Abstract:
A sling for controlling urinary incontinence is disclosed. The sling is formed from a tube having substantially lengthwise inextensible end portions and an elastically lengthwise extensible intermediate portion between the end portions. The intermediate portion has a U-shape which cradles the urethra. The end portions extend through the abdominal tissue to anchor the intermediate portion in position. The sling places the urethra under a transverse compressive load to hold it closed and prevent inadvertent urination. The tube is formed from interlaced filamentary members. Interlacing may be by warp knitting, weaving using a leno weave or braiding using a tri-axial braid structure. The end portions have a rough texture to facilitate anchoring in the tissue of the abdominal wall. The intermediate portion is smooth and soft to prevent tissue erosion.

Description:
FIELD OF THE INVENTION  
       [0001]     This invention relates to a device implantable within the abdomen to treat urinary incontinence.  
       BACKGROUND OF THE INVENTION  
       [0002]     In the United States, more than 13 million people suffer from the effects of urinary incontinence. Although significant numbers of men are afflicted, women suffer-from this disorder in disproportionate and overwhelming numbers.  
         [0003]     Some factors which lead to incontinence in women include the effects of childbirth, hysterectomies, urinary tract infections, relaxation of the pelvic muscles and the thinning of urethral tissue associated with hormone reduction during menopause. These factors contribute to a weakening of the urinary sphincter muscles (located beneath the bladder surrounding the urethra) which may lead to “stress incontinence”, “urge incontinence” or a mixture of both types of incontinence. Stress incontinence is associated with the involuntary leakage of urine due to increased pressure on the bladder occasioned by such mundane actions such as coughing, sneezing, laughing, bending or lifting heavy objects. Urge incontinence occurs when one has the need to urinate but is unable to prevent leakage until proper facilities are reached.  
         [0004]      FIG. 1  shows a sling  10  presently used for treating urinary incontinence. Sling  10  comprises an elongated flat strap or tape of material that is surgically implanted within the person&#39;s abdomen  12  between the vagina  14  and the urethra  16 . The sling  10  has a U-shaped portion  18  that cradles and supports the urethra. Extension portions  20  attached to the U-shaped portion extend through the abdomen away from the vagina and anchor the sling within the abdomen. The extension portions may be attached to the pubic bone  22  as shown or may merely be anchored within the tissue of the abdomen. The U-shaped portion  18  places the urethra under compression and constricts it so that it takes some muscular effort to exert pressure on the bladder and force urine from it through the constricted urethra. The tension in the sling determines the amount of muscular effort required to effect urination.  
         [0005]     There are several disadvantages to this device. It is not always possible to establish the proper sling tension. Too much tension means that it will be difficult, if not impossible, for the person to urinate using muscular contractions that compress the bladder. Too little tension means that the disorder remains uncorrected despite the person having undergone the procedure. It is, furthermore, difficult to adjust the tension once the sling is implanted. Adjustment is desirable because over time, the muscles and other tissue of the abdomen change in their compliance, strength and tone, and what may be sufficient tension at one point in time may be too much or too little later, leading to problems which must again be addressed by invasive surgery. Probably the worst problem associated with slings currently in use is known as “erosion”, whereby, in response to normal movement and pressure of the abdominal muscles, the edge of the sling, being relatively sharp, cuts through the abdominal tissue and enters the urethra. Erosion is indicated by burning pain during urination.  
         [0006]     There is clearly a need for an improved sling for the treatment of urinary incontinence that does not suffer the disadvantages of present treatment devices.  
       SUMMARY OF THE INVENTION  
       [0007]     The invention concerns a urinary incontinence sling positionable in the abdomen between the urethra and the vagina to compress the urethra. In one embodiment, the sling comprises an elongated tube having opposite end portions and an intermediate portion positioned between the end portions. The intermediate portion is bendable to form a substantially U-shaped cradle positionable adjacent to the urethra. The end portions are positionable so as to extend through the abdomen in a direction away from the vagina. The end portions are in anchoring engagement with living tissue forming the abdomen. The intermediate portion compresses the urethra with a predetermined force.  
         [0008]     The tube has a cross sectional shape which may be circular, oval or elliptical for example. Preferably, the tube comprises a plurality of interlaced filamentary members. The filamentary members may be interlaced by knitting, weaving or braiding. The end portions are substantially inextensible, and the intermediate portion is lengthwise elastically extensible.  
         [0009]     In another embodiment, an elastically expandable and contractible body is positioned within the intermediate portion of the tube. The body has a predetermined internal pressure. The pressure substantially determines the compressive force exerted on the urethra by the tube.  
         [0010]     The tube may comprise a pouch positioned at the intermediate portion of the tube. The pouch is defined by closing the tube at two locations in spaced apart relation to one another. The pouch is used to contain the expandable and contractable body within the intermediate portion.  
