Abstract:
A medical device is provided which forms a physical barrier between the two ends of a cut vas during a vasectomy procedure, comprising a biodegradable, polymeric cap that is applied over at least one prostatic end of the vas, the cap including a fastener for preventing premature dislodgement.

Description:
RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Application No. 60/975,093, filed Sep. 25, 2007. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to the surgical technique of vasectomy, and, in particular, a device which covers and occludes the cut ends of the vas during the vasectomy procedure. 
     BACKGROUND OF THE INVENTION 
     Vasectomy is a surgical procedure that interrupts the continuity of the vas deferens (vas) in order to prevent sperm from passing from the testis into the ejaculate, thus preventing sperm from uniting with the ova. Vasectomy is the most effective contraceptive method available to men. While vasectomy is considered to be a permanent procedure, it can be reversed with varying degrees of success. 
     There are many surgical techniques that have been devised for vasectomies, with varying degrees of effectiveness. Recent research has confirmed that fascial interposition increases the effectiveness of ligation and excision, and the lowest failure rates for vasectomy have been reported by physicians using a combination of cautery and fascial interposition. As used herein, “fascial interposition” refers to the surgical technique of interposing a layer of fascial membrane, from the fascial sheath which surrounds the vas, between the two cut ends of the vas. 
     The inventors have found that the most common cause of vasectomy failure is early recanalization. As used herein, “recanalization” refers to the spontaneous regrowth of one or more tubules between the cut ends of the vas deferens. It occurs most commonly within three weeks to two months after vasectomy and is diagnosed by the successful passage of sperm from the testes into the semen. 
     When properly done, fascial interposition prevents recanalization by interposing a tissue barrier between the cut ends of the vas. However, the surgical technique of fascial interposition is time-consuming and requires considerable surgical skill. Many surgeons consider fascial interposition to be too difficult. In addition, fascial interposition may be difficult to implement in men who have a history of bacterial infections such as sexually transmitted infections, or parasitic infections, such as filariasis, which may cause fibrotic changes in scrotal tissues. 
     SUMMARY OF THE INVENTION 
     To improve and facilitate vasectomy procedures, an easier, more reliable way of doing fascial interposition is the present invention, which provides a device in the form of a biodegradable, fluid impermeable polymeric cap that takes the place of fascial interposition. Rather than relying on the manipulation of delicate and variable tissue layers, this cap provides an impermeable barrier between the two ends of the cut vas. This invention provides a device that takes the place of fascial interposition. 
     More particularly, the device is a vas deferens cap (vasectomy cap), which when applied to the vas, provides a physical barrier to cover the cut end of one or both ends of the vas. In one embodiment, the vasectomy cap covers only the abdominal or prostatic end of the vas. The vasectomy cap may, however, be applied with a hand-held applicator that simultaneously cuts the vas and clamps the device over both ends of the cut vas. 
     The essential functionality of the vasectomy cap is twofold:
         a) the vasectomy cap provides an impermeable barrier that prevents early recanalization of the vas; and   b) the vasectomy cap includes one or more features to prevent dislodgement, such as anchoring teeth and/or a provision for a suture or one or more hooks that would pass through the vas and anchor the device to the vas.       

     In an embodiment, the device is formed of a polymeric material that is bio-compatible, such as a biodegradable plastic. The vasectomy cap is preferably of low stiffness, with enough flexibility so as not to erode either the vas or other surrounding tissue layers, but with stiffness sufficient to grip the vas as described below. Suitable polymer/copolymer types include, but are not limited to, polyureas, polyurethanes, poly(ethylene/-vinyl acetate), polyvinylchloride, polyesters, polyamides, polycarbonate, polyethylene, polypropylene, polystyrenes, polytetrafluoroethylene, polyhydroxyalkanoates, and silicone. The device may be stiffer at the surface covering the cut end of the vas, and more flexible at the end furthest from the cut end of the vas. 
     The vasectomy cap may be applied to the vas by surgeons using either a no-scalpel vasectomy (NSV) technique or a standard incision technique. These two techniques are slightly different ways to approach the vas and bring a loop of the vas outside of the scrotum, also referred to as isolating the vas. This constitutes the first part of the vasectomy procedure, prior to the step of occluding the vas. With the NSV technique, a ringed clamp is used to fix the vas through the scrotal skin, and then the dissecting forceps are used to puncture the skin, spread open the puncture, grasp the vas, and then bring a loop of the vas outside the scrotal skin. The NSV technique involves the exposure and isolation of a small loop of the vas, which is usually a shorter length than exposed by the standard incision technique. However, the vasectomy cap may be used to occlude the vas irrespective of which technique is used to approach and isolate a loop of the vas. 
