A surgical suture is made of an elongate, hollow braid of high strength fibers. The braid defines an elongate, longitudinally-extending, central chamber that is open and without any core material extending therein so that, when a surgeon's knot is tied with the suture, the cross-sectional shape of the braid collapses upon itself and is reduced in size in response to pressures experienced when the knot is tightened thereby producing a low profile knot that resists slippage. Preferably, the braid is of a size corresponding to a USP size 5-0 to USP size 7 suture and has one or more, preferably a pair, of color contrasting monofilaments woven therein to enhance suture visibility. Methods of making a flattened suture and of utilizing the high strength suture to maintain body tissues in an engaged position to promote healing are also provided.

BRIEF SUMMARY OF THE INVENTION

This invention relates to a surgical suture, and more particularly, to a high-strength surgical suture providing improved knot tie down characteristics that enable surgeons to form low profile knots having superior knot security.

Sutures are elongate implant devices used to maintain body tissues together to promote natural healing and/or to compress blood vessels to stop bleeding. Sutures are typically knotted to hold divided wound edges together, and the mechanical performance of surgeons' knots has an effect on proper wound healing. If a suture and/or knot fails, it should fail due to breakage, not due to knot slippage. Examples of tests for determining the mechanical performance of knotted sutures are discussed in the article by Zimmer et al. titled “Influence of Knot Configuration and Tying Technique on the Mechanical Performance of Sutures” published in The Journal of Emergency Medicine, Volume 9, pages 107-113, 1991.

Sutures are manufactured in various sizes, typically according to standards established by the United States Pharmacopeia (USP). Suture size is typically determined by the diameter or gauge of the round cross-section of the suture. See Table 1 provided below.

Surgical sutures, particularly those of USP size 5-0 and greater, have been constructed having a core of fibers extending within an outer braided cover or sheathing of fibers. See prior art suture100illustrated inFIG. 1. Suture100has an outer braided sheathing of fibers102surrounding a twisted core of fibers104and has a round cross section (ie., the x dimension equals the y dimension as illustrated inFIG. 1). Examples of surgical sutures having cores are also provided by U.S. Pat. No. 4,946,467 issued to Ohi et al., U.S. Pat. No. 4,546,769 issued to Planck et al., and U.S. Pat. No. 6,045,571 issued to Hill et al. The core fibers are used to increase the strength of the suture and to provide the suture with a rounded cross-section. Needles used with sutures typically have a round cross-section and make round holes, and it has been believed desirable to make the cross-section of sutures as round as possible to fill the round holes to reduce bleeding. Thus, cores enable the roundness of the cross-section of the suture to be maintained during use. However, such sutures have experienced problems relating to the different elongation to break between the core and cover materials and problems relating to the core popping through the cover.

Surgical sutures have been made of high strength materials. For example, U.S. Pat. No. 5,318,575 issued to Chesterfield et al. discloses so-called “high-strength” fibers to manufacture spiroid and hollow braided surgical sutures having cores. An example of a high strength fiber is ultra-high molecular weight, extended-chain polyethylene high-tenacity fiber sold under the tradename “SPECTRA”. U.S. Pat. No. 4,790,850 issued to Dunn et al., U.S. Pat. No. 4,792,336 issued to Hlavacek et al., U.S. Pat. Nos. 5,628,756 and 5,540,703 issued to Barker, Jr. et al. and U.S. Pat. No. 5,456,722 issued to McLeod et al. disclose high-strength, ultra-high molecular weight polyethylene fibers in relatively large diameter surgical cables used as prosthetic ligaments, tendon implants, and the like. Also see U.S. Pat. No. 6,716,234 B2 issued to Grafton et al. and U.S. Patent Application Publication Nos. U.S. 2003/0050667 A1 and U.S. 2003/0139775 A1 which disclose high-strength sutures made in part of ultra-high molecular weight polyethylene fibers, such as those sold under the trademarks “SPECTRA” and “DYNEEMA”.

Fibers of contrasting colors have been utilized in surgical sutures to enhance suture visibility, and suture handling properties have been improved with coatings including various lubricants and the like. For example, U.S. Pat. No. 3,949,755 issued to Vauquois discloses a braided suture having fibers of contrasting colors, and U.S. Pat. No. 4,043,344 issued to Landi et al., U.S. Pat. No. 4,047,533 issued to Perciaccante et al., and U.S. Pat. No. 5,019,093 issued to Kaplan et al. disclose various coatings utilized on sutures.

