Patent Publication Number: US-2020285448-A1

Title: Suture having a restraining element at an end method and use thereof

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This invention is a continuation-in-part of U.S. patent application Ser. No. 14/887,496, filed Oct. 20, 2015, which claims priority to U.S. Provisional Application No. 62/066,597, filed Oct. 21, 2014, the contents of each of which are incorporated herein by reference in their entireties. 
    
    
     FIELD 
     This invention relates, in general, to the method of producing features on polymer fibers, more particularly on a non-needled end of a surgical suture device through the application of energy, radiofrequency, heat, or ultrasonic energy. More particularly, the suture devices are self-retaining suture devices. The invention further relates to such devices and methods of using the devices. 
     BACKGROUND 
     Various surgical methods employing sutures have been used in the past for closing or binding together wounds in human or animal tissue, such as skin, muscles, tendons, internal organs, nerves, blood vessels, and the like. More specifically, the surgeon may use a surgical needle with an attached conventional suture (which can be a smooth monofilament or can be a multi-filament) to pierce the tissue alternately on opposing faces of the wound and thus sew the wound closed. Whether the wound is accidental or surgical, loop stitching is the method often used, especially for surface wounds. The surgical needle is then removed and the ends of the suture are tied, typically with at least three overhand throws to form a knot. 
     Since the time of their conception, self-retaining sutures (sometimes referred to as barbed sutures), which are generally of the same materials as conventional sutures, have offered numerous advantages over closing wounds with conventional sutures. A self-retaining suture includes an elongated body that has one or more spaced retainers, which project from the body surface along the body length. The retainers are arranged to allow passage of the self-retaining suture in one direction through tissue but resist movement of the self-retaining suture in the opposite direction. Thus, the main advantage of self-retaining sutures has been the provision of a non-slip attribute. Accordingly, self-retaining sutures do not have to be knotted at the completion of the stitch, the requirement for a surgical follower to maintain tension on a continuous stitch, as is done in the application of conventional sutures, is also eliminated. However, like a conventional suture, a self-retaining suture may be inserted into tissue using a surgical needle. 
     While the retainers provide the strength necessary to prevent the fiber from slipping backwards and eliminates the need for tying a knot at the termination point of the stitch, the initial placement of the stitch may require the use of some means to anchor the suture in the local tissue. In response to this need, stitch initiation features have been incorporated into some self-retaining devices. Stitches may be initiated through the creation of a typical surgeon&#39;s knot or through the addition of clips or other mechanical clamping devices appended to the suture. Stitches may be initiated through the use of integral looped ends, tabs, buttons and reverse retainer elements. However, many of these anchoring means suffer from defects or are burdensome or costly to prepare, and thus the present invention seeks to provide an improved anchoring means. 
     For example, U.S. Patent Publication No. 2005/0267531 discloses a barbed suture device that is produced with a variety of anchoring elements attached to the non-needled end of the device. However, preparing these anchoring elements requires multiple secondary operations with great precision in the production of the anchors and the subsequent attachment to the fiber. This increased demand for secondary operations increases the cost to produce the device. U.S. Patent Publication No. 2009/0248067 discloses an anchoring device with a looped end with barbed type projections, while U.S. Pat. No. 8,403,017 similarly discloses a suture having a looped end. 
     U.S. Patent Publication No. 2006/0116718 discloses a prosthetic screen tacking device that is produced with a perpendicular foot at one end, while U.S. Pat. No. 5,964,765 discloses a single-piece soft tissue fixation device that includes an elongated element terminating in a tip at one end and a receptacle at the other end which can be bonded with each other in a welded joint. The device is made of a heat-bondable, biocompatible material that can be ultrasonically or thermally welded. The tip and receptacle of the device can be textured or contoured or otherwise complementarily configured to promote mutual engagement prior to and during bonding. It should be noted, that the receptacle component is not intended to provide the stitch initiation functionality, but rather to provide a replacement for a knot with a welded joint of the looped suture. Producing these geometries, however, is difficult. 
     U.S. Patent Publication No. 2003/0149447 discloses a barbed suture device that is produced with a stopper on the non-needled end. It is proposed that the device can be produced through injection molding, cutting ribbon or stamping ribbon stock to produce the desired shapes. These methods, including the use of injection molding, however, limits options of materials given the required melt viscosity, and through any of these methods, may ultimately result in weaker sutures. U.S. Pat. No. 8,297,330 discloses a welded end effector, in which a knot is first tied in the suture, and subsequent fusing the knot to form a stopper. This method is inefficient since it requires the initial formation of a knotted structure, and then the application of energy may result in notches or dents due to the inherently open initial knotted structure. Similarly, U.S. Pat. Nos. 8,323,316 and 8,333,788 each disclose the use of a knotted end effector, where the end effector includes a knot including a plurality of throws. The initial formation of a knotted structure is to be avoided through the present invention. 
     PCT Publication No. WO 2012/004758 discloses a suture thread that is produced with a stopper on the non-needled end of the fiber. It is proposed that the stopper may be molded or heated and the free end of the suture fiber is inserted into the molten polymer to seal the fiber to the stopper. This method of production requires the addition of the secondary component to the base fiber in a molten condition and the thermal exposure to the molten polymer may result in a loss of strength in the base fiber due to elevated temperature exposure. 
     While the aforementioned publications have attempted to improve sutures by preparing end effectors, each of the attempts have been either ineffective, inefficient, or pose processing problems. There remains a need to produce a stitch initiation feature that does not require significant secondary processing steps, such as the formation of a knot, or the addition of secondary components, such as addition of molten material, and which results in a strong anchor to hold the suture in place. 
     SUMMARY 
     The present invention provides sutures, methods of making sutures, apparatuses for making sutures, and methods of using sutures, the sutures including a termination feature at its distal or trailing end. The invention may provide a suture having a first end and second end and a length therebetween, with a termination feature at the second end, and may include a plurality of retainers formed on the surface of the length of suture. The termination feature includes a coiled portion of a suture that has been subjected to exertion of energy to weld the coil into a stable anchor for the suture. 
     The suture may be formed by various methods, including one method of forming a suture including the steps of providing a length of suture material, the suture having a first end and second end and a length therebetween, and the suture including a plurality of retainers formed on the surface of the length of suture; winding the second end about a winding pin to form a coil, such that the coil does not become entangled; and subjecting the coiled second end to application of energy, the energy being sufficient to melt at least a portion of the coiled second end and form a solid unitary termination feature. 
     The method may include a method of continuously forming at least two sutures, each suture having a termination feature at a distal end and formed from a continuous line or strand of suture material. This method may include the steps of: providing a suture fiber having a first end and a second end, and an axial length suitable to form a termination feature-containing suture, the suture fiber being contained in such a fashion that the first end of the suture may be pulled though a winding pin without damage to the suture fiber; inserting the first end of the suture through a first end of a winding pin and out the second end of the winding pin, where the winding pin is disposed within an open interior of a welding die; gripping the first end of the suture with a gripping element, and pulling the first end of the suture in approximately a 90 degree angle with regard to the central axis of the winding pin; causing the suture to be wound about the outside of the winding pin so as to create a coil of suture; moving a welding horn into contact with the coil of suture; applying energy to the coil of suture so as to deform the coil of suture; allowing the deformed coil of suture to solidify to form a termination feature; and may additionally include the step of severing the suture at a location between the termination feature and the second end of the suture. 
