Auxetic stents with increased flexibility

Abstract

Stents with enhanced flexibility useable for treating venous stenosis. In embodiments, a stent is configured to be auxetic, expanding axially as it is expanded radially, to prevent the imposition of tension on portions of a blood vessel adjacent to the stented portion of the blood vessel, and thereby prevent a narrowing of the adjacent portions and improving luminal gain. The stent may be fabricated from a plurality of cells, with a subset of the cells omitting cross members, thereby increasing the stent's flexibility to allow the stent to be curved to conform to vessel curvature.

Description

AUXETIC STENTS WITH INCREASED FLEXIBILITYFIELD

[0001] The present disclosure relates to stents useable in medical settings, and in particular, auxetic stents useable for managing venous stenosis that have increased flexibility.BACKGROUND

[0002] According to Centers for Disease Control and Prevention statistics, the annual incidence of venous thromboembolism is estimated at 900,000 per year (Ito 2 per 1,000). Post- thrombotic syndrome (PTS) is a long-term complication associated with deep venous thrombosis (DVT) that can lead to long-term symptoms including pain, swelling, and heaviness. Given the relatively high prevalence and associated symptoms, previous studies have suggested an annual socioeconomic impact in the US of at least $200 million associated with chronic venous disease.BRIEF DESCRIPTION OF THE DRAWINGS

[0003] Fig. 1 is a perspective view of an example auxetic stent that includes interleaved cells with no cross member to enhance flexibility, according to various embodiments.

[0004] Fig. 2 depicts an example cel I that may comprise the example auxetic stent of Fig. 1, in a compressed configuration, according to various embodiments.

[0005] Fig. 3 depicts the example cell of Fig. 2 in an expanded configuration to illustrate its various components, according to various embodiments.

[0006] Fig. 4 depicts the example auxetic stent of Fig. 1 in an unrolled configuration, illustrating the placement pattern of the interleaved cells with no cross member, according to various embodiments.

[0007] Fig. 5 depicts a second example auxetic stent in an unrolled configuration, illustrating a second placement pattern of the interleaved cel Is with no cross member, according to various embodiments.

[0008] Fig. 6 depicts a third example auxetic stent in an unrolled configuration, illustrating a third placement pattern of the interleaved cells with no cross member, according to various embodiments.

[0009] Fig. 7 is a flowchart of an example method for using an auxetic stent, according to various embodiments.DETAILED DESCRIPTION

[0010] In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which are shown by way of illustration embodiments that may be practiced. It is to be understood that other embodiments may be utilized andstructural or logical changes may be made without departing from the scope. Therefore, the following detailed description is not to be taken in a limiting sense, and the scope of embodiments is defined by the appended claims and their equivalents.

[0011] Various operations may be described as multiple discrete operations in turn, in a manner that may be helpful in understanding embodiments; however, the order of description should not be construed to imply that these operations are order dependent.

[0012] The description may use perspective-based descriptions such as up / down, back / front, and top / bottom. Such descriptions are merely used to facilitate the discussion and are not intended to restrict the application of disclosed embodiments.

[0013] The terms "coupled” and "connected,” along with their derivatives, may be used. It should be understood that these terms are not intended as synonyms for each other. Rather, in particular embodiments, "connected” may be used to indicate that two or more elements are in direct physical contact with each other. "Coupled” may mean that two or more elements are in direct physical contact. However, "coupled” may also mean that two or more elements are not in direct contact with each other, but yet still cooperate or interact with each other.

[0014] For the purposes of the description, a phrase in the form “A / B” or in the form "A and / or B” means (A), (B), or (A and B). For the purposes of the description, a phrase in the form "at least one of A, B, and C” means (A), (B), (C), (A and B), (A and C), (B and C), or (A, B and C). For the purposes of the description, a phrase in the form “(A)B” means (B) or (AB) that is, A is an optional element.

[0015] The description may use the terms "embodiment” or "embodiments,” which may each refer to one or more of the same or different embodiments. Furthermore, the terms "comprising,” "including,” “having,” and the like, as used with respect to embodiments, are synonymous.

[0016] The two main contributing factors in the pathophysiology of post-thrombotic syndrome (PTS) are venous outflow obstruction due to narrowing related to chronic venous fibrosis and incompetency of the venous valves. In patients with venous outflow obstruction due to chronic fibrosis, treatment with venous stenting has been shown to improve flow with shortterm clinical relief. However, more than one out of four stents occluded within three years in patients with PTS. While the pathophysiology of PTS is not completely understood, prior studies have suggested that one of the main contributing factors is venous outflow obstruction due to narrowing related to chronic venous fibrosis (venous stenosis). Consequently, application of direct radial force from a stent in a venous stenosis is not an ideal treatment, due to the redistribution of applied radial force in a longitudinal direction and the resulting incomplete expansion of the vein, namely, a narrowing of the vein adjacent to the stent placement.

[0017] However, employing active longitudinal control with longitudinal tensile strain in the treated segments will reverse the adjacent vein narrowing seen with current treatment options, and also apply direct longitudinal strain on the diseased segment (in addition to radial expansion). Through these biomechanical methods, active control and redistribution of longitudinal forces will result in an overall increased venous luminal volume and improved venous flow. One potential method to apply both radial expansion and longitudinal expansion is with the use of stents with auxetic geometries. Auxetic stents will elongate during radial expansion and thus not create tension on the adjacent vein segments, which will improve the overall luminal volume gain in the stented and non-stented segments.

[0018] However, a given section of vein requiring treatment with an auxetic stent may fol low a curved path, sometimes including multiple curves in different directions or dimensions. Existing auxetic stent designs may present unacceptably high resistance to bending to conform to the natural path of the vein. As a result, a placed stent may cause uneven and unnecessary stress and / or strain on various parts of the patient’s vein, which could result in long-term complications and undesirable health outcomes.

[0019] Disclosed embodiments herein include auxetic stents that are configured to have increased flexibility (bendability) compared to existing stents. In some embodiments, portions of a plurality of cells comprising the auxetic stent are designed to improve overall stent flexibility, such as without certain axially-oriented struts found in some prior stents. The specially designed cells may be integrated into the stent in repeating patterns, such as a spiral configuration, to provide essentially uniform flexibility across the length of the stent, and in any bending direction.

[0020] In an example embodiment, a stent may be provided for use in an anatomical structure, including a first plurality of cells folded so as to exhibit auxetic properties upon expansion, each of the cells in the first plurality of cells including a cross member, and a second plurality of cells folded so as to exhibit auxetic properties upon expansion, each of the cells in the second plurality of cells lacking a cross member, wherein the first and second plurality of cells are interleaved with each other. Other embodiments will be described herein.