While the aforementioned sutures may be satisfactory for their intended purposes, there is a need for an improved surgical suture that is made of high strength fibers and that possesses improved knot-tying and knot-security properties. To this end, a lubricious, multi-filament suture, permitting the construction of a secure knot having a low profile and improved knot security, is desired. In addition, the suture should have enhanced visibility and handling characteristics.

The invention addresses the foregoing objects by providing a surgical suture made of an elongate woven braid of fibers that include ultra-high molecular weight polyethylene fibers. The braid of fibers is hollow and is without any core material extending therein. The absence of a core enables the cross-sectional shape of the braid of fibers to become altered in response to pressures exerted thereon when the suture is knotted so that a knot having a low profile is formed. Preferably, the braid of fibers is of a size corresponding to a suture with the range from about USP sizes 5-0 to 7 (ie., the suture has a diameter in the range from about 0.100 to 0.999 mm).

According to another aspect of the present invention a method is provided for maintaining body tissues in an engaged position to promote healing. A suture is used to stitch the body tissues together and at least one knot is tied with the suture to hold the body tissues together for at least a predetermined period of time that is required for proper healing. The suture is an elongate woven braid of fibers including ultra-high molecular weight polyethylene fibers, and the braid of fibers is hollow without a core material extending therein. During the tying step, the cross-sectional shape of the braid of fibers changes in response to pressures experienced during knotting thereby providing a knot having a low profile. Preferably, the suture has an initial size, before knotting, corresponding to a USP size 5-0 to USP size 7 suture (ie., a diameter between about 0.100 to 0.999 mm).

DETAILED DESCRIPTION

The invention relates to a surgical suture made of an elongate, hollow braid of high strength fibers and a method of making the suture. In addition, the invention relates to a method of utilizing the high strength suture to maintain body tissues in an engaged position to promote healing.

Typically, surgical sutures are made to have round cross-sections of sizes corresponding to those identified on the size chart provided above in Table 1. Sutures made of a hollow braid of fibers that correspond to a USP size 5-0 to a USP size 7 suture include a reinforcing core material extending within the braid. SeeFIG. 1. The core material fills the central open void within the braid so that a desired round cross-section is maintained throughout use of the suture as discussed above. For examples of such sutures, see the disclosures provided by U.S. Pat. No. 5,318,575 issued to Chesterfield et al., U.S. Pat. No. 6.045,571 issued to Hill et al., and U.S. Pat. No. 6,716,234 B2 issued to Grafton et al. and U.S. Patent Application Publication Nos. U.S. 2003/0050667 A1 and U.S. 2003/0139775 A1. Sutures smaller than USP size 5-0 sutures are too small to have central open voids and have been made without a core material simply because adequate space for a core material is not available. U.S. Pat. Nos. 5,628,756 and 5,540,703 issued to Barker, Jr. et al. and U.S. Pat. No. 5,456,722 issued to McLeod et al. disclose large braided surgical cables having diameters of at least 1 to 3 mm. These braids are made of 9 to 13 picks per inch and from large denier ends (ie., minimum 650 denier) on an eight carrier braider providing a total minimum denier of 5200 denier (ie., 8×650). Thus, such large braids also provide no void or open space in which a core material can be extended.

As best illustrated inFIGS. 2 and 3, the suture10according to the present invention is a hollow braid of fibers12of a size within a range of USP size 5-0 to USP size 7 (ie., has a diameter between about 0.1 to about 0.999 mm as measured when in a round condition as illustrated inFIG. 2). Unlike prior art sutures of like sizes, the suture10is coreless without any core material extending within the hollow braid12. Thus, the braid12defines an elongate, longitudinally-extending, central chamber14that is without a core material extending therein.FIG. 2illustrates a cross-section of suture10when disposed in a circular configuration. However, the suture10according to the present invention can also be provided in an oval, relatively flat, or tape-like configuration as illustrated inFIG. 3since the braid12is coreless and can collapse upon itself For purposes of this application, the size of suture10corresponds to diameter measurements taken when suture10is disposed in a substantially circular cross-sectional configuration, such as shown inFIG. 2.

The coreless, hollow-braided suture10provides improved knot-tying and knot-security capabilities. When a knot is tied with suture10, the cross-sectional shape and size of suture10at the knot changes and becomes reduced since the pressure exerted during the formation of the knot causes the suture10to collapse upon itself at the knot site. This reduces the length, width, volume and mass of the knot providing it with a profile that is significantly less than that of a similarly sized prior art suture having a core. Thus, the presence of the open central chamber14and the absence of any core material therein for the above referenced range of suture size permits the ready formation of low profile knots that remain secure without slippage for an extended period of time. This results in significant advantages relative to knots tied with prior art braided sutures that have a core material, since the presence of a core material limits the ability of a prior art suture to collapse upon itself during knot tying and tightening actions.