     An apparatus may be included, which is used for forming a suture having a termination feature. The apparatus may include, among other components, a welding horn having a welding tip; a welding die having an open interior sized to be similar to the welding tip; and a winding pin disposed within the open interior of the welding die, the winding pin having a first end and second end and an open axial center connecting the first end and second end. The apparatus may further include a gripping element for grasping the suture material and pulling it to a desired length during the formation process. 
     Another aspect of the invention includes a method of forming a suture including the steps of: winding a second end of a suture material having a first end and a second end and a length therebetween about a winding pin to form a coil, such that the coil does not become entangled, where the winding pin includes: a first cylindrical component having a central axis defining an open interior, the open interior being defined by a side wall and terminating in an open end, the first cylindrical component having a slot extending through the side wall extending from the open end to a termination point axially offset from the open end; and a second cylindrical component having a central axis defining an at least partially open interior, the open interior being defined by a side wall and terminating in an open end, the second cylindrical component having a slot extending through the side wall extending from the open end to a termination point axially offset from the open end; the first and second cylindrical components being in concentric configuration with each other, where the first and second cylindrical components may be independently rotated with respect to each other; subjecting the coiled second end to application of energy, the energy being sufficient to melt at least a portion of the coiled second end and form a solid unitary termination feature. 
     In other aspects of the invention, there is an apparatus for forming a suture having a termination feature including: a welding horn having a welding tip; a welding die having an open interior sized to be similar to the welding tip; a winding pin, where the winding pin includes: a first cylindrical component having a central axis defining an open interior, the open interior being defined by a side wall and terminating in an open end, the first cylindrical component having a slot extending through the side wall extending from the open end to a termination point axially offset from the open end; and a second cylindrical component having a central axis defining an at least partially open interior, the open interior being defined by a side wall and terminating in an open end, the second cylindrical component having a slot extending through the side wall extending from the open end to a termination point axially offset from the open end; the first and second cylindrical components being in concentric configuration with each other, where the first and second cylindrical components may be independently rotated with respect to each other. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
         FIG. 1  depicts one exemplary suture of the present invention, which includes a termination feature at its distal end. 
         FIG. 2  depicts one embodiment of an assembled welding horn and welding nest. 
         FIG. 3  depicts an exploded view of the components of a welding horn, which may be useful in the present invention. 
         FIG. 4  depicts a welding die and winding pin assembly in separated configuration. 
         FIG. 5  depicts one step in feeding a suture into the welding die assembly. 
         FIG. 6  depicts another step in feeding a suture into the welding die assembly. 
         FIG. 7  depicts the suture fed into the welding die assembly. 
         FIG. 8  depicts the suture in wound fashion in the welding die assembly. 
         FIGS. 9 and 9A  depict the suture in wound fashion with welding die separated from winding pin. 
         FIG. 10  depicts a welding horn in the downward, welding position. 
         FIGS. 11A-11D  depict various termination features. 
         FIG. 12  is a suture coil formed by an embodiment of the present invention. 
         FIG. 13  is an alternative winding pin. 
         FIG. 14  depicts a winding pin of  FIG. 13  in use in three sequential steps. 
         FIG. 15  shows a winding pin with slots aligned. 
         FIG. 16  shows a winding pin with fiber loaded therein. 
         FIG. 17  depicts the winding pin in a winding position with fiber loaded therein. 
         FIG. 18  shows a partial sectional view of a winding pin of the present invention. 
         FIG. 19  shows a semi-transparent view of a winding operation of the present invention. 
         FIG. 20  shows an alternate embodiment of a winding pin drive element. 
         FIG. 21  shows an alternate form of winding a fiber of the present invention using a winding bar. 
         FIG. 22  shows a partially transparent view of the winding operation of  FIG. 22 . 
         FIG. 23  shows a wound fiber prepared by the operation of  FIG. 21 . 
         FIG. 24  shows an alternate embodiment of a winding device and welding cartridge of the present invention. 
         FIG. 25  shows a welding die useful in the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention relates to sutures having a suitably strong end effector or termination feature at a non-needle end of the suture device. More particularly, the suture may include at least one retainer along its axial surface and may more desirably include a plurality of retainers. The suture may therefore be known as a self-retaining suture, such as those known and described in U.S. Patent Publication No. 2005/0267531 and U.S. Pat. No. 8,100,940, the entire contents of each of which are incorporated herein by reference. The retainers, if used, may be formed by any desired means, including cutting, shaping, molding, or other retainer-forming means. The description below will reference a suture having retainers formed on its surface, but a suture with no retainers (e.g., an “unbarbed” suture) may be used in the present invention. 
     The suture device may include multiple strands that are interconnected and therefore may include more than one trailing (or non-insertion, or non-needle end). Any or all of the trailing ends may include a termination feature of the present invention. As used herein, the terms “termination feature”, “end effector” and “anchor” may be used interchangeably, and refer to the anchoring device at the trailing end of a suture. The present anchors offer a number of improvements over the prior attempts to prepare an anchoring element, including improved strength, and easier/less costly manufacturing parameters. The present invention forms an anchor without requiring the addition of materials (such as molten materials or other added elements) and also forms the end effector without the initial step of forming a knot prior to welding. The present anchor provides a strong fused termination device at the non-needle end of the suture, which adds stability and strength to the device. Further, the present invention allows for a number of varying shapes depending upon the desired use. The invention requires minimal thermally induced fiber property losses, since the formation need not expose the device to elevated temperature conditions. The present invention is capable of being formed in a continuous in-line processing methodology, which reduces manufacturing costs and allows repeated suture formation with ease. 
     In one embodiment of the present invention, a method of forming an anchor at a non-needle end of a suture is provided. The suture material includes at least one polymeric fiber, which has a first end, second end, and a body therebetween, where the body extends along a central longitudinal axis. The suture may include any material or combinations of materials that are suitable for use in surgical procedures, including polymeric and/or metallic materials. Further, the material of the suture desirably should include weldable materials, such as those materials that can be melted and/or deformed under the presence of energy, including ultrasonic energy. The suture material may be absorbable or non-absorbable, and may include, for example, polydioxanone, polyglycolic acid (PGA), polylactic acid (PLA), polycaprolactone (PCL), trimethylene carbonate, and copolymers thereof, as well as polypropylene, polyvinylidene fluoride, polyamide (nylon), polyester (polyethylene terephthalate), and other commonly used suture-forming materials. 
     The resulting suture has a length of suture extending between its first and second ends along its central longitudinal axis, and may have any cross-sectional configuration, including circular, elliptical, triangular, square or diamond-shaped, and the like. The outer surface of the suture body may have one or more retainers formed thereon, such as cut retainers as explained above. The suture may be of substantial length and stored in a spool or other housing which allows for easy removal of the suture strand without entangling the suture. For example, a spool of suture may include sufficient length of suture to form at least five termination feature-containing sutures, or at least ten termination feature-containing sutures, or at least fifty termination feature-containing sutures. The first end of the resulting termination feature-containing suture is the “insertion” or “leading” end, and may include a component to allow for insertion into tissue, such as a needle. The second end is the trailing or distal end. The first end (the insertion end) may be formed by severing a continuous length of suture material either before or after the formation of a termination feature of the present invention, and may include a needle secured thereto. Thus, at least two implantable sutures each including a termination feature (anchor) can be formed from a continuous length of suture formed in accordance with the methods described herein. Alternatively, the termination features may be formed on an individual length of suture, without the need for cutting the suture during the termination feature forming process. 
