MX2007012271A - Flexible stent - Google Patents

Abstract

A flexible stent structure includes a plurality of axially spaced strut portions defining generally tubular axial segments of the stent and constructed to be radially expandable. A helical portion is interposed axially between two strut portions and has a plurality of helical elements connected between circumferentially spaced locations on the two strut portions. The helical elements extend helically between those locations and the length of a helical element is sufficient so that, when the stent is in a radially expanded state, it can simultaneously withstand repeated axial compression or expansion and bending.

Description

FLEXIBLE ENDOPROTESIS BACKGROUND OF THE INVENTION The present invention is generally related to expandable tubular structures that can be inserted in small spaces within living bodies and, more particularly, has to do with a structure that has the ability to bend or flex in shape. important and repeated at different points along its length without mechanical failure and without substantial changes in its geometry. A "stent" or stent is a tubular structure that, in its radially compressed or folded state, can be inserted into the confined space of a living body, such as, for example, an artery or some other vessel. After insertion, the endoprosthesis can expand radially to increase the space in which it is located. The endoprostheses are usually characterized as balloon or balloon expansion type (BX, balloon-expanding) or self-expanding type (SX, by "self-expanding"). with balloon, it needs a balloon or balloon, which is usually part of an introduction system, to expand the endoprosthesis from the inside and expand the vessel A self-expanding endoprosthesis is designed, selecting the material, geometry or techniques of manufacture, to expand it from the folded state to the expanded state once it has been released into the desired vessel In certain situations, to expand the affected vessel, a force greater than the expansion force of the self-expanding endoprosthesis is needed. In order to help a self-expanding endoprosthesis expand, a balloon or other similar device may be used.The endoprostheses are used, in general, in the treatment of both Vascular and non-vascular ages. For example, a folded stent can be inserted into a blocked artery, which subsequently expands to restore blood flow in the artery. Before releasing the stent, it would usually retain its folded state within a catheter or the like. After finishing this procedure, the endoprosthesis remains inside the patient's artery in an expanded state. The health and, sometimes, the patient's life depends on the ability of the stent to maintain its expanded state. Many available stents are flexible when in the folded state to facilitate the introduction thereof, for example, into an artery. Some are flexible after they are deployed and expanded. Even after deployment, the stent may, in certain applications, be subjected to significant bending or bending, axial compressions, and repeated shifts at various points along its length, for example, when a stent is inserted into the femoral artery. superficial. The above can cause serious deformation and fatigue, which would result in the failure of the stent. There is a similar problem with regard to stent-like structures. An example would be a stent-like structure used in conjunction with other components in a valve introduction system, which has a catheter as a base. This endoprosthesis type structure contains a valve, which will be placed in a vessel.

SUMMARY OF THE INVENTION In accordance with the present invention, a stent or stent-like structure was fabricated in such a way that along its length it has different types of tubular portions. This structure generally contains strut portions and helical portions, where the strut portions were manufactured primarily to provide radial expansion and radial strength and the helical portions were manufactured primarily to allow for flexing and repeated axial compression and expansion. There is a likelihood that the structure of the stent requires its axial bending and compression properties at the same time, so as to allow a significant and repeated bending, while in the axially compressed or expanded state and allow axial compression while in the flexed state. Preferably, the strut portions are disposed between the helical portions or the helical portions are disposed between the strut portions. In a preferred embodiment, the stent is of the self-expanding type and the strut and helical portions are alternated along the stent. The endoprosthesis is preferably manufactured in such a way that, in the expanded state, the helical portions allow an axial compression or expansion of about 20% (preferably, between about 15% and 25%) and, simultaneously, allow bending with a minimum bending radius of approximately 13 mm (preferably, approximately between 10 mm and 16 mm). According to another aspect of the invention, the helical portions are made of helical elements that extend helically around the axis of the stent between points of two different strut portions, which are circumferentially spaced apart by a distance greater than about 25% the circumference of the stent (which is equivalent to a 90 degree extension around the axis of the stent) when it is in the expanded state. In accordance with yet another aspect of the invention, a helical portion is made of helical elements that extend helically about the axis of the stent between points of two different strut portions. In one embodiment, a helical element is bidirectional, because it extends between two points, first in one circumferential direction, then in the other and has a point. In accordance with a further aspect of the invention, a stent has a plurality of axially spaced strut portions that define generally tubular axial segments of the stent and which are fabricated to radially expand. Between two strut portions a helical portion is interposed, the helical portion having a plurality of helical elements connected between points circumferentially separated into two strut portions. Between these points a helical element extends helically, and at least a portion of the helical portion has a larger diameter than a strut portion when the stent is in the expanded state.

In an alternate embodiment, at least a portion of the helical portion has a diameter smaller than that of the strut portion when the stent is in the expanded state. In one embodiment, the helical element is wound at least 90 degrees between the strut elements connected to this helical element. In another embodiment, the helical element is wound at least 360 degrees between the strut elements connected to the helical element. In an alternate embodiment, the covered stent grafts are made of a biocompatible graft material that covers the exterior, the interior, or both the exterior and the interior of the stent. The covered stent may have any of the embodiments of a stent structure of the present invention. Covered stent devices are used, for example, in the treatment of aneurysms, dissections and tracheobronchial stenosis. The stent may also be coated with a polymer and / or a drug eluting material, as is known in the art.