Preferably, the braid12is made of high strength fibers16, such as ultra-high molecular weight polyethylene fibers, to compensate for the absence of a core material. For example, braid12can be made entirely (100%) of ultra-high molecular weight polyethylene fibers, or alternatively, can include one or more strands of a different fiber/filament. Preferably, the high strength fibers16in the braid12form at least 75%, or 90%, of the total fibers of the braid12, so that a suture10having high strength is provided despite the absence of a core material.

In a preferred embodiment, the suture10includes one or more, preferably two, strands of a color contrasting monofilament18to enhance suture visibility during surgery. The ultra-high molecular weight polyethylene fibers16are typically white or translucent. Thus, the suture10preferably includes a strand or stands of a monofilament18that is of a highly-visible contrasting color and that is woven in the braid12with the ultra-high molecular weight polyethylene fibers16. As an example, the monofilament18can be a deep blue color. Alternatively, strands of other colors can be utilized. Preferably, the color-contrasting monofilament18is a color-extruded monofilament of polypropylene or polydioxanone. To this end, preferably a colorant or pigment is compounded into a resin before the resin is extruded to form a color-extruded monofilament. Thus, preferably the monofilament18is not subjected to a post-formation dyeing step as typically required for polyester and nylon materials.

By way of example, the braid of suture10can include 8, 16, 24, or 32 ends braided together at approximately 50-70 pics per inch. The various numbers of ends used are for the purpose of changing the resultant size of the finished braid while holding the denier constant. Preferably, the suture10includes only ultra-high molecular weight polyethylene fibers16and one or more, preferably a pair, of color-contrasting monofilaments18of a color-extruded monofilament of polypropylene or polydioxanone. As a specific example, the braid12can include sixteen ends braided together with fourteen ends being ultra-high molecular weight polyethylene fibers16and a pair of ends being color-contrasting polypropylene monofilaments18located at opposed positions within the braid. Preferably the color contrasting monofilaments18comprise no more than 25% of the total fibers of the braid12. In addition, preferably the suture10is of a size within a range of USP size 5-0 to USP size 7 (ie., has a diameter of at least about 0.1 mm and less than 1.0 mm), and optionally, the suture10can be coated with wax, silicone, silicone rubber, PTFE, PBA, ethyl cellulose or like coating to improve handling, lubricity of the braid, abrasion resistance, and like characteristics.

A method of maintaining body tissues in an engaged position to promote healing is also provided by the present invention. To this end, a USP size 5-0 to USP size 7 suture is utilized to stitch body tissues together and a surgeon's knot is tied with the suture to hold the body tissues together for at least a predetermined period of healing time. As discussed above, the suture10is an elongate woven braid of fibers including ultra-high molecular weight polyethylene fibers, and the braid of fibers is hollow and has an elongate, longitudinally-extending, central chamber that is open and without a core material extending therein. Thus, during knot tying, the braid12at the site of the knot is reduced in size, diameter, and shape in response to pressures experienced during tying thereby producing a knot having a reduced mass, volume, and profile.

EXAMPLES

An example of a coreless braided suture according to the invention and tests with respect to the dimensions and security of knots formed with the suture are provided below and are contrasted with sutures having cores according to the prior art. General information concerning braid construction is disclosed by U.S. Pat. No. 6,045,571 issued to Hill et al., and general information concerning suture knot construction and tests of mechanical performance of knots are disclosed in the article of Zimmer et al. titled “Influence of Knot Configuration and Tying Technique on the Mechanical Performance of Sutures” published in 1991 in The Journal of Emergency Medicine, Volume 9, pages 107-113. The disclosures of both of these references are incorporated herein by reference.

For testing purposes, a USP size 2 braided suture according to the invention was made with a sixteen-carrier New England Butt braider No. 1. Each carrier held 110 denier DYNEEMA ultra high molecular weight polyethylene fiber, and the braider was equipped with a cross shaft gear of 82 and a lower change gear of 24. The gears provide an expected pick count of 62 picks per inch (PPI). The braided suture according to the present invention was flattened by being passed over and under two rollers before transition to a smaller step roll (1.185 inch) and five passes to a roller before final take up on an iron head. The rollers can be made of metal or ceramic, and the geometry of the rollers to each other serve to flatten the braid. SeeFIG. 3for an example of the shape of the flattened braid.

