Endoprosthesis percutaneously inplantable in the body of a patient

An endoprosthesis is percutaneously implantable in the body of a patient by means of a catheter, this endoprosthesis being changeable from a small lumen during insertion to a larger lumen conforming to the functional position. This implant has a hose-like netting produced from at least one elastic filament, such netting having the structure of a wire mesh fence with meshes forming polygons, wherein the filaments each grip around each other in the corner points of the meshes following each other in the direction of the longitudinal axis of the prosthesis. According to an alternative embodiment, the endoprosthesis is a hose-like netting produced from elastic filament, such netting having the structure of a wire mesh fence with meshes forming polygons, wherein the meshes have connection zones with two filaments twisted around each other, such connection zones in each case extending in the longitudinal direction of the prosthesis.

BACKGROUND OF THE INVENTION
 1. Field of the Invention
 The present invention relates to an endoprosthesis percutaneously
 implantable by means of a catheter in the body of a patient, particularly
 in tubular vessels or organs, said endoprosthesis being designed in the
 form of an oblong, hollow body and, upon placement in the correct position
 during implantation, being changeable from a small lumen during insertion
 into a larger lumen conforming to its functional position.
 2. The Prior Art
 Prostheses capable of being inserted percutaneously and changeable in their
 lumen are known. They serve the purpose of opening or widening vascular
 lumina either by mechanical expansion by means of known balloon catheters
 from a small to a larger lumen, or such a prosthesis expands by itself
 after prior compression by spring force prior to the implantation, due to
 the initial stress produced in the spring during the compression.
 EP-A-0,292,587 describes an endoprosthesis that is received on a balloon
 catheter and expandable by dilation, as well as detachable from the
 catheter and placed in a vessel. This prosthesis is a "stent" manufactured
 by knitting or crocheting from metal or plastic thread material into the
 form of a hose-like hollow body, in connection with which the individual
 stitches consist of loosely meshing loops. During expansion, widening, due
 to dilation of the balloon of the catheter, the meshing loops undergo
 plastic deformation, and the expanded prosthesis thus remains in its
 expanded position.
 Self-expanding stents have been described in the prior art, for example in
 EP-A-0,183,372, U.S. Pat. No. 4,732,152 and DE-OS 4,137,857. Prior to
 their implantation, these prostheses are compresses against inherent
 spring return forces to a reduced cross section, inserted into the body in
 the compressed state, and, upon placement in the correct position, expand
 again in the respective vessel or hollow body of the patient's body due to
 cancellation of the force of retention, and are fixed thereby.
 The endoprosthesis described in EP-A-0,183,372 is one which, for the
 purpose of implantation, is compressed to a reduced cross section and then
 pushed in the compressed state by means of a pusher through a catheter
 previously inserted in the vessel, until it is positioned in the right
 position in the vessel. Such advancing of the prosthesis through the
 catheter requires a considerable expenditure of force because the
 displacement is counteracted by high frictional forces.
 A woven and elastically designed endoprosthesis has been described earlier
 in U.S. Pat. No. 4,732,152, which, in the compressed state, is kept
 together by a double cover, which is closed at the distal end. This cover
 is pulled back from the folded prosthesis in the same way as a stocking is
 pulled from the foot of a wearer. For the purpose of avoiding the friction
 occurring in this process, liquid may be filled in between the two leaves
 of the cover. However, this system, which seems to be initially suitable
 due to the reduction of the frictional resistances, is very complicated
 with respect to handling.
 DE-OS 4,137,857 describes a hollow body. This prosthesis is compressed
 against the action of resetting spring forces to a cross section that is
 reduced versus the widened functional position, and kept in this position
 by means of a mountable covering. After the covering has been mounted, the
 prosthesis automatically widens to a cross section conforming to the
 functional position. The covering, which may be a meshwork approximately
 in the form of a round crocheting, extends over the entire length of the
 prothesis and consists of at least one through-extending filament and one
 pull-up line. The prosthesis, which is kept in a radially compressed
 position by the covering, can be advanced, for example on a guide wire, or
 also rigidly received axially on the end of a probe or catheter.
 Finally an endoprosthesis is known, for which no documentation is available
 in the form of a published reference made from a memory alloy. This
 endoprosthesis is an oblong hollow body with a jacket that is broken many
 times and embodied in the way of a stretched metal.