BRIEF DESCRIPTION OF THE DRAWINGS The above description, as well as other objects, features and additional advantages of the present invention will be understood more fully from the following detailed description of the currently preferred modalities and, however, illustrative in accordance with the present invention, when reference should be made to the accompanying drawings, in which: Figure IA is a plan view of a first embodiment of stent in accordance with the present invention, the stent is shown in the unexpanded state. Figure IB is a plan view of the first embodiment of an endoprosthesis according to the present invention, the stent is shown in the radially expanded state. Figure 2 is a plan view of a second embodiment of a stent in accordance with the present invention. Figure 3 is a plan view of a third embodiment of a stent in accordance with the present invention. Figure 4 is a plan view of a fourth embodiment of a stent in accordance with the present invention. Figure 5 is a sectional view of an end of a fifth embodiment of a stent in accordance with the present invention. Figure 6 is a longitudinal view of the lateral contour of the same embodiment of Figure 5. Figure 7A is a plan view of another embodiment of a stent in accordance with the present invention. Figure 7B is a plan view of another embodiment of the stent in accordance with the present invention. Figure 8 is a sectional view of one end of another embodiment of the stent in accordance with the present invention. Figure 9 is a longitudinal view of the lateral contour of the embodiment shown in Figure 8. Figure 10A is a sectional view of one end of an alternate embodiment of a stent in accordance with the present invention that includes the graft material that covers the external surface of the stent. Figure 10B is a sectional view of an end of an alternative embodiment of a stent in accordance with the present invention that includes the graft material covering the inner surface of the stent. Figure 10C is a sectional view of an end of an alternative embodiment of a stent in accordance with the present invention that includes the graft material covering the outer surface and the inner surface of the stent. Figure HA is a side view of an alternative embodiment of a stent in accordance with the present invention that includes the graft material attached to the strut portion, the graft material covers the strut portion and the helical portion. Figure 11B is a side view of an alternate embodiment of a stent in accordance with the present invention that includes a plurality of sections of the biocompatible graft material., where between each of the sections of the graft material there is a separation. Figure 11C is a side view of an alternative embodiment of a stent in accordance with the present invention that includes a plurality of sections of a biocompatible graft material, where there is an overlap between the graft material of adjacent sections. Figure 11D is a side view of an alternative embodiment of a stent in accordance with the present invention that includes a biocompatible graft material, the graft material having a protrusion in the helical portions. Figure HE is a side view of an alternate embodiment of a stent in accordance with the present invention that includes a biocompatible graft material, the graft material having a plurality of longitudinal openings in the helical portions. Figure 11F is a side view of an alternate embodiment of a stent in accordance with the present invention, the graft material has a protrusion in the helical portions and the graft material has a plurality of longitudinal openings on the helical portions. Figure 11G is a side view of an alternate embodiment of a stent in accordance with the present invention that includes a biocompatible graft material having a plurality of helical openings corresponding to the pitch of the helical elements. Figure 11H is a side view of an alternate embodiment of a stent in accordance with the present invention that includes a plurality of sections of the biocompatible graft material, each of the sections to be attached to either the strut portion or the portion helical, where between each of the sections of the graft material there is a separation.

Figure 11J is a side view of an alternative embodiment of a stent in accordance with the present invention that includes a plurality of sections of biocompatible graft material, each of the sections to be attached to either the strut portion or the portion helical, where the adjacent sections of the graft material overlap. Figure 12A is a plan view of an alternate embodiment of a stent in the expanded state. Figure 12B is a planar view of the stent of Figure 12A in the folded state, such that the spacing between the helical elements is the same as in all helical portions. Additionally, the length of the stent is the same both in the folded state and in the expanded state. Figure 12C is a plan view of the stent of Figure 12A in the folded state, such that the spacing between the helical elements changes over the entire helical portion. Additionally, the stent is longer in the folded state than in the expanded state. Figure 13 is a plan view of an alternative embodiment of a stent in accordance with the present invention.