[0021] Fig. 1 depicts an example auxetic stent 100, which may be used to treat venous stenosis with improved luminal gain. Stent 100 is depicted as a tubular structure with a hollow center in a moderately expanded configuration. Mandrel 102 may be used as part of the process in manufacturing stent 100 to expand stent 100, such as to its final deployment diameter. Examining stent 100 more closely reveals various cells 104a, 104b, 104c, 104d, and 104e that do not contain axially oriented struts. These cells 104a to 104e are only a representative few ofsuch cells spaced along the length of stent 100 at regular intervals, as will be discussed in greater detail below.

[0022] Stent 100 may be manufactured from any material suitable for use in its intended appl ication(s). In implementations intended for medical use, such as implantation or placement within a blood vessel such as a vein, stent 100 maybe manufactured from a suitable biologically inert material or materials, for example, a metallic alloy such as stainless steel or nitinol, or a polymer. Materials may be selected for their elastic or plastic qualities, with the response to expansion and relaxation as considerations. In the case of nitinol, the material also possesses a shape memory, viz. the material will deform but return to a pre-set shape upon reaching a predetermined temperature. This may be useful when the stent 100 should be configured to best fit a particular anatomical structure, but may need to be deformed during the process of insertion. Following insertion, the temperature of stent 100 may be adjusted to cause it to revert to its memorized shape that conforms with the target anatomical structure.

[0023] Some materials, such as types of metal, may be subject to various treatments to alter their elastic point, to emphasize plastic or elastic qualities, as desired for the particular application. For example, in medical applications, a more plastic, deformable material may be desired over a material that is elastic, as stent 100 may need to maintain its size following expansion to ensure the vein remains unobstructed. Such materials may exhibit little to no reduction in size following expansion. Other materials may retain a modest amount of elasticity following plastic deformation, to allow stent adjustment following initial placement. As discussed above, in one embodiment, stent 100 may be formed from nitinol. Expansion of stent 100 within a patient may be accomplished using well-known medical techniques, such as via an inflating endoscopic or catheter balloon.

[0024] In addition to fabricating stent 100 from nitinol, steel, and / or cobalt-chromium, other materials including other shape memory materials could be used, depending upon the needs of a given embodiment.

[0025] In a suitable fabrication process, the tube comprising stent 100 is cut using lasers, then the tube is expanded to the desired final diameter and shape. The stent 100 is then chemically or mechanically polished to remove any oxide and also to ensure a smooth surface that is best for fatigue resistance. A passivation layer may also be created chemically to provide a corrosion resistant barrier on the outer surface of the stent. Furthermore, the wall thickness of the tubing of stent 100 can be adjusted to provide greater or lesser strength for both radial and crush (e.g., axial) dimensions. A thicker wall may be needed when there is a greater chance of deformation of the stent 100 while in place; however, a thicker wall reduces flexibility. Thus, the selection of wall thickness results in a balance or trade-off between flexibility and strength.Furthermore, the number of bridges along the length of the stent 100 which give it its auxetic property can enhance or reduce flexibility, depending on whether there are fewer or greater numbers of bridges, respectively. This will be discussed in further detail below.

[0026] It should be understood that the selection of materials for manufacturing stent 100 and / or treatment processes on the materials of stent 100 can be made to achieve desired performance characteristics of stent 100. For example, a given embodiment of stent 100 may be manufactured and treated to change shape primarily in a plastic mode, where changes to the shape of stent 100 are maintained once formed without further expansion or contraction, and so deliver a minimum of ongoing force to a surrounding vessel. Such an embodiment may be expanded (such as via a catheter balloon during insertion) so that the surrounding vessel wall is in tension and imposes a force against the stent 100, which stent 100 resists but is not significantly compressed, and does not impose additional forces or stresses against the vessel. With such an embodiment, the amount of tension placed upon the vessel wall can be fine-tuned (e.g. minimized or possibly eliminated) and adjusted during insertion of stent 100 by controlling the amount that stent 100 is expanded. Further, where stent 100 can be expanded to different degrees in different locations, such a stent 100 may allow tension on the vessel wall to vary across the length and diameter of stent 100.

[0027] In another embodiment, stent 100 may be manufactured to have elastic characteristics to provide a predetermined amount of force in opposition to compression, resulting in the vessel wall being placed under tension and expanding until the vessel wall tension balances the outward (radially expansive) force imposed by stent 100. Further treatments may allow a stent 100 to exhibit varying degrees of plasticity / elasticity across its length, e.g. one end or section of stent 100 may provide an outward force by elasticity, while the other end or another section of stent 100 may provide a second, different outward force and / or may provide only plastic deformation, with no or an insubstantial amount of outward force. Such configurations may be manufactured, for example, by individually treating or manufacturing each cel I to achieve a desired performance characteristic(s), and then assemblingstent lOOfrom a variety of cells treated in various ways to achieve a stent 100 with variable or selective elastic / plastic characteristics across its length and diameter.

[0028] Fig. 2 depicts a cell 200 that is a constituent in stent 100. Cell 200 is depicted in its closed, unexpanded configuration. As will be discussed in more detail below, the cel I 200 may be joined or formed with identical adjacent cells to form a stent 100. It will be understood by a person skilled in the art that these cells 200 may be wrapped around or otherwise configured to form the tubular configuration depicted in Fig. 1. Joining identical cells 200 at various ends allows a stent 100 to be constructed of any arbitrary diameter and length, as may be requiredfor a given application. As can be seen in Fig. 1, joining of the various cells effectively gives stent 100 a mesh configuration, by virtue of its interconnected cells.

[0029] The number and / or size of cells 200 contributes to the overall compressed size and dimensional properties of stent 100. For a given size of cell 200 and angle of the flexible junctions (discussed below with respect to Fig. 3), a greater number of cel Is 200 joined vertically will result in a larger diameter stent 100, while a fewer number will result in a smaller diameter stent 100. From a manufacturing perspective, a given diameter of mandrel 102 (Fig. 1) used to form the stent 100 will have a maximum number of cells 200 that encircle mandrel 102 when the cells are in an unexpanded configuration. This maximum number will depend on the overall size of the cell 200, which is primarily determined by the flexible junctions. Increasing the diameter of the mandrel 102 will al low for an increased number of a given size of cell 200 to be utilized. Thus, for a given number of cells 200, larger or smaller cells 200 will result in correspondingly larger or smaller diameter stents 100. Longitudinally, joining a greater number of cells 200 length-wise will result in a longer stent 100. The arrangement of the various folded struts comprising cell 200, discussed below with respect to Fig. 3, contributes to the auxetic properties of stent 100, namely, the degree to which stent 100 lengthens axially as it is expanded radially. The number of cells 200 as well as the arrangement of struts further contributes to the maximum amount of expansion or compression that stent 100 can provide.