         [0011]     In another embodiment, the urinary incontinence sling comprises elongated end portions oppositely disposed and an intermediate portion positioned between the end portions. The intermediate portion is bendable to form a substantially U-shaped cradle positionable adjacent to the urethra. The end portions are substantially inextensible and are positionable so as to extend through the abdomen in a direction away from the vagina. The end portions are in anchoring engagement with living tissue forming the abdomen. The intermediate portion compresses the urethra with a predetermined force. In this embodiment, the intermediate portion is preferably lengthwise elastically extensible. The end portions preferably comprise elongated straps and the intermediate portion comprises a tube. An elastically expandable and contractible body may be positioned within the tube that comprises the intermediate portion. The body has a predetermined internal pressure that substantially determines the compressive force exerted on the urethra by the intermediate portion. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0012]      FIG. 1  is a partial perspective anatomical view of the female abdominal region illustrating use of a prior art incontinence sling;  
         [0013]      FIG. 2  is a perspective view of a sling according to the invention;  
         [0014]      FIG. 3  is a side view of an embodiment of a sling according to the invention;  
         [0015]      FIG. 4  is a partial sectional view of an abdomen in the medial plane;  
         [0016]      FIG. 5  is a partial perspective view on an enlarged scale taken from within circle  5  of  FIG. 4 ;  
         [0017]      FIG. 6  is a perspective view of an embodiment of a sling according to the invention;  
         [0018]      FIG. 7  is a perspective view showing the sling of  FIG. 6  implanted within an abdomen;  
         [0019]      FIG. 8  is a perspective view of an embodiment of a sling according to the invention;  
         [0020]      FIG. 9  is a side view of an embodiment of a sling according to the invention and a tool for implanting the sling within an abdomen; and  
         [0021]      FIGS. 10-12  illustrate steps in the use of the tool shown in  FIG. 9  to implant the sling in an abdomen. 
     
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS  
       [0022]      FIG. 2  shows an incontinence sling  30  according to the invention. Sling  30  comprises an elongated flexible tube  32  having opposite end portions  34  and  36 . An intermediate portion  38  is positioned between end portions  34  and  36 . The intermediate portion  38  is bendable to form a substantially U-shaped cradle  40  positionable adjacent to the urethra  16  as shown in  FIGS. 4 and 5 . End portions  34  and  36  are positionable so as to extend through the abdomen  12  away from the vagina  14 . The end portions  34  and  36  anchor the sling  30  in position within the abdomen as described in detail below.  
         [0023]     End portions  34  and  36  are substantially inextensible lengthwise, especially in comparison with center portion  38 , which is lengthwise elastically extensible. By varying the longitudinal stiffness as a function of position along the sling  30  it is possible to achieve better control over the transverse compressive force applied to the urethra and thereby avoid the aforementioned problems associated with too little or too much sling tension. Furthermore, because they are substantially inextensible, the end portions  34  and  36 , which anchor the sling  30  within the abdomen, are less susceptible to the effects of “sling recoil” as described in detail below.  
         [0024]     In a preferred embodiment, sling  30  is formed from warp knitted polypropylene monofilaments.  
         [0025]     Polypropylene is preferred because it is bio-compatible, provokes a healing response from living tissue and has a history of success as a material implantable within the human body. Other polymers such as nylon, polyester and polytetrafluoroethylene are also feasible as are bio-absorbable materials such as polyglycolic acid, polylactic acid, PEA, PEUR, PEG and PLLA.  
         [0026]     Warp knitting is preferred because it provides a filamentary mesh structure that yields a substantially lengthwise inextensible tube  32 , advantageous for reasons discussed in detail below. The axial stiffness that governs the lengthwise extensibility of the various portions may be controlled by increasing or decreasing the number of warp yarns in a portion, by introducing warp yarns having greater or lesser diameter, by making the warp yarns from materials having greater or lesser moduli of elasticity, or by a combination of any of these techniques. The substantially inextensible end portions  34  and  36  preferably have an extensibility between about 10% to about 20% per unit load, with about 15% extensibility per unit load being most preferred.  
         [0027]     Tube  32  may also be woven, the leno weave being preferred for woven embodiments because it too produces an axially inextensible structure. Braiding is also feasible, with the triaxial braid providing the desired control over lengthwise elongation of the tube. The tube may also be a substantially continuous membrane, preferably formed of expanded polytetrafluoroethylene.  
         [0028]     The tube  32  preferably has a round cross-section with a diameter of about 7 mm. Other cross-sectional shapes, such as oval, ellipsoidal or polygonal are of course feasible. The width of tube  32  is about 10 mm when flattened in contact with the abdominal tissue as shown in  FIG. 5 . The tube  32  is about 12 inches long before implanting.  
