Patent Application
20150351752
The field of art to which this invention relates is surgical sutures, in particular, methods of tipping surgical sutures, surgical sutures made by such methods, and apparatuses for tipping surgical sutures.
Surgical sutures and attached surgical sutures are well known in the art. During the course of a surgical procedure, it is typically necessary for the surgeon to use surgical needles and attached sutures for a variety of purposes, including to approximate tissue. It is desirable, in many of these procedures, that the maximum diameter of the needle, typically the diameter at the blunt or proximal end of the needle, and the maximum diameter of the suture be as close to the same size as possible, and it is also advantageous for the suture diameter to be larger. This design is necessary or desirable so that a hole and pathway in tissue resulting from a surgeon passing the needle through the tissue during a surgical procedure is substantially filled by the body of the suture. This is especially important when joining or approximating highly vascularized tissue in order to prevent oozing or seepage of blood through the pathway and hole produced by the needle. In addition, pathways for bacteria are effectively closed off to prevent infections. Originally, most surgical needles had an eye at their blunt or proximal ends through or in which a surgical suture was mounted or attached. As can be appreciated, this meant that the blunt end of the needle had to have a sufficient size to allow for an eye to be placed in the blunt end of the needle and to accommodate at least double the maximum diameter of a suture strand folded around the eye feature of the needle. This doubling of the suture and the requisite increased size of the blunt end of the needle resulted in a needle-suture combination with a large cross-sectional area that was passed through the tissue. The resulting hole and pathway in the tissue, produced when the needle was passed through tissue, was substantially greater than the cross-sectional area of the attached suture remaining within the tract to approximate or fix the tissue; as described herein, such a pathway may lead to post-implantation complications such as bleeding, infections, etc.
Over the years, in order to improve surgical procedures and patient outcomes, various techniques have been developed to eliminate the eye in the blunt or proximal end of the needle and find other techniques or methods by which a suture strand can be attached to the blunt or proximal end of a surgical needle. One example of an improved suture attachment technique that has been developed is the forming of a channel in the blunt or proximal end of a needle by a conventional metal forming process. In order to attach an end of a suture to a surgical needle having a channel, the distal end of the suture is placed in the channel and the channel is mechanically swaged in a conventional manner to mechanically secure the suture end in the needle channel. Another technique known in this art for attaching suture strands to surgical needles is to drill a bore hole into the proximal end of a surgical needle using conventional processes such as laser drilling and mechanical drilling. In a similar manner, the distal end of a surgical suture is placed into the bore hole and the proximal end of the needle containing the bore hole is conventionally mechanically swaged, although other attachment or securement methods may be used such as gluing. As can be appreciated, it is still required that the diameter or maximum dimension of the blunt or proximal end of a needle having a suture mounting channel or bore hole be substantially larger than the diameter of the body of an attached suture, and hence when such needle-suture combinations are used to join tissue, the suture still does not completely fill the resulting hole and pathway in tissue formed by the needle.
Processes have evolved that may produce a multi-diameter suture, wherein the body of the suture is substantially larger than the portion of the suture (i.e., the tip) that is attached or mounted to a non-eyed needle, either in a channel or bore hole. The processes known in the art for producing reduced diameter suture tips typically alter the flexibility of the suture in the reduced sections in a negative manner by causing an increase in fiber stiffness or a loss of suture diameter consistency, thereby producing variable needle attachment strength. There remains a need in this art for novel processes and apparatuses to produce a suture with a novel tip section having a reduced cross sectional area that maintains the suture material properties of yield stress and suture flexibility at the needle attachment location, while providing consistent needle attachment strength through improved suture tip physical dimensions. There have been various approaches to suture tipping in the art.
U.S. Pat. No. 3,890,975 (McGregor), discloses a braided suture that is subjected to sizing through the application of tension when dipped in a liquid resin solution. The suture is dried to remove the solvent and to allow the coated region to solidify. Since the braided suture is subjected to tension, there is a reduction in diameter as the braided elements begin to align axially thereby compacting the core fibers. As the liquid resin dries, the coated region or tip of suture containing the tensioned coated fibers is locked into the reduced diameter configuration. The uncoated region resumes the original diameter when the tension is released. The sizing operation is conducted to ensure that the suture will release at a more consistent force from the needle after crimping. This process is only applicable to braided sutures, and the final suture diameter is dependent upon the quality or density of the braided suture utilized.
