the device represented in fig1 for implanting endoprosthesis 1 has basically a tubular , flexible outer body 2 and an elongated , flexible core element 3 . tubular outer body 2 is represented in lengthwise section from break line x to its distal end . at its proximal end , tubular body 2 is provided with a handle 5 . elongated core element 3 is placed in tubular body 2 , where core element 3 is designed to be longer than tubular body 2 and also has a handle 6 . toward its distal end , core element 3 exhibits a region b , which serves to receive endoprosthesis 1 . this region b exhibits at its proximal end a shoulder 8 made from x - ray opaque material . distally contiguous to this is a section 9 , the diameter of which is reduced . following section 9 is an area 10 in which a relief in the form of a stamping 11 is impressed and which exhibits a somewhat larger diameter than section 9 preceding it . the form of relief or stamping 11 corresponds to the structure of the inner surface of folded endoprosthesis 1 . contiguous to area 10 lies a section 13 that exhibits approximately the same diameter as section 9 . following this is a ring 14 , which is also made of x - ray opaque material and which is designed to be somewhat larger in diameter than section 13 . finally , at its distal end , core element 3 has a blunt , cone - shaped tip 15 . extending the entire length of core element 3 is a lumen 16 in which a guide wire 17 can be inserted . for the sake of better clarity , endoprosthesis 1 is depicted outside of the device and folded up in this representation . in this way , the correlation between the form of stamping 11 and that of folded endoprosthesis 1 can be seen . it can also be clearly seen from this representation that the length of area 10 , which is provided with stamping 11 , is shorter than the length of the endoprosthesis ; it preferably totals approximately 10 - 50 % of the length of the endoprosthesis . as a result of this length of stamping 11 , the flexibility of the device in region b of endoprosthesis 1 is affected as little as possible by the piled up material and the form locking in the stamping area . on the other hand , however , a reliable form - locking connection between enclosed endoprosthesis 1 and core element 2 is guaranteed . fig2 shows the device in a ready - to - use condition . here endoprosthesis 1 is enclosed folded up between core element 3 and tubular outer body 2 . at the same time , the inner surface of endoprosthesis 1 meshes with core element 3 along stamping 11 impressed in area 10 . stamping 11 corresponds to the structure of the inner surface of endoprosthesis 1 , so that a large number of form - locking meshing sites are formed between area 10 of core element 3 and endoprosthesis 1 . since the individual threads of a layer of endoprosthesis 1 diverge when the latter is folded up , differences in the location of the threads with respect to stamping 11 could result in the region of the proximal and distal ends of endoprosthesis 1 . for this reason , it is advantageous to provide sections 9 and 13 , which have a smaller diameter than area 10 , between the latter , which is provided with stamping 11 , and the ends of endoprosthesis 1 . a first type model of the device can be seen in fig3 in an enlarged cross section along line a -- a of fig2 . endoprosthesis 1 is enclosed between tubular outer body 2 and core element 3 . the distance between the outer diameter of core element 3 and the inner diameter of tubular outer body 2 is chosen in such a way that the inner layer of endoprosthesis 1 is pressed into the recesses resulting from stamping 11 . the depth of stamping 11 corresponds to approximately 50 % of the thickness of the inner layer of the semifinished material used in endoprosthesis 1 . in this case , a thin wire is used as the semifinished material for manufacturing endoprosthesis 1 . however , the same ratio applies if endoprosthesis 1 is punched out , for example , from thin sheet metal or is made of strip metal . the above - mentioned depth of stamping 11 ensures a good form - locking connection between core element 3 and endoprosthesis 1 by means of a large number of form - locking meshing sites 20 and guarantees , in addition , sure radial separation and unfolding of released endoprosthesis 1 , because the form - locking connection does not affect the relative motion of the layers of semifinished material in relation to one another . a second type model of the device is illustrated in fig3 a in an enlarged cross section along line a -- a in fig2 . in this example , core element 3 has a coating or sheath 3a . the advantage of such a coating or sheath 3a is that it can exhibit properties other than those of core element 3 . the change in diameter required in this area can be easily obtained as well by means of this sheath or coating 3a . thus , for example , the thermoplasticity of core element 3 can be lower than that of coating or sheath 3a . consequently , the depth of stamping 11 can be easily influenced by the thickness of coating or sheath 3a . sheath 3a can be manufactured very easily , for example , by shrinking a contracting tube onto core element 3 . the operation of the device is explained by means of fig4 . using the device , endoprosthesis 1 is inserted folded ( fig2 ) in a body canal 22 , which is only