recess. The rupture strength in the weakened segment may be controlled to a value which makes the needle separable from the suture by a sharp tug, and preferably to a value between about 3 and about 26 ounces.
In the aspect of the invention in which it is desired to minimize or eliminate any unfilled space in the needle holes made in tissue during surgical sewing, the outside dimensions of the needle and the suture may be controlled so that the diameter of the suture (except at its tip) is substantially as great as, or somewhat greater than the maximum lateral dimension of the needle.
The invention is particularly applicable to monofilament sutures, although it is also applicable to multifilament sutures, e.g., covered, twisted and braided sutures, provided that the suture tips are first unified by resin impregnation, fusing or other technique. By "unified" it is meant that the treated portion of the suture is transformed from a collection of loose, individual filaments to a single, coherent stucture. Such unification is commonly employed in the art to prevent brooming of cut ends and to facilitate needle attachment. Reducing the diameter of the tip of a multifilament suture which is not first unified will produce an undesirable "brooming" effect in which loose ends of individual fibers of the suture stick out where they have been severed adjacent the reduced diameter tip.
As stated above, U.S. application Ser. No. 409,974 teaches swaging in a drilled needle one end of a braided suture which is unified by impregnating with a resin and is smaller in apparent diameter than the remainder of the suture. The teachings of Ser. No. 409,974 relative to the resin impregnation of sutures to obtain a unified structure is hereby incorporated by reference. The smaller diameter suture end in Ser. No. 409,974 is obtained by impregnating the suture tip with a resin while the suture is under tension. The unified suture end thus produced has an apparent diameter somewhat smaller than the remainder of the suture because the fibers of the tip are compacted relative to the remainder of the suture, but there are the same number of fibers in the smaller diameter tip as in any other portion of the suture.
In contrast, in the embodiment of the present invention utilizing a braided or other multifilament suture, the amount of diameter reduction or actual cross-sectional area reduction at the suture tip is at least 10 percent of the cross-sectional of the area of the remainder of the suture and there is at least 10 percent less suture material in the cross-section of the smaller diameter suture end than in the remainder of the suture.
To reduce the diameter, or cross-sectional area of a suture end for the preparation of the needle-suture combination of this invention, the suture end may be ground down to the desired diameter and to the desired length of the cutaway portion. The grinding is carried out by known techniques and in known equipment, such as in a jeweler's lathe or in a grinding machine such as that described in British Pat. No. 1,180,276 of American Cyanamid Company.
Another method of producing a suture end of the desired reduced diameter which is applicable for monofilament sutures is to produce a continuous monofilament with spaced segments of reduced diameter, each such segment being cut to provide two reduced diameter suture ends. A continuous filament of this type may be prepared by providing pulsation during the extrusion of the monofilament, or periodic partial slowdown of the rate of polymer feed to the extrusion orifices.
The sutures suitable for use in the preparation of the reduced suture tip needle-suture combination of this invention include monofilament and multifilament sutures having a unified tip. Suitable suture materials include natural materials such as collagen (including catgut and extruded collagen), silk, cotton and linen, and synthetic polymers, such as nylon, polypropylene and polyesters, such as polyethylene terephthalate, and homopolymers and copolymers of lactide and glycolide.
When the suture tips are reduced in area for providing easy separability of the needle from the suture in accordance with one aspect of this invention, it has been found that the remaining strength of the suture is less than would be expected if the strength and cross-sectional areas were directly proportional. For example, the rupture strength of 2-0 catgut suture reduced to size 5-0 at the tip segment is only about 1/1.3 times the rupture strength that would be expected based on the relative areas of the original suture cross section and the cross section of the reduced portion of the suture tip.
With multifilament sutures, the entire cross-sectional area of the suture is not made up of suture material since there is, of necessity, some free space between the suture strands. The proportion of the total cross-sectional area of a suture which is occupied by the suture strands is called "suture density". The suture densities of multifilament structures are calculated from the volume of the sample of the suture and the volume of the fiber therein in accordance with the formula: ##EQU1## in which S is the volume of the suture, F is the volume of the fiber, and D is the suture density.
