FR2784573A1 - One-piece tubular endoprosthesis for anatomical duct - Google Patents

Abstract

The endoprosthesis has a one-piece tubular structure with zigzag lengthwise elements (3a, 3b) extending basically parallel to its lengthwise axis (1a) and with their tips (5a, 5b) joined by intermediate connectors (7a, 7b). Adjacent lengthwise elements are connected by crosspieces (13a, 13b), and are separated by spaces (23) which expand to form open cells when the endoprosthesis is deployed.

Description

 The invention relates to a stent for a cavity or anatomical conduit, and in particular for a blood vessel.

 To resolve vascular problems, and more generally to overcome deficiencies in anatomical conduits (urethra, vessel, etc.), it is known today to use stents which it is proposed to introduce endoscopically.

 Among these stents, the invention applies in particular to wideners (or dilators) of vessels commonly called "stents".

 Two typical examples of such stents can be found in US-A-4,739,762 and WO-A-96/03092.

 Compared to known stents, the invention aims to provide a stent which effectively supports the vascular wall, which can be placed in tortuous places, which has a small footprint in its radially tightened implantation state, which can be radially deployed under the effect of a radial internal force (in particular obtained by means of at least one expansion balloon) and which has mechanical and shape characteristics such that it can adapt in particular to vessels coronary, that its implantation can be carried out safely and which does not risk disturbing the anatomical duct, once implanted.

 For this, an important characteristic of the invention consists in that the endoprosthesis comprises a one-piece tubular structure having longitudinal stays, extending along a succession of broken lines (that is to say in the form of waves) generally. parallel to the general axis radially to which the structure is deployable, the broken lines having vertices connected by intermediate sections and being arranged substantially in phase (that is to say possibly with a slight phase shift), two adjacent props , arranged side by side, being interconnected by crosspieces.

 It will be noted that this form was "in broken lines" (or in the form of waves in the radially tightened state of the stent) extending substantially in the longitudinal direction of the stent promotes the adaptation of the tortuous vessels and a efficient match between flexibility and mechanical strength of the prosthesis, while offering a very small diameter in the tightened state and cells of appropriate sizes in the radially deployed state.

 According to an important additional characteristic, it is advised that the endoprosthesis of the invention is such that its crosspieces are distributed by transverse lines (preferably directed generally substantially perpendicular to the general axis of the endoprosthesis, at least in the state radially constricted thereof) and that these same crosspieces are either first crosspieces defining cusps, each creating an axial discontinuity along the two struts thus connected, or second crosspieces connecting two adjacent struts together, while now maintaining the "axial" continuity of each of these struts.

 In connection with this, it is moreover advised that, per line of sleepers, there is at least one first sleeper interposed between two successive second sleepers, on a perimeter of the structure.

 This will optimize the flexibility / radial mechanical resistance to crushing ratio after the prosthesis has been deployed.

 Also for this purpose, another characteristic advises that between two second crosspieces located away from the free ends of the structure, where a determined broken line is constituted by a thin branch of material, this line turns back at least twice, substantially as a hairpin, a first time at the location of a first axial discontinuity, then presenting two sections arranged side by side, up to another axial discontinuity, located at another location on the general axis of the structure, where said line will preferably turn back a second time substantially as a hairpin, then presenting a third section extending substantially parallel to the first two, next to them, up to a second crosspiece located in alignment of the first discontinuity in a transverse direction (substantially perpendicular) to the general axis of the structure.

 As for the nature of the cells which provide mechanical lightening of the structure and whose evolution from the tightened state to the deployed state, as well as the dimensions in the two states, significantly condition the quality of the stent, an additional feature advises that these cells each have a shape comprising several broken lines (that is to say "empty" spaces in the form of a broken line extending substantially parallel to the general axis of the stent) and connected between them at the location of the first crosspieces, in the radially tightened state of the structure, each broken line preferably having at least two vertices connected in pairs by substantially rectilinear intermediate sections.

 Still to promote the deformation capacity of the endoprosthesis, while obtaining cells of sizes and shapes favorable to the desired effect of internal reinforcement of the anatomical duct, another preferred characteristic of the invention recommends that at least some of the crosspieces s 'extend, in an oblique direction relative to the general axis of the stent, each between two adjacent props.

 The shape of the stent in its radially deployed state is also characteristic.