Tables 2 and 3, provided below, show the effects on suture diameter of flattening the braided suture of the invention. To this end, Table 2 provides diameter measurements in mils of fifteen samples of the suture according to the invention that were not subjected to the above referenced flattening procedures, and Table 3 provides diameter measurements in mils of fifteen samples of the suture according to the invention that were subjected to the above referenced flattening procedures. Low diameters, high diameters and average diameters are measured for each sample and overall averages are listed below the last line of the tables.

For testing purposes, a USP size 2 braided suture having a core according to the prior art was also made with a sixteen-carrier New England Butt braider No. 1. Each carrier held 110 denier DYNEEMA ultra high molecular weight polyethylene fiber. The braid was formed as a cover over a center core of a three ply of 220 denier DYNEEMA ultra high molecular weight polyethylene fiber. The braider was equipped with a cross shaft gear of 82, a lower change gear of 24, and a small step roll (1.185 inch). The gears provide an expected pick count of 62 picks per inch (PPI).

Various tests were run with the above referenced suture according to the invention and the above referenced prior art suture having a core. In addition, different types of knots were tested for the sutures. As will be discussed in greater detail, the tests show that the coreless suture according the invention can be used to create knots of lower profile and of better security than the comparative prior art sutures.

The test utilized a MTS Reliance RT/5 test frame with a 500 N load cell installed on the MTS Reliance RT/5 test frame. For each knot30to be evaluated, a suture was tied around a 4.75 inch roll of paper20covered with a 0.25 inch layer of foam rubber22as illustrated inFIG. 4. All knots tested included a square knot followed by one or more square or granny throws. Beginning with the second throw of each knot, equal tension was applied to each throw of the knot configuration by the pneumatic jaws24of the MTS Reliance RT/5 test frame with an extension rate of 500 mm/min to a final tension of 6.2 lbf, which represents 80% of the USP knot pull tensile strength requirement of the suture. Thereafter, the ears26of the knot30were trimmed to approximately 3 mm, and the suture was removed from the roll20by cutting the suture at the midpoint28opposite the knot30at the back of the roll20. SeeFIG. 5. The knot dimensions of the removed suture was then measured and its knot security tested on an Instron 3300 tensile strength instrument. SeeFIGS. 6 and 7.

The dimensions of each knot30was measured on a Nikon Measurescope MM-11 microscope. The knot30was placed on the plate of the microscope with suture ends32and34extended, and weights were used to hold the knot in a fixed position. The width and length of the knot was measured in inches with the microscope along x-coordinate and y-coordinate directions. SeeFIG. 7.

Patient side knot security was tested for each knot30by placing the suture ends,32and34, of the knot between fiber grips36of the Instron tensile strength instrument. SeeFIG. 6. The tensile strength was tested, and it was observed wether or not the knot slipped (S) or broke (B). The peak load observed before breakage or slippage was recorded as well as the mode of separation, ie., S or B.

The results of the tests are shown in the following Tables. Table 4 provides the results of tests on the present invention, Table 5 provides the results of tests on the above described comparative suture having a core, and Table 6 provides the results of tests on a poly-blend suture having a core made according to U.S. Pat. No. 6,716,234 B2 issued to Grafton et al. The tested knots include a two throw square knot with additional square throws. The standard convention for a square throw “=” is used. For example, a knot type identified as “1=1=1=1” is a two throw square knot (“1=1”) with two additional square throws (“=1=1”), and a knot type identified as “1=1===1” is a two throw square knot (“1=1”) with three additional square throws (“=1=1=1”). Table 7 provides a summary of the knot dimension and knot security measurements listed in detail in Tables 4-6.

The results of tests for knots that include a two throw square knot with one or more additional granny throws are provided in Tables 8-9. To this end, the standard convention for a granny throw “x” is used. For example, a knot type identified as “1=1x1” is a two throw square knot (“1=1”) with an additional granny throw (“x1”), a knot type identified as “1=1x1x1” is a two throw square knot (“1=1”) with two additional granny throws (“x1x1”), and a knot type identified as “1=1x1x1x1” is a two throw square knot (“1=1”) with three additional granny throws (“x1x1x1”). Table 8 provides the results of tests on the present invention, Table 9 provides the results of tests on the above described comparative suture having a core, and Table 10 provides a summary of the knot dimension and knot security measurements listed in detail in Tables 8 and 9.

As indicated by the results in the above referenced Tables, the coreless braided suture of the invention permits surgeons to construct knots that snug down to a lower profile (ie., height) than that permitted by the comparative sutures having cores. In addition, the results demonstrate that the coreless braided suture of the invention provides better knot security (ie., less slippage).

While preferred sutures and methods of use have been described, various modifications, alterations, and changes may be made without departing from the spirit and scope of the invention as defined in the appended claims.