indicated schematically , in the known manner and is advanced until the distal end region b of the device is positioned so that enclosed endoprosthesis 1 is at the desired location in body canal 22 . at the same time , the advance of folded endoprosthesis 1 in body canal 22 is monitored by means of known processes such as fluoroscopy . the location of endoprosthesis 1 is readily visible due to x - ray opaque rings 8 and 14 , which are fitted on core element 3 in the area of the two ends of enclosed endoprosthesis 1 . once endoprosthesis 1 is in the intended final position , core element 3 is locked into position and endoprosthesis 1 is slowly released by pulling back tubular outer body 2 . the two handles 5 and 6 are used for this purpose . since endoprosthesis 1 is self - expanding , the released portion begins to unfold and rest against the inner wall of body canal 22 . in unfolding , the length of endoprosthesis 1 is shortened accordingly . since there is a direct connection between the shortening of endoprosthesis 1 and the inner diameter of body canal and the diameter of endoprosthesis 1 in its inserted , unfolded state but the final amount of expansion is not known exactly , the final position of unfolded endoprosthesis 1 cannot be determined with certainty beforehand . thus the position of endoprosthesis 1 must also be monitored during the unfolding . if monitoring shows that it is positioned correctly , endoprosthesis 1 can be completely released by pulling back tubular body 2 to the area of shoulder 8 of core element 3 . if , however , it is discovered during the unfolding that endoprosthesis 1 is not in the correct position , it can be folded back up again in tubular body 2 by moving tubular body 2 forward . this makes it possible for endoprosthesis 1 to then be repositioned accordingly and released again in the new position in the manner described above . by means of a form - locking connection between endoprosthesis 1 and core element 3 , which is achieved via stamping 11 , which corresponds to the structure of the inner surface of endoprosthesis 1 , and via endoprosthesis 1 , which meshes with stamping 11 , it can be ensured , on the one hand , that the forces exerted to move core element 3 with respect to outer body 2 can be kept to a minimum and , on the other hand , that sure radial separation of self - expanding endoprosthesis 1 from core element 3 is still guaranteed even after a long period of storage . in short , sure and reliable operation is achieved by way of a device with this design . it can also be manufactured easily and inexpensively . the process for producing a stamping for this type of device can go as follows : an endoprosthesis 1 is pushed unfolded onto region b of core element 3 . then endoprosthesis 1 is folded up in the area of section 9 of core element 3 in which there is no stamping . next , tubular outer body 2 is pushed forward up to the proximal end of area 10 of core element 3 . endoprosthesis 1 is secured in position in this way . endoprosthesis 1 is subsequently folded up in the area where it is exposed by a pressing die , which is in itself known , and pressed by the pressing die on area 10 of core element 3 . the pressing die is now warmed with hot air so that endoprosthesis 1 , which has been pressed together , is heated and in this way pressed into the thermoplastic material of core element 3 or into its coating or sheath 3a . after removing the pressing die , tubular outer body 2 is pushed forward until its distal end lies against the back side of tip 15 of core element 3 and endoprosthesis 1 is thus completely enclosed . a corresponding process is utilized if a hardened plastic is used instead of the thermoplastic material . while this process is being carried out , it is absolutely imperative that shoulder 8 does not rest against the proximal end of endoprosthesis 1 . it automatically rests against the proximal end of endoprosthesis 1 once endoprosthesis 1 comes unmeshed from core element 3 upon release . shoulder 8 serves then as an abutment for endoprosthesis 1 when the remaining portion of the endoprosthesis still enclosed in tubular body 2 is released . obviously , processes are also conceivable in which the same endoprosthesis is always used to form the stamping . furthermore , it is also possible to impress the stamping by means of a positive cast of an endoprosthesis formed on the pressing die .
a device for implanting endoprostheses has a tubular outer body and an elongated core element placed inside of the outer body . to operate the device , both the core element and the tubular body are provided with handles at their proximal ends . in order to produce a form - locking connection between the endoprosthesis and the core element , the core element exhibits a region in which is impressed a stamping corresponding to the inner form of the endoprosthesis . as a result , there are a great number of form - locking meshing sites between the enclosed , folded endoprosthesis and the core element . a device with this type of design permits a partially released endoprostheses to be folded back up in a radially contracted state again by pushing the tubular body forward so that the endoprosthesis may be repositioned . in addition , sure and reliable operation is achieved by this type of stamping of the core element .