For convenience, it is best to determine volumes in samples at fixed lengths of 9.000 meters, or 9 × 10 5 centimeters. This is convenient because fiber denier is defined as weight in grams per 9,000 meters. At this length, the volume of the suture in cubic centimeters is: ##EQU2## where d is the diameter of the suture in centimeters. The volume in cubic centimeters of the individual fibers, F, at the same length would be: ##EQU3## or ##EQU4## where r is the density of the suture material in grams per cubic centimeter.
The suture density of multifilament structures may range from about 0.50 to nearly unity depending on the compactness of the structure. The suture density of braided sutures for example, generally runs from about 0.70 to about 0.95, and most usually from about 0.80 to about 0.92.
The load at which a reduced tip suture will rupture may be estimated from the equation: ##EQU5## wherein P is the rupture load, in pounds;
T is the tensile strength of the suture material, in pounds per square inch;
A is the area, in square inches, of the reduced diameter portion of the suture;
D is the suture density of the suture, being unity in the case of a monofilament; and
K is a constant factor, empirically determined and representing the degree of weakening at the reduced tip portion of the suture over and above the weakening to be expected from its reduced area.
The reduced tip area required to obtain a desired level of rupture strength at a tip portion of a suture may be calculated from another form of the same equation: ##EQU6## in which A,K,P,D, and T are as defined above.
It is usually desired that the suture be rupturable at its reduced tip portion by a force of from about 3 ounces to about 26 ounces, or from about 0.2 to about 1.6 pounds; and these limits may be inserted in the above equation as the limiting values for P. Selecting an average P value of 0.8 provides leeway for differences in individual sutures and for differences in the grinding of their tips and assures rupture strengths within the desired range for most of the reduced tip sutures. The value of K is experimentally determined for each suture material by comparing the actual breaking strength of a reduced diameter suture to the strength calculated on the basis of the tensile strength of the material and the diameter of the reduced tip. For example, a sample of chromic catgut is known to have a tensile strength of 65,000 psi. A size 5-0 catgut would accordingly be expected to have a breaking strength of 1.85 pounds. When the tip of a 2-0 catgut is reduced to size 5--0, however, the breaking strength is determined to be 1.4 pounds, and a value for K is computed as 1.85/1.4 or 1.3. Values of K for other suture materials are readily determined in a like manner.
BRIEF DESCRIPTION OF THE INVENTION
The invention will become more readily apparent upon consideration of the following detailed description when taken in connection with the accompanying drawings wherein:
FIG. 1 is an enlarged elevation, partly in cross-section of the blunt end of a needle and the reduced diameter end of a suture before the suture end is inserted into the recess in the blunt end of the needle;
FIG. 2 is an enlarged elevation, partly in cross-section of the suture-needle combination of this invention after the suture end of FIG. 1 has been inserted into the recess in the blunt end of the needle and the blunt end has been swaged;
FIG. 3 is an enlarged elevation similar to FIG. 2 but showing rupture of the suture near its juncture to the needle after application of tension thereto;
FIG. 4 is a transverse cross-section of the suture at plane 4--4 of FIG. 1; and
FIG. 5 is a fragmentary elevation of a continuous filament with reduced diameter from which sutures with reduced diameter ends can be cut.
DETAILED DESCRIPTION
As may be seen in FIGS. 1 to 3, needle 11 has a cylindrical hole 12 in its blunt end 13 which may be formed by drilling or closed channel. Suture 14, for most of its length, has about the same diameter as needle 11, but at suture end 16, the diameter is reduced to fit into hole 12. The length of suture end 16 is preferably somewhat greater than the depth of hole 12 so that there is a segment of suture end 16 extending beyond the juncture of the needle and the suture when the suture end is fully inserted into the hole.
The application of cold pressure to the blunt end of the needle after insertion of the suture end into the hole produces swaged portion 17 at the blunt end of the needle and compresses the suture within the hole to reduce its transverse dimension within the hole somewhat, as shown in FIGS. 2 and 3.