[0030] Fig. 3 depicts the various components of cell 200. Cell 200 includes a first strut 302 and a second strut 304. Each of first strut 302 and second strut 304 comprise first and second segments 302a and 302b, and first and second segments 304a and 304b, respectively. First and second segments 302a and 302b are delineated by a flexible junction 306, and first and second segments 304a and 304b are delineated by a flexible function 308. In embodiments, flexible junctions 306 and 308 may be bends formed in each of first strut 302 and second strut 304. In other embodiments, flexible junctions 306 and 308 may be formed separately to join the respective first and second segments 302a, 302b, 304a, 304b together, and may be made from the same or a different material than each of the various segments. In still other embodiments, flexible junctions 306 and 308 may be manufactured from a material selected for plasticity over elasticity, while the various struts and segments may be manufactured with relatively rigid materials not subject to, or subject to little, plastic deformation. Alternatively or additionally, the materials may be subject to processing that alters their elastic point to emphasize either plasticity or elasticity, depending on the needs of a given implementation. For example, in some embodiments, all segments 302a, 302b, 304a, and 304b, along with flexible junctions 306 and 308, may be manufactured from a single material, with the material treated or processed foreach segment and / or junction to achieve the desired properties, e.g. junctions 306 and 308 are treated to emphasize plasticity, while struts 302 and 304 are treated to emphasize elasticity.

[0031] First and second struts 302 and 304 are tied together by a cross member 310, which, in the depicted embodiment, is joined to first segment 302a at a junction 312a, and is joined to first segment 304a at a junction 312b. Junctions 312a and 312b may be similar in nature to flexible junctions 306 and 308, or may be more rigid. As a person skilled in the relevant art will appreciate, in the depicted embodiment junctions 312a and 312b will not typically be subject to the same amount of flexure as flexible junctions 306 and 308, and so may be implemented in a more rigid fashion. Junctions 312a and 312b, as can be seen in Fig. 3, are attached proximate to first segment ends 326 and 328, respectively, and distal from flexible junctions 316 and 322.

[0032] In embodiments, joining members 314 and 320 are attached to second segments 302b and 304b at junctions 316 and 322, respectively. Junctions 316 and 322 may be of a similar type as junctions 312a and 312b, insofar as they may not experience the same degree of flexure as flexible junctions 306 and 308. As can be seen in the depicted embodiment, junctions 316 and 322 are located relatively proximate to flexible junctions 306 and 308, respectively, and relatively distal from second segment ends 330 and 332. In other words, as can be seen in Fig. 3, junctions 316 and 322 are not placed equidistant between flexible junctions 306, 308 and second segment ends 330, 332, but rather are closer, and hence more proximate, to flexible junctions 306 and 308 and further from second segment ends 330, 332. The arrangement of the various junctions 312a, 312b, 316, and 322, and thus the placement of cross member 310 and joining members 314 and 320 with respect to struts 302 and 304 determines the overall geometry of cell 200, and likewise determines the amount of axial expansion expressed by a cell 200 upon expansion. As will be understood in the depicted embodiment, moving the various junctions 312a, 312b, 316, and 322 closer to the respective centers of first segments 302a and 302b, and second segments 304a and 304b, will result in a lesser degree of axial expansion; likewise, moving the various junctions further away from the respective centers will result in a greater degree of axial expansion. It should be understood that placing the junctions 312a, 312b, 316, and / or 322 away from the center of their respective members may facilitate increased flexibility, and reduce columnar and / or longitudinal rigidity of the stent 100.

[0033] As seen in Fig. 3, in some embodiments, joining members 314 and 320 attach at junctions 316, 322, respectively, to form an acute angle 334 and 336. Likewise, cross member 310 attaches at junctions 312a and 312b to form acute angles 338 and 340. As can be seen, angles 334, 336, 338, and 340 are acute in the sense that they are less than 90 degrees. In embodiments, a suitable acute angle 334, 336, 338, and 340 may be 20-60 degrees. In someembodiments, angles 334, 336, 338, and / or 340 are each formed from a substantially curved bend, which meets to the respective first and second members 302 and 304 (at junctions 312a, 312b, 316, and / or 322) in a substantially perpendicular orientation, and then curves to create an initially parallel section between respective joining members 314, 320, cross member 310, and first and second members 302 and 304. The joining members 314, 320, and / or cross member 310 may then diverge away from the first and second members 302 and 304 distal from the angles 334, 336, 338, and / or 340. The formation of angles 334, 336, 338, and / or 340 into acute angles can provide several benefits to the stent design of the cross member at the insertion site: facilitating successful loading / crimping of the stent into a deliverable catheter after production (e.g. laser nitinol cutting) and expansion; facilitating axial / longitudinal stent compression and elongation; facilitating radial expansion from a loaded / crimped state; and, facilitating the foregoing benefits while minimizing stress / strain at the insertion site of the cross members, which may reduce long-term risk of stent fracture.

[0034] Fig. 4 illustrates a stent 400 that has not been formed into a tubular shape. Thus, stent 400 illustrates the structure of stent 100 if stent 100 were sliced axially and unfurled. As can be seen, stent 400 is comprised of a plurality of cells 200 that are attached to each other, resulting in a mesh of interleaved cells. For the purposes of this description, the term ‘interleaved’ refers to the placement or formation of different types or configurations of cells within a given stent.

[0035] In embodiments, the cells 200 are intermixed with a plurality of cells that lack a cross member, as seen in cel Is 402a through 402i. Note that not all cells missing a cross member have associated reference numbers. The cells 402a to 402i that lack a cross member are staggered laterally across the length of the stent 400. Within a line or band of cells 200, such as band 404, every fourth cell lacks a cross member. As a result, when stent 400 is formed into a tubular shape, the interleaved cells, including cells 402a to 402i, form a series of spiral patterns along the length of the stent 400. These spiral arrangements of cells without cross members impart additional flexibility to the stent 400 to permit controlled bending off-axis. Thus, the stent 400 is able to more closely conform to a vein or other structure that itself may twist or bend, without imposing unnecessary stress on the structure.

[0036] Referring back to Fig. 3, each cell 200, as illustrated in the various figures, may be combined with adjacent cells 200 to form a stent 100. Each cell 200 joins with other cells via first segment ends 326 and 328, second segment ends 330 and 332, and joining member ends 318 and 324. While the terms ‘join’ and ‘cel I’ may indicate the individual nature of the cel Is, some or all of the structures can be formed simultaneously or sequentially to arrive at the final stent structure.

[0037] Referring to Figs. 1 and 4 (discussed above) for the general arrangement of cells in a stent 100, it may be recognized that each first segment end 326 and 328 is connected to a corresponding second segment end 330 and 332, respectively, of an adjacent cell 200. The attachment of each first segment end 326 and 328 to adjacent second segment ends 330 and 332 may effectively create a second pair of flexible junctions. As these second flexible junctions serve the same function as flexible junctions 316 and 322 across a stent 100, these second flexible junctions may be configured identically to flexible junctions 316 and 322. It will be understood that flexible junctions 316 and 322 along with the second flexible junctions play a primary role in defining the expansion and crimping behavior of a stent 100, in embodiments.