     These and other aspects of the present invention will become apparent to those skilled in the art after a reading of the following description of exemplary embodiments when considered in conjunction with the drawings. It should be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the invention as claimed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1A  is a cross-sectional view of the device being applied to the vas, with a first flap wrapped around each side. 
         FIG. 1B  is a cross-sectional view of the device after the vas has been cut. 
         FIG. 1C  is a cross-sectional view of the device after a second flap is wrapped around each side. 
         FIG. 2  is a top view of the device lying flat. 
         FIG. 3  is a side elevational, cross-sectional view of the device of  FIG. 2 , taken along lines II-II. 
         FIG. 4  is a side elevational, cross-sectional view of the device of  FIG. 2 , taken along lines III-III. 
         FIG. 5  is an alternative embodiment of a vasectomy cap. 
         FIG. 6  is a cross-sectional view of the embodiment of  FIG. 5 , taken along lines VI-VI. 
     
    
    
     DETAILED DESCRIPTION 
     The present invention is directed to a device for capping one or both exposed ends of the vas lumen that are cut during a vasectomy procedure. The vasectomy cap attaches to the vas and serves as a cap to cover one or both ends of the vas, thus preventing early recanalization. The vasectomy cap can be applied by a hand-held surgical instrument (applicator) that also may be used to cut the vas. 
     In the course of a vasectomy, the surgeon creates an opening through the skin of the scrotum and pulls a loop of the vas and fascial tissues outside the scrotum. He then removes extraneous fascial tissues from the vas. Once a loop of the vas has been clearly identified and isolated, the vasectomy cap is applied. 
     Referring to the Figures in general, and  FIG. 2  in particular, one embodiment of the device for capping the open ends of the vas lumen is shown generally as  10 . As shown in  FIG. 2 , the device  10  is lying flat in a ready to apply configuration. The embodiment shown in  FIG. 2  comprises two symmetrical portions, and thus two caps. The symmetrical portions each comprise three flaps, which are identical mirror images of each other on the right and left portions. These include a main rectangular body flap  11 , a rectangular first flap  12 , and a rectangular second flap  13 . The two symmetrical portions are removably connected along cut lines  14   a  by an intermediate connector  14 . The cut lines  14   a  may also initially serve as fold lines during application of the device. A further fold line  15  also separates the main body flap  11  from the first flap  12  and second flap  13 . Fold line  15  allows the first flap  12  and second flap  13  to be folded onto the inner surface of the main body flap  11 , as will be explained in greater detail below. 
     Each main body flap  11  comprises a proximal end  11   a  adjacent the intermediate connector  15 , an opposed distal end  11   b , a forward edge  11   c , an inner surface  11   d , and a fastener element  17  along the proximal end  11   a  and the forward edge  11   c . A plurality of spaced-apart barbs  16  are formed on the distal portion of the inner surface  11   c . The first flap  12  comprises a distal end  12   a , a rearward edge  12   b , an inner surface  12   c , and a faster element  18  along the rearward edge  12   b  for subsequent mating engagement with fastener element  17 . A plurality of spaced-apart barbs  16  are formed substantially over the entire inner surface  12   c . The second flap  13  comprises a proximal end  13   a , a rearward edge  13   b , an inner surface  13   c , and a fastener element  18  along the proximal end  13   a  and rearward edge  13   b  for subsequent engagement with fastener element  17 . A plurality of spaced-apart barbs  16  are formed substantially over the entire inner surface  13   c.    
       FIG. 3  illustrates the cross-section of the embodiment  10  illustrated in  FIG. 2  through the first flap  12  and the main body flap  11 . One exemplary type of fastener comprises interlocking rib  17  and groove  18  fastener elements; however, other suitable fasteners known to those skilled in the surgical arts may be used. 
       FIG. 4  illustrates the cross-section through the main body flap  11 , and shows the shape of one form of interlocking groove  17  fastener element.  FIG. 4  also illustrates the attachment points or barbs  16 , which cover the distal portion of the main body  11  opposite the first flap  12 , but which are not present on the surface opposite the second flap  13 . 