         [0029]     Implanting of sling  30  is described with reference to  FIGS. 3-5 . As shown in  FIG. 3 , curved tunneling needles  42  are attached to end portions  34  and  36  of tube  32 . Tunneling needles  42  are used to penetrate the abdominal tissue and draw the sling  30  through the abdomen  12  on opposite sided of the urethra  16  as shown in  FIG. 4 . As shown in detail in  FIG. 5 , an incision  44  is made in the vagina  14  adjacent to the urethra  16 . Needles  42  are inserted through the incision  44  to pass on opposite sides of the urethra  16 . The needles  42  are forced through the abdomen tissue  46  and exit through the abdominal anterior surface where they are drawn out of-the patient, thereby drawing the sling  30  through the incision  44 , around the urethra  16  and through the abdominal tissue  46 . The appropriate tension is placed on the sling and the end portions  34  and  36  are trimmed so that they remain beneath the surface of the skin of the abdomen.  
         [0030]     Sling  30  is anchored in position by end portions  34  and  36 . Anchoring may be effected in various ways, for example, by the intergrowth of abdominal tissue  46  through the end portions  34  and  36 . For such anchoring, it advantageous to provide end portions  34  and  36  with appropriate material properties, surface texture and porosity that favors tissue ingrowth so that a strong anchoring of the sling is quickly achieved. Materials such as polypropylene are used in the end portions because polypropylene is known to provoke an aggressive healing response in living tissue. The surface texture of the end portions may be enhanced by the addition of a knap or by annealing the surface by the application of heat, or by using a particular stitch or multifilament yarn which gives a desired roughness. Furthermore, the porosity of the end portions  34  and  36  may be tailored to have interstitial spaces sized to promote tissue ingrowth. Porosity may be controlled by weave or stitch density as well as by varying the size of the filaments and their type, i.e., multifilaments, monofilaments and texturized filaments may be combined to yield a desired effect. The healing response may also be encouraged by the use of coatings on the end portions  34  and  36  such as thrombin and collagen.  
         [0031]     It is advantageous that cradle  40  have a smooth, soft surface that helps to mitigate erosion. To that end, the intermediate portion  38  may have different characteristics from the end portions  34  and  36 , for example, the density of the weave, knit or braid may be greater to better distribute the forces applied to the urethra  16 . Alternately, it may be advantageous to form intermediate portion  38  from a lower density material with a correspondingly softer surface.  
         [0032]     Two advantages of the sling  30  according to the invention may be explained with reference to  FIGS. 1 and 5 . The first advantage is how the sling  30  mitigates or eliminates the detrimental effect of erosion. As explained above (see  FIG. 1 ), erosion occurs as a result of normal body movement and describes a condition whereby the edge  48  of the U-shaped portion  18  of prior art incontinence sling  10  cuts through the abdominal tissue  46  and enters the urethra  16 . This happens largely because prior art slings are flat strips with two opposite edges that are relatively stiff and sharp as compared with the tissue in which they reside. If the strip forming the prior art sling is twisted when it is implanted, the risk of erosion is greatly increased. However, as shown in  FIG. 5 , sling  30  according to the invention is a tube and not a flat strip, and therefore cannot present an edge to any portion of the tissue between the vagina  14  and the urethra  16  regardless of its orientation or if it is twisted. Tubular slings  30  according to the invention are far less likely to cause erosion than prior art flat strip slings because they have no sharp edge.  
         [0033]     The second advantage of the sling  30  is provided by the manner of interlacing the filamentary members comprising the tube  32  which emphasizes control over the axial stiffness of the tube. As explained above for the sling  30  according to the invention, the particular knit, weave or braid is chosen to produce a substantially lengthwise inextensible tube (i.e., little to no stretch under tensile load). The advantage of an inextensible tube is that, once set during implantation, the pressure exerted on the urethra  16  by the sling will not change significantly due to “recoil” of the sling.  
         [0034]     Recoil occurs most acutely with prior art slings  10 , shown in  FIG. 1 , that have significant axial flexibility. As the sling  10  is drawn through the abdominal tissue during implantation, it encounters significant resistance in the form of surface drag. The drag applies a tensile load to the sling, notably the extension portions  20 , which, if flexible, will stretch lengthwise, placing the sling in a state of elastic tension within the abdominal tissue. Further tension (and stretching) may be applied to the extension portions  20  as the sling  10  is adjusted to apply pressure to the urethra  16 . Because the extension portions  20  have stretched, they are under tension and therefore they constantly try to shrink back to their nominal length and relieve the tension. This shrinkage occurs during the healing process before the extension portions are anchored and the result is an increase in the force applied to the urethra as the U-shaped portion  18  is drawn toward the extension portions  20 . The increased force on the urethra  16  caused by the recoil of the sling may mean that too much pressure is exerted by the sling  10 , making it difficult to impossible to urinate by exerting muscle pressure on the bladder.  