[0038] Some cells are joined along an axial direction via the joining member ends 318 and 324, with a joining member end 318 attaching to a corresponding joining member end 324 of an adjacent cell 200. In the depicted embodiments, this connection effectively forms a second cross member, similar to cross member 310 in configuration, via the combination of a joining member 314 and a joining member 320 of an adjacent cell 200. Thus, this second cross member may be of a similar construction as cross member 310, and the connection between joining member ends 318 and 324 may be configured, or of a type, to result in a second cross member that is substantially identical to cross member 310 in terms of performance and material characteristics. For example, the joining member ends 318 and 324 may be welded or soldered together, or as noted above, the structures may be formed together as desired using any of a number of suitable manufacturing techniques.

[0039] For forming cells that lack a cross-member, some cells 200 may omit crossmember 310, resulting structurally in two disconnected halves to define a cell, otherwise defined as an open cell. Alternatively or additionally, joining members 314 and 320 instead may be omitted from a cell 200 and its neighbors; as a joining member 314 when attached to a corresponding joining member 320 of an adjacent cell, omitting these structures is comparable to omitting a cross member 310.

[0040] In some embodiments, omitting joining member 314 and 320 may be preferable, as it allows a cell 200 to remain connected as a single piece, rather than two separate disconnected halves. Whether it is preferable to remove / omit joining members 314 and 320 or cross member 310 may depend upon the specifics of a given embodiment, such as how stent 100 is to be fabricated. While the term ‘remove’ is used in various locations throughout the disclosure, it is not intended to suggest that the cross member is necessarily first formed and then removed, but rather that it is not present in the deployed stent, regardless of the manufacturing method that lead to the stent formation. In other words, the stent could beformed without certain cross members, or certain cross members could be formed and then later excised.

[0041] As will be understood, joining cells 200 both axially and circumferentially (for a tubular stent) can be repeated to provide a stent 100 of any diameter and axial length suited for a given intended use. Moreover, as noted above, while stent 100 is described genera Ilyas being comprised of a plurality of discrete cells 200 that are joined together, this is only one possible method of manufacture, and is described to help illustrate the general structure of stent 100 rather than suggest a preferred method of manufacture. It should be understood that a stent 100 or a portion thereof may be manufactured as a singular unit, such as by spinning together one or more strands of suitable material such as wire, or via other pieces, larger or smaller, using any suitable manufacturing method, such as welding, soldering, tying, twisting, casting, 3D- printing, or another method known or later developed.

[0042] In addition to removal of cross member 310 and / or joining members 314 and 320, to allow for further control of axial expansion of a stent 100 beyond the natural expansion resulting from the configuration of each cell 200, cross member 310 and second cross member formed from joining members 314 and 320 (collectively referred to herein as "cross member” or "cross members”) may be configured to plastically deform via bending when either axial compression or tension is applied to a stent 100 that has been at least partially expanded. This deformation allows adjustments to be made to the axial length of a stent 100 while maintaining a constant expanded diameter, viz. without requiring the stent 100 to be radially expanded or crimped.

[0043] In some embodiments, the geometry of the unit cell 200 of Figs. 2 and 3 comprising an auxetic stent, such as stents 400 (Fig. 4), 500 (Fig. 5, discussed below), and / or 600 (Fig. 6, discussed below), may be modified to advantageously impart desired structural properties and mechanical behavior to the stent upon deployment into a lumen. Similarly, the number of cells arranged circumferentially and longitudinally may be selected to impart specific structural properties and mechanical behavior to the stent. For example, certain embodiments may employ stents of varying geometry, both at the unit cell level and at the stent level, to exhibit a range of radial stiffness and axial stiffness values. The selection of radial and axial stiffness, for a given embodiment, in turn governs the force transmitted to a vessel structure in the radial and axial directions when the stent is deployed and expanded within the vessel lumen. Similarly, a stent geometry may be designed or tuned such that a specific amount of extension in the axial direction is produced when a stent implementing the geometry is expanded in the radial direction. As such, auxetic stents generated using the unit cell approach described herein can be used to actively control the degree of longitudinal force or stress borne by the vessel towhich the stent is expanded, both in the vessel wall immediately surrounding the expanded stent and i n the vessel adjacent to, or upstream / downstream from, the stent. Such active control of the vessel wall mechanical stresses using auxetic stent designs according to the various embodiments disclosed herein may be employed, for example, to mitigate undesirable narrowing of adjacent vessel diameter commonly observed with the deployment of non-auxetic stents.

[0044] In some embodiments, structural properties and mechanical behavior of a stent comprised of unit cells, such as cell 200, configured according to the schematic of Fig. 3, may be adjusted by modifying the locations at which the individual struts are connected. For example, the locations of the junctions 312a and 312b where cross member 310 joins the fi rst and second struts 302 and 304 may be moved closer to, or further from, the respective centers of first segments 302a and 304a. Such a design modification can be employed to alter the amount of axial length change of the stent and the amount of longitudinal stress engendered in the vessel wall when the stent is expanded radially, aswell as alter the radial and axial stiffness of the stent. The number of unit cells in a stent’s circumferential direction may also be varied to produce changes in stent structural properties and mechanical behavior. It will further be appreciated that variation of strut thickness and / or cross-sectional area properties or material properties will also manifest as changes in a stent’s radial stiffness, axial stiffness, amount of axial length change during radial expansion, and / or the longitudinal stress engendered in the vessel wall.

[0045] While Figs. 1 and 4 illustrate a stent with a spiral pattern formed by omitting a cross member from every fourth cell in a given band 404 and staggering / offsetting the omitted cross member by one from adjacent bands, other patterns may be possible, e.g. omitting a cross member from every other cell, every third cell, every fifth cell, every sixth cell, etc. Some examples of alternative arrangements are depicted in Figs. 5 and 6, discussed below. The spacing of the omitted cells may also depend upon the diameter of the stent, including the size of each cell and the number of cells present in a given band 404. A larger diameter stent and / or a stent with smaller cells that allows an increased number of cells in band 404 can allow for a greater spacing between spirals.

[0046] The pattern of cells with omitted cross members may be tailored to achieve a desired level of flexibility, with the removal of a greater number of cross members resulting in a more flexible stent. For example, great flexibility may be intentionally provided to one or both ends of the stent, such as the terminal 25% at the ends of the stent, while maintaining a middle section, such as the middle 50%, that has a lower degree of flexibility. However, it should be understood that a greater number of removed cross members may likewise result in a stent that has diminished resistance from being compressed by force exerted by surrounding structures.

[0047] Furthermore, although Figs. 1 and 4 illustrate a spiral pattern, other patterns may be employed depending on the needs of a given embodiment. Similarly, the number of missing cross members may vary across the length of the stent. For example, a given stent 100 may have several bands 404 in one section where every third cross member is not present, and other sections where every fourth cross member is not present. Such embodiments may allow theflexibility of the stent 100 to vary along its length, so that portions of the stent that will need to traverse a curve are more flexible, while portions that are located in relatively straight sections of a vessel or other structure are more rigid but provide better support to keep the structure open, and thus help keep the vessel open.