     The resulting termination feature-containing suture includes, at its second or trailing end, a termination feature. The termination feature generally includes a wound coil of suture, which has been subjected to energy sufficient to weld the suture coil to itself. The resulting termination feature has improved strength and can be used as an anchor to hold the suture in place after insertion in tissue, where the termination feature abuts the tissue into which the suture is inserted, providing an anchoring effect. One particular embodiment of the termination feature includes a termination feature which is free of any other components added to it, such as adhesives or strengthening agents. This embodiment may thus provide a termination feature that consists of the suture material and no added elements or components. The termination feature may be any shape, and may have an open interior (an “eyelet”) or may have a closed structure. As noted above, the termination feature avoids the step of first forming a knotted structure and then subjecting that knotted structure to energy. The desired termination feature is formed into a coil, desirably while within the forming apparatus, and then that coil is subjected to energy to cause sufficient welding. It is understood that avoiding the need for initially forming a knot is not only more efficient but results in an anchor that is structurally different than knotted sutures. 
     In one method of forming a suture with a termination feature, the polymeric suture fiber is inserted in a cavity which contains a slotted pin element. The fiber is engaged with the slotted pin element within the cavity. Rotation and optional axial movement of the slotted pin element causes the fiber to wind about the circumference of the pin within the cavity forming a spiraled coil of fiber. Once a sufficient length of fiber has been wound into the cavity into a spiraled coil, the resulting coil of fiber is subjected to an energy source, such as ultrasonic forces. The transference of energy is achieved through the contact of a contact unit interface with the coiled material, and the coiled fiber is converted into fused polymer geometry having the general shape of the contact unit interface. The coiled fiber is preferably not entangled, that is, there are not overlapping coils such that the coil cannot be unwound without forming knotted regions. In the present invention, after the coil is formed, if the suture is pulled in either direction, the coil will unwind without knot formation. 
     The contact unit interface may include a welding horn and/or die. If desired, the suture material may be cut either prior to or after the formation of the end effector. In some methods, any excess suture material is severed prior to welding the termination feature. After the termination feature is formed, the remaining length of suture may be cut at a desired location, providing the length of suture with termination feature on its second end. This end that is left after cutting may be a cut that forms the leading end of the suture, onto which a needle or other insertion device may be secured. 
     The present invention also includes methods of packaging the inventive sutures, such that the suture and/or end effector does not become tangled or otherwise stuck to the packaging material. 
     As will be described in greater detail below, one type of an apparatus to form the termination feature of the present invention includes components such as a welding horn and base, the base including a winding pin and welding die. As used herein, the terms “down” or “downward” shall refer to the direction moving from the top of the welding horn toward the base of the winding post. The terms “down” and “downward” can apply to any component in the invention. Similarly, the terms “up” or “upward” shall refer to the direction from the base of the winding post to the top of the welding horn. The terms “up” or “upward” similarly can apply to any component in the invention. For example, if welding horn ( 200 ) is located in an “up” position, this means that the welding horn  200  has been moved in a direction that moves away from the winding post and welding die. Likewise, if the welding horn  200  is located in a “down” position, this means that welding horn  200  has been moved in a direction towards the winding post and welding die. 
     Referring to  FIG. 1 , one example of a self-retaining suture device  100  is illustrated. The suture device  100  in  FIG. 1  includes a monofilament fiber  110 , but it is understood that multi-filament sutures, including braided sutures and sutures having concentric filaments may be used. In  FIG. 1 , the suture  100  has been produced with a triangular cross section, but other cross-sections may be useful, including, for example, a circular cross-section. The monofilament fiber  110  has an outer surface, and may include a plurality of retainer elements  140  that have been cut into or otherwise formed on the outer surface of the fiber  110 . Methods of cutting retainers  140  into a suture  100  are well-known, and include methods described in U.S. Pat. No. 6,848,152, the content of which is incorporated by reference herein in its entirety. Retainer elements  140  are not required, and the sutures of the present invention may be free of retainers on the suture. 
     The suture  100  includes first, leading end  115  (which may be termed the “proximal end” or “insertion end” and may optionally include a needle  130  secured thereto) and second, trailing end  150 . The trailing end  150  of the fiber  110  is produced with a termination feature  120  (also referred to as an “end effector” or “anchor”), which is formed by the techniques outlined in this disclosure. The termination feature  120  desirably consists of the suture material itself, but may optionally include additives or strengthening materials before or after welding. In embodiments where the termination feature  120  is free of additives or strengthening materials, it is understood that trace materials of contaminants may be present, but that other materials other than the suture material itself are not intentionally added. 
     The termination feature  120  may be produced in a variety of geometries, including having a circular, triangular, rectangular (including, for example, diamond or square shaped), or other geometric cross section. Edges and corners of the termination feature  120  may be rounded or smooth, if desired. The termination feature  120  may have any desired thickness, and may have varying degrees of thickness throughout the termination feature  120  if desired. Further, there may be a tapered section extending from the outer surface of the suture fiber  110  to the termination feature  120 . Various geometric configurations may be considered depending upon the use of the suture  100 , including the location of placement in a patient, the type of tissue to be secured and the necessary strength of the fixation. In soft tissues, for example, where there is the potential for dilation of the suture tract, it may be desired to provide a termination feature  120  with a large bearing surface, oriented perpendicular to the central axis of the fiber  110 . The termination feature  120  abuts the tissue into which the suture is inserted, having an anchoring effect. 
       FIG. 1  shows such a device, having a termination feature  120  that is oriented so as to be perpendicular to the central axis of the fiber  110 . That is, the termination feature  120  has a major diameter that is perpendicular to the central axis of the suture fiber  110 . The termination feature  120  may have a generally flat disk-like shape or it may have a curved distal end  160 , as can be seen in  FIG. 1 . In firm tissues, it may be desirable to produce a termination feature oriented such that its diameter is substantially parallel to the axis of the fiber  110 , such as a “lollipop-type” configuration seen in  FIG. 11B . In some instances, it may be desirable to lock the suture back onto itself through the use of a looping mechanism, or with a termination that provides an engagement feature or open eyelet through which a suture may be passed. 
     The suture  100  may have any desired length and cross sectional diameter, including those described in greater detail below. It is particularly desirable that the cross-sectional diameter of the termination feature  120  be greater than the largest measured diameter of the suture  100 . Thus, the ratio of the diameter of the termination feature  120  to the largest diameter of the suture  100  should be greater than 1.1:1, and may be up to about 10:1. More desirably, the ratio of the diameter of the termination feature  120  to the largest diameter of the suture  100  may be about 4:1 to about 10:1. The size and shape of the termination feature  120  will be described in greater detail below, but it is useful to provide a termination feature  120  that is large enough to act as a suitable anchor, while at the same time having a termination feature  120  that is sufficiently small to be manufactured and packaged appropriately. As used herein, the term “diameter” does not necessarily refer to a circular cross-section, and the term “diameter” can refer to the largest distance from opposing ends of device, such as opposing corners of a square. 