         [0035]     Sling  30 , being substantially lengthwise  20  inextensible, avoids the problems associated with sling recoil. As they are drawn through the abdominal tissue  46 , the end portions  34  and  36  of sling  30  do not stretch significantly and thus will not recoil and change the pressure on the urethra after implanting of the sling. Furthermore, because there is so little elastic tension within the end portions  34  and  36  as compared with the center portion  38  where the elasticity is concentrated, the pressure on the urethra may be established more precisely and reliably, as it is not necessary to account for the elasticity of the entire sling, only the more limited central portion  38 . Thus, by concentrating the elasticity of the sling in the center portion  38  (and not in the end portions  34  and  36 ) the problem of changing sling tension due to recoil is substantially reduced or eliminated.  
         [0036]     An alternate embodiment of a sling  50  allowing for adjustability of the pressure on the urethra is shown in  FIG. 6 . Sling  50  is formed from a tube  52  having end portions  54  and  56  and an intermediate portion  58  as described above. A pouch  60  is positioned in the intermediate portion  58 . Pouch  60  may be formed in any number of ways and preferably by sealing the tube closed at two points  62  and  64  in spaced apart relation to one another. Sealing may be by heat fusion, sewing, interknitting, interweaving or interbraiding of the tube. Once the sling  50  is implanted, as shown in  FIG. 7 , pouch  60  is filled with a compound such as silicone that is bio-compatible. The silicone body  66  is injected through a needle  68  in liquid form and then cures to form an elastic solid. While body  66  is curing a gas is injected into it to form a chamber  70  within the body  66 . After the body  66  is cured, the gas is replaced by a liquid. The body  66  with chamber  70  then forms an expandable and contractible body like a balloon within pouch  60  within which a fluid is maintained. If it becomes necessary to later change the pressure exerted by the sling  50  on the urethra  16 , this may be accomplished by inserting a needle into the chamber  70  and pumping in or removing fluid to increase or decrease the volume of the body  66 .  
         [0037]      FIG. 8  illustrates another embodiment of a sling  72  according to the invention. Sling  72  has a tubular intermediate portion  74 . From each end of intermediate portion  74  straps  76  and  78  extend. This sling embodiment is formed so as to be lengthwise inextensible so as to mitigate sling recoil. Straps  76  and  78  are relatively thin so as to better promote tissue ingrowth and anchoring during healing. The intermediate portion  74  has the tubular configuration so as to avoid erosion.  
         [0038]      FIG. 9  shows another embodiment of a sling  80  according to the invention. Sling  80  is similar to sling  30  but has openings  82  positioned between the end portions  84  and  86  and the intermediate portion  88 . The openings  82  allow tunneling needles  90  to be positioned within the end portions for implantation into the abdominal tissue. Tunneling needles  90  are attached to a tool  92  which facilitates manual manipulation of the needles and also allows for the deployment of mechanical anchors  94  as shown in  FIGS. 10-12 .  
         [0039]     The needles  90  are inserted into the vaginal incision as described previously and through the abdominal tissue. The mechanical anchors  94 , in the form of a type of staple having deformable legs  96 , are attached to the end portions  84  and  86  but are deployable into engagement with the abdominal tissue by a mechanism (not shown) associated with the tools  92 . After the sling  80  is positioned as desired ( FIG. 10 ) the legs  96  of the anchors  94  are deployed ( FIG. 11 ) to engage the abdominal tissue and anchor the sling  80  in position. Tunneling needles  90  are then removed ( FIG. 12 ) and the sling  80  remains anchored in place by the engagement between legs  96  and the abdominal tissue.  
         [0040]     All of the sling embodiments according to the invention may have radiopaque markers installed to render the sling visible by fluoroscope techniques and thereby facilitate sling positioning within the abdomen. The markers may, for example, be positioned at point locations to indicate boundaries and orientation of the sling, and/or the markers may comprise filamentary members coated with radiopaque material and interlaced with the filamentary members comprising the sling to render the length of the sling visible during implanting.  
         [0041]     Slings according to the invention provide numerous advantages over prior art slings including the mitigation or elimination of erosion, the elimination or reduction of recoil effects on urethral pressure as well as providing a sling wherein the pressure on the urethra may be adjusted without the need for invasive surgery. Furthermore, the sling itself, being a tube, provides a guide for the disposition of anchoring systems or other accessories in that the tube interior defines a path through the abdominal tissue.