[0048] Fig. 5 illustrates a second example embodiment of a stent 500, with a different pattern of cells where cross members are not present. As can be seen, cells 502a, 502b, 502c, 502d, 502e, and 502f lack cross members, and are arranged in a spiral pattern. Similar to the stent 400 of Fig. 4, withi n a band 504 the cel Is with missing cross members are spaced from each other by three cells with cross members, so that every fourth cell does not have cross member. However, in contrast to the stent 400 of Fig. 4, the cells with the missing cross members are offset from cells with missing cross members in adjacent bands by two cells, so that cells with missing cross members in a given band 504 are staggered and offset from two cells with missing cross members in the bands that are immediately adjacent on either side of band 504.

[0049] Fig. 6 illustrates a third example embodiment of a stent 600, with yet another different pattern of cells with missing cross members. As with stents 400 and 500, cells 602a, 602b, 602c, 602d, 602e, 602f, 602g, 602h, and 602i form a spiral pattern. However, within a band 604, every other cell is lacking a cross member, rather than every fourth cell as in stents 400 and 500 of Figs. 4 and 5, respectively. Similar to stent 500 of Fig. 5, the cells with missing cross members in a given band 604 are staggered and offset from cells that lack cross members in immediately adjacent bands on either side of band 604. However, owing to every other cell lacking a cross member in a given band 604, the spiral pattern is similar to stent 400 of Fig. 4, albeit with twice the density of cells with missing cross members.

[0050] The various patterns of the example stents 400, 500, and 600 may offer different amounts of flexibility. A given stent may, in some embodiments, utilize the patterns of any or all of stents 400, 500 and 600 in various regions to achieve varying degrees of flexibility in different regions of the stent. For example, sections of a stent that will be positioned in anatomical structures with little to no curves may utilize the pattern of stent 400, while sections of the same stent that will be positioned in anatomical structures with more acute or complex curves may employ the pattern of stent 500 or even 600, as a greater flexibility in those portions may be desirable.

[0051] While the patterns described above and referenced in the figures showed ordered patterns of cells in which certain cells have cross members and others do not, it is also possible, in certain embodiments, to have an irregular array of cells in which some cells do not have cross members and other cells do have cross members, but they do not form an ordered pattern.

[0052] Fig. 7 provides the operations of an example method 700 for using an auxetic stent, such as stent 100, for treating venous stenosis. The operations of method 700 may be carried out in whole or in part using a stent, such asstent 100. In operation 702, the vessel (such as a blood vessel) portion requiring treatment is located and assessed, along with the nature of any adjacent vessel portions. Following assessment, in operation 704 a stent of an appropriate diameter and length, and having the appropriate auxetic properties, e.g. correct or ideal amount of axial expansion to radial expansion, is selected or fabricated.

[0053] In operation 706, in some embodiments, the stent may lack any removed cross members, but is then modified prior to insertion by selective removal of cross members from some cells in the stent in a suitable pattern and spacing to achieve an appropriate or desired amount of flexibility of the stent, with consideration of the structure of the vessel to be stented. In other embodiments, the stent may be initially fabricated without cross members in certain cells in a spiral or other fashion and with any differing patterns to accommodate varying curves pre-fabricated, rather than employing removal of the cross members following fabrication and / or just prior to insertion into a patent. In still other embodiments, a stent may be manufactured with a spiral or other pattern of open cells (without cross members), and then further adjusted by selective removal of additional cross members from various sections of the stent to adjust the flexibility for some or all portions of the stent.

[0054] Finally, in operation 708, the axial length may be adjusted and the stent bent as appropriate to relieve any stress on the adjacent vessel portions, to prevent the diameter of the adjacent vessel portions from narrowing and to improve luminal gain in the stented vessel portion. In cases where the vessel is curved, the removed cross members can allow the stent to be curved off-axis (curved or bent longitudinally) without introducing excessive strain on the vessel, thereby allowing the stent to be curved to fit the shape of the vessel while still preventing undesirable narrowing of adjacent vessel diameter. As discussed above, the axial force may be a compression, to cause the cross members to bend and shorten the axial length, or a stretching, to cause the cross members to straighten and lengthen axially, or may be a combination of compression and stretching on different circumferential portions of the stent to cause the stent to assume a curved configuration while expanded. The open cells allow the axial force required to adjust the stent to be lessened and / or to reduce the force exerted by the stent agai nst a bend.

[0055] It will be appreciated that the stent, in the disclosed embodiments, may operate in a range of diameter configurations, including a compressed diameter suitable for delivery into a vessel, a fully expanded diameter which may be equal to or larger than the maximum expected diameter of the target vessel, and any of a continuous range of intermediate diameters between these two extremes. In typical use, when the stent is expanded from its compressed state at the site of intervention, it may first come into contact with the vessel at an intermediate diameter. The diameter of first contact may be smaller than the desired diameter for an optimal therapeutic result. Accordingly, after first contacting the vessel, the stent may then be further expanded in diameter, to achieve the desired vessel lumen diameter. This additional expansion may be caused by the desirable elastic or superelastic properties of the stent, and may be further aided by adjunctive interventions such as balloon venoplasty. Given the auxetic properties of the stent, such additional expansion will be accompanied by simultaneous increase in axial length, which may be controlled or constrained, as described above.

[0056] It wi II be further appreciated that alternate embodiments of an auxetic stent may be readily generated based on a unit cell geometry by varying the size of the unit cell and the number of unit cells connected circumferentially to form a tubular configuration. In various embodiments, the number of cells connected circumferentially to form a tubular configuration in a stent may vary between 4 cells and 50 cells, with the cells sized to produce stent diameters between 1mm and 100mm after radial expansion. Similarly, unit cells may be combined in the axial direction to generate stents of different length. As such, using the approaches described herein, stents may be produced that are suitable for deployment into vessels of varying sizes for different applications or mechanical effect.