 This endoprosthesis automatically widens from a smaller insertion lumen to
 a larger lumen. However, this endoprosthesis has little flexibility and in
 any case potentially has the hazard of fatigue fractures when implanted
 via a joint. Not all of the struts forming the jacket are connected with
 each other in the corner points, and, in the implanted state, such struts
 may thus detach themselves from the vascular wall and protrude into such a
 wall.
 SUMMARY OF THE INVENTION
 Contrary to the above mentioned prior art, it is an object of the present
 invention to provide an endoprosthesis which, as compared to the stents
 known according to the state of the prior art, is more flexible and has
 superior strength and stability in the expanded state.
 This object is achieved in accordance with the present invention in that
 the endoprosthesis is a hose-like netting produced from at least one
 elastic filament, such netting having the structure of a wire screen fence
 with mesh forming polygons, in which the filaments each grip around each
 other in their corner points in the direction of the meshes following one
 another in the direction of the longitudinal axis of the prosthesis.
 An endoprosthesis of the invention, which may be self-expanding by means of
 a balloon catheter, is adaptable to the requirements in any given
 application in a simple way, and represents a flexible structure that is
 implantable without problems also in joint regions and then capable of
 following the movements of the joint of the patient without impediment. In
 particular, it has been found that as compared to the prior art, such an
 endoprosthesis has an enhanced ratio between a small and a large radius in
 the widened position. This means that the insertion catheter to be
 inserted during implantation can be kept smaller than possible in
 connection with known prostheses.
 It has been found that it is especially preferable if the hose-like netting
 forming the endoprosthesis comprises at least one through-extending
 filament, which is braided into a round shape, forming meshes.
 Alternatively, the endoprosthesis can be produced from an initially flat
 netting that is then rolled into a hose shape, whereby two longitudinal
 edges of the netting are then joined with each other by means of a
 longitudinal seam.
 According to a particularly preferred embodiment of the invention,
 provision is made that the filaments loosely grip around each other, in
 each of the meshes adjacent to each other in the longitudinal direction of
 the prosthesis. In this manner, the prosthesis can be shortened from its
 maximum length so that the filaments will be abutting each other in the
 corner points of the meshes, by pushing the meshes together.
 With such an embodiment, the endoprosthesis is one that can be changed in
 its length within predetermined limits, whereby in the case of maximum
 axial expanse, the filaments gripping around each other abut one another
 in the corner points of the meshes. On the other hand, in the case of a
 shortening, these filaments grip around each other with more or less axial
 play. The special advantage of such an embodiment of the prosthesis is
 that whenever the length is adjusted to a length smaller than the maximum
 length, no shortening occurs during widening because the material required
 for widening in the radial direction has not be made available by
 shortening the length, but is available through the filaments of the
 individual meshes which do not abut one another axially.
 Furthermore, it has been found that it is desirable if the filaments are
 provided in the corner points of the meshes with interlocks engaging one
 another in a form-locked way. Such interlocks provide the prosthesis with
 a particularly pronounced strength in its widened condition.
 The aforementioned interlocks may be depressions formed by compressing the
 filaments intersecting each other in the stretched condition of the
 prosthesis in the corner points to approximately the thickness of one
 filament. These depressions engaging each other in the stretched condition
 of the prosthesis in a form-locked way in their locking positions, thereby
 provide a form-closed lock in each corner point.
 Instead of having the filaments loosely gripping around one another in the
 corner points of the meshes forming polygons, it is possible also to
 provide an embodiment in which, in the corner points of the meshes
 following each other in the direction of the longitudinal expanse of the
 prosthesis, the filament of each mesh is looped around the filament of the
 other mesh, forming an eye. Naturally, reducing the length of an
 endoprosthesis so formed by axial compression is limited, as compared to
 the embodiment with filaments that loosely grip around each other in the
 corner points.
 According to another embodiment, provision is made that the filaments
 crossing each other in the corner points of the meshes are connected with
 each other, which means that the points of intersection are stabilized in
 this way. This naturally leads to a comparatively high stiffness of such
 an endoprosthesis. Stabilization can be realized in many different ways,
 for example by gluing, fusing or soldering of the filaments at the points
 of intersection. Also, at the points of intersection, the filaments can be
 enclosed by clips or joined with each other by clamping such filaments
 together.
 An additional embodiment for achieving the object of the invention is one
 in which the endoprosthesis is a hoselike netting produced from elastic
 filaments, such netting having the structure of a mesh wire fence with
 meshes forming polygons, and that the meshes each have connection zones
 with two filaments twisted around each other, such zones of connection
 extending in the longitudinal direction of the prosthesis.