An even more detailed description of the invention will now be given with reference to the accompanying drawings in which:
in FIG. 1, an anatomical duct enlarger (or "stent") according to the invention is illustrated, in a radially constricted state thereof (representation developed flat),
FIG. 2 is an enlarged view of the detail marked II in FIG. 1,
FIG. 3 is a view of the stent of FIG. 1 in a radially deployed state and on a reduced scale,
FIG. 4 shows an alternative embodiment of the expander in a view identical to that of FIG. 1,
FIG. 5 shows in enlarged view the detail marked V in FIG. 4 (radially tightened state of the expander).

FIG. 6 shows another variant of FIG. 1,
FIG. 7 shows a possible embodiment of detail VII of FIG. 6 (enlarged view),
FIG. 8 shows a possibility of repetition on several stages of the shape of FIG. 7, and
FIG. 9 shows a possibility of inclination of transverse lines when at least some of them are located at the adjacent vertices of the broken struts of props.

 It will now be noted that in FIGS. 1, 3, 4 and 6, the expander which has been shown has been shown in a view developed flat, the parts cut laterally to the left continuing at the right lateral end.

 It should therefore be imagined that the structure illustrated is presented as a tubular structure with a longitudinal axis la for the structure marked 1 in FIG. 1, with a form of cylindrical tube of circular section.

 In this case, it is a widener (or "stent") for blood vessel, and in particular for coronary or iliac vessel.

 The expander 1 is presented as a one-piece metal structure. Preferably, it is a thermal shape memory alloy (usually called "NrTIoL", registered trademark) consisting of a nickel and titanium alloy which can be obtained by laser cutting or by electroerosion, from a flat plate which is then closed on itself or, directly, from a cylindrical tube of circular section with solid wall which is cut to obtain the desired design.

 The thickness of the strands or branches of material 3 constituting the structure of the endoprosthesis 1 can be approximately 0.2 to 0.3 mm, with a width l, of strand (see FIG. 2) of approximately 0.1 at 0.15 mm. The length of the structure can be from 15 to 120 mm approximately.

 In the enlarged view of FIG. 2, it can be seen that the structure 1 comprises a succession of props (3a, 3b, 3c ... 3g) extending along a succession of broken lines in the form of waves (location identical to that stays), these lines extending in a general direction parallel to the longitudinal axis 1 a.

 Like the forestay or the broken line 3f, each line is presented as a branch section having a succession of vertices, such as 5a, 5b, 5c, for part of the forestay 3f, these vertices ( or apex) being separated two by two by straight connecting sections such as 7a, 7b.

 It can be seen that the broken lines, or the props, thus defined are arranged side by side, in phase, that is to say that at the location of a line such as 9 perpendicular to the axis la, the was 3a ... 3g have a vertex, all the vertices along this line 9 being directed in the same direction, that is to say in this case with a fold oriented to the left of the figure.

 Between two vertices of the same forestay, such as the vertices 5c and 5d of the forestay 3f of FIG. 2, two adjacent forestays arranged side by side (such as the forestays 3e and 3f) are interconnected by crosspieces, such as 11a and 11b for these transverse links located between the vertices 5c and 5d.

 In reality, on the endoprosthesis of Figures 1 and 2, there are two types of crosspieces for the transverse connection in groups of two adjacent stays. First, there is what we have chosen to call "second sleepers", as marked 13a and 13b in Figure 2 in two places away from one another along the axis 1a and which are provided in this case to join respectively the props 3c, 3d and 3f, 3g. Then there is what has been called "first sleepers", such as 11a and 11b cited above.

 The second sleepers are pieces of material which form a full mechanical connection between two adjacent stays without creating any discontinuity in the branch sections that they connect. The first sleepers, on the contrary, constitute, individually, each time a double bond which, while connecting two adjacent stays, arranged side by side, breaks the continuity of each of the stays concerned along its broken line, thereby defining a cusp. rounded, as can be clearly seen in FIG. 2 at the place of the two elementary crosspieces 11a, 11b which together form a so-called "first crosspiece" between the props 3e and 3f.

 Thus, both the second crosspieces (such as 13a, 13b) constitute not only a transverse connection of two stays between them, but also a "longitudinal" or "axial" connection by not interrupting the continuity of said stays along their line. respective broken, as much the first crosspieces (such as 11a, 11b) define "axial" discontinuities which will increase the flexibility or the capacity of deformation of the structure. Note that the arcuate or rounded shape of the first crosspieces (lla, 11b) will prevent them from being aggressive towards the duct. In the same way, the substantially "H" or "I" shape with rounded corners of the second crosspieces will ensure that the structure is as little traumatic as possible.

