Abstract:
A vasocasostomy stent of the present invention comprises an elongate tube including a wall defining an inner lumen and a plurality of apertures extending along a substantial length of the tube. A method of anastomosis for a vas deferens comprises inserting an apertured stent into free ends of a severed vas, slidingly advancing the free ends of the severed vas toward each other over the stent until the free ends are in abutment, and securing the free ends of the severed vas together over the stent.

Description:
THE FIELD OF THE INVENTION  
         [0001]    The present invention relates to a vascular stent and in particular to an anastomosis stent for reversing vasectomies.  
         BACKGROUND OF THE INVENTION  
         [0002]    With the right environment, bones can mend, nerves can regenerate, and skin will heal. Unfortunately, some things that are broken or damaged are extremely difficult to repair. This difficulty is particularly evident when the damage has been surgically caused in the first place.  
           [0003]    For example, in a vasectomy, the vas deferens, which carries sperm from the testes to the urethra, is severed in two. The severed ends are then either tied off or left to freely dangle. In some cases, when the vas is separated, the cut includes removing a section of the vas to insure that the ends of vas cannot rejoin. A vasectomy is generally considered to be a permanent procedure.  
           [0004]    However, like many elective procedures, vasectomy patients sometimes regret the procedure and seek to have a vasovasostomy (i.e., anastomisis of the vas), which attempts to reconnect the severed ends of the vas. With a reconnected vas deferens, the flow of sperm is restored to permit fertile ejaculation for conceiving a child.  
           [0005]    Unfortunately, joining what has been separated is easier said than done. A wide catalog of vasectomy devices and vasectomy reversal devices has been presented for restoring a vas deferens. Many of these devices have been patented and include: biodegradable stents, such as those disclosed in U.S. Pat. No. 5,192,289, U.S. Pat. No. 5,425,739 and U.S. Pat. No. 4,674,506; removably insertable plugs, valves, stents, such as in U.S. Pat. No. 3,589,355, U.S. Pat. No. 4,682,592, U.S. Pat. No. 4,200,088, and U.S. Pat. No. 3,613,661; and various clamping and suturing devices, such as those disclosed in U.S. Pat. No. 4,245,638, U.S. Pat. No. 3,766,926, and U.S. Pat. No. 4,553,542. These patents, and many others directed to reversing a vasectomy, or directed to performing a reversible vasectomy, evidence the continuing and unfinished search for mastering the problem of restoring a severed vas deferens.  
           [0006]    Several physiological factors unique to the vas deferens have acted in combination to frustrate prior attempts at reversing vasectomies. First, the opposed free ends of the severed vas frequently are of an unmatched diameter. In particular, the portion of the severed vas extending from the testes becomes dilated with spermatic buildup. On the other hand, the opposed free end of the severed vas retains its extremely small inner lumenal diameter in an undilated state. This inner lumenal mismatch between the free ends of the severed vas is quite difficult to work with in suturing together the free ends of the severed vas. Suturing the vas, with its small inner lumenal diameter, also creates risks such as stricture. A severed end of the vas also may be scarred and/or irregular shaped. If a section of the vas is removed during the vasectomy, rejoining the vas can be even more difficult due to the short length of available vas. This situation can necessitate a more radical procedure such as a vasoepididymostomy.  
           [0007]    Accordingly, even with the wide variety of devices introduced over the last 40 years for solving the problem of performing vasectomies (and reversing them) the physiological factors surrounding vasectomies have prevented a satisfactory solution to reversing vasectomies.  
         SUMMARY OF THE INVENTION  
         [0008]    A vasocasostomy stent of the present invention comprises an elongate tube including a wall defining an inner lumen and a plurality of apertures extending along a substantial length of the tube. A method of anastomosis for a vas deferens comprises inserting an apertured stent into opposed free ends of a severed vas, slidingly advancing the opposed free ends of the severed vas toward each other over the stent until the free ends are in abutment, and securing the free ends of the severed vas together over the stent.  
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0009]    [0009]FIG. 1 is a perspective view of a vasovasostomy stent, according to an embodiment of the present invention.  
         [0010]    [0010]FIG. 2 is a sectional view of FIG. 1 as taken along lines  2 - 2 , according to an embodiment of the present invention.  
         [0011]    [0011]FIG. 3 is a sectional view of FIG. 1 as taken along lines  3 - 3 , according to an embodiment of the present invention.  
         [0012]    [0012]FIG. 4 is a schematic view of preparing a vas for acceptance of a vasovasostomy stent of the present invention, according to an embodiment of the present invention.  