DETAILED DESCRIPTION OF THE INVENTION Reference will now be made, in more detail, to a preferred embodiment of the invention, of which an example is illustrated in the accompanying drawings. As much as possible, the same reference numbers will be used in all the drawings and the description will refer to the same or similar parts. Figures IA and IB are flat views of a first embodiment of the stent 10 in accordance with the present invention, shown respectively in the unexpanded and expanded states. As used herein, it should be understood that the term "flat view" describes a flat view not rolled up. This could be visualized as making a cut in a tubular endoprosthesis to open it along a line parallel to its axis and extend it flat. Therefore, it should be noted that in the actual stent, the upper edge of Figure IA will be attached to the lower edge. The endoprosthesis (10) is made of a common material in self-expanding stents, such as, for example, Nitinol, nickel and titanium (Ni / Ti) alloy, as is well known in the art. Normally, the stent is laser cut from a tube having a diameter of, for example, about 5 mm (Figure IA). Then, it expands and adjusts in a diameter of approximately 8 mm (FIG. IB) and for the previous unfolding it would be folded up to a suitable diameter at the application of, for example, about 3 mm. However, it is contemplated that the present invention be applicable to any type and size of stents. The endoprosthesis (10) is generally formed by a strut portion (12) and a helical portion (14), where the strut portion (12) is axially aligned and alternates with the helical portion (14). In a preferred embodiment, the strut portion (12) is positioned at either end of the stent (10). The strut portion (12) will expand radially when deployed. Each strut portion (12) includes a strut ring (16) having a pattern of strut element (16a) of the wave type that moves circumferentially around the stent. Each strut element 16a has a width equal to the tip-to-tip distance around the stent and a length equal to the tip-to-tip distance along the length of the stent. It will be noted that the strut ring (16) could be partially straightened (stretched vertically in Figure IB), so as to widen the strut elements (16a) and reduce their length. The above is equivalent to radially expanding the stent (10). Preferably, the material from which the endoprosthesis (10) is made is such that the strut element (16a) will retain a certain wave-like shape in the radially expanded state. For the introduction, the endoprosthesis would be folded, placed in a catheter and expanded after the catheter has been inserted into the vessel and the stent has been advanced out of the catheter. Each helical portion is constituted by a plurality of helical elements (18) that are side by side, each of which is wound helically around an axis of the stent (10). The helical portion (14) can be radially expanded at the time of deployment and, in the deployed state, can be compressed, expanded and bent. The helical elements (18) may be connected between opposing individual wave portions of the strut element (16a) of different strut portion (12). In this embodiment, each helical element (18) rotates or completely rotates around the surface of the stent (10). However, this rotation or rotation may be less than or greater than one complete revolution. Preferably, the helical portion is fabricated so as to allow repeated axial compression or expansion of approximately 20% (preferably, approximately between 15% and 25%) and allows, simultaneously, bending with a minimum bending radius of approximately 13. mm (preferably, approximately between 10 mm and 16 mm), all without fail. In general, if the helical element (18) is wound at least 90 degrees between the strut elements (16a) which are connected to the helical elements (18), an improvement in the flexibility and in the axial compression can be obtained. . Alternatively, the helical element (18) is wound at least 360 degrees between the strut elements (16a) which are connected to the helical elements (18). Figure 2 is a plan view of a second embodiment of the stent (20), similar to the stent (10) of Figure 1. The main differences lie in the structure of the strut portions (12 ') and in that there are helical portions left and right (14R and 14L, respectively). Each strut portion (12 ') includes two strut rings (26) and (27) adjacent and connected by the short link (28). The opposite and very close points of the strut elements (26a) and (27a) are connected by the short links (28), such that each strut portion (12 ') has a structure of double strut ring. It could also be connected to the multiple strut rings to form a larger strut portion. The advantage of having strut portions of two or more rings is that they offer greater radial rigidity with respect to the strut portion of a single ring and can stabilize the strut portions, such that the degree of affectation due to axial forces is smaller. In a right helical portion (14R), the elements (18) move clockwise on the surface of the endoprosthesis (10) and in a left helical portion (14L) they move in the opposite direction to that of clock hands . Essentially, the helical elements (18) are floating and, thus, allow relatively greater displacements around and along the axis of the stent, between the two strut ring portions of each end. It will be noted that, in this embodiment, the diameter of the stent in each helical portion (14R) and (14L) is equal to the diameter of the stent in the strut portions (12) on either side. However, this does not necessarily have to be the case, as will be evident from the additional modalities that will be described later. The benefit of using right and left helical portions is that when the stent is deployed, the two portions rotate in opposite directions, maintaining the relative rotational positions of the different axial portions of the stent.

Figure 3 is another embodiment of the stent (30) in accordance with the present invention. It is similar to the endoprosthesis (20) of Figure 2, with the exception that the helical portions (34) include the helical element (38), which moves bidirectionally (first counterclockwise and then clockwise) around the perimeter of the stent (30), between the connection points of two different strut portions (121). The helical element (38) is wound at least 90 degrees from a first strut portion (12 ') to the tip (35) and is rolled 90 degrees from the tip (35) to a second strut portion (12') in order to maintain flexibility. The unidirectional helical elements (18) of FIGS. A and IB can allow the adjacent strut portions to rotate with respect to each other. The bidirectional helical elements (38) limit the amount of rotation that the adjacent strut portions can make between themselves around the axis of the stent and yet are still flexible to the bend and in the axial direction. Figure 4 is a plan view of a fourth embodiment of a stent in accordance with the present invention. In this case, the endoprosthesis (40) has the strut portions (12 '), the helical portions (14L) and (14R) (see Figure 2) and helical portions (34) (see Figure 3). The advantage of this construction is that the combination of different