     The termination feature  120  is desirably composed of the suture fiber  110 , which has been wound and subsequently formed into a solid structure, such as through the application of energy. As noted, it is particularly preferred that the termination feature  120  be free of any additional materials, however, it may be desired to include one or more compositions that are capable of filling in any potential gaps in the wound fiber and/or strengthen the final welded termination feature  120 . As will be described below, the fiber  110  is wound into a coil while the suture is contained in the welding apparatus, and is then welded to form the termination feature  120 . In this method, there is no pre-forming step, such as the formation of a knot or other structure, prior to winding and welding. The wound portion of the fiber  110  may include a plurality of retainers  140  or it may be free of retainers  140 . 
     Referring to  FIGS. 2 and 3 , an apparatus for manufacture of the suture  100  and termination feature  120  is depicted. The apparatus may include a welding horn  200  and a welding nest  300  (welding nest  300  may be considered the “base” of the welding apparatus). The welding horn  200  is designed to mate with the welding nest  300  to provide the termination feature  120  as desired. The welding nest  300  may include a raised mounting plate  301  that is mounted to a top side of support pillars  302 . In the depicted Figure, two pillars  302  are shown, but more than two support pillars  302  may be used if desired. Each pillar  302  has an upper end and bottom end, the upper end being secured to the mounting plate  301 . The bottom end of the pillar  302  is mounted to a nest base plate  304 . The pillars  302  may be detachable from either the mounting plate  301  or the nest base plate  304 . The nest base plate  304  may include a means to attach the welding nest  300  to a secure surface for welding. For example, the nest base plate  304  may include a series of through bore mounting holes  303  that enable attachment of the welding nest  300  to a supporting structure during use. 
     Referring to  FIG. 3 , a number of components in the welding assembly are depicted. This Figure includes a number of individual components that are described herein in detail, but it is understood that modifications of assembly may alter or remove one or more of the components described herein without modifying the function and use of the assembly. The assembly seen in  FIG. 3  includes an ultrasonic horn  201 , which is a length and design that is suitable to the frequency of the particular ultrasonic generator that has been selected. Frequencies of from about 15 kHz to about 40 kHz, and more specifically about 20 kHz may be useful in forming the termination feature  120  of the present invention, and the ultrasonic horn  201  of the invention should be suitable to deliver the intended frequencies. The ultrasonic horn  201  may be produced with a threaded bore  202  at its upper end that is utilized to attach the horn to an ultrasonic welding booster/transducer assembly (not shown). The horn  201  has an axis that runs through its length from the threaded bore  202  to an ultrasonic horn tip  205 . 
     The horn  201  may be any desired shape or configuration, including a cylindrical shape, or having a cross-section that has varying geometry. Preferably, the horn  201  is tapered, having a larger cross-sectional diameter at its upper end and tapering to a smaller cross-sectional diameter at its lower end. The horn  201  may include a stepped elliptically shaped cylindrical wall  203 . In a preferred embodiment, the ultrasonic horn  201  is produced with a reduced diameter shoulder  204  that is intended to engage with an insert ring  210  during the welding process. The insert ring  210  is desirably polymeric material, but may be metallic or include other materials if desired. An ultrasonic horn tip  205  is disposed at the lower end of the horn  201 . The ultrasonic horn tip  205  is sized and shaped to fit within a receiving bore  222  of a welding die  220 . The horn tip  205  and the welding die  220  are sized and shaped so as to provide the desired structure and geometry of the termination feature  120 . In use, the coiled suture fiber is placed between and within the horn tip  205  and welding die  220 , and then energy is applied. 
     It may be desired to include an elastic element in contact with the welding die  220 , such as beneath the welding die  220 , so as to allow the welding die  220  to remain engaged with the horn tip  205  during the application of energy. As the horn  201  oscillates vertically, the spring force acting upon the die helps to maintain the welding die  220  in contact during the weld cycle. It has also been found that if the welding die  220  remains in substantially tight engagement with the horn  201  during the cycle, that the welding of the upper coils of fiber may be diminished and the weld that is produced is similar in appearance to those produced within a cavity in the face of the horn. Preferred welding conditions are achieved through the addition of a frictional drag component to the cage leg elements. The necessary frictional drag component of die movement ensures that the welding die  220  does not vibrate in unison with or in exact frequency with the ultrasonic horn  201 . While the elastic element and drag elements may be achieved through the use of elastic material and ball plungers, the use of springs, air or other springs, as well as spiral displacement of the welding die  220  or the use of external damping elements such as brake or shock absorber style elements are also feasible. In one embodiment, the device includes an elastic element in combination with a separate damping element, which allows the welding die to vibrate or otherwise move out of synchronization with the ultrasonic horn during the cycle. 
     The welding die  220  is placed in a location that may secure the suture fiber  110  between it and the horn tip  205  in use. Thus, the welding die  220  may be disposed in a coaxial configuration with the horn  201 , such that if the horn  201  and/or the welding die  220  are moved in an axial fashion (e.g., up and down), a suture fiber  110  may be placed into the space therebetween. 
     The welding die  220  may include a receiving bore  222  that is sized and shaped to match the desired edge shapes and sizes that are desired for the final termination feature  120  to be formed. The external size and shape of the ultrasonic horn tip  205  is sized and shaped to mate with the receiving bore  222  so as to form the final termination feature  120 . Additionally, the welding die may include a central counter bore  224  that is sized to receive insert ring  210 . As can best be seen in  FIG. 4 , the outer diameter of the insert ring  210  is sized to fit tightly into the central counter bore  224  of the welding die  220 . The insert ring  210  and/or the welding die  220  may include a feature or series of features on its underside (not seen in  FIG. 4 ), which will engage with posts  252  of guide unit  250  for secure attachment. For example, the welding die  220  may include a plurality of through bores  221  as seen in  FIG. 3 .  FIG. 4  shows the relationship between welding die  220  and winding pin  260 . As can be understood, the shapes and sizes of the die and horn components will dictate the resulting shape and size of the termination feature  120 . 
     The various components described above may be made from any desired materials, provided that the materials selected are suitable for withstanding ultrasonic frequencies and delivering to the suture  100  to provide the termination feature  120 . For example, the insert ring  210  may be manufactured of any suitable polymer material including polyolefins, polyesters, pvdf, Teflon based materials, PEEK and other suitable polymers. Alternatively, the insert ring  210  may be made from metallic materials with a lower hardness than the material utilized to produce the ultrasonic horn  201 , such as bronze, aluminum, and other metallic materials having a lower hardness than the ultrasonic horn  201 . The ultrasonic horn  201  may be made from metallic materials, such as titanium, aluminum, or stainless steel. 
     The welding nest assembly  300  includes a fixture plate  240 , which is placed and held within the mounting plate  301 , and may be removable or may be secured in the mounting plate  301 . The fixture plate  240  may include a central counter bore  242 . The welding nest  300  may also include a post insert plate  230 . The outer diameter of the post insert plate  230  is sized and shaped to fit snugly within the counter bore  242  located within the fixture plate  240 . The post insert plate  230  may be removably or permanently secured to the fixture plate  240  and may include a series of through bores  241  to receive posts  252  of guide unit  250 . The post insert plate  230  may additionally incorporate a central through bore  233 . The central through bore  233  is sized to slidably receive a winding pin  260 . 