[0057] Stents such as stent 100 (or another embodiment herein) used to treat venous stenosis may be from about 1 mm to about 100 mm in diameter, such as 6 mm to 30 mm diameter which is typical of veins, and from about 5 mm to about 300 mm in length, such as 220 mm that is typically needed for clinical application, fully expanded (the specific stent measurements for each specific use herein, unless otherwise specifically stated, are at full expansion of the stent - all diameters are outside diameters). Specific stents for use in treating venous stenosis include (diameter x length) 5 mm x 20 mm, 5 mm x 30 mm, 5 mm x 40 mm, 5 mm x 50 mm, 5 mm x 60 mm, 5 mm x 70 mm, 5 mm x 80 mm, 5 mm x 90 mm, 5 mm x 100 mm, 5 mm x 110 mm, 5 mm x 120 mm, 5 mm x 130 mm, 5 mm x 140 mm, 5 mm x 150 mm, 5 mm x 160 mm, 5 mm x 170 mm, 5 mm x 180 mm, 5 mm x 190 mm, 5 mm x 200 mm, 5 mm x 220 mm, 5 mm x 240 mm, 6 mm x 20 mm, 6 mm x 30 mm, 6 mm x 40 mm, 6 mm x 50 mm, 6 mm x 60 mm, 6 mm x 70 mm, 6 mm x 80 mm, 6 mm x 90 mm, 6 mm x 100 mm, 6 mm x 110 mm, 6 mm x 120 mm, 6 mm x 130 mm, 6 mm x 140 mm, 6 mm x 150 mm, 6 mm x 160 mm, 6 mm x 170 mm, 6 mm x 180 mm, 6 mm x 190 mm, 6mm x 200 mm, 6 mm x 220 mm, 6 mm x 240 mm, 7 mm x 20 mm, 7 mm x 30 mm, 7 mm x 40 mm, 7 mm x 50 mm, 7 mm x 60 mm, 7 mm x 70 mm, 7 mm x 80 mm, 7 mm x 90 mm, 7 mm x 100 mm, 7 mm x 110 mm, 7 mm x 120 mm, 7 mm x 130 mm, 7 mm x 140 mm, 7 mm x 150 mm, 7 mm x 160 mm, 7 mm x 170 mm, 7 mm x 180 mm, 7 mm x 190 mm, 7 mm x 200 mm, 7 mm x 220 mm, 7 mm x 240 mm, 8 mm x 20 mm, 8 mm x 30 mm, 8 mm x 40 mm, 8 mm x 50 mm, 8 mm x 60 mm, 8 mm x 70 mm, 8 mm x 80 mm, 8 mm x 90 mm, 8 mm x 100 mm, 8 mm x 110 mm, 8 mm x 120 mm, 8 mm x 130 mm, 8 mm x 140 mm, 8 mm x 150 mm, 8 mm x 160 mm, 8 mm x 170 mm, 8 mm x 180 mm, 8 mm x 190 mm, 8 mm x 200 mm, 8 mm x 220 mm, 8 mm x 240 mm, 10 mm x 20 mm, 10 mm x 30 mm, 10 mm x 40 mm, 10 mm x 50 mm, 10 mm x 60 mm, 10 mm x 70 mm, 10 mm x 80 mm, 10 mm x 90 mm, 10 mm x 100 mm, 10 mm x 110 mm, 10 mm x 120 mm, 10 mm x 130 mm, 10 mm x 140 mm, 10 mm x 150 mm, 10 mm x 160 mm, 10 mm x 170 mm, 10 mm x 180 mm, 10 mm x 190 mm, 10 mm x 200 mm, 10 mm x 220 mm, 10 mm x 240 mm, 12 mm x 20 mm, 12 mm x 30 mm, 12 mm x 40 mm, 12 mm x 50 mm, 12 mm x 60 mm, 12 mm x 70 mm, 12 mm x 80 mm, 12 mm x 90 mm, 12 mm x 100 mm, 12 mm x 110 mm, 12 mm x 120 mm, 12 mm x 130 mm, 12 mm x 140 mm, 12 mm x 150 mm, 12 mm x 160 mm, 12 mm x 170 mm, 12 mm x 180 mm, 12 mm x 190 mm, 12 mm x 200 mm, 12 mm x 220 mm, 12 mm x 240 mm, 14 mm x 20 mm, 14 mm x 30 mm, 14 mm x 40 mm, 14 mm x 50 mm, 14 mm x 60 mm, 14 mm x 70 mm, 14 mm x 80 mm, 14 mm x 90 mm, 14 mm x 100 mm, 14 mm x 110 mm, 14 mm x 120 mm, 14 mm x 130 mm, 14 mm x 140 mm, 14 mm x 150 mm, 14 mm x 160 mm, 14 mm x 170 mm, 14 mm x 180 mm, 14 mm x 190 mm, 14 mm x 200 mm, 14 mm x 220 mm, 14 mm x 240 mm, 16 mm x 20 mm, 16 mm x 30 mm, 16 mm x 40 mm, 16 mm x 50 mm, 16 mm x 60 mm, 6 mm x 70 mm, 16 mm x 80 mm, 16 mm x 90 mm, 16 mm x 100 mm, 16 mm x 110 mm, 16 mm x 120 mm, 16 mm x 130 mm, 16 mm x 140 mm, 16 mm x 150 mm, 16 mm x 160 mm, 16 mm x 170 mm, 16 mm x 180 mm, 16 mm x 190 mm, 16 mm x 200 mm, 16 mm x 220 mm, 16 mm x 240 mm, 18 mm x 20 mm, 18 mm x 30 mm, 18 mm x 40 mm, 18 mm x 50 mm, 18 mm x 60 mm, 18 mm x 70 mm, 18 mm x 80 mm, 18 mm x 90 mm, 18 mm x 100 mm, 18 mm x 110 mm, 18 mm x 120 mm, 18 mm x 130 mm, 18 mm x 140 mm, 18 mm x 150 mm, 18 mm x 160 mm, 18 mm x 170 mm, 18 mm x 180 mm, 18 mm x 190 mm, 18 mm x 200 mm, 18 mm x 220 mm, 18 mm x 240 mm, 20 mm x 20 mm, 20 mm x 30 mm, 20 mm x 40 mm, 20 mm x 50 mm, 20 mm x 60 mm, 20 mm x 70 mm, 20 mm x 80 mm, 20 mm x 90 mm, 20 mm x 100 mm, 20 mm x 110 mm, 20 mm x 120 mm, 20 mm x 130 mm, 20 mm x 140 mm, 20 mm x 150 mm, 20 mm x 160 mm, 20 mm x 170 mm, 20 mm x 180 mm, 20 mm x 190 mm, 20 mm x 200 mm, 20 mm x 220 mm, 20 mm x 240 mm, 22 mm x 20 mm, 22 mm x 30 mm, 22 mm x 40 mm, 22 mm x 50 mm, 22 mm x 60 mm, 22 mm x 70 mm, 22 mm x 80 mm, 22 mm x 90 mm, 22 mm x 100 mm, 22 mm x 110 mm, 22 mm x 120 mm, 22 mm x 130 mm, 22 mm x 140 mm, 22 mm x 150 mm, 22 mm x 160 mm, 22 mm x 170 mm, 22 mm x 180 mm, 22 mm x 190 mm, 22 mm x 200 mm, 22 mm x 220 mm,22 mm x 240 mm, 24 mm x 20 mm, 24 mm x 30 mm, 24 mm x 40 mm, 24 mm x 50 mm, 24 mm x 60 mm, 24 mm x 70 mm, 24 mm x 80 mm, 24 mm x 90 mm, 24 mm x 100 mm, 24 mm x 110 mm, 24 mm x 120 mm, 24 mm x 130 mm, 24 mm x 140 mm, 24 mm x 150 mm, 24 mm x 160 mm, 24 mm x 170 mm, 24 mm x 180 mm, 24 mm x 190 mm, 24 mm x 200 mm, 24 mm x 220 mm, 24 mm x 240 mm, 26 mm x 20 mm, 26 mm x 30 mm, 26 mm x 40 mm, 26 mm x 50 mm, 26 mm x 60 mm, 26 mm x 70 mm, 26 mm x 80 mm, 26 mm x 90 mm, 26 mm x 100 mm, 26 mm x 110 mm, 26 mm x 120 mm, 26 mm x 130 mm, 26 mm x 140 mm, 26 mm x 150 mm, 26 mm x 160 mm, 26 mm x 170 mm, 26 mm x 180 mm, 26 mm x 190 mm, 26 mm x 200 mm, 26 mm x 220 mm, 26 mm x 240 mm, 28 mm x 20 mm, 28 mm x 30 mm, 28 mm x 40 mm, 28 mm x 50 mm, 28 mm x 60 mm, 28 mm x 70 mm, 28 mm x 80 mm, 28 mm x 90 mm, 28 mm x 100 mm, 28 mm x 110 mm, 28 mm x 120 mm, 28 mm x 130 mm, 28 mm x 140 mm, 28 mm x 150 mm, 28 mm x 160 mm, 28 mm x 170 mm, 28 mm x 180 mm, 28 mm x 190 mm, 28 mm x 200 mm, 28 mm x 220 mm, 28 mm x 240 mm, 30 mm x 20 mm, 30 mm x 30 mm, 30 mm x 40 mm, 30 mm x 50 mm, 30 mm x 60 mm, 30 mm x 70 mm, 30 mm x 80 mm, 30 mm x 90 mm, 30 mm x 100 mm, 30 mm x 110 mm, 30 mm x 120 mm, 30 mm x 130 mm, 30 mm x 140 mm, 30 mm x 150 mm, 30 mm x 160 mm, 30 mm x 170 mm, 30 mm x 180 mm, 30 mm x 190 mm, 30 mm x 200 mm, 30 mm x 220 mm, 30 mm x 240 mm.