types of helical elements allows to have a mixture properties as those described herein, which gives the opportunity to further optimize the overall performance of the endoprosthesis in the case of a determined application. Figure 5 is a sectional view perpendicular to the axis of a fifth embodiment of the endoprosthesis (30 '), in accordance with the present invention and Figure 6 is a side contour view of the same embodiment. The stent has the structure shown in Figure 3, with the exception that the helical portions (38 ') have a diameter greater than that of the strut portions (12'). In this construction, there is an increase in radial stiffness of the helical portions, although to a lesser extent than the strut portions. When all portions of the stent have the same diameter, the helical portions may not exert as much force outwardly on the vessel as the strut portions when the strut expands. The geometry of Figure 6 will tend to force the helical portions to expand more than the strut portions, increasing the outward force of the helical portions, equaling the radial stiffness. The Nitinol structures have a biased stiffness, such that the force needed to collapse the structure back into the collapsed state is, in general, greater than the force that continues to dilate the affected vessel when the stent is in its expanded state. In the case of some of the Nitinol self-expanding stents, a balloon will be used to aid the expansion / dilation of the vessel. The biased stiffness is enough to keep the cup open, but the outward force may not be enough to open the cup (or it may take a longer time to open it). Therefore, it would be a good resource to use a stent with the type of geometry shown in Figure 5 together with the expansion performed with the aid of a balloon or with other applications that require additional expansive force. Figure 7A is a plan view of another embodiment of the stent (40B ') in accordance with the present invention. The stent (40B ') includes a strut member (42). The strut member (42) moves helically from one end of the stent (40B ') to the other. The strut member (42) forms the main body of the stent (40B '). In this embodiment, each strut element (44a) is connected, by means of a helical element (46), to a strut of the next winding of the strut member (42). In this embodiment, the helical element (46) of the helical portion (45) moves helically less than a full 360 degree turn around the stent (40B1). The helical element (46) moves in a direction opposite to the direction from which the strut member (42) moves helically around the stent (40B '). Preferably, the helical elements (46) are axially butted to form a kind of spring that allows great flexibility and axial expansion, while the strut member (42) provides radial resistance and keeps the stent in the expanded state . Figure 7B is a plan view of another embodiment of the endoprosthesis (40C) in accordance with the present invention. The stent (40C) is similar to the stent (40B1) and includes the strut member (42). The strut member (42) moves helically from one end of the stent (40C) to the other. The strut member (42) forms the main body of the stent (40C). In the present embodiment, each strut element (44a) is connected, by means of a helical element (47), with a strut of the next winding of the strut member (42). In this embodiment, the helical element (47) moves helically around the stent (40C) in the same direction in which the strut member (42) moves helically around the stent (40C). At each end, the endoprosthesis (40C) has transition helical portions (49) and strut portions (48) that allow at each end of the stent (40C) to have a strut portion (48). The stents (40B ') and (40C) have the advantage that the flexible helical elements are distributed in a more continuous manner along the length of the stent and can offer greater continuity in flexibility. Those of skill in the art will realize that various modifications can be made to the stent (40B1) or (40C), depending on the requirements of some particular design. For example, in a particular winding, it may be desirable not to connect, all of the strut elements (44a), but a smaller number of them, with the next winding, thus reducing the number of helical elements (46). The helical elements (46) may extend less than one turn or any integer or non-integral multiple of turns. The stent could also be manufactured from a plurality of tubular sections, each of which would have the construction of the endoprosthesis (40B1) or (40C) and be longitudinally joined by another type of section. Figure 8 is a sectional view perpendicular to the axis of a stent modality (20 ') in accordance with the present invention and Figure 9 is a side contour view of the same embodiment. The stent has the structure shown in Figure IA, with the exception that the helical portions (14 ') are reduced to a smaller diameter than that of the strut portions (121). In this construction, the helical portions will exert on the vessel wall a smaller force than if the helical portions had the same diameter. By reducing the force that the endoprosthesis exerts on the wall of a vessel, the magnitude of the damage caused in a vessel can be reduced and a better performing endoprosthesis can be offered. Figures 10A-10C are sectional views perpendicular to the axis of the stent in accordance with the present invention. The covered stents 60, 70 and 80 have the stent structure of the present invention in accordance with any of the embodiments described in the foregoing, where there are helical portions interposed between strut portions. In one embodiment, the biocompatible graft material (62) covers the exterior (64) of the covered stent (60), as shown in Figure 10A. Alternatively, the biocompatible graft material (62) covers the interior (74) of the stent (70), as shown in Figure 10B. Alternatively, the graft material (62) covers the exterior (64) and the interior (74) of the stent (80), as shown in Figure 10C. The graft material (62) can be made from any number of polymers or other biocompatible materials that have been woven or given the shape of a sheet or woven surface. Alternatively, the stent may be coated with a polymer and / or a drug eluting material, as is known in the art. Figures HA-11J are views of the lateral profile of covered stent grafts having the characteristics of the flexible stent structure of the present invention. The stent graft (100) includes a continuous sheath of graft material (102) covering the stent (10), as shown in Figure HA. The graft material (102) is attached to the strut portions (12). The graft material (102) covers and is not attached to the helical portions (14). The graft material (110) includes a plurality of sections (111) of the graft material (112) covering the structure of the stent, as shown in Figure 11B. The graft material (112) is attached to the strut portions (12). The graft material (112) covers at least a portion of the helical portions (14) and is not attached to the helical portions (14). An offset (115) is located between the adjacent sections (111) of the graft material (112). As usual, the size of the separation (115) will vary from 0 (which means there is no separation) to