 Concerning the second sleepers, their length, equal to the thickness ~ of the space (void) that they interrupt between two adjacent stays, will advantageously be in the radially constricted state of the prosthesis as illustrated in FIG. 2 , less than the width of these same second sleepers measured perpendicular to the thickness ~. In particular, 72 will be twice as large as e, thus ensuring a solid, full bond.

 As can be seen in FIG. 2 at the location of the line marked 15a which extends perpendicular to the longitudinal axis la, the sleepers are, by perpendicular lines thus defined, aligned by group of sleepers, from place to place place, along the axis la.

 Thus, on the prosthesis of FIG. 1, there are six lines of crosspieces marked successively 15a, 15b, 15c, 15d, 15e, 15f. We could find more, even less. It will be noted that on each line of sleepers thus defined, there is alternately a second sleeper (such as 13a) then two double first sleepers, and so on alternately. On the same line of sleepers, there are therefore advantageously more areas of discontinuity than areas of axial continuity, which promotes the flexibility of the stent.

 In FIG. 1, it will also be noted that with the exception of the free ends (or end parts) 10a, 10b of the endoprosthesis, where the first lines of sleepers (respectively 15a and 15f), the closest to the end corresponding are located between the fourth and fifth vertices of the broken lines defined by the props, the other intermediate lines (15b ...) are located between the second and third vertices of each prop, assuming that one moves continuously, always in the same direction, in the general direction of the axis 1a, from one end to the other of the structure.

 The alternation recommended above between the first sleepers and the second sleepers (namely two first sleepers arranged successively along a same line, such as 15a, between two second sleepers) makes it possible to define the following preferred construction, with regard to the repetitive meandering shape of a section of the branch of material 3 which constitutes the basic element of the structure 1, as shown in FIGS. 1 and 2. Thus, between two second crosspieces, such as 13a and 13b in FIG. 2, located on two successive lines of crosspieces (15a and 15b), the corresponding section of the elementary branch 3 of material which connects these crosspieces travels as follows: it is a broken line generally parallel to the axis la and that firstly follows part of the forestay 3d, up to the transverse line 15b where the section of forestay 3d turns back, substantially in a hairpin, at the place of the element of first cross-member forming a rounded apex 21a, thus allowing (by this cusp) a connection between the aforementioned section of forestay 3d and the adjacent section 3e of the forestay whose broken line, parallel to the first, extends to the line of sleepers 15a where a second cusp area appears at the location of the first cross member (or discontinuity area) rounded already cited, 111, where the forestay section 3e joins the section of forestay following 3f which, itself, descends (again parallel to the previous two) against the second (3rd) to join the second cross 13b, at the location of line 15b, where the forestay 3f continues axially, without discontinuity , as can be seen in Figure 2 below line 15b.

 It will be noted that the cusps which appear alternately in one direction and in the other (upwards and downwards in FIG. 2), when one follows the path of a section of the elementary branch 3 of the structure, both appear at the vertices of the broken line that we follow, that is to say between the second and third vertices of this line (it being specified that we are then located away from the two free end zones 10a, 10b where the hairpin cusps appear between the fourth and fifth vertices of the broken line in question, in the example shown).

 With such an arrangement of struts and crosspieces, the structure presented defines closed cells as marked 23 and 25 in FIGS. 1 or 2, for two of them (these are cells located away from the free ends 10a and 10b). These two cells are identical to each other and to the others, except as regards the cells extending at the location of said free ends.

 In the tightened state of the structure, these cells have a shape defined by several broken lines (that is to say in the form of waves) arranged side by side in a direction parallel to the axis la and which are connected between they, two by two adjacent, at the location of the first corresponding crosspieces which are found in this case along line 15b, in the example illustrated. Thus, the cells that have just been presented have, in this tightened state of the structure, a sort of substantially "H" shape, the branches of the "H" each having a wavy shape, in waves.

 At the ends of the ends 10a, 10b, we find this shape in "H". But the branches of this "H" are longer and therefore have more undulations (in this case four vertices or apex, instead of two for the branches located between the zones 10a, 10b).

 In Figure 3, we can see the shape that the cells take in the radially deployed state of the structure, more precisely, and away from the ends 10a, 10b, the endoprosthesis presents itself in a way with a succession of 'stages, such as 30.40.50, for three of them, staggered in the direction la (here perpendicular to it) to draw the structural aspect of this "stent".

 In this case, the substantially zigzag undulations of two successive and adjacent stages 30, 40 are in phase opposition. Each wavy line defining a stage is presented as an uninterrupted succession of "V" oriented alternately towards an axial end 10a, then the other 10b. These "V", which are slightly oblique, have broken apex zones, tilted sideways alternately to the right, then to the left in the figure, depending on whether you are following an "erect V" or, following it, an "inverted V" (see references 51,52).