U.S. Pat. No. 4,832,025 (Coates), discloses a method for treating braided sutures that involves melt fusion of the tip region for insertion into a surgical needle. The suture is heated to an elevated temperature sufficient to effectively “melt fuse” a portion of the outer filaments of the multifilament suture. Such temperatures are typically in the range of about 260° C. to 300° C. (500° F. to 572° F.). The suture then stiffens upon cooling. Surface melting of the outer filaments has the effect of holding the filaments together when the suture is cut. It also causes stiffening of the suture which facilitates insertion of the suture end into the drilled bore hole of a needle. However, this melt fusion process has several significant drawbacks. Firstly, the melt fusion of filaments weakens the suture, whose tensile strength is degraded in proportion to the extent of melt fusion. Secondly, melt fusion causes an irreversible change in the suture filaments, which results in permanent stiffening and significant loss of the outer braided sheath tensile strength; and, this may result in sheaths that fracture and release independent of the core fibers causing bunching of the suture sheath during use.
U.S. Pat. No. 5,007,922 (Chen, et al.) discloses a method of producing monofilament sutures with regions of reduced diameter suture. The suture is wound in a helical or spiral configuration about a drum unit. The drum unit contains a region that is capable of expanding to produce an effectively larger perimeter dimension about the drum through the use of a split drum design. Once the fiber is wound about the perimeter of the drum, a heating element is positioned against the side of the drum tangentially along an axis that is parallel to the central axis of the drum. The heating element increases the temperature of any suture that is exposed along this line of contact along the side of the drum. After a satisfactory amount of heating has occurred, the drum is actuated such that the perimeter of the drum is increased. Since the suture is wound about the perimeter of the drum, the regions of heated suture are drawn down to accommodate the change in this dimension. This process results in reduced diameter regions within the suture that are highly oriented, beyond the orientation of the remaining non-heated regions of the suture. In addition to the change in molecular alignment, the resultant suture diameters of the exposed regions will vary depending upon the amount of deformation experienced in either overheated or under-heated segments of fiber windings.
U.S. Pat. No. 8,216,497 (Lindh, et al.) discloses various methods for forming tissue holding devices having predetermined shapes suitable for use in surgical applications, and devices formed in accordance with such methods are also provided. These methods include press-forming methods, and press-forming methods in combination with profile punching. Tissue holding devices formed in accordance with such methods include various configurations for a core and a plurality of tissue holding elements, such as barbs, extending outwardly from the core. The processes provide a method to shape an extruded fiber, at an elevated temperature, into a broader configuration that enables punch press-type technology to be applied to remove sections of the formed fiber component to form solid barbed elements. Their intention is to maintain a center region that is closer to the cross-sectional area of a traditional suture with appendages essentially extending from this core. Since the cross-sectional area of the core of the fiber is sized to be equivalent to a comparative non-barbed suture, the strength is essentially the same as the traditional comparative fiber. The process, as disclosed, relies on the displacement of the entire length of fiber to produce a uniform billet that is to be subjected to punching of the fiber. The punching operation produces a fiber with an oval configuration with extensions from a central core region to ensure that the fiber meets the knot tensile strength requirements for a comparably sized round suture. Due to the large displacement of the entire fiber volume to create a pre-punch billet, the straight tensile strength of the suture body is reduced relative to an unformed extruded suture because of the loss of orientation in the bulk forming process. Additionally, due to the reliance of bulk billet production, the process of forming and cutting cannot be linked into a continuous form and cut process due to the space required for said production.
Although the suture tipping processes of the prior art are adequate for their intended purpose, there are certain deficiencies attendant with their use. The deficiencies include loss of flexibility of the suture in the tipped region, fibrillation of the tipped region, alteration of the suture material yield stress, variability in finished tip geometry and limited applicability to non-braided sutures.
There is a need in this art for novel suture tipping processes and novel apparatuses for producing monofilament sutures having novel tip structures or sections that overcome the disadvantages of the processes of the prior art.
It is an object of the present invention to provide a needle-suture combination, which when used to join tissue, results in the hole pathway in tissue produced by the needle being substantially filled by the monofilament suture joining the tissue.
It is a further object of the present invention to provide a novel process for producing novel suture tip section on a monofilament suture.
It is yet a further object of the present invention to provide a suture having a tip with a novel cross-section.
Still yet a further object of the present invention is to provide a novel apparatus for producing a novel tip section on a monofilament suture.
Accordingly, the present invention discloses methods for producing a surgical suture having a reduced cross sectional area portion from monofilaments of various polymeric materials. The monofilament is subjected to the application of mechanical shaping of the fiber element, optionally coupled with thermal treatment, to produce a deformed cross-sectional portion of the suture body. The deformed suture body region is subsequently subjected to a trimming operation within a punching or stamping die. The reduced section of the suture body region is severed to form a suture having a reduced cross-sectional area end portion. Preferably, each reduced region is severed approximately in the center of the trimmed reduced cross-sectional area portion to form a suture having both ends with a reduced cross-sectional area, although it may be severed in other locations.