[0058] A method of treating a ureteral stricture in a human may comprise implanting a stent similar to or as described herein into the ureteral stricture in the human in need thereof.

[0059] Stents identical or similar to stent 100 (or another embodiment herein) used in treating strictures in a cystic duct or common bile duct or in treating biliary tract diseases may be from about 1 mm to about 30 mm in diameter and from about 5 mm to about 200 mm in length, fully expanded (the specific stent measurements for each specific use herein, unless otherwise specifically stated, are at full expansion of the stent - all diameters are outside diameters). Specific stents for use in biliary treatments include (diameter x length) 5 mm x 20 mm, 5 mm x 30 mm, 5 mm x 40 mm, 5 mm x 50 mm, 5 mm x 60 mm, 5 mm x 70 mm, 5 mm x 80 mm, 5 mm x 90 mm, 5 mm x 100 mm, 5 mm x 110 mm, 5 mm x 120 mm, 5 mm x 130 mm, , 5 mm x 140 mm, 5 mm x 150 mm, 5 mm x 160 mm, 5 mm x 170 mm, 5 mm x 180 mm, 5 mm xl 90 mm,5 mm x 200 mm, 6 mm x 20 mm, 6 mm x 30 mm, 6 mm x 40 mm, 6 mm x 50 mm, 6 mm x 60 mm,6 mm x 70 mm, 6 mm x 80 mm, 6 mm x 90 mm, 6 mm x 100 mm, 6 mm x 110 mm, 6 mm x 120 mm, 6 mm x 130 mm, 6 mm x 140 mm, 6 mm x 150 mm, 6 mm x 160 mm, 6 mm x 170 mm, 6 mm x 180 mm, 6 mm x 190 mm, 6 mm x 200 mm, 8 mm x 20 mm, 8 mm x 30 mm, 8 mm x 40 mm, 8 mm x 50 mm, 8 mm x 60 mm, 8 mm x 70 mm, 8 mm x 80 mm, 8 mm x 90 mm, 8 mm x 100 mm, 8 mm x 110 mm, 8 mm x 120 mm, 8 mm x 130 mm, 8 mm x 140 mm, 8 mm x 150 mm, 8 mm x 160 mm, 8 mm x 170 mm, 8 mm x 180 mm, 8 mm x 190 mm, 8 mm x 200 mm, 10 mm x 20 mm, 10 mm x 30 mm, 10 mm x 40 mm, 10 mm x 50 mm, 10 mm x 60 mm, 10 mm x 70 mm, 10 mm x 80 mm,10 min x 90 mm, 10 mm x 100 mm, 10 mm x 110 mm, 10 mm x 120 mm, 10 mm x 130 mm, 10 mm x 140 mm, 10 mm x 150 mm, 10 mm x 160 mm, 10 mm x 170 mm, 10 mm x 180 mm, 10 mm x 190 mm, and 10 mm x 200 mm.

[0060] A method of treating a ureteral stricture in a human may comprise implanting a stent similar to or as described herein into the ureteral stricture in the human in need thereof.

[0061] Stents identical or similar to stent 100 (or another embodiment herein) used in treating strictures in the human ureter or in treating urinary tract diseases associated with a uretal stricture may be from about 1 mm to about 100 mm in diameter and from about 5 mm to about 500 mm in length (fully expanded). In other embodiments, uretal stents may comprise from about 1 mm to about 15 mm in diameter and a length of from about 5 mm to about 500 mm in length. In other embodiments, uretal stents may comprise from about 1 mm to about 12 mm in diameter and a length of from about 5 mm to about 500 mm in length. In further embodiments, uretal stents may comprise from about 1 mm to about 3 mm in diameter and a length of from about 5 mm to about 500 mm in length. In further embodiments, uretal stents may comprise from about 1 mm to about 2 mm in diameter and a length of from about 5 mm to about 500 mm in length. Specific stents of the design herein for ureter implantation include those having the diameter x length of 1 mm x 10 mm, 1 mm x 20 mm, 1 mm x 40 mm, 1 mm x 60 mm, 1 mm x 80 mm, 1 mm x 100 mm, 1 mm x 120 mm, 1 mm x 150 mm, 1 mm x 200 mm, 1 mm x 250 mm, 1 mm x 300 mm, 1 mm x 350 mm, 1 mm x 400 mm, 1 mm x 500 mm, 2 mm x 10 mm, 2 mm x 20 mm, 2 mm x 40 mm, 2 mm x 60 mm, 2 mm x 80 mm, 2 mm x 100 mm, 2 mm x 120 mm, 2 mm x 150 mm, 2 mm x 200 mm, 2 mm x 250 mm, 2 mm x 300 mm, 2 mm x 350 mm, 2 mm x 400 mm, and 2 mm x 500 mm.

[0062] A method of treating a stricture in the gastrointestinal tract in a human may comprise implanting a stent similar to or as described herein into the gastrointestinal tract stricture in the human in need thereof.

[0063] Stents identical or similar to stent 100 (or another embodiment herein) used in treating strictures in the gastrointestinal tract may be from about 1 mm to about 100 mm in diameter and from about 5 mm to about 500 mm in length (fully expanded).