     The fixture plate  240  may be produced with a means to secure the fixture plate  240  to the mounting plate  301 . For example, as can be seen in  FIG. 3 , fixture plate  240  includes several through threaded bore features  243  that are located about the perimeter of the plate  240 . These threaded through bores  243  are utilized to attach the fixture plate  240  to the mounting plate  301 . The central portion of the fixture plate  240  may be produced with a through bore for passage of the winding pin  260 . 
     The assembly may optionally include a guide unit  250 , which may include a through bore  251  that is slidably engageable with the winding pin  260 . Extending from the upper surface of the guide unit  250  are a plurality of posts  252  that may have a shouldered or larger diameter region  253 . The posts  252  are arranged and sized to mate with through bore holes  243  in the fixture plate  240 . In some embodiments, there may be four posts  252 , but any desired number of posts may be included. The shouldered or larger diameter region  253  of post  252  is desirably larger in diameter than the through bore holes  243  in the fixture plate  240  to provide a secure hold. The winding pin  260  may have a tapered inner through bore  262 . Further, the winding pin  260  has a first end  263  and a second end  261 , the first end  263  having a larger outer diameter than the second end  261 , and the first end  263  optionally being coupled with a winding knob  270 . The second end  261  of winding pin  260  may be slidably engaged with the central opening of the post insert plate  230 . 
       FIGS. 4-10  show examples of a useful welding die, post insert, and winding pin, as well as depict one method of the formation of a termination structure  120  of the present invention.  FIG. 4  illustrates a welding die assembly  220  in an “up” position relative to the welding post  233  and the winding pin  260 . The winding pin  260  may have a hollow tapered bore  262  that exits at the second end  261  of the pin. The hollow interior of the winding pin  260  is desirably sized to have a larger diameter than the diameter of a suture fiber  110  to be used. The suture fiber  110 , prior to formation of a termination feature, can therefore be fed through the interior of the winding pin  260  without restriction or damage. The internal diameter of the pin  260  may be tapered, ending at a notch  402  at the second end  261  of the pin  260 . The interior diameter of the pin  260  may be smaller at the second end  261  of the pin  260  than on the first end  263  of the pin. This inner taper may be useful in enabling smooth feeding of a suture fiber into the pin  260 . Welding die  220  may have a partial channel or notch  401  on its downward side, with the channel  401  being sized sufficiently to allow passage of a suture fiber  110  therethrough. 
     Referring now to  FIG. 5 , one method of feeding a length of suture into the winding pin is depicted. In this embodiment, a length of suture  510  may be inserted through the first end  263  of the winding pin  260  and fed “upward” towards the second end  261  of the winding pin  260 . Since there is no pre-formed knot or other structure, the suture  510  is capable of being fed through winding pin  260  and out second end  261 . The suture  510  may then be bent as illustrated, and the first end  501  of the suture  510  may be passed through the channel  401  and through the notch  402 . Second end  502  of the suture  510  remains sticking out through the first end  263  of the winding pin  260 . Although the die  220  is illustrated in a separated condition from the winding knob  270 , the die  220  may be located in a nested position on top of the winding knob  270 . 
     Referring now to  FIGS. 6 and 7 , the rotation of the winding pin  260  is illustrated. It should be noted that the welding die  220  is illustrated in the “raised” position only for the sake of providing visualization of the suture fiber  510  as it would form a wrapped geometry  601  when inside of the welding die  220 . In use, the welding die  220  may be lowered (or, alternatively, the winding pin  260  raised) so that the winding pin  260  is located within the interior of the welding die  220 .  FIG. 7  illustrates the position of the winding pin  260  relative to the top of the welding die  220  during winding, with the welding die  220  in the “down” position for the winding operation to be conducted. The winding pin  260  is disposed within the interior of the welding die  220 , such that the second end  261  of the winding pin  260  is nearly flush with the upper region of the welding die  220  during the winding operation. This flush configuration and the location of the winding pin  260  in this configuration is identified as reference numeral  701 . The suture fiber  510  wrapping is illustrated as a dashed line within the welding die  220 . In this configuration, the winding pin  260  and welding die  220  are in the “winding position”. As can be seen, the first end  501  of the suture fiber  510  extends out through the channel  401  and notch  402 . Although not seen in  FIG. 7 , the second end  502  of the suture extends through the bottom of the winding pin  260 . 
     Referring now to  FIG. 8 , the first end  501  of the suture fiber  510  has been wound in the welding die  220  and is illustrated as coil  801  wrapped around the winding pin  260 . Alternatively, the first end  501  may be left partially inside of the channel in the welding die  220  and may be trimmed from the coil  801  either before application of energy to the coil  801 , during the down stroke of the ultrasonic horn  201 , or after welding is complete. Similarly, the second end  502  of the suture may be cut at any desired time in the welding process or it may remain unsevered until the welding is complete. The length of suture  510  desired is achieved by cutting the second end  502  at a desired length away from the termination feature  120 . More desirably, the second end  502  is cut after welding is complete, thus forming a resulting suture having a termination feature. 
     Referring now to  FIG. 9 , the coiled fiber  801  is illustrated, after winding is complete. The welding die  220  has been lifted in the Figure to allow viewing of the coil  801  only, but it is noted that in use, the welding die  220  would not be removed during use as the interior of the welding die  220  helps to maintain the coil  801  in its coiled configuration. As seen in  FIG. 9 , the winding pin  260  has been lowered to a “welding position” (identified by reference numeral  901 ) by retracting the winding pin  260  in the “downward” direction. The winding pin  260  is lowered a sufficient length, such as until the notched end  402  of the winding pin  260  is substantially flush with the top surface of the post insert plate  230 . In an alternative embodiment, the winding pin  260  may remain at least partially in an “up” position relative to the post insert plate  230 . This alternative arrangement may be useful, for example, in creating an open eyelet structure within the termination feature. 
     Referring now to  FIG. 10 , the ultrasonic horn  201  is lowered into the welding position and is subsequently energized. The operation illustrated in this figure involves the downward motion of the welding die  220  due to contact with the shoulder  204  of the horn  201  with the insert ring  210  during the welding cycle. Therefore, the welding die  220  may be movable relative to the welding post  270 . This mode of action enables the adjustment of a gap between the ultrasonic horn tip  205  and the top of the post insert plate  230 . The ultrasonic horn tip  205  may be at least substantially, and desirably fully within the open interior of the welding die  220 , however, the wall of the tip cylinder  205  does not necessarily contact the inner bore  211  of the insert ring  210 . In preferred embodiments, a clearance of about 0.0005-0.002 inches between the side wall of the horn tip  205  and the interior wall of the insert ring  210  is desired to prevent contact. 
     Thus, in the aforementioned embodiment of the method of formation of a termination structure  120 , an assembly including a welding die assembly  220 , winding pin  260  extending therethrough and axially movable through the welding die assembly  220 , and welding horn  201  are provided. In this embodiment, the welding horn  201  and welding die assembly  220  are moved so as to be separated from each other, and winding pin  260  is contained within the middle open space of the welding die assembly  220 . A suture fiber  510  is fed through the inner open interior of the winding pin  260  such that the suture fiber  510  extends out of the second end  261  of the winding pin  260 . The winding pin  260  is rotated axially and/or the suture fiber  510  is moved circumferentially about the outside of the winding pin  260  to create a coil  801 . A winding knob  270  may optionally be used to effectuate winding. 