An aspect of the present invention is a method of tipping a monofilament surgical suture, consisting of the following steps. A length of monofilament surgical suture is provided having a first end, a second end, and a body having a maximum cross-sectional dimension. The suture is formed to have a formed section having a transition section and a tip section. At least part of the formed section is trimmed to create a trimmed section to provide a suture having a transition section and a tip section, the tip section having a cross-section with an outer perimeter. The maximum dimension of the cross-section of the tip section is less than the maximum cross-sectional dimension of the body of the suture.
Another aspect of the present invention is a monofilament suture having a formed distal tip. The suture has a suture filament having a body, a proximal end, and a distal end. The body of the suture has a maximum cross-sectional dimension. The filament has a tip section on the distal end, and, a transition section between the suture filament body and the tip section. The tip section has a cross-section having an outer perimeter and a maximum dimension. The perimeter has at least two connected segments. The maximum dimension of the cross-section of the tip section is less than the maximum cross-sectional dimension of the body of the suture.
Yet another aspect of the present invention is an apparatus for tipping a monofilament surgical suture. The apparatus has an alignment frame for receiving a monofilament suture strand, preferably having a first clamp and a second clamp. There is a forming press for forming a section of the suture. The press has a base plate, and a slidably mounted upper plate allowing for vertical motion. A lower forming die is mounted to the base plate. The lower forming die has a planar top surface, a forming cavity, and walls extending upwardly from the top surface to form part of the cavity; the walls have a top. An upper forming die is mounted to the upper plate. The upper forming die has a planar lower surface, a forming cavity, and walls extending downwardly from the lower surface to form at least part of the cavity; the walls have a top. Edges extend from the tops of the walls of the upper and lower forming dies. The apparatus has a cutting press. A punching die set is mounted to the cutting press for cutting a formed suture section into a trimmed suture tip. The punching die set has an upper die plate, a lower die plate, and at least one cutting die. The alignment frame is removably mounted to the forming press between the upper and lower forming dies, and the alignment frame is removably mounted to the cutting press between the upper and lower plates of the die set.
Still yet another aspect of the present invention is an apparatus for tipping a monofilament surgical suture. The apparatus has an alignment frame, preferably having a first clamp and a second clamp, for receiving a monofilament suture strand. There is a forming press for forming a section of the suture. The press has a base plate, and a slidably mounted upper plate allowing for vertical motion. A lower forming die is mounted to the base plate. The lower forming die has a planar top surface, a forming cavity, and walls extending upwardly from the top surface to form part of the cavity, the walls having a top. An upper forming die is mounted to the upper plate. The upper forming die has a planar lower surface, a forming cavity, and walls extending downwardly from the lower surface to form at least part of the cavity, the walls have a top. Cutting edges extend from the tops of the walls of the upper and lower forming dies.
These and other aspects and advantages of the present invention will become more apparent from the following description and accompanying drawings.
The novel tip forming process of the present invention is useful with any monofilament suture. Examples of commercially available monofilament sutures that can be tipped with the process of the present invention include PROLENE® suture, PRONOVA® suture, PDS® suture, NUROLON® suture, surgical gut suture, and stainless steel sutures and the like. The sutures may be made from conventional biocompatible polymeric materials, both synthetic and natural materials such as surgical gut. The sutures may be made from absorbable or non-absorbable polymers, or combinations thereof. The absorbable polymers include conventional biocompatible, polymers such as lactide, polylactic acid, polyglycolic acid, glycolide, polydioxanone, polycaproactone, copolymers and blends thereof and the like. The nonabsorbable polymers include conventional biocompatible polymers such as, polyolefinspolyamides (polyhexamethylene adipamide (nylon 66), polyhexamethylene sebacamide (nylon 610), polycapramide (nylon 6), polydodecanamide (nylon 12) and polyhexamethylene isophthalamide (nylon 61) copolymers and blends thereof), polyesters (e.g. polyethylene terephthalate, polybutyl terephthalate, copolymers and blends thereof), fluoropolymers (e.g. polytetrafluoroethylene and polyvinylidene fluoride), polyolefins (e.g., polypropylene including isotactic and syndiotactic polypropylene and blends thereof, as well as, blends composed predominately of isotactic or syndiotactic polypropylene blended with heterotactic polypropylene (such as are described in U.S. Pat. No. 4,557,264 issued Dec. 10, 1985 assigned to Ethicon, Inc. hereby incorporated by reference) and polyethylene including ultra high molecular weight polyethylene and the like and combinations thereof. The sutures may also be made from conventional biocompatible metals and metal alloys including surgical stainless steels, Nitinol, etc.
The sutures that may be tipped using the novel process of the present invention may have a variety of conventional suture sizes ranging from size 5 to size 10-0 The sutures tipped by the novel processes of the present invention are mounted to conventional surgical needles made from conventional biocompatible materials such as metal alloys including surgical stainless steel, tungsten-rhenium alloys, etc. If desired, the surgical needles may be made from other biocompatible materials including ceramics, polymeric materials and composites, etc. The needles will preferably have proximal needle mounting ends having drilled bore holes or channeled features for receiving a distal suture tip and mounting it to the needle. The suture tips may be mounted or secured (i.e., attached) to the proximal suture mounting ends of the surgical needles by conventional attachment techniques including mechanical swaging, gluing, melting, etc. The maximum dimension at the proximal mounting end of the needle after the suture tip has been mounted and secured (i.e., attached) in place will preferably be less than or equal to the maximum diameter of the body of the needle.