 An endoprosthesis with the above features is characterized by a
 particularly pronounced strength and stability in the expanded widened
 state without impairing the flexibility of the hoselike netting.
 In such an endoprosthesis, the connection zones comprising two filaments
 twisted around each other extend in the longitudinal direction of the
 prosthesis. According to a further embodiment, the connection zones can
 also extend along--imaginary--screw thread-like lines of an also imaginary
 cylinder jacket extending from the prosthesis, forming a helix structure.
 In this connection, the arrangement also may be selected in such a way
 that the helix structure is broken by changing the direction of successive
 meshes in a way such that with part of the meshes, the connection zones
 extending between such meshes extend at an angle relative to the zones of
 connection between other meshes, which leads to a structure as found in
 connection with "fish scales".
 With such an endoprosthesis, meshes adjacent each other in the
 circumferential direction each can be formed by two filaments, and meshes
 following each other in the axial direction as well as meshes joined with
 each other in each case via a connection zone each can be formed by the
 same two filaments. Alternatively, meshes disposed adjacent to each other
 in the circumferential direction each can be formed by two filaments, and
 the meshes disposed adjacent to each other axially and in the
 circumferential direction each can be formed by one of these filaments and
 another filament. Thus, the filaments participate in the axial direction
 and progressively from one mesh to the next in the formation of meshes
 disposed adjacent to each other in the circumferential direction,
 extending one after the other around the stent in the way of stairsteps.
 Such a formation of the stent has been found to be easily producible and
 to be advantageous with respect to its strength and stability in the
 widened state.
 Another preferred embodiment of the invention is characterized in that in
 the corner points of the meshes disposed radially adjacent to each other,
 the filaments each are twisted around against each other with a winding in
 a way such that under axial tensile forces, the locks formed by the
 twistings become disengaged, and the prosthesis, when losing its radial
 bearing strength, undergoes a lengthwise expansion as well as a change in
 cross section, leading to a small lumen.
 An endoprosthesis so formed can be advanced with a small cross section and
 corresponding longitudinal expanses without problems, for example in a
 blood vessel, by means of a suitable catheter, and subsequently brought
 into its functional position by radial widening associated with
 predetermined shortening.
 Furthermore, with such an embodiment, the filaments can be provided with
 depressions engaging each other form-locked in the expanded state, by
 pressing them together in the zones of connection, such zones being
 twisted against each other, which, in the widened state, results in
 superior locking and thus in greater radial bearing strength and
 stability.
 According to another embodiment, provision is made that one filament
 extends in each case without twisting in the connection zones in the
 longitudinal direction of the prosthesis, and that the other filament is
 wound around this filament in the form of a spiral. Such an embodiment
 permits a limited sliding of the one filament along the straight-lined
 section of the other filament, and, in view of the spiral-like windings,
 also permits a compression and stretching of the one filament. This
 permits a superior adaptation of an endoprosthesis so formed within curved
 areas.
 Another further embodiment includes a lock with at least one retaining bar,
 which extends in the longitudinal direction of the prosthesis and is
 solidly anchored in the netting with its one end, as well as provided on
 the other end with a hook for engaging a mesh. During radial widening of
 an endoprosthesis fitted with such a lock, the end of the retaining bar
 fitted with the hook slides across the meshes as the prosthesis is
 radially widened and the netting is shortened at the same time. The hook
 grips behind the filaments of the mesh, with the result that following the
 widening, the hose-like netting is prevented from radial compression in
 that any increase in length caused by a radial reduction is no longer
 possible.
 Desirably, the retaining bar can extend along the hose-like netting on the
 outer side and, in the implanted state, thus can be received between a
 vascular wall and the hose-like netting. It is assured in this way that no
 impairment of the lumen will occur under any circumstances. However, the
 retaining bar may also extend through the meshwork of the netting in the
 way of a warp thread, which keeps the lumen free as well.
 According to another preferred embodiment of the second variation of the
 invention, provision is made that the meshes comprise through-extending
 first filaments and second filaments connecting the first ones with each
 other. The second filaments are each wound around the first filaments by
 one mesh length and project at the end of the respective mesh to an
 adjacent first filament, and are wound again around the adjacent first
 filament again across one mesh length, and again project to another first
 filament at the end of the respective mesh. Thus, this type of mesh
 formation continues and the second filaments, upon winding around a first
 filament, each extend around an imaginary cylinder jacket of the
 endoprosthesis in a progressively, stair-step manner.