     After the coil  801  is formed, the winding pin  260  may be axially moved in a downward position (e.g., moved in a direction away from the welding horn  201 ) or it may remain in the “up” position. The welding horn  201  and welding die assembly  220  are brought closer together, such that the coil  801  is entrapped within the space provided by the welding horn  201  and welding die assembly  220 . Excess suture fiber  510  may be trimmed from the coil  801  either before application of energy to the coil  801 , during the down stroke of the ultrasonic horn  201 , or after welding is complete. Energy is applied to the coil  801  and optionally pressure and/or temperature increases may be applied to the coil  801  as well. The suture fiber  510  is allowed to at least partially melt and then the energy (and optional pressure and temperature) are removed, and the now-welded coil  801  is allowed to solidify. The resulting suture  510  now has a suitable termination feature  120  on its end. The suture fiber  510  may be severed at any desired location to provide a desired length of suture. 
     The welding end of the ultrasonic horn tip  205  is designed to have any of a number of geometries, including flat, conical, spherical convex, spherical concave and polyhedral geometries. It may alternatively have a textured configuration. It has been found that the use of a spherical concave tip design provides lateral compaction of the coiled fiber  801  during the welding cycle. The coiled fiber orientation, coupled with the lateral compaction, provides the transmission of the ultrasonic energy through the tangential contact edges of the coiled fiber  801  to form an essentially solid end termination for the suture  510 . In contrast to previous methods in which a knot is first tied in the suture material, this mode of welding restricts the creation of crossing fibers or of a random orientation of fibers, which can create undesirable notch effects in the termination feature. The inventive methods thereby increase tensile strength of the resulting termination feature  120  and provide a structurally different termination feature  120 . In addition, the present methods avoid the need for pre-welding steps such as tying a knot, which not only avoids the risk of malfunction, but also allows for easier and quicker processing of sutures. 
     As noted above, the termination feature  120  may be produced in multiple geometries, depending upon the purpose and desired look and feel. The size and shape of the termination feature  120 , as well as any surface texture or configuration, may vary depending upon the desired suture. Various termination feature configurations are depicted in  FIGS. 11A-11D .  FIG. 11A  shows a termination feature  1000  having a large tissue bearing surface. The termination feature  1000  includes a raised surface  1010 , such as a bulbous or convex surface, and includes a round circumference  1020 . The embodiment of  FIG. 11A  has an orientation that is perpendicular to the longitudinal axis of the suture  1030 . The suture  1030  extends substantially from the center of the termination feature  1000 .  FIG. 11A  may be modified such that the suture  1030  extends from a side of the circumference  1020 , giving a “lollipop” type configuration. The thickness and the cross-sectional diameter of the circumference  1020  of the termination feature  1000  may vary as desired. 
       FIG. 11B  shows an alternate configuration with a raised surface  1110 , but the termination feature  1100  has a square or rectangular circumference  1120 . The corners of the circumference  1120  may be rounded or they may have sharp angles. The suture  1130  in this embodiment extends from the outer circumference  1120  of the termination feature  1100 , similar to a “lollipop” configuration.  FIG. 11B  may be modified such that the suture  1130  extends from the center of the termination feature  1100 . The thickness and the cross-sectional diagonal of the circumference  1120  of the termination feature  1100  may vary as desired. 
     Alternatively, the termination feature may include an eyelet or open configuration, such as that seen in  FIGS. 11C and 11D .  FIG. 11C  shows a termination feature  1200  having a central eyelet  1210 , and a rounded circumference  1220 . It is understood that the circumference  1210  need not be rounded and may have other geometries. In this configuration, the suture  1230  extends from the side of the circumference  1220 , such as a lollipop configuration. The size of the eyelet  1210  may vary as desired, but it is desirable that the diameter of the eyelet  1210  be larger than the cross-sectional diameter of the suture  1230 . The interior sides of the eyelet  1210  may be substantially smooth and may be rounded if desired. The eyelet  1210  need not be round and may alternatively be different geometric shapes.  FIG. 11D  shows a similar termination feature as in  FIG. 11C , but the termination feature  1300  of  FIG. 11D  includes an eyelet  1310 , where the suture  1330  extends from the interior of the eyelet  1310 . The termination feature  1300  also includes an outer circumference  1320 . As with the other termination features, the termination feature  1300  need not necessarily have a rounded circumference, and the eyelet  1310  need not have a round configuration. The size of the eyelet  1310  may vary as desired, but it is desirable that the diameter of the eyelet  1310  be larger than the cross-sectional diameter of the suture  1330 . 
     The termination feature ( 1200 ,  1300 ) may be produced with eyelet features  1220  or  1320  through modifications to the welding process as described previously. For example, the production of a termination feature ( 1200 ,  1300 ) with an eyelet ( 1220 ,  1320 ) may be formed by leaving the winding pin  260  in an at least partially “upward” position during welding, that is, the winding pin  260  may remain at least partially within the interior of the welding die  220  during the welding process (during the application of energy). The winding pin  260  therefore creates a region within the coil during welding. After welding, the pin  260  may be lowered and reveal the anchor including an open eyelet. 
     The various configurations for termination features, including shapes, sizes, cross-sectional diameters, presence of thicker or thinner regions, or textured surfaces may be produced through the use of a welding die  220  and ultrasonic horn tip  205  that includes the desired shapes, sizes, textures. Alternatively, the termination features (e.g.,  120 ) may be subjected to secondary processing such as stamping, cutting, reforming, annealing, surface treating, abrading, or other mechanical or chemical treatments to produce different geometries, shapes, textures or other characteristics desired. In some embodiments, after the suture is formed with termination feature  120 , the suture and/or termination feature may be subjected to a heat sterilization treatment, which may provide some annealing to the suture and/or termination feature  120 . Such heat treatment may be at temperatures of from about 40° C. to about 80° C., and more specifically from about 50° C. to about 60° C., and most desirably about 55° C. 
     Referring to  FIG. 12 , the suture coil  801  that is formed through the winding process previously illustrated, for example, in  FIGS. 5-9  is illustrated in the absence of the winding fixture. The coil  801  is formed with a distal coil end  802 , which is terminated by the second end of the suture  502  bending inward towards the center point of the coil and downwards passing through an inner cavity  805  of the formed suture coil  801 . The coil  801  has an opposing proximal end  803 , which terminates with a first end of the suture  501  bending outwards away from the diameter of the suture coil  801 . The inner diameter of the cavity  805  may be larger than the cross-sectional diameter of the suture  501  passing through the cavity  805 , due to the use of a hollow pin during the winding operation. This difference in diameter may be equivalent to the doubling of the wall thickness of the hollow pin. 
