Abstract:
A patch for replacement of a portion of bladder wall following partial cystectomy includes a multi-layered membrane of soft silicone with a thickness of about 600 microns so as to be sufficiently elastic to be able to withstand the dilatations due to expansion and deflation of the bladder, a surface layer of texturized silicone that is arranged to face an outside of a bladder to reduce a risk of adhesion of fibrotic capsule, and an inner coating of pyrolytic turbostatic carbon that is arranged to face an inside of the bladder.

Description:
BACKGROUND OF THE INVENTION 
     The present invention refers to a patch for replacement of a portion of bladder wall, following partial cystectomy. 
     As is known, when a portion of a patient&#39;s bladder is affected by a serious pathology, such as partial malignancy, this portion of bladder must be removed to prevent the disease from spreading to the whole bladder. Removal of this portion of bladder creates a hole in the bladder which is closed by means of a patch sutured to the perimeter of the bladder wall defining this hole. 
     These patches are taken from the patient&#39;s bowel turned inside out. That is to say, during surgery the portion of bladder affected by the malignancy is removed, Then, a patch is removed obtained by cutting the patient&#39;s bowel wall in situ, taking care to wash and clean it carefully to eliminate any source of infection, due above all to the intestinal mucus. Finally, this patch is sutured to the bladder wall to close the hole left by removal. 
     This system nevertheless presents some drawbacks. In fact during surgery it is not possible to eliminate the intestinal mucus entirely from the new bladder, resulting in possible infections. 
     Furthermore these patches of bowel wall have a short average life. In fact they are unable to go beyond a life of 10 years because of tearing of the intestinal wall which wears out in a period of less than 2-3 years. 
     Various attempts to produce synthetic patches have not been successful, mainly because the inner surface of the patch did not withstand encrustation from urine. 
     SUMMARY OF THE INVENTION 
     Object of the present invention is to overcome the drawbacks of the prior art, by providing a patch for replacement of a portion of bladder wall following partial cystectomy which is reliable and long-lasting. 
     Yet another object of the present invention is to provide such a patch that is practical for the surgeon and at the same time easy to produce. 
     The patch for replacement of a portion of bladder wall following partial cystectomy according to the invention comprises a multi-layered membrane of soft silicone with a thickness of about 600 microns. 
     In this manner the patch is sufficiently elastic to be able to withstand dilatations due to expansion and deflation of the bladder. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further characteristics of the invention will be made clearer by the detailed description that follows, referring to purely exemplifying and therefore non limiting embodiments thereof, illustrated in the appended drawings, in which: 
         FIG. 1  is a plan view of a patch according to a first embodiment of the invention, shown from the side destined to face towards the outside of the bladder. 
         FIG. 2  is a plan view of the patch of  FIG. 1 , but shown from the side destined to face towards the inside of the bladder; 
         FIG. 3  is an enlarged cross sectional view of a portion of the patch, in which the section is taken along the sectional plane III-III of  FIG. 1 ; 
         FIG. 4  is a plan view, partially cut away, of a patch according to a second embodiment of the invention, shown from the side destined to face towards the outside of the bladder; 
         FIG. 5  is a plan view of the patch of  FIG. 4 , but shown from the side destined to face towards the inside of the bladder; 
         FIG. 6  is an enlarged cross sectional view of a portion of the patch, in which the section has been taken along the sectional plane VI-VI of  FIG. 4 ; and 
         FIG. 7  is a perspective view, illustrating diagrammatically the application of the patches according to the first and second embodiment of the invention to a bladder. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     With reference for now to  FIGS. 1-3  a patch according to the first embodiment of the invention, denoted as a whole with reference number  1 , is described. The patch  1  is made from a multi-layered membrane ( FIG. 3 ) of soft silicone, with a thickness of about 600 microns so as to be sufficiently elastic to be able to withstand the dilations due to expansion and deflation of the bladder. 
     The silicone used, for example, may be made of copolymers of dimethyl and metavinyl siloxane, reinforced with silica or silicon. A medical silicone is preferably used, such as for example that known by the code number MED 4735™ and marketed by Nusil Technology. 
     The membrane  2  of the prosthesis  1  preferably consists of 20 layers of silicone, each with a thickness of about 30 microns. 
     The layers of silicone are overlapped in the semi liquid state and then the layered membrane  2  is placed in an oven for vulcanisation at a temperature of about 150° C. and for a time ranging from 30 min to 1 h, according to the size of the patch that is to be produced. After the vulcanisation cycle, the multi-layered silicone membrane is in its optimal consistency of softness and elasticity and is no longer in the semi-liquid state. 
     The last, outermost layer  3  of the silicone membrane, destined to face towards the outside of the bladder, is advantageously texturised so as to obtain a rough surface which serves to minimize the risk of adhesion of the fibrotic capsule to the patch  1 . The texturising process involves only the last outer layer  3 . Once the last layer of silicone  3  has been applied, it is evaporated with cyclohexane for 10 minutes and is sprinkled with normal cooking salt (NaCl) before vulcanization. The silicone membrane  2  with the salted final layer  3  is then placed in the oven for vulcanization. 
     This procedure of salting of the last layer  3  and vulcanization is repeated twice. At the end of the two cycles of salting and vulcanization, the final device is dipped into water and brushed to eliminate the salt from the last layer  3 . 
     The surface of the patch  1  destined to face towards the inside of the bladder is coated with a microfilm  4  of highly biocompatible biomaterial, such as for example pyrolytic turbostratic carbon, having a thickness of about 0.2-0.3 microns. 