 Of course, two adjacent stages 30, 40 or 40, 50 are periodically connected to each other (in this case all three "erect V"), by a "second crosspiece", such as 13c, 13e, therefore each defined by a "H" oblique (see also 13f, 13g).

 When there are no such crosspieces, the adjacent "broken" vertices of the "Vs" of two stages are separated in pairs, parallel to the axis la.

 At the ends 10a, 10b, the aforementioned waves lengthen the "V", as shown in FIG. 3.

 By comparing FIGS. 1 and 3, it will also be noted that during the radial expansion, the second crosspieces (13a, 13b) remain substantially in their same inclined position relative to the axis 1a (angle a, FIG. 1, with 5 <a <60), which explains the shape of the structure at the vertices of the "V", in the radially deployed state of FIG. 3.

 The version illustrated in Figures 4 and 5 shows an alternative structure 10 in its radially tightened state. The difference compared to the preferred version of FIGS. 1 and 2 is that there are no longer "first sleepers" but only "second sleepers" at the location of the sleeper lines identical to those of the two above-mentioned figures. Thus, on the transverse line 15 ′ a, it is more clearly seen in FIG. 5 that the adjacent struts such as 3 ′ a, 3 ′ b, 3 ′ c, 3 ′ are successively connected two by two (3 'a, 3'b and 3'c, 3'd) only by a "second crosspiece", respectively 13'a and 13'b, these crosspieces, like the others, in no way interrupting the axial continuity of the props, this which gives a more rigid structure. The cells thus defined by the struts and crosspieces are therefore themselves different from those of structure 1. These are, in the tightened state of structure 10, spaces in the form of broken lines extending generally parallel to axis 1'a of the structure (see cells 23 ′ and 25 ′ in FIG. 4), the lines thus drawn being longer towards the axially opposite free ends 10 ′ a and 10 ′ b (in this case six vertices ) in the intermediate zone (four summits in this case).

 The variant embodiment shown in FIG. 6 differs from that of FIG. 1 in that the sleepers of the sleeper lines 15'a, 15'b, 15'c, are the image in the mirror of the sleeper lines 15 ' d, 15'e, 15'f (that is to say symmetrical with respect to a plane perpendicular to the axis 1'b of the prosthesis 100 shown).

 Under these conditions, this prosthesis 100 in its radially deployed state will appear like prosthesis 1 in FIG. 3, except as regards the orientation of the second crosspieces substantially in the shape of "H" located on the lower part, this orientation corresponding of course to that shown in Figure 6 (lines 15'a, 15'b, 15'c).

 In FIG. 7, we wanted to illustrate the fact that the crosspieces may possibly not be located between two vertices of axial broken lines, but on the contrary at the location of these vertices, from floor to floor.

 Thus, in FIG. 7, a zone of "stent" has been represented at the location of such a vertex which could, for example, correspond to the line of vertices comprising the apex 5c of FIG. 2, with the exception that in the embodiment of Figure 7, the "cross lines" and the "vertex lines" (both perpendicular to the general axis of the endoprosthesis cylinder) are combined.

 Thus, in this figure 7 we find successively, along the line 71, perpendicular to the general axis schematically 1'c of the stent, a double first cross 11 "a, 11" b, a second cross 13 "a, arched, then again two first double sleepers.

 Such an embodiment cannot in particular constitute a transition zone between the lower and upper parts of the widener 100 of FIG. 6, thus making it possible to pass from an inclination in one direction to an inclination in the other, of the second crosspieces , between the top and the bottom of the figure.

 It should be noted, however, that the arrangement of the crosspieces, as illustrated in FIG. 7 at the place where the vertices of the props in a broken line, can be reproduced over several stages (or even at all stages, and this alternately in one direction then in the other, following the shape of the broken line considered).

 In FIG. 8, four radial stages 81, 82, 83, 84 have also been partially illustrated joined in pairs, between immediately adjacent stages, by second crosspieces, such as 130a, 130b, 130c, arranged in staggered rows, as are the second sleepers of Figures 1,3,4 or 6, in particular. Note the orientation alternately to the left, then to the right, of these curved crosspieces, also for the "first double crosspieces", at each remaining vertex.