approximately 20% of the length of the helical portion (14). The graft material (120) includes a plurality of sections (121) of the graft material (122) covering the structure of the stent, as shown in Figure 11C. The graft material (122) is attached to the strut portions (12). The graft material (122) covers and is not attached to the helical portions (14). The sections (121) of the graft material (122) are positioned such that between adjacent sections (121) there is an overlap (125) of the graft material (122). In general, the size of the overlap (125) will vary from 0 (meaning there is no separation) to approximately 40% of the length of the helical portion (14). The covered stent (130) includes a continuous cover of graft material (132), as shown in Figure 11D. The graft material (132) is attached to the strut portions (12). The graft material (132) covers and is not attached to the helical portions (14). The graft material (132) has, in the helical portions (14), a protrusion (133). The covered stent (140) includes a continuous cover of graft material (142), as shown in Figure HE. The graft material (142) has, in the helical portions (14), a plurality of longitudinal openings (144). The stent graft (150) includes a continuous sheath of graft material (152), as shown in Figure 11F. The graft material (152) has a protrusion (153) in the helical portions (14) and a plurality of longitudinal openings (154) in the helical portions (14). The covered stent (160) includes a continuous cover of graft material (162), as shown in Figure 11F. The graft material (162) has helical openings (164) in the helical portions (14), which are in correspondence with the pitch and the angle of the helical portions (14). The graft material (170) includes a plurality of sections (171) of the graft material (172) covering the stent (10), as shown in Figure 11H. The sections (171) may be attached to the strut portions (12) or the helical portions (14). An offset (175) is located between the adjacent sections (171) of the graft material (172). Generally, the size of the gap (175) will vary from 0 (which means there is no separation) to about 20% of the length of the helical portion (14). The graft material (180) includes a plurality of sections (181) of the graft material (182) that cover the stent (10), as shown in Figure 11J. The sections (181) may be attached to the strut portions (12) or the helical portions (14). The sections (181) of the graft material (182) are positioned such that between adjacent sections (181) there is an overlap (185) of the graft material (182). In general, the size of the overlap (185) will vary from 0 (meaning there is no separation) to approximately 40% of the length of the helical portion (14). Figures 12A, 12B and 12C are plan views of the stent (200) in accordance with the present invention. Figure 12A shows the endoprosthesis (200) in an expanded state that, between the helical elements (18), has a separation (202). Figures 12B and 12C show the stent (200) in two different compression states. In Figure 12B, the stent (200) is compressed in such a way that the spacing (212) between the helical elements (18) that are side by side is approximately the same throughout the helical portion (14). The size of the gap (212) between the helical elements (18) that are side by side can vary in the expanded state, from 0 to approximately the size of the gap (202), for example, as shown in Figure 12A . In other words, when the size of the spacing is equal to 0, there is no space between the helical elements (18) that are side by side and, therefore, these helical elements (18) that are side by side are in contact each. The helical elements of the endoprosthesis shown in Figure 12B have been wound several times around the stent, such that in the folded state, the total length (211) of the stent in the folded state is equal to the total length (201). ) of the stent in the expanded state shown in Figure 12A, thus eliminating the reduction. In Figure 12C, the stent (200) is compressed in such a way that the helical element (18) is elongated and the spacing (222) between the helical elements (18) that are side by side varies over the entire axial length of the Helical portion (14). The size of the spacing (222) between adjacent helical elements (18) can vary, for example, from 0 to approximately the size of the spacing (202) in the expanded state, as shown in Fig. 12A. In other words, when the size of the spacing is equal to 0, there is no space between the helical elements (18) that are side by side and, therefore, these helical elements (18) that are side by side are in contact each. In Figure 12C, the total length (221) of the stent in the folded state is greater than the total length (201) of the stent in the expanded state. To fold the stent, an additional method may be offered, such that the length of the helical portions is shorter in the folded state than in the expanded state. For example, if the stent of Figure 12A were folded in a manner similar to that shown in Figure 12B, with the exception that there is no separation between the helical elements that are side by side, the stent would have the length (211) in the folded state, which is shorter than the length (201) in the expanded state. In one embodiment, a folding method provides an endoprosthesis in which the total length is the same in the folded state as in the expanded state and there is no separation between helical elements in the folded state. As described in the foregoing, a preferred embodiment of the stent is one which allows repeated axial compression and expansion of approximately 20% and which allows, simultaneously, bending with a minimum bending radius of approximately 13 mm. One method for manufacturing a stent of the present invention with the specific objective of flexibility is to vary the ratio between the sum of the gap space in the helical portion and the total length. If this ratio increases, then the flexibility of the stent increases. This relationship will also approximate the maximum axial compression that the endoprosthesis will allow. It can be observed that, for safety, the maximum axial compression may be limited by other factors, such as deformation in the helical elements. Figure 13 is a plan view of a stent (300) in accordance with the present invention. The stent (300) is similar to other embodiments described in the foregoing, with the exception that it includes various configurations and various axial lengths of the strut portions and various configurations and various axial lengths of helical portions. The strut portions (302) positioned in the outermost portion of the stent (300) include long strut members (301). The long strut elements (301) have a length (311). The length (311) of the long strut element (301) is greater than the length (312) of the strut portions (304) located in the internal portion of the stent (300). The long strut elements (301) disposed at the ends of the stent may have the advantage of providing better anchoring and presenting an area for adjacent stents to overlap., but they do not prevent the helical portion from being flexible. In some vasculatures, notably in the femoropopliteal arteries, the length of the