     Referring to  FIG. 13 , an alternative style of pin for winding a fiber from a location above the welding die, the benefits of which will be discussed later, is presented. In this embodiment, pin  1400  includes two concentric cylindrical elements, an inner cylindrical element  1405  and outer cylindrical element  1435 . Each of the cylindrical elements has an interior that is at least partially open, and defined by an outer wall. The outer surface of the inner cylindrical element  1405  is at least partially in contact with the inner surface of the outer cylindrical element  1435 . The inner cylindrical element  1405  includes a slot  1410 . The slot  1410  extends from an open end  1415  of the pin  1400  at least partially along the length of the inner cylindrical element  1405 . The upper edge  1420  of the slot  1410  may be greater in width than the width of the slot  1410  at a region closer to the open end  1415  of the inner cylindrical element  1405 . A first edge  1425  of the slot  1410  extends between the open end  1415  of the pin and the upper edge  1420  of the slot  1410  in a relatively straight line perpendicular to the central axis of the pin  1400 . A second, opposing edge  1430  of the slot  1410  extends in an at least curvilinear direction between the open end  1415  of the pin and the upper edge  1420  of the slot  1410 . 
     In this embodiment, the upper end of the inner cylinder  1405  is attached to a winding system driver (not shown). The outer cylinder  1435  is illustrated with an outer slot  1440 , which extends at least partially along the axial length of the outer cylinder  1435 , and may have a curvilinear shape as it extends along the axial length of the outer cylinder  1435 . The degree of curvature of the outer slot  1440  may vary as desired. In use, rotation of one of the cylinders ( 1405 ,  1435 ) relative to the other cylinder creates a passage  1445  of varying size and length depending upon the shape of the slots ( 1410 ,  1440 ) and the degree of curvature of each. As the cylinders ( 1405 ,  1435 ) are rotated relative to each other, the size and shape of the passage  1445  extending from outside the pin  1400  to the interior of the pin is changed. 
     While the particular embodiment shown in  FIG. 13  utilizes slots each having curvilinear features or geometries, it is understood that combinations that utilize straight slots in combination with or instead of curvilinear slots are also feasible, and the use of a straight slot in the outer cylindrical element with a curvilinear slot in the inner element may be used. The preferred embodiment utilizes an inner cylindrical element with a slotted feature that is primarily cut in a straight line. The use of a straight slot may be effective to maintain the maximum strength of the inner cylindrical element, since it is smaller in diameter than the outer cylinder, while simplifying the removal of the wound fiber from the pin  1400  prior to welding. While the inner cylinder  1405  has been illustrated as a hollow cylinder with a slot, a solid pin with a slot formed in the side of the pin extending away from the open end  1415  of the pin may be preferable. 
     Referring now to  FIG. 14 , operation of the slotted winding pin  1400  (of  FIG. 13 ) is illustrated in at least three sequential steps ( 1500  being the first step,  1510  the second step, and  1520  the third step). The first step  1500  of the winding process is initiated in an open position to receive the fiber  501 . In this position, the two cylindrical components ( 1405 ,  1435 ) are rotated relative to each other to align the inner slot  1410  and outer slot  1440  to provide a passage for the fiber  501  to lay into the pin  1400  at the open end  1415  of the pin. The fiber  501  is placed into the device such that at least a portion of the fiber  501  is contained within the interior of the pin  1400  and at least a portion of the fiber  501  extends out through the open end  1415  of the pin, and at least a portion of the fiber  501  extends out of the pin  1400  through the passage  1430  formed by aligning the slots ( 1410 ,  1440 ). 
     In the second step ( 1510 ), the inner cylinder  1405  and outer cylinder  1435  are rotated with respect to each other so as to cause the slots at the open end  1415  of the pin to no longer align with each other. In this position, there is a passage  1430  remaining between the inner cylinder  1405  and outer cylinder  1435 , but there is no passage  1430  at the open end  1415  of the pin  1400 . Thus, there is a closed end  1460  at the open end  1415  of the pin  1400 . The fiber  501  is drawn slightly proximally towards the termination position  1465  of the outer slot  1440 . As the cylindrical components ( 1405 ,  1435 ) are rotated with respect to each other further about their axes, the passage  1430  size and/or length is reduced further. In this position (embodied by step  1520 ), the fiber  501  exits from within the pin  1400  through a reduced size/length passage  1430 . This passage  1430  may be axially located at a distance from the open end  1415  of the pin that enables the formation of a sufficient quantity of fiber coils, so to produce the desired termination feature. 
     Once the fiber  501  is in this final position and the passage  1430  is sized to the desired configuration by rotating the inner and/or outer cylinder with respect to each other, the winding operation may be performed to wind the fiber  501  about the pin  1400 . Once the fiber  501  winding is completed, the cylindrical components ( 1405 ,  1435 ) may be rotated back to the position to create the open passage  1430  extending to the open end  1415  of the pin, and thereby creating a fully open passage  1430 . The winding pin  1400  may then be removed from the resulting coiled fiber from the upper (distal) end of the coil ( 802 , in  FIG. 12 ). This action may be assisted through the use of a stripper ring to facilitate the removal of the pin  1400  without disturbing the coiled fiber  801  within the die. 
     Referring now to  FIG. 15 , the winding pin  1400  with the slots aligned and open (creating passageway  1430  that extends to the open end  1415  of the pin) is positioned over a post insert plate. An intermediary slidable stripper  1460  may be positioned between the winder pin  1400  and the welding die  220 . The stripper  1460  is produced with a lower barrel portion  1465  that is sized to fit within the upper portion of the welding die  220  and substantially fills the cylindrical space between the outer surface of the winder pin  1400  and the inner diameter of the welding die  220 . The stripper  1460  may optionally be produced with a flange like region  1470  for use in lifting or lowering the stripper  1460 . The inner diameter of the stripper  1460  is sized to be in slidable engagement with the outer surface of the winding pin  1400 . 
       FIG. 16  shows the winder pin  1400  the fiber  501  loaded within the open center of the pin  1400  such that one end of the fiber  501  extends through the open end  1415  of the pin  1400  and a second end of the fiber  502  extends through the passage  1430  formed by alignment of the two slots ( 1410 ,  1440 ). The welding die  220  is shown in a retracted position, prior to the winding operation occurring. The slot  401  in the base of the welding die  220  is also illustrated. In some embodiments, the winding pin  1400  may be attached to an engageable feature  1600 , such as a drive spline, gear, v-belt, or frictional drive element. The engageable feature  1600  may be utilized to spin the welding pin  1400 . 
       FIG. 17  illustrates the winder pin  1400  in the winding position, with the fiber  501  loaded into the winder pin  1400  as described above, and the welding die  220  located about the winder pin  1400 . The stripper  1460  is in the “up” position. The next step in the welding operation is to move the stripper  1460  downward within the open bore of the welding die  220  prior to the winding cycle initiation. 
     As seen in  FIG. 18 , the winder pin  1400  is again presented, however, the view is a partial sectional view whereby the welding die  220 , insert ring  210  and welding post  233  are sectioned to reveal the inner cavity of the die  220 , with the pre-winding positioning of the fiber  501 . Additionally, the details of the inner cavity profile are also visible. The insert ring is bored through with a stepped diameter. This stepped profile remains in contact with an ultrasonic horn during the welding cycle, described above. Additionally, there is a tapered region  1620  located at the top of the through bore of the welding die  220 , which mates up to a radiused edge of the insert ring  1610  to form an undercut feature in the mated components. The undercut feature provides a point of contact with the pre-weld coiled fiber (e.g.,  801 ) when the stripper  1460  is removed. This undercut prevents the stressed coiled fibers from relieving themselves of the internal post coiling stresses prior to welding, and possibly springing upwards out of the welding die  220 . 
