. . "The reinforcement 52 of each tubular element 9 or 11 extends from the sleeve 10 over only a part of the length of said tubular element, in such a way that the remaining part can be cut, for example in order to adapt the length of the tubular element 9 to that of the prostatic segment 101/102, or to adapt the length of the tubular element 11 with respect to the site of a stenosis in that portion of" . .