affected artery may be large, often more than 10 cm. To treat these long sections of affected arteries, multiple stents may be needed. A common procedure in this case is to overlap the adjacent stents, so that the vessel to be treated is covered. When some conventional stents overlap in this way, the mechanism that gives them flexibility is impeded to act and this artificial stiffening can cause many problems, among which are the fracture of the stents. An advantage of the present invention is that the elements that allow bending and axial flexibility (helical portion) are different from the elements that provide the radial structure (strut portion), so that the strut portions in the adjacent stents can overlap without impeding the movement of the helical portion and thus, provide the total flexibility of the stent. The helical portion (303) that is adjacent the helical portion (302) includes helical elements (18) that are connected to each strut element (301) of the strut portion (302). The helical portion (303) can provide a large percentage of the surface area for optimized delivery of a drug or other therapeutic agent. The strut portion (304) is connected in each strut element (16a) by the side (320) of the strut portion (304) with the helical portion (303) by means of the helical element (18) and is connected each two strut elements (16a) on the side (321) of the strut portion (304) with the helical portion (309). The helical portion (309) provides a smaller percentage of the surface area and a greater flexibility than that of the helical portion (303). This type of configuration can offer the transition from a stiffer helical portion having a large percentage of the surface area to a more flexible helical portion. The helical portion (309) has a ratio of the sum of the lengths (323) of separation to the length (324) of the helical portion (309) greater than the sum of the lengths (325) of separation to the length (326). ) of the helical portion (303), so that the helical portion (309) will, in general, be more flexible. The strut portion (306) has half the strut members (305) as the strut portions (302) or (304) and, therefore, will generally have a larger open area compared to the strut portion. (302) or the strut portion (304). One advantage of a stent including a portion having a greater open area than other portions of the stent is that the larger open portion of the stent may be placed on top of an arterial bifurcation and not impede blood flow. While the strut portion having the highest density of strut elements can impede blood flow. The stent structure of the present invention, namely the flexible helical portions which are flanked by the strut portions, offer an optimized structure, in which the strut portions stabilize a naturally unstable helical structure and the helical portions provide a flexibility net There is great potential for optimizing the design if the various modalities of the two portions are combined. The flexible stents and covered stents of the present invention can be placed inside the vessels using those procedures that are well known in the art. Flexible stents and covered stents can be loaded from the proximal end of a catheter, advanced through the catheter and released at the desired site. Alternatively, flexible stents and covered stents can be transported near the distal end of the catheter in a compressed state and released at the desired site. Flexible stents or covered stents may be self-expanding or may be expanded using means such as an inflatable balloon segment of the catheter. After stents or covered stents have been placed in the desired intraluminal site, the catheter is removed. The flexible stents and covered stents of the present invention can be placed inside the lumen of a body, such as vascular vessels or conduits of any mammalian species, including humans, without damaging the vessel wall. . For example, the flexible endoprosthesis can be placed inside a lesion or an aneurysm for the treatment thereof. In one embodiment, the flexible stent is placed in a superior femoral artery after insertion into the vessel, the flexible stent, or the covered stent offer at least about 50% coverage of the vessel.

Although, the presently preferred embodiments of the present invention have been described for illustrative purposes, those skilled in the art will realize that many additions, modifications and substitutions can be made without departing from the scope and spirit of the invention, as defined in the appended claims. For example, an endoprosthesis could be made only by right helical portions or only by left helical portions or the helical portions could have multiple inversions in the winding direction, instead of just one. Likewise, the helical portions could have any number of turns per unit length or a variable pitch and the strut rings and / or the helical portions could have different lengths along the stent.

Claims (72)

1. CLAIMS: 1. A flexible endoprosthesis that includes: a helical portion that includes a plurality of individual helical elements, disposed side by side and that are wound around an axis of the stent, the helical portion can expand radially after deployment and can be compressed , expand and bend in the deployed state; and a strut portion on each side of the helical portion, each of the strut portions contains axially aligned strut members having a first end connected to the helical elements of the helical portion, the strut portions can radially expand after the deployment. The stent according to claim 1, wherein the helical elements are wound at least 90 degrees between the strut elements which are connected to the helical elements in the unfolded state. The stent according to claim 1, wherein the helical elements are wound at least 360 degrees between the strut elements which are connected to the helical elements in the unfolded state. The stent according to claim 1, further comprising one or more additional helical portions and one or more additional strut portions, wherein at least one of these helical portions is connected to the second end of one of the strut portions; the additional helical portions or will be connected, respectively, to the additional strut portion (s), such that each of the helical portions is interposed between a pair of strut portions. The stent according to claim 4, wherein the helical elements of each of the helical portions are wound in the same direction. The stent according to claim 4, wherein the helical elements of at least one of the helical portions are wound in the opposite direction to that of the helical elements of another of the helical portions. The stent according to claim 1, wherein one or more pairs of helical portions are spaced apart and flanked by the strut portions, the helical elements of a portion of the pair will be wound in a direction opposite to that of the helical elements of the other portion of the pair. The stent according to claim 1, wherein the strut members of the strut portion have a wave pattern of the individual wave portions, each individual wave portion having a tip. The stent according to claim 8, wherein each of the helical elements is connected to one of the respective tips of the strut elements. The stent according to claim 8, wherein some of the helical elements are connected to some of the tips of the strut elements. The stent according to claim 8, wherein each two tips of the strut elements are connected by the respective one of the helical elements. The stent according to claim 8, wherein the strut portion includes a plurality of strut elements and the tips of the individual wave members will be connected to each other by means of a link. The stent according to claim 4, wherein at least one of the strut portions includes a plurality of strut members, the strut members of the strut portion have a wave pattern of individual wave portions, each wave portion Individual has a tip and the tips of the individual wave members will connect to each other by means of a link. The stent according to claim 13, wherein the strut portion (s) is at each end of the stent. 