 With a further development of the two embodiment variations explained
 above, it is desirable to provide for limiting the length of the stent,
 the hose-like netting is fitted with warps extending in the longitudinal
 direction of the stent, which warps may be connected with the filaments
 forming the meshes at least within the zone of the ends of the prosthesis.
 These warp threads may include textile filaments and may be arranged
 closely adjacent to each other in a way such that they form a jacket
 enclosing the stent.
 According to a further embodiment of the last-mentioned feature, the warp
 threads may include biodegradable material and/or may be designed as
 medication depots, releasing medications in the course of their
 degradation. An example of such a biodegradable material is vegetable
 fiber or animal fiber.
 According to yet another further embodiment, provision is made that the
 warp threads include extensible material such as textured textile threads.
 However, the warp threads may also include nonelastic material having a
 high density and proton number, which has been found to be particularly
 advantageous in connection with implantations under X-ray control because
 such a material absorbs X-rays to a high degree and is, therefore, highly
 visible in the X-ray image. Examples of such materials include titanium
 wire or stainless steel wire.
 The filaments, whether first or second, can be made from biocompatable
 materials, such as polyamide fibers like nylon fibers or polyolefin fibers
 such as polyethylene fibers or polypropylene fibers. These fibers have a
 diameter which ranges between 0.01 mm and 1.0 mm.
 Desirably, with the two embodiment variations discussed above, the ends of
 the filaments are bent off and joined with the netting at the face ends of
 the hose-like netting as well, in order to effectively avoid injury in the
 course of implantation, or in the implantation site. For example, the
 bentoff ends of the filaments may be braided in, glued, soldered or fused
 at the face ends of the hose-like netting, or also may be shaped as eyes.
 According to another embodiment of these two variations, which is important
 as well, provision is made that the filaments forming the meshes of the
 hose-like netting are rounded off or flattened on the side facing the
 lumen, in order to obtain favorable properties of flow on the inside wall
 of a vessel receiving such an endoprosthesis. The term "lumen" refers to a
 blood vessel.
 Finally, it has been found to be desirable if in connection with these two
 embodiment variations, the filaments forming the netting are comprised by
 a superelastic material, or a memory material, for example such as
 nitinol.
 Within the framework of the present invention, both embodiment variations
 can be realized in the form of balloon-expandable or also self-expanding
 endoprosthesis.
 Other objects and features of the present invention will become apparent
 from the following detailed description considered in connection with the
 accompanying drawings which discloses several embodiments of the present
 invention. It should be understood, however, that the drawing is designed
 for the purpose of illustration only and not as a definition of the limits
 of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS
 Turning now in detail to the drawings, the endoprosthesis 10 illustrated in
 FIGS. 1 to 4 is comprised of a hose-like netting 11 with the meshes 12
 forming polygons. These meshes are formed by the filaments 13, 14, which
 grip around each other at the corner points 15 without any fixed
 connection; and these filaments are the ones of the meshes disposed
 adjacent to each other in the longitudinal direction of the prosthesis.
 Especially FIGS. 3 and 4 where the endoprosthesis is shown unwound.
 illustrate the wire mesh fence-like structure of the netting 11, whereby
 the arrow 16 indicates the bearing direction, the latter extending
 transversely to the longitudinal axis of the prosthesis. FIG. 3 shows the
 mesh pattern, with filaments adjacent each other at each of the corner
 points 15 with maximum lengthwise expansion of the prosthesis 10. FIG. 4
 shows the mesh pattern of an axially compressed prosthesis, in which the
 filaments 13, 14 grip around each other at the corner points with much
 play. The term "mesh" or "meshes" refers to the actual cord or wire
 network, and not the spaces therebetween.
 The prosthesis 10 according to the invention may be either self-widening or
 balloon-expandable, whereby no axial reduction during widening occurs at
 all if the prosthesis is made shorter in the unexpanded condition versus
 its maximum lengthwise expansion, and approximately has a mesh pattern
 according to FIG. 4. If the filaments 13, 14 grip around each other at the
 corner intersection points 15 without play with maximum expansion of the
 prosthesis lengthwise, in the manner as shown in FIG. 3, then the radial
 widening naturally leads to a reduction in length. On the other hand, if
 such a prosthesis is axially compressed prior to its expansion widening in
 accordance with the mesh pattern according to FIG. 4, then no reduction at
 all in length occurs during widening, which means that exact positioning
 is assured at the site of the implantation.