Referring to
The novel suture tip 120 of the present invention is further illustrated in
In order to produce the desired tapered tip geometry, the main body or fiber 110 of the suture 100 may be processed through the use of either manual or automated processes. An example of a manual process of the present invention is the following. The process initially involves the use of an alignment frame 300 coupled with the use of a forming press, preferably with thermal capability; and, in a secondary operation a formed section of the suture filament 110 is subjected to a stamping process during which the trimming of the excess material produced during the forming operation is removed from the suture filament body 110 and tip 120 through the use of a matched die set. It is within the scope of the present invention to form the novel suture tips of the present invention utilizing an automatic process as well.
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A magnified partial view of the lower forming die 455 is seen in
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Although the forming and cutting operations have been described as utilizing a separate forming press and a separate punch press, the forming and cutting operations may be performed with a single press apparatus combining the forming components and the punch or cutting components. In addition, when the edge segments 680 are formed as cutting edges, the use of a separate cutting die may not be required to trim the suture tip and/or transition section.
It should be noted that although the apparatus of the present invention as described and illustrated is symmetrical, the apparatus of the present invention may also be designed and constructed to be asymmetrical. In such an asymmetric configuration only a single formed and shaped tip section 120 would be produced on an end of the suture filament 110 to produce the suture 100 having novel tip sections 120. During the asymmetric forming process, the filament section 110 adjacent to tip 120 would be cut to have a plain cut end with diameter 112.
An alternative embodiment for the production of multiple formed fibers on a manual process is also disclosed. Referring to
It can be seen that when utilizing the winding style alignment frame that the subsequent forming and trimming operations require modification. Both the forming die and the trimming die are produced with multiple parallel forming and trimming features that will form and trim each length of fiber within the alignment frame.
While the process of the present invention has been illustrated and described as a manual process whereby the fiber is held in a fixed position within a clamping frame, it is anticipated that the process would be automated utilizing a spool feed type continuous process.
In the spool feed process, the suture fiber to be tipped is fed from a payout spool into the tipping forming unit. The leading end of the fiber is positioned within an indexing head. The indexing head draws the fiber into a heating/forming station. The heating forming station may be configured with a set of forming dies similar to the ones previously disclosed. The dies may be mounted for vertical travel and may optionally be heated. Alternatively, the die may be run only in a cooled configuration. The heating of the fiber may be achieved through the use of a heating source that is located at the same axial position as the forming die station along the length of the suture. The heating source is positioned in a plane that is rotated 90 degrees relative to the plane of the forming station, for example, if the forming station traverses vertically, then the heating station is mounted in the horizontal position to provide heating of the fiber while the fiber is positioned within the forming station. Heating sources include but are not limited to conventional infrared heaters, heated convection mediums such as air streams, or other conductive sources such as heated dies, and the like and equivalents thereof.
The operation of the forming station for some polymeric materials involves the application of heat to the fiber and then the subsequent application of the forming die contact and pressure. The forming die, which may be operating at a lower temperature than the heating source, imparts the reshaping of the fiber while the die contact serves to cool the fiber during the forming step. Alternatively, for materials that have a Tg that is lower than room temperature, the heating of the material may not be necessitated and the forming operation may be conducted at ambient room temperature.
Upon completion of the forming step, the formed fiber is advanced to the trimming station whereby the punch and receiver dies are engaged to trim the excess material from the formed fiber. The trimming die may be configured to cut the fiber near and within the reduced cross sectional region of the tipping blank to provide a finished length of fiber from the previously advanced and tipped fiber.
The fiber is not exposed to elevated tension during the heating/forming operations. The fiber feeding mechanism only advances the indexed amount of fiber through both the payout and take-up mechanism maintaining the same relative motion of the fiber.
The use of the trim form process of the present invention ensures that the tipped sutures are always dimensionally consistent providing an improved degree of precision not capable with bulk processing such as extrusion or roll forming. This dimensional consistency enables repeatable attachment strengths when surgical needles are swaged onto the trimmed tips. Additionally, other features, such as indents, corrugations, opposing partial spirals or raised features, may be formed on the fiber tip geometry. The incorporation of these features may improve the needle attachment strength.
Additionally, fiber fibrillation due to over drawing of the fibers is avoided and the rigidity of the tipped fiber is not increased relative to the main body of the suture.
Although this invention has been shown and described with respect to detailed embodiments thereof, it will be understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention.