     Experimental laboratory and bench tests with a scanning electron microscope have been performed on samples of silicone strips coated with such a biomaterial. These samples were dipped into human urine for one week and subjected to torsion, bending and folding stress for cycles of 10,000 times. Microscope scanning did not yield any sign of deterioration due to the corrosive effect of urine. 
     With reference to  FIGS. 4-6  a patch  100  according to a second embodiment of the invention is described, in which like or corresponding elements to those already described are indicated with the same reference numerals and are not described in detail. 
     In this case the patch  100  has a multi-layered membrane  2  of soft silicone provided with a hole  5  having a larger diameter than the diameter of the ureters  20 ,  20 ′ and of the urethra  21  (shown in  FIG. 7 ). This hole  5  can have a diameter of 20 mm. 
     The hole  5  is made with a special surgical instrument consisting of a handpiece or punch, with a squared section tip 3 cm long and a final diameter between 8 and 14 charrrier (Ch), to comply with the possible dimensions of the ureters  20 ,  20 ′ and the urethra  21 . 
     The hole  5  is closed by a portion of membrane  6  with a substantially discoid shape and a larger diameter than the hole  5 . The portion of membrane  6  is similar to the multi-layered membrane  2  but can be without the texturized layer on the outer surface. The portion of membrane  6  is applied to the inner surface of the patch  100  destined to face towards the inside of the bladder, by means of melting or heat bonding of the silicones in a single layer with the membrane  2 , and subsequent vulcanization in an oven. 
     Finally the inner surface of the patch  100 , together with the portion of membrane  6 , are coated with the microfilm of pyrolytic turbostratic carbon  4 . 
     The patches  1  and  100  can be produced in any shape and size. The patches  1  and  100  can preferably have a rectangular shape 200 mm×300 mm or a square shape with a 200 mm side. 
     For both patches  1  and  100  the whole manufacturing cycle must be performed in a controlled atmosphere, that is with controlled contamination, in a white room. Once processing is completed, the patches  1 ,  100  are placed in a double blister pack closed with a sheet of Tyvek to avoid contamination, and sent for an ETO (ethylene oxide) sterilization cycle. 
     At this point the patches  1 ,  100  are ready to be used during a surgical session. 
       FIG. 7  shows diagrammatically a bladder  40  with the relative ureters  20 ,  20 ′ and urethra  21 . 
     If the area of the bladder  40  affected by malignancy is distant from the ureters  20 ,  20 ′ e urethra  21 , the surgeon removes this affected area and applies a patch  1  to cover the removal hole by means of suture stitches  7  which connect the perimeter of the patch  1  to the bladder wall  50  around the removal hole. 
       FIG. 7  also shows the case in which the area of the bladder  40  affected by malignancy is near one 20 of the ureters. In this case the surgeon removes said affected area detaching it from the relative ureter  20 . 
     Then, the surgeon makes a hole  9  in the portion of membrane  6  of the patch  100 . In order to pierce the portion of membrane  6 , the surgeon can use the same hand piece or punch used to pierce the membrane  2  during production of the patch  100 . The tip of the punch is chosen according to the size of the ureter  20  and the hole  9  is made with the Ch measurement that the surgeon considers appropriate according to the size of the ureter  20  during the surgical procedure. 
     The ureter  20  is inserted into the hole  9  of the patch  100 , which, being elastic, tightens slightly around the tube of the ureter  20 . Then, the portion of membrane  6  of the patch  100  is fixed to the ureter  20  by means of four suture stitches  11  disposed in a square, around the tube of the ureter  20  and passing through the portion of membrane  6  and through the tissue of the ureter  20 . 
     Finally the perimeter of the patch  100  is fixed, by suture stitches  10 , to the bladder wall  40  around the ureter  20 . 
     For example, for the suture stitches  7 ,  11  and  10  a curved cylindrical needle must be used and Monocryl Ethicon™ 4-0 e 5-0 thread can be used, produced by Johnson &amp; Johnson and consisting of polyglecaprone, that is: a copolymer made by synthesis of glycolide (75%) and epsilon caprolactone (25%). This thread is not coated, is monofilament and is not braided. The manufacturer indicates this thread as the most suitable for sutures in general for soft tissue and vessels, amongst which are included the ureters and urethra. 
     There are, however, other suture materials which could conveniently be adapted to the cases in question and to the requirements of the patches; it is left to the surgeon&#39;s discretion to choose the one most congenial to him. 
     The holes for passage of the suture stitches  7 ,  11  and  10  in the ureter  20  and in the bladder  40  do not constitute a risk of leakage of liquid, in that in a few hours the tissue reforms. In order to avoid leakage of urine (liquid) the holes of the suture stitches  7 ,  11  and  10  are bonded and closed with one cc (one drop) of surgical glue, such as Glubran 2™ for example, normally available on the market. 
     The Monocryl™ thread used for the suture stitches is absorbed in about 90-120 days, but begins its downward curve of loss of tension on the 22nd day, ending and losing 75% of its tensile strength on the 28th day. From the 28th day tensile strength is no longer present in the thread, but by this date the ureter  20  and the patches  1  and  100  are kept fixed by the glue and above all by the formation of the fibrotic capsule which acts as a retaining element for the ureter and the patches  1  and  100 . It should be noted that the fibrotic or polyproteic capsule forms in about 30 days. 
     Numerous changes and modifications of detail within the reach of a person skilled in the art can be made to the present embodiment of the invention, without thereby departing from the scope of the invention as set forth in the appended claims.