 FIGS. 3 and 4 show that the filaments 13, 14 grip around each other at the
 corner points of the polygon forming meshes 12 where these corner points
 are adjacent with respect to the longitudinal direction of the prosthesis.
 The corner points are adjacent to each other. This construction for the
 endoprosthesis is the precondition for its radial bearing strength, which
 is indicated by the arrow 16 between the FIGS. 3 and 4. Arrow 16 is
 directed transversely to the longitudinal axis of the prosthesis.
 An enhancement of the radial bearing strength of the prosthesis of the
 invention is achievable if the filaments forming the meshes are provided
 at the points of intersection with locks engaging each other in an
 interlocking manner. FIGS. 5 and 6 show that with maximum longitudinal
 expansion of the length of the prosthesis, the filaments 13, 14
 intersecting each other at the corner points 15 of the polygons are
 compressed crosswise relative to the longitudinal expanse of the
 prosthesis in such a way that each filament is received in an interlocking
 way in a depression 17, 18 of the other filament. Thus, both filaments are
 jointly reduced to the thickness of about one filament and hooked into
 each other as a result of the interlocking engagement, thereby providing
 an enhancement of the radial bearing strength of the endoprosthesis.
 In the embodiment according to FIG. 7, the netting 11' forming the
 endoprosthesis differs from the netting 11 according to FIG. 3 only in
 that in the points of intersection 15' of the filaments 13', 14', only one
 of the filaments is looped around the other filament, forming an eye 19.
 The radial bearing strength is increased by this embodiment as well;
 however, as opposed to the embodiment according to FIG. 3, no shortening
 is possible by axial compression.
 The jacket of an endoprosthesis as shown in unwound manner in FIG. 8 in a
 cutout view relates to a netting 21 in which the meshes 22 are designed as
 hexagons and separated from each other, both by filaments 23, 24 and by
 connection zones 25 where said filaments extend in an oblique angle with
 respect to the longitudinal axis of the prosthesis and said connection
 zones extend parallel to said longitudinal axis. In each of said
 connection zones, two filaments 23, 24 are twisted with each other. Such
 twistings form locks engaging each other in an interlocking way, which
 locks, in the radially expanded state, provide an endoprosthesis formed by
 said netting 21 with its strength and stability in the widened condition.
 The twistings of the filaments 23, 24 participating in the formation of the
 meshes are shaped in the connection zones 25 in such a way that they
 engage one another when the prosthesis is in the widened condition,
 thereby securing the prosthesis in its widened position, but disengage
 from each other when axial tensile forces are applied to the prosthesis,
 thereby permitting a reduction of the cross section of the prosthesis to a
 Comparatively small lumen.
 Accordingly, this prosthesis is an endoprosthesis expandable by means of a
 balloon catheter. The endoprosthesis is received on the balloon section of
 the catheter with suitable expanse lengthwise, and with radial widening
 upon implantation, for example in a blood vessel, undergoing a
 corresponding axial shortening until the twistings looping around one
 another lock in an interlocking manner.
 In connection with the netting 21 illustrated in an enlarged cutout view in
 FIG. 9, the meshes following each other in the longitudinal direction of
 the prosthesis each are formed by the same two filaments 23, 24.
 Accordingly, the two filaments extend from their connection zones 25, 25',
 (FIGS. and 12) respectively, with an angle of about 60.degree. outwardly
 to the connection zones between the circumferentially adjacent meshes 22,
 and from these connection zones back again to a connection zone with the
 mesh following in the longitudinal direction of the prosthesis. This is
 shown in FIG. 9 by the filament 24, represented by the fully drawn lines,
 on the one hand, and by the filament 23 represented by the dashed lines,
 on the other hand. The connection zone 25 with the twistings 27 forming
 the locks in the expanded state is shown as well.
 With the embodiment according to FIG. 10, on the other hand, the filaments
 23', 24' in each case form the meshes 22 not following one another in the
 longitudinal direction of the prosthesis, but the filaments participate
 progressively from one mesh to the next in the formation of the meshes
 22', the latter being disposed adjacent to each other in a direction, that
 extends helically along the length of the prosthesis. Accordingly, the
 individual filaments are progressively braided around the hose-like
 netting from one mesh to the next in the longitudinal direction of the
 prosthesis. These patterns and the connection zones 27' provided with the
 twistings forming locks are shown by the filaments represented by fully
 drawn lines, on the one hand, and dashed lines on the other hand as well.
 the embodiment according to FIG. 11, the filament 23" extends in the
 connection zone 25' in a straight line, and the filament 24" is spirally
 wound around the filament 23". In this way, the filament 24" is capable of
 sliding to a limited extent on the straight-lined section of the filament
 23" and also of undergoing a compression or stretching within
 predetermined limits. This endoprosthesis consequently is characterized by
 excellent flexibility and, furthermore, imparts superior adaptation in
 regions of flexion.