         [0013]    [0013]FIG. 5 is a schematic view of insertion of a vasovasostomy stent into a vas, according to an embodiment of the present invention.  
         [0014]    [0014]FIG. 6 is a schematic view of a vasovasostomy stent secured within a vas, according to an embodiment of the present invention.  
         [0015]    [0015]FIG. 7 is a sectional view of FIG. 6 as taken along lines  7 - 7 , according to an embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]    In the following detailed description of the preferred embodiments, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific embodiments in which the invention may be practiced. It is to be understood that other embodiments may be utilized and structural or logical changes may be made without departing from the scope of the present invention. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present invention is defined by the appended claims.  
         [0017]    As shown in FIG. 1, vasovasostomy stent  10  comprises tube  12  with first end  14 , second end  16 , and wall  20  defining lumen  22 . Wall  20  further comprises patterned body  30  defining a plurality of apertures  32  and undulating outer surface  33 .  
         [0018]    [0018]FIG. 2 is a sectional view of FIG. 1 as taken along lines  2 - 2 . As shown in FIG. 2, stent  10  further comprises smooth surfaced end portions  36  and alternating recesses  40  and protrusions  42 , which in combination with apertures  32 , define undulating outer surface  33 . Apertures  32  are distributed radially in a pattern about wall  20 . Each aperture  32  defines an unobstructed pathway from the outside of stent  10  (e.g., outer surface  33 ) to the inside (e.g., inner lumen  22 ) of stent  10 .  
         [0019]    [0019]FIG. 3 is a sectional view of FIG. 1 as taken along lines  3 - 3 . As shown in FIG. 3, wall  20  defines inner lumen  22  and apertures  32  of patterned body  30 .  
         [0020]    In one embodiment, stent  10  preferably has a length of about 0.10 inches, an outer diameter of about 0.01 inches (i.e., about 0.25 mm), and an inner diameter for lumen  22  of about 0.006 inches (i.e. about 0.15 mm). This length is sufficient to facilitate suturing the free ends of a severed vas, yet short enough to be less than an expected radius of curvature of the vas during normal physiologic use and functioning. The outer diameter of stent  10  is about two to three times the undilated, inner lumenal diameter of the vas, yielding an oversized vasvasostomy stent. Meanwhile, the inner lumenal diameter of inner lumen  22  of stent  10  is at least substantially the same as the inner lumenal diameter of vas (e.g., about 0.1 mm), and is preferably even one and one-half to two times larger (e.g., about 0.15 to 0.2 mm) than the inner lumenal diameter of vas, to ensure patentcy and prevent stricture at the suturing site, even after accounting for epithelial growth. Smooth surfaced end portions  36  preferably have a length of about 0.0015 inches while patterned body portion  30  (defining a plurality of apertures  32 ) has a length of about 0.077 inches. Apertures  32  preferably have a diameter of about 0.007 inches (i.e., about 0.18 mm) while wall  20  preferably has a thickness of about 0.002 inches. While apertures  32  are preferably generally circular shaped, apertures  32  optionally are formed from one or more different shapes such as oblong shapes, rectangular shapes, slots, etc. that define unobstructed passages through wall  20 .  
         [0021]    While the above dimensions identify one embodiment of the present invention, stent  10  optionally is made in different sizes, either smaller or larger, to the extent necessary to accommodate a differently sized vas deferens. In these cases, an inner diameter of stent  10  is sized to maintain a relationship of being substantially the same as an inner lumenal diameter of an undilated vas deferens, and even one and one-half to two times as larger than the inner lumenal diameter of the vas deferens. Likewise, the outer diameter of stent  10  is sized to maintain a relationship of being about two to three times larger than the inner lumenal diameter of an undilated vas deferens.  
         [0022]    Stent  10  preferably is made from Nitonol, a well known surgical alloy, and alternatively can be made from other known surgical metallic alloys including stainless steel, Titanium, etc. Alternatively, stent  10  is made from semi-flexible, resilient non-metallic material with sufficient rigidity to maintain the patentcy of the vas. In each case, stent  10  preferably is made from a permanent, non-absorbable material.  