[0064] A method of treating a stricture in the colon in a human may comprise implanting a stent similar to or as described herein into the stricture in the colon in the human in need thereof.

[0065] Colonic stents identical or similar to stent 100 (or another embodiment herein) may be from about 20 mm to about 40 mm in diameter and from about 20 mm to about 150 mm in length. In some embodiments, the colonic stents may be from about 20 mm to about 35 mm in diameter and from about 40 mm to about 140 mm in length. In other embodiments, thecolonic stents may be from about 26 mm to about 32 mm in diameter and from about 40 mm to about 120 mm in length.

[0066] A method of treating a stricture in the esophagus in a human may comprise implanting a stent similar to or as described herein into the stricture in the esophagus in the human in need thereof.

[0067] Esophageal stents identical or similar to stent 100 (or another embodiment herein) may be from about 10 mm to about 25 mm in diameter and from about 3 cm to about 20 cm in length. In some embodiments, the colonic stents may be from about 15 mm to about 25 mm in diameter and from about 5 cm to about 15 cm in length. In other embodiments, the colonic stents may be from about 17 mm to about 23 mm in diameter and from about 5 cm to about 15 cm in length.

[0068] A method of treating a tracheobronchial stricture in a human may comprise implanting a stent similar to or as described herein into the tracheobronchial stricture in the human in need thereof.

[0069] In some embodiments, the tracheobronchial stents may be from about 5 mm to about 25 mm in diameter and from about 10 mm to about 100 mm in length. In some embodiments the tracheobronchial stents may be from about 6 mm to about 22 mm in diameter and from about 10 mm to about 100 mm in length. Specific examples of tracheobronchial stent sizes for uses here include the expanded diameter x length combinations of from 8 mm x 20 mm, 8 mm x 30 mm, 8 mm x 40 mm, 10 mm x 20 mm, 10 mm x 30 mm, 10 mm x 40 mm, 10 mm x 60 mm, 12 mm x 20 mm, 12 mm x 30 mm, 12 mm x 40 mm, 12 mm x 60 mm, 12 mm x 80 mm, 14 mm x 20 mm, 14 mm x 30 mm, 14 mm x 40 mm, 14 mm x 60 mm, 14 mm x 80 mm, 16 mm x 20 mm, 16 mm x 30 mm, 16 mm x40 mm, 16 mm x 60 mm, 16 mm x 80 mm, 18 mm x 20 mm, 18 mm x 30 mm, 18 mm x 40 mm, 18 mm x 60 mm, 18 mm x 80 mm, 20 mm x 20 mm, 20 mm x 30 mm, 20 mm x40 mm, 20 mm x 60 mm, and 20 mm x 80 mm.

[0070] A method of treating a salivary duct stricture in a human may comprise implanting a stent similar to or as described herein into the salivary duct stricture in the human in need thereof. Examples of salivary duct stents of use herein include those from about 0.5 mm to about 3 mm in diameter and from about 1 mm to about 40 mm in length.

[0071] A method of treating a neurovascular condition in a human may comprise implanting a stent similar to or as described herein into the appropriate structure in the human in need thereof. Specifically, a stent may be implanted into a venous sinus (venous sinus stenting, or VSS), such as a dural venous sinus. Also, implanting a stent into a transverse sinus may be employed to treat intracranial hypertension, including Idiopathic intracranial hypertension ( 11 H) or chronic intracranial venous hypertension (CIVHS). VSS has been demonstrated effective intreating IIH, but can result in stent-adjacent stenosis. Stents according to the embodiments disclosed herein can alleviate these stenosis symptoms.

[0072] In some embodiments, neurovascular stents may be from about 5 mm to about 12 mm in diameter and from about 20 mm to about 100 mm in length. Specific examples of stent sizes for use in such conditions include the expanded diameter x length combinations of from 5 mm x 20mm, 5 mm x 30 mm, 5 mm x 40 mm, 5 mm x 50 mm, 5 mm x 60 mm, 5 mm x 70 mm, 5 mm x 80 mm, 5 mm x 90 mm, 5 mm x 100 mm, 6 mm x 20mm, 6 mm x 30 mm, 6 mm x 40 mm, 6 mm x 50 mm, 6 mm x 60 mm, 6 mm x 70 mm, 6 mm x 80 mm, 6 mm x 90 mm, 6 mm x 100 mm, 7 mm x 20mm, 7 mm x 30 mm, 7 mm x 40 mm, 7 mm x 50 mm, 7 mm x 60 mm, 7 mm x 70 mm, 7 mm x 80 mm, 7 mm x 90 mm, 7 mm x 100 mm, 8 mm x 20mm, 8 mm x 30 mm, 8 mm x 40 mm, 8 mm x 50 mm, 8 mm x 60 mm, 8 mm x 70 mm, 8 mm x 80 mm, 8 mm x 90 mm, 8 mm x 100 mm, 9 mm x 20mm, 9 mm x 30 mm, 9 mm x 40 mm, 9 mm x 50 mm, 9 mm x 60 mm, 9 mm x 70 mm, 9 mm x 80 mm, 9 mm x 90 mm, 9 mm x 100 mm, 10 mm x 20mm, 10 mm x 30 mm, 10 mm x 40 mm, 10 mm x 50 mm, 10 mm x 60 mm, 10 mm x 70 mm, 10 mm x 80 mm, 10 mm x 90 mm, 10 mm x 100 mm, 11 mm x 20mm, 11 mm x 30 mm, 11 mm x40 mm, 11 mm x 50 mm, 11 mm x 60 mm, 11 mm x 70 mm, 11 mm x 80 mm, 11 mm x 90 mm, 11 mm x 100 mm, 12 mm x 20mm, 12 mm x 30 mm, 12 mm x 40 mm, 12 mm x 50 mm, 12 mm x 60 mm, 12 mm x 70 mm, 12 mm x 80 mm, 12 mm x 90 mm, and 12 mm x 100 mm.

[0073] It will be appreciated that the configurations disclosed herein are exemplary in nature, and that these specific embodiments are not to be considered in a limiting sense, because numerous variations are possible. The subject matter of the present disclosure includes all novel and nonobvious combinations and subcombinations of the various systems and configurations, and other features, functions, and / or properties disclosed herein.

[0074] The following claims particularly point out certain combinations and subcombinations regarded as novel and nonobvious. These claims may refer to "an” element or “a first” element or the equivalent thereof. Such claims should be understood to include incorporation of one or more such elements, neither requiring nor excluding two or more such elements. Other combinations and subcombinations of the disclosed features, functions, elements, and / or properties may be claimed through amendment of the present claims or through presentation of new claims in this or a related application. Such claims, whether broader, narrower, equal, or different in scope to the original claims, also are regarded as included within the subject matter of the present disclosure.

Claims

CLAIMS1. A stent for use in an anatomical structure, comprising: a first plurality of cells folded so as to exhibit auxetic properties upon expansion, each of the cells in the first plurality of cells including a cross member; and a second plurality of cells folded so as to exhibit auxetic properties upