in the following description , the same reference numerals have been used to describe the various features of the instrument of the present invention as were used in wo - a - 9606567 . to facilitate the following discussion , however , the order of the figures has been changed and the reference numerals used to describe the female urinary system have been altered . with reference to fig1 - 6 , the surgical instrument of the present invention comprises a cylindrical tubular shank 10 having at one end thereof a handle 11 . at the other end of the shank there is a socket 14 . a cylindrical shaft 15 ( see fig2 and 5 ) is rotatably mounted in the shank and can be rotated manually by means of a knob 16 mounted to one end of the shaft . the other end of the shaft 15 forms a cylindrical portion 17 ( see fig5 ) of smaller outside diameter than the shaft , which joins a portion 18 having external threads , a smooth end portion 19 of further reduced diameter joining the threaded portion 18 , end portion 19 forming a guide pin at said other end of the shaft . portions 18 and 19 are received in the portion of socket 14 projecting from the shank . the surgical instrument as described so far is in agreement with the instrument disclosed in wo - a - 9606567 except that the end portion 14 ′ of socket 14 is flattened from opposite sides ( see fig1 and 2 ), so that the cross section of said end portion is non - circular . the surgical instrument also includes an exchangeable and disposable needle 21 which at one end thereof is attached to the shank at one end of the needle and extends over substantially a quarter of a circle to the other , free end thereof in order to follow substantially the profile of the pubis between the vagina and the abdominal wall . the needle has uniform circular cross section and has a smooth , preferably polished outside surface . at the free end thereof the needle forms a point 22 by being terminated by a conical portion . for attachment of needle 21 to shank 10 the needle forms at said one end thereof a straight portion 30 which is cylindrical but has milled flat faces 31 ( see fig3 ) over that part of said portion 30 , extending from the adjacent end of the needle , which shall be received by socket portion 14 ′. the needle should be oriented in a predetermined rotational position in relation to the shank , and more particularly it should project at right angles to the plane of handle 11 . this rotational position is secured by the non - circular shape of socket portion 14 ′ and the end portion of the needle having the flat faces 31 , which fits into socket portion 14 ′. the end portion of the needle having the flat faces 31 joins the body of the needle over the conical portion 32 , which tapers towards a shoulder 33 ( see fig3 ). an axial blind hole extends from the end surface of the needle said hole having a threaded portion 23 and inwardly thereof a narrower , cylindrical portion 24 . guide pin 19 is dimensioned to be guidingly received by said latter portion when the threaded portion 18 for attaching needle 21 to the rest of the surgical instrument is screwed into threaded portion 23 of the blind hole by rotating shaft 15 by manual rotation of knob 16 , the end surfaces of the shank and the needle being pressed against each other . also this attachment is in agreement with that described in wo - a - 9606567 . when the method as described in wo - a - 9606567 is practiced , two needles 21 a and 21 b ( see fig6 ) are each connected to each end of a tape 26 . according to the present invention , the tape 26 of the preferred embodiment comprises a mesh or netting forming openings of the order of 1 mm . a suitable material for the tape 26 is prolene ®, a knitted polypropylene mesh having a thickness of 0 . 7 mm manufactured by ethicon , inc ., sommerville , n . j ., usa . this material is approved by fda in usa for implantation into the human body . the netting ( tape ) 26 preferably has a width of approximately 10 mm and is enclosed in a thin polyethylene sheath 34 which , in flattened condition , has substantially the same width as the tape 26 although a difference in width is shown in fig2 in order to make the provision of the sheath 34 more clear . the length of the netting 26 should be approximately 400 mm . the netting 26 and the sheath 34 are interconnected by means of two rows 35 of stitching . the end portion of the sheath 34 is attached to the conical portion 32 ( see fig3 ) of the needle 21 by means of a suitable strong glue , and the interconnection of the needle 21 and sheath 34 is covered by a shrink hose 36 ( see fig3 and 4 ) made of rubber , which extends from the shoulder 33 over the conical portion 32 and partly over the cylindrical end portion 30 of the needle 21 . the shrink hose 36 is substantially flush with the surface of the needle 21 at the shoulder 33 . by this arrangement the netting 26 is securely attached to the needle 21 . the purpose of sheath 34 is , above all , to facilitate the insertion of the netting 26 in the manner described in wo - a - 9606567 , i . e ., when the netting 26 is pulled at the ends thereof from the vaginal wall to the abdominal skin and to avoid that rough edges of the netting irritate or damage the body tissues . when the tape has been positioned in the correct position as a sling around the urethra ( as described hereinafter in connection with the method of the present invention shown in fig7 - 14 ) the polyethylene sheath 34 shall be removed , and in order to facilitate the removal the sheath 34 should be perforated at the longitudinal center thereof as indicated by a dot - and - dash line 37 in fig6 so that the two halves of the sheath 34 can be withdrawn from the body by pulling at the respective outer ends thereof , the halves being separated at the perforation under the influence of the pulling force . the purpose of the polyethylene sheath 34 is also to protect the netting 26 during attachment to the needles 21 a , 21 b and during handling before and during insertion into the body . the longitudinal center of the tape 26 and sheath 34 should be indicated by a visible colour mark 38 , ( see fig6 so that the surgeon readily can see when the netting 26 is symmetrically located with reference to urethra during the surgery . the method of the present invention will now be described in detail with reference to fig7 - 14 . in fig7 - 14 , the relevant parts of the female lower abdomen are disclosed diagrammatically , the vagina being designated 40 , the vaginal wall 42 , the urinary bladder 44 , the urethra 46 , the pubic bone 48 , and the abdominal wall 50 . the first step of the surgery for implanting tape 26 is disclosed in fig7 and comprises penetration of the vaginal wall 42 by needle 21 a a cut having first been made in said wall 42 , and , also penetration of the soft tissue at one side of urethra 46 , the needle 21 a then , according to fig8 being passed close to the back of the pubic bone 48 and then through the abdominal wall 50 above the pubic bone 48 . a cut can be done through the abdominal wall 50 for the passage of the needle 21 a therethrough , but if the needle 21 a is pointed , it may be sufficient to let the needle 21 a penetrate into the abdominal wall 50 , from the inside thereof , and to make a registering cut in the abdominal wall 50 on the outside thereof . the shank 10 of the instrument is now disconnected from needle 21 a , fig9 by rotating shaft 15 at knob 16 so that the threaded portion 18 of the shaft 15 is unscrewed from the threaded portion 23 in needle 21 a , the needle 21 a then being withdrawn from the abdominal wall 50 by means of forceps and the tape 26 being pulled into and through the tissue as illustrated in fig1 . the other needle 21 b is now attached to the shank 10 , fig1 , and is passed through a cut in the vaginal wall 42 to pass through the soft tissue at the other side of the urethra 46 . the needle 21 b is passed through the abdominal wall 50 ( see fig1 ) and then , after having been disconnected from the shank 10 , is withdrawn from the abdominal wall 50 ( see fig1 ), all in the same way as in the earlier procedure with the first needle 21 a . tape 26 is now located at each side of urethra 46 as shown in fig1 and is tightened with the loop formed by the tape 26 located on the inside surface of the vaginal wall 42 ( see fig1 ). the surplus of the tape 26 at the outside of the abdominal wall 50 is cut off . then , the tape 26 is left as an implant in the body to form an artificial ligament attached to the abdominal wall 50 and providing the support for the urethra 46 as required in order to restore urinary continence . another kind of tape 26 , which may be used in the method according to the present invention , can be more closely woven than the tape 26 mentioned above and can be of such material that the tape 26 , after a shorter or longer period , will be completely resorbed . by the development of fibroblast proliferation stimulated by the tape 26 the reinforcement of the tissue required in order to restore the urinary continence will be obtained .