15. The stent according to claim 1, wherein the helical elements extend helically in a first direction from a first strut element to a tip and then in the opposite direction from the tip to the second strut element. 16. The stent according to claim 1, which further includes one or more additional helical portions and one or more additional strut portions, where one of the additional helical portions or portions is connected to the second end of one of the strut portions, the additional helical portion (s) will be connected , respectively, with the additional strut portion (s), so that each of the helical portions is interposed between a pair of strut portions and at least one of the helical portions includes helical elements extending helically in a first direction from the first strut portion to a tip and then in the opposite direction from the tip to a second strut portion. The stent according to claim 16, wherein at least one of the helical portions includes the helical elements that will be wound in the opposite direction to that of the helical elements of another of the helical portions. 18. The stent according to claim 1, wherein the helical portion has a diameter greater than that of the strut portions. The stent according to claim 4, wherein at least one of the helical portions has a larger diameter than at least one of the strut portions. The stent according to claim 1, wherein the helical portion has a diameter smaller than that of the strut portion. The stent according to claim 4, wherein at least one of the helical portions has a smaller diameter than at least one of the strut portions. 22. The stent according to claim 1, further including a biocompatible graft material that covers the external surface of the stent. 23. The stent according to claim 1, further including a biocompatible graft material that covers the inner surface of the stent. 24. The stent according to claim 1, further including a biocompatible graft material that covers the external surface and the internal surface of the stent. 25. The stent according to claim 1, further including a biocompatible graft material attached to at least one of the strut portions, the graft material covers the strut portions and the helical portion. 26. The stent according to claim 1, further comprising a plurality of sections of biocompatible graft material, each of the sections of graft material will be attached to one of the strut portions and will cover the attached strut portion and a portion thereof. of an adjacent helical portion, where between each of the sections of the graft material there is a gap. 27. The stent according to claim 26, wherein the spacing is less than about 20% of the length of the helical portion. 28. The stent according to claim 1, further comprising a plurality of sections of biocompatible graft material, each of the sections of graft material will be attached to one of the strut portions and will cover the attached strut portion and a portion thereof. adjacent helical, where there is an overlap of the graft material of adjacent sections of graft material. 29. The stent according to claim 28, wherein the overlap is less than about 40% of the length of the helical portion. 30. The stent according to claim 1, which further includes a biocompatible graft material, the graft material will be attached to at least one of the strut portions, the graft material covers the strut portions and the helical portion and the Graft material has a protrusion in the helical portion. 31. The stent according to claim 1, which further includes a biocompatible graft material, the graft material will be attached to at least one of the strut portions, the graft material covers the strut portions and the helical portion and the Graft material has a plurality of longitudinal openings in the graft material of the helical portion. 32. The stent according to claim 1, which further includes a biocompatible graft material, the graft material will be attached to at least one of the strut portions and covers the strut portions and the helical portion, the graft material has a protrusion in the helical portion and the Graft material has a plurality of longitudinal openings in the graft material of the helical portion. 33. The stent according to claim 32, which further includes a biocompatible graft material, the graft material will be attached to at least one of the strut portions and covers the strut portions and the helical portion, the graft material has a plurality of helical openings that are in correspondence with the pitch of the helical elements. 34. The stent according to claim 1, further comprising a plurality of sections of biocompatible graft material, each of the sections will be attached to either the strut portion or the helical portion. 35. The stent according to claim 34, wherein a separation is provided between each of the sections of the graft material. 36. The stent according to claim 35, wherein the spacing is less than about 20% of the length of the helical portion. 37. The stent according to claim 1, which further includes a plurality of sections of biocompatible graft material, each of the sections will be attached to either the strut portion or the helical portion, where the adjacent sections of the graft material are overlap. 38. The stent according to claim 37, wherein the overlap is less than about 40% of the length of the helical portion. 39. The stent according to claim 1, wherein the spacing between the adjacent helical elements of a helical portion is approximately the same as in the compressed state of the stent. 40. The stent according to claim 39, wherein the spacing is in the range of 0 to the magnitude of a spacing between adjacent helical members of a helical portion in the deployed state. 41. The stent according to claim 1, wherein the adjacent helical elements of a helical portion are in contact with each other in the compressed state. 42. The stent according to claim 1, wherein the spacing between the adjacent helical elements of a helical portion varies along the length of the helical portion in the compressed state. 43. The stent according to claim 42, wherein the spacing is in the range of between 0 and the magnitude of a spacing between adjacent helical members of a helical portion in the unfolded state. 