     When pressure is exerted to close the flaps  12 ,  13  against the main body flap  11 , the edges of the flaps become bound to the main body by the engagement of the interlocking rib  17  and groove  18  fastener elements. The locations of the rib  17  and groove  18  fastener elements could be switched, with no change in function or effectiveness, and other engagement mechanisms could be used by those skilled in the art of medical device design. 
     Turning to  FIGS. 1A through 1C , application of the device is illustrated.  FIG. 1A  illustrates how the device is positioned around the vas, either manually or with an applicator. As shown in the Figure, the device is placed with the two symmetrical portions on either side of the loop  21 , separated by the intermediate connector. The main body flap  11  is fitted inside the loop  21  and anchored with barbs  16 . The first flap  12  is then closed over the loop  21  and anchored. The second flap  13  has been folded beneath main body flap  11  for this step. 
     After this is done, two parallel cutting blades are used to cut the device  10  along vasectomy cap along the fold lines  14   a  on either side of the intermediate connector piece  14 , as well as cutting and removing a short segment of the vas loop  21 . Alternatively, two separate cuts could be made using scissors or a scalpel. An advantage of this technique is that the surgeon will have a small segment of the vas loop  21  to send to a pathologist for histological examination, in order to verify that the correct structure was cut. Many surgeons do this in order to document that the surgery was performed correctly. 
       FIG. 1B  shows the device  10  and the vas loop  21  after the cutting operation is complete. Because the vas loop  21  is under tension and is stretched when it is pulled from the scrotum  20 , it will retract after being cut, but the barbs  16  prevent the vas from retracting back into the scrotum  20 . However, the distal inner surface of main body flap  11  does not have barbs, thus permitting the cut vas  21  to retract slightly so that the second flap  13  may be folded over, anchored, and secured with fastener elements  17 ,  18 . 
     Lastly,  FIG. 1C  shows each symmetrical portion after the second flap  13  has been folded and engaged with the main body flap  11  via the fastening elements  17 ,  18 . 
     The size of the device  10  is adapted to fit around the vas. The outside diameter of the vas in adult males ranges from approximately 1.5 to 3.0 mm in diameter, or a circumference ranging from between about 4.5 and 9.5 mm. Thus, the width of each symmetrical portion to accommodate the largest vas diameter should be between about 12 and 14 mm. This would allow each portion to encircle the vas. Two or three different widths could be made to best accommodate the variation in the size of the vas. The length of each side, such as the length of side  11   c , could be from about between 1 and 2 cm. 
       FIGS. 5 and 6  illustrate an alternate embodiment of the vas cap, with a linear post  40  with barbs  42  that are inserted into the lumen of the vas, and a cap  41  that covers the end of the vas  21 . Supplemental barbs  43  also may be formed inside the cap  41  to provide additional attachment to the vas  21 . 
     Since the vas develops a point of fibrosis following vas occlusion due to the tissue reaction provoked by sperm that are no longer contained in the vas, the vas cap could be made of a biodegradable polymer that would disintegrate and be completely metabolized within about 3 to 12 months after the procedure. As described above, various type of biodegradable polymers may be used having the desired characteristics, including polymers and co-polymers chosen from among the following types: poly(dl-lactide), poly(l-lactide), polyglycolide, poly(dioxanone), poly(glycolide-co-trimethylene carbonate), poly(l-lactide-co-glycolide), poly(dl-lactide-co-glycolide), poly(l-lactide-co-dl-lactide), poly(glycolide-cotrimethylene, and polyhydroxyalkanoates. 
     Although the present invention has been described with an exemplary embodiment, it is to be understood that modifications and variations may be utilized without departing from the spirit and scope of the invention, as those skilled in the art will readily understand. Such modifications and variations are considered to be within the purview and scope of the appended claims and their equivalents. For instance: The device could be impregnated or coated with an anti-infective agent. The surfaces of the device could be roughened so that it can be easily visualized after implantation by sonic imaging equipment. The device could be made radio-opaque by the blending of radio-opaque material in the plastic polymer; e.g., silver particles or other agents known to those skilled in the medical device arts, so that it can be easily visualized after implantation by X-ray imaging techniques. The device could made visible to magnetic resonance imaging techniques by the inclusion of ferromagnetic or paramagnetic particles in the plastic as known to those skilled in the medical device arts, so that it can be easily visualized after implantation. Additionally, in lieu of barbs, the device could be anchored with other types of securing elements such as a medical glue or tissue adhesive, through the use of sutures, clamps, or others.