 FIGS. 12 and 13 show a netting as illustrated in FIG. 8, with FIG. 12
 showing the unexpanded state, whereas FIG. 13 illustrates the widened
 condition. However, as opposed to the embodiment shown in FIG. 8, in the
 embodiment according to FIGS. 12 and 13, provision is made for special
 locking means in the form of at least one retaining bar 30 extending in
 the longitudinal direction of the prosthesis, such bar being rigidly
 connected at its one end and--at 31--with the meshwork forming the
 netting, whereas the other end of the retaining bar has a hook 32. This
 retaining bar may, extend on the outside along the netting forming the
 endoprosthesis, or through the meshwork in the way of a warp thread.
 When radial expansion occurs from the condition with a small lumen as
 illustrated in FIG. 12, the hook 32 slides across the meshes due to the
 reduction in length correspondingly occurring with such expansion, and, in
 the way as shown in FIG. 13, grips behind the filaments of the mesh,
 which, following widening, effectively prevents the length from increasing
 again, and thus any reduction in cross section.
 With the endoprosthesis according to FIG. 8, the connection zones 25 are
 each comprised by two filaments 23, 24, which are twisted with each other
 and extend in the longitudinal direction of the prosthesis. However, in
 the embodiment according to FIG. 14, the connection zones 35, 35'--the
 latter being twisted with each other--are partly arranged obliquely
 relative to a longitudinal axis of the prosthesis, and accordingly extend
 like a screw thread around an imaginary cylinder jacket of the prosthesis
 partly the connection zones 35, 35' are aligned with an angle relative to
 the first-mentioned connection zones. Due to such change in direction of
 the connection zones, the helix structure is changed.
 FIG. 14 shows the filaments 33 by the fully drawn lines, whereas the other
 filaments 34 are shown by the dashed lines. The course followed by the
 filaments 33 shown in the drawing by the fully drawn lines is indicated by
 the numerals 1 to 7 associated with said filaments. The filaments 33 each
 form with a filament 34 a plurality of connection zones 35 between the
 adjacent meshes 32, such zones extending inclined relative to the
 longitudinal axis of the prosthesis, and at an angle relative to the
 latter the connection zones 35' extending approximately at right angles
 relative to the longitudinal axis of the prosthesis. The connection zones
 35' consequently extending in the circumferential direction on the
 imaginary cylinder jacket of the prosthesis.
 The connection zones 35 are arranged in one direction which is oblique to
 the longitudinal and all of the connection zones 35' are arranged in the
 circumferential direction.
 The embodiment according to FIGS. 15 and 16 relates to a prosthesis with
 the rectangularly shaped meshes 42, which are comprised by the first
 filaments 43 extending parallel with each other in the longitudinal
 direction of the prosthesis, and the second filaments 44, the latter being
 wound around the first filaments 43. The filaments 43 are shown in the
 drawing by the dashed lines and the second filaments 44 by the fully drawn
 lines.
 In this connection, the arrangement is selected in such a way that the
 second filaments 44 each are wound around a second, through-extending
 filament 43, and then project at the end of a mesh 42 to the adjacent,
 through-extending filament 43, and are again looped around the latter in
 the longitudinal direction of the prosthesis. Thus the second filaments 44
 progress, extending around the jacket of the prosthesis in the form of
 stairsteps in the longitudinal direction of the prosthesis. For the
 purpose of illustrating the course of the second filaments 44 shown by the
 fully drawn lines, the numerals 1 to 7 are associated with said filaments.
 FIG. 16 illustrates in an enlarged cutout view a through extending first
 filament 43, around which a second filament 44 is wound up to the corner
 point of the meshes 42 disposed adjacent to one another, such second
 filament then extending further to an adjacent filament. The filament 44
 is denoted by the numeral 3. Another second filament 44, which is denoted
 by the numeral 4, meets with the first filament 43 in the corner point
 shown, and is twisted with the latter, in order to then project at the end
 of the mesh 42 in the circumferential direction to the next
 through-extending filament 43.
 While several embodiments of the present invention have been shown and
 described, it is to be understood that many changes and modifications may
 be made thereunto without departing from the spirit and scope of the
 invention as defined in the appended claims.