44. The stent according to claim 4, wherein the strut portions and / or the helical portions may have a variation in axial length with respect to the length of the stent. 45. The stent according to claim 44, wherein the strut members of the strut portion have a wave pattern of individual wave portions, each individual wave portion has a tip and each of the helical elements is connected with a respective one. of the tips on one side of the side strut elements and some of the helical elements are connected with some of the tips on the other side of the side strut elements. 46. The stent according to claim 45, wherein each two tips of the strut elements are connected by the respective one of the helical elements. 47. The stent according to claim 4, wherein one of the helical portions has a ratio of the sum of lengths of separation to the length of the helical portion greater than the second of the helical portions. 48. The stent according to claim 4, wherein one of the strut portions has fewer strut elements than the second of the strut portions. 49. The stent according to claim 48, wherein one of the strut portions has half the strut elements as the second of the strut portions. 50. A flexible stent including: a helical portion that includes a plurality of individual helical elements, disposed side-by-side and that are wound around an axis of the stent, the helical portion can expand radially after deployment and can be compressed, expanded and bending in the deployed state; and a strut portion on each side of the helical portion, each of the strut portions contains helically aligned strut elements having a first end connected to the helical elements of the helical portion, the strut portions can radially expand after the deployment. 51. The stent according to claim 50, wherein each of the helical elements extends one or more complete 360-degree turns about an axis of the stent. 52. The stent according to claim 50, wherein each of the helical elements extends at least 90 degrees about an axis of the stent. 53. A method for minimizing or eliminating reduction in a flexible endoprosthesis, the method comprises rotating a plurality of individual helical elements disposed side by side, the helical elements being wound helically around an axis of the endoprosthesis to form a portion helical, the helical portion will radially expand at the time of deployment and will compress, expand and bend in the unfolded state and a strut portion on each side of the helical portion, each of the strut portions includes axially aligned strut elements that have a first end connected with the helical elements of the helical portion, the strut portions will expand radially at the time of deployment. 54. The method according to claim 53, wherein the axial length of the stent in the deployed state is equal to the axial length of the stent in the folded state. 55. The stent according to claim 53, wherein the spacing between the helical elements disposed side by side of the helical portion is approximately the same as in the folded state of the stent. 56. The stent according to claim 53, wherein the helical elements disposed side by side of the helical portion are in contact with each other in the folded state of the stent. 57. The method according to claim 56, wherein the axial length of the stent in the deployed state is equal to the axial length of the stent in the folded state. 58. The method according to claim 53, wherein the axial length of the stent in the folded state is less than the axial length of the stent in the deployed state. 59. A method for folding a flexible stent, the method comprises elongating a plurality of individual helical elements disposed side-by-side to a folded state, the helical elements will be wound helically about an axis of the stent to form a helical portion, the portion helical will expand radially at the time of deployment and will compress, expand and bend in the unfolded state and a strut portion on each side of the helical portion, each of the strut portions includes axially aligned strut members having a first end connected to the helical elements of the helical portion, the strut portions will expand radially at the time of deployment. 60. The stent according to claim 59, wherein the spacing between the helical elements disposed side by side of the helical portion varies along the length of the helical portion in the folded state. 61. The method according to claim 59, wherein the axial length of the stent in the deployed state is less than the axial length of the stent in the folded state. 62. A method for placing a flexible endoprosthesis inside a mammal, in the lumen of a body, the method comprises placing one or more endoprostheses in place, the flexible endoprosthesis includes a helical portion containing a plurality of helical elements i Individuals arranged side by side, the individual helical elements are wound helically around an axis of the endoprosthesis, the helical portion will expand radially at the time of deployment and will compress, expand and fold in the deployed state; and a strut portion on each side of the helical portion, each of the strut portions includes axially aligned strut members having a first end connected to the helical elements of the helical section, the strut portions will expand radially at the time of the deployment. 63. The method according to claim 62, wherein the mammal is a human being and the light of the body is a vessel or conduit. 64. The method according to claim 62, wherein the mammal is a human being and the light of the body is a superior femoral artery. 65. The method according to claim 62, wherein the endoprosthesis further includes a biocompatible graft material that covers the external surface of the stent and / or the internal surface of the stent. 66. A method for treating an affected vessel or conduit, the method comprises the steps of: driving a catheter to the desired site; advancing, through the catheter, a flexible endoprosthesis, the flexible endoprosthesis contains a helical portion that includes a plurality of individual helical elements disposed side by side wound helically around an axis of the endoprosthesis, and a portion of an endpiece on each side of the endoprosthesis. the helical portion, each of the strut portions includes axially aligned strut members having a first end connected to the helical elements of the helical section; ejecting the endoprosthesis from the catheter at the desired site, causing the helical portion to expand radially and for the end portions to expand radially, the helical portion can be compressed, expanded and bent in the deployed state. 67. The method according to claim 66, wherein the desired site is a vascular site. 68. The method according to claim 66, wherein the desired site is a superior femoral artery. 69. The method according to claim 66, wherein the desired site is a lesion. 70. The method according to claim 66, wherein the desired site is an aneurysm. 71. The method according to claim 66, wherein the endoprosthesis further includes a biocompatible graft material that covers the external surface of the stent and / or the internal surface of the stent. 72. The method according to claim 66, wherein the stent further includes a coated polymer and / or a drug eluting material.