The application of tension to the needle suture combination after it has been used during a surgical procedure results in rupture of the suture in the segment of reduced diameter adjacent the needle-suture juncture, as shown in FIG. 3. The cross-sectional area 18 of the suture at the needle end is smaller than the cross-sectional area in the remainder of the suture, as shown in FIG. 4.
In FIG. 5, monofilament 21 comprises a series of segments 22 having the full desired suture diameter and a series of short segments 23 of reduced diameter and cross-sectional area. Segments 22 are twice the desired suture length because they will be cut in half to make two sutures. Segments 23 will also be cut, as shown at 24 so that each short segment provides two suture ends of reduced diameter.
EXAMPLES 1 to 8
Samples of size 2-0 catgut sutures, having an outer diameter of 0.016 inches were ground at one end to the diameter of a 5-0 suture (0.006 inches). The ground down suture ends were inserted into channels in needles normally used for 5-0 sutures and swaged. For comparison purposes the opposite ends of some of the sutures (which were of normal diameter) were inserted into channels in needles normally used for 2-0 sutures and swaged. The samples were tested for needle separation values by pullout or breaking and the results were as follows:
Sample No. Reduced Diameter End Original Diameter End ______________________________________ 1 17 oz. 482 gm. 61/2 lb. 2.95 kg. 2 23 oz. 652 81/4 lb. 3.74 3 24 oz. 680 6 lb. 2.72 4 27 oz. 765 5 lb. 2.27 5 20 oz. 567 -- 6 21 oz. 595 -- 7 21 oz. 595 -- 8 28 oz. 794 -- Average 23 oz. 652 gm. 61/2 lb. 2.95 kg. ______________________________________
EXAMPLES 9 to 12
Samples of size 3-0 catgut sutures, having an outer diameter of 0.012 inches were ground at one end to the diameter of a 5-0 suture (0.006 inches). The ground down suture ends were inserted into channels in needles normally used for 5-0 sutures and swaged. For comparison purposes the opposite ends of some of the sutures (which were of normal diameter) were inserted into channels in needles used for 3-0 sutures and swaged. The samples were tested for needle separation values and the results were as follows:
Example No. Reduced Diameter End Original Diameter End ______________________________________ 9 24 oz. 680 gm. 5 lb. 2.27 kg. 10 27 oz. 765 4 lb. 1.81 11 31 oz. 679 5 lb. 2.27 12 19 oz. 539 -- Average 25 oz. 709 gm. 42/3 lb. 2.12 kg. ______________________________________
In those instances in which the invention is utilized to minimize leakage around the suture through sewn tissues, the suture tip is ground down to a diameter which will permit its insertion into a needle of approximately the same diameter as the remainder of the suture. In conventional commercial production, the suture diameter is always considerably less than the needle diameter. For example, a needle having a diameter of 0.026 inches may be used with sutures ranging in size from 5-0 (0.004 inches) to 2-0 (0.016 inches). Thus, even the largest suture available for this particular needle has only about 62 percent of the diameter of the needle.
In accordance with one aspect of the present invention, the tip of a catgut suture (0.016 inch diameter) may be ground down to the size of a 5-0 suture and then inserted into a needle having a diameter of 0.017 so that the suture diameter is about 94 percent that of the needle diameter. In this instance, the suture substantially fills the needle hole made in the sewn tissue and eliminates, or substantially eliminates a leakage therethrough.
In the practice of this embodiment of the invention suture tips are ground down sufficiently to permit the suture to be inserted into a needle whose diameter is such that the suture diameter is at least about 85 percent of the needle diameter. It is preferred that the suture diameter be no greater than the needle diameter because otherwise the suture would have to enlarge its own hole, resulting in the necessity to apply more tension during sewing than would otherwise be required and in increased danger of tearing delicate tissues.
The invention has been described with respect to preferred embodiments but other embodiments and modifications will be apparent to those skilled in the art.