         [0023]    Stent  10  is sized for insertion into opposed severed ends of a vas for maintaining the free ends of a severed vas in abutment with each other to facilitate suturing in order to reverse a vasectomy. Undulating surface  33  of stent  10  facilitates frictional engagement of vas against stent  10  during suturing of the free ends of the severed vas while apertures  32  of stent  10  facilitate epithelial tissue growth through stent  10  for vas to establish its own smooth wall lining that is enmeshed with lumen  22  of stent  10 . In particular, the unobstructed passages formed by apertures  32  facilitate epithelial growth from outer surface  33  of stent, through apertures  32 , and into and along inner lumen  22  of stent  10 . This enmeshed combination of epithelial lining and stent  10  produce an inner lumenal diameter of the restored vas deferens that is more than sufficient to carry sperm, and which insures patentcy at the point of suture, largely due to the rigidity and large diameter of inner lumen  22  of stent  10 . Finally, the outer diameter of stent  10  is sufficiently large to avoid the prior art sealing problem from mismatched diameters of free ends of a severed vas, since the outer diameter of stent  10  is larger than the sometimes dilated free vas end extending from the testes.  
         [0024]    A method of the present invention for reversing a vasectomy with a vasovasostomy stent, according to an embodiment of the present invention, is shown in FIGS.  4 - 7 . FIG. 4 schematically illustrates preparing two separated portions of a vas for reconnection with stent  10 . Since an inner lumenal diameter of a vas is very small, this method first includes temporarily expanding this inner lumenal diameter of a vas with a dilator. As shown in FIG. 4, vas  50  includes two separated end portions  51  and  52 , each having end surface  53 , outer surface  54 , inner lumen  56 , and wall  58 . Dilator  70  includes operative section  72  of an increasing diameter.  
         [0025]    Using dilator  70 , each severed end portion  51  and  52  of vas  50  is dilated one at a time. In particular, with severed end portions  51  and/or  52  temporarily secured, dilator  70  is separately introduced into each open end of severed end portions  51 , 52  of inner lumen  56  of vas  50  and advanced to expand the inner diameter of inner lumen  56  by stretching wall  58 . Wall  58  of vas  50  is viscoelastic and therefore will the hold shape of the expanded inner diameter long enough to complete insertion and securing of stent  10  within vas  50 . Dilator  70  preferably has an outer diameter that is two to three times the normal inner lumenal diameter of the vas, so that upon dilation of vas, stent  10  can be readily introduced and advanced into the vas. Any variety of dilators known in the art can be used.  
         [0026]    As shown in FIG. 4, severed end portion  51  illustrates an undilated vas deferens prior to use of dilator  70  while severed end portion  52  illustrates a dilated vas deferens after use of dilator  70 .  
         [0027]    [0027]FIG. 5 illustrates stent  10  with its opposite ends  14 , 16  inserted in opposed severed end portions  51  and  52  of vas  50 . With stent  10  positioned within severed end portions  51 , 52  of vas  50 , each severed end portion  51 , 52  is then grasped and pulled together so that end surfaces  53  are in abutment over stent  10 , as shown in FIG. 6. If desired various clamping and grasping devices known in the art are optionally used for handling the vas during advancement and suturing over stent  10 .  
         [0028]    [0028]FIG. 6 illustrates free ends portions  51  and  52  of severed vas  50  secured together over stent  10 . This securing step is preferably performed using sutures, clips, lasers, and/or staples, all of which are known in the art and which are optionally woven into and through apertures  32  and lumen  22  of stent  10 , as necessary.  
         [0029]    [0029]FIG. 7 is a sectional view of stent  10  secured within restored vas  50 . As shown, inner lumen  22  of stent  10  is relatively smooth due to epithelial growth from vas (extending through apertures  32  of patterned body  30  from outer surface  33  into inner lumen  22 ). This growth creates an enmeshed combination of epithelial lining  60  and of inner lumen  22  of stent  10  that defines new inner lumenal structure  70  that extends through stent  10 .  
         [0030]    The vasovasostomy stent of the present invention carries numerous advantageous features including patterned body with an undulating outer surface to facilitate suturing of the vas through frictional engagement of the stent against the vas inner lumen. The stent&#39;s oversized outer diameter insures sufficient patentcy of the restored vas while alleviating inner lumenal diameter mismatches of the severed vas ends by normalizing both inner lumenal diameters to a common-sized larger inner lumenal. Finally, the apertured wall of stent  10  enhances epithelial growth to form a smooth inner lumen wall lining within stent  10 .  
         [0031]    While specific embodiments have been illustrated and described, herein for purposes of description of the preferred embodiment, it will be appreciated by those of ordinary skill in the art that a wide variety of alternate and/or equivalent implementations may be substituted for the specific embodiments shown and described without departing from the scope of the present invention. Those with skill in the chemical, mechanical, electromechanical, electrical, and computer arts will readily appreciate that the present invention may be implemented in a very wide variety of embodiments. This application is intended to cover any adaptations or variations of the preferred embodiments discussed herein. Therefore, it is manifestly intended that this invention be limited only by the claims and the equivalents thereof.