       FIG. 19  shows a semi-transparent view of a typical winding operation to indicate the wrapping of the fiber  501  about the winding pin  1400  within the die  220  relative to the passage  1430  of the winding pin  1400 . As can be seen, the fiber  501  is wound about the outer surface of the outer cylinder  1435  to form the coiled fiber. Any number of windings may be used to create the coiled fiber (e.g.,  801 ). When the coiled fiber is formed to a desired coil size, the inner cylinder  1405  and outer cylinder  1435  are rotated with respect to each other to create the open passage  1430  extending to the open end  1415  of the pin  1400 , in order to facilitate removal of the wound coil ( 801 ) from the pin  1400 . The coil may be welded, as described above. 
     As seen in  FIG. 20 , an alternate embodiment of a winding pin drive element is shown. In this embodiment, an engagement element includes a spur gear  1700  mounted to a winding axel  1720 , which is in turn coupled to a winding pin base  1730 . Additionally, bearings  1710  to support the winding axel  1720  are incorporated to ensure the proper vertical orientation of the winding pin during rotation and to counteract any thrust loading as a result of the winding drive. 
     Referring to  FIG. 21 , an alternate form of winding is illustrated. In this embodiment, the trailing end of the fiber  502  is threaded through a split welding post  233 . The split face  1800  is illustrated. In this variant, the free end of the fiber is passed over a cross member  1810 , and is pulled laterally through a channel in the welding die  220 . The cross member  1810  may be passed through a bore  1820  in the insert member and is engaged at the opposite end with a pocket located in the opposing side of the through bore of the welding die  220 . Additionally, the split face welding post enables full clamping of the fiber  501  during the welding cycle. The clamp surface  1830  of the split post may be produced as a monolithic structure in the base material of the welding post or it may incorporate other compressible or resilient materials to minimize the potential for marring of the compressed fiber. The use of a resilient clamping surface also enables the accommodation of variation in the raw fiber diameter. 
       FIG. 22  shows a partially transparent rendering of the configuration of  FIG. 21 . The cross member  1810  in this embodiment includes a feature  1840  that is utilized to push or pull the cross member  1810  through the receiving bore. The embodiment incorporates sliding gate like elements  1850  that temporarily maintain the fiber  501  in a clamped or restricted state in the central region of a cylindrical winding pillar  1860 . The gate elements  1850  enable the use of winding dies that are more cartridge-like, which may be wound in preparation for welding offline and then inserted into a welding die carrier for welding. Once the cartridge like die is placed upon a split welding post receiver, the split welding post closes up to the final diameter of the desired termination, the gates are opened and the coiled fiber is able to come into contact with the welding post for welding. Unlike the previously described systems, there is no central pin to form the coil during the winding process. Instead, the fiber is wrapped around a clamped vertical fiber element  1870  through the relative rotation of the welding die cartridge about the cylindrical winding pillar. The winding operation may continue until a tightly formed coil is produced, and a slight plastic deformation of the wound fiber occurs. Alternatively, the tightly wound coil may be subjected to a source of thermal energy to enable the stresses within the coil to relieve and for the coil to remain in position. 
     As seen in  FIG. 23 , upon completion of the winding operation, the cross member  1810  is released from the winding die, and the resultant coil  1900  is formed. 
     Referring now to  FIG. 24 , an additional embodiment of a winding device and associated welding cartridge is disclosed. In this embodiment, the winding and welding cartridge utilizes slide gate elements that fit within a receiver track  2000  located on the bottom side of the welding cartridge  2001 . Additionally, the gate elements incorporate locator pin holes  2005  and  2010 . The outermost locator hole  2010  is utilized during the winding operation to ensure that the fiber (e.g.,  501 ) is guided towards the center of the cartridge during winding. When the cartridge  2001  is placed upon a split welding post for welding, the gates are opened and held in the open position by the inner locator hole  2005 . The engagement pin, not shown, that engages the locator holes  2005 ,  2010  engages with a cartridge locator hole  2015 . The first end of the fiber  501  exits from the center bore of the cartridge and the second free end of the fiber  502  passes through a notch  2020  located at the top of the cylindrical portion  2025  of the cartridge  2001 . Once the fiber is positioned within the cartridge  2001 , a winder knob  2035  is inserted into the upper portion of the cartridge  2001 . A notch  2030  located in the winding element  2032  of the knob engages the fiber  501  within the cartridge  2001 . The winder knob  2035  is rotated relative to the cartridge  2001 . As the knob  2035  is rotated, the first free end of the fiber  501  is maintained in a fixed position and the second free end is drawn into the cartridge  2001  cavity as a coil of fiber is formed about the winder element  2032 . Similar to the other embodiments, a stripper  1460  may optionally be included to facilitate removal of the wound coil from the winding element  2032 . The winding of fiber in this manner results in the free end of the fiber  502  exiting at the top end of the restraining element and the first end  501  of the fiber bends immediately within the fixture, thus forming into the most proximal coil ( 803 , in  FIG. 12 ) in the coiled fiber. 
       FIG. 25  shows a welding die  220  as mounted to a series of cage leg elements  2100 . The cage leg elements  2100  pass through the mounting plate  301  to the underside assembly of the fixture. The mounting plate  301  has four side edges  2110 , which each has at least one threaded passage  2105  therein, wherein each threaded passage  2105  is substantially perpendicular to one of the four edges  2110  of the mounting plate  301 . The threaded passages  2105  each independently extend from one edge  2110  towards the center of the mounting plate  301 , where each threaded passage  2105  intersects with a through bore passage  2135  intended to receive a cage leg element  2100 . Within each threaded passage  2105 , at least one ball plunger element  2115  has been installed, where the ball plunger  2115  presses against a cage leg element  2100 . Underneath the welding die  220 , and above the mounting plate  301 , a compressible elastic element  2130  may be provided. It has been found that the quality of the welded terminations is improved through the incorporation of an elastic element  2130 , as well as inclusion of the ball plunger elements  2115 . The final design may include one or more of the elastic element  2130  or ball plunger elements  2115 . 
     When an elastic element  2130  is placed beneath the welding die  220 , it enables the welding die  220  to remain engaged with an ultrasonic welding horn  201  during the application of energy. As the horn  201  oscillates vertically, the spring force acting upon the welding die  220  helps to maintain the welding die  220  in contact during the weld cycle. It has also been found that if the welding die  220  remains in tight engagement with the horn  201  during the welding cycle, the welding of the upper coils of the fiber (e.g.  501 ) may be diminished and the weld that is produced may be similar in appearance to a weld produced within a cavity in the face of the horn. Preferred welding conditions are achieved through the addition of a frictional drag component to the cage leg elements  2100 . The frictional drag component of die movement helps restrict the welding die  220  from vibrating in unison with or in exact frequency with the ultrasonic horn  201  during use. This gives a more uniform welding of the fiber. While the elastic element  2130  and drag elements have been described as being achieved through the use of elastic material and ball plungers, the use of springs, such as air or other types of springs, as well as spiral displacement of the welding die  220 , or the use of external damping elements such as brake or shock absorber style elements are also feasible. Thus, in use, it is desired to create a frictional drag of the die movement, which may be achieved through any of the aforementioned means.