 In Figure 9, we wanted to represent the case where the adjacent stays, such as 30a, 30b, 30c, 30d, are not strictly in phase, but where they have a slight phase shift such as a line of crosspieces 150a is now oriented obliquely to the general longitudinal axis (100a) of the structure and to its normal (angle ss with 5 <(3 <20). In the example, two "second sleepers" 130'a, 130 ' b follow each other, side by side.

However, we may prefer the above-mentioned alternation of the first and second sleepers, per line. This oblique arrangement of the transverse lines could be applied to the examples of structure of FIGS. 1, 4 or 6, with a helical portion arrangement of these lines, then along the tubular wall of the expander;

Claims (10)

 1. Endoprosthesis for anatomical conduit comprising a one-piece tubular structure (1.10) having longitudinal stays (3a, 3b, ...; 3'a, 3'b, ...) extending along a succession of broken lines , generally parallel to a general axis (la, 1'a) radially to which the structure is deployable, the broken lines having vertices (5a, 5b, ....) connected by intermediate sections (7a, 7b ...) and being arranged substantially in phase, two adjacent stays, arranged side by side, being interconnected by crosspieces (13a, 13b; 11a, 11b).  2. Endoprosthesis according to claim 1, characterized in that two adjacent stays being separated, in the radially tightened state of the endoprosthesis, by a space (23.25; 23 ', 25') of determined thickness, the length cross members equal to this thickness (e) is less than the width (l2) of said stays measured perpendicular to said length.  3. Endoprosthesis according to any one of claims 1 or 2, characterized in that:  the crosspieces are distributed by lines (15a, 15b ...; 15'a ...) directed transversely to the general axis of the endoprosthesis,  -these crosspieces are either first crosspieces (11a, 11b, 21a) defining cusps each creating an axial discontinuity along the two struts thus connected, or second crosspieces (13a, 13b; 13'a ...) connecting together two adjacent stays, while maintaining the continuity of each of these stays.  4. Endoprosthesis according to claim 3, characterized in that by line of sleepers (15a, 15b ...), there is successively, on a perimeter of the structure, at least one first sleeper interposed between two second sleepers.  5. Endoprosthesis according to any one of claims 3 or 4, characterized in that, between two second crosspieces (13a, 13b) located away from the free ends, at the location of two successive lines of crosspieces (15a, 15b), a determined broken line which is constituted by a thin branch of material turned back at least twice, substantially as a hairpin, a first time at the location of a first axial discontinuity (21a), then presenting two sections (3d, 3e) interconnected and arranged side by side, up to another axial discontinuity (lla) located at another point on the general axis of the structure, where said line turns back a second time substantially as a hairpin hair then having a third section (3f) extending substantially parallel to the first two it extends, next to them, to a second crosspiece (13b) located in alignment (15b) of the first disco ntinuity in a direction substantially perpendicular to the general axis of the structure, in the radially tightened state of the stent.  6. Endoprosthesis according to any one of claims 3 to 5, characterized in that the struts and the cross-pieces connecting them of two adjacent struts, arranged side by side substantially parallel to said general direction of the structure, define closed cells (23,25; 23 ', 25') each having, in the radially tightened state of the structure, a shape comprising several broken lines arranged side by side in said general direction of the structure and linked together, two by two, at the place of the first sleepers (11a, 11b, 21a).  7. Endoprosthesis according to any one of the preceding claims, characterized in that at least some of the crosspieces (13a, 13b) extend, between two adjacent stays'3a, 3b, 3c; 3'a, 3'b, 3'c ...), in an oblique direction a with respect to the general axis (la, a ...) of the endoprosthesis.  8. Endoprosthesis according to any one of the preceding claims, characterized in that the crosspieces (13a, 13b; lla, llb) are connected to said stays away from the vertices, at least in a radially tightened state of the endoprosthesis.  9. Endoprosthesis according to resell ication 3, characterized in that at least some of the first and second sleepers (lla, 11b; 21a ...) are located, by lines, at the location of the tops of said broken struts of props, at least in the radially tightened state of the stent.  10. Endoprosthesis according to any one of claims 1 to 8, characterized in that it has a succession of stages staggered in said general direction (la, 1'a ...), two successive stages (30.40, ...) being connected together locally by said crosspieces (13a, 13b, 13c, 13e, ...), these stages being each defined by a wavy line extending transversely to the general direction (1a, 7 ' a), two adjacent lines being arranged substantially in phase opposition and each comprising an uninterrupted succession of substantially "V" shapes oriented alternately towards an axial end (10a) of the stent, then towards the other (10b), these "V "with broken apex areas (51,52), tilted obliquely alternately to one side and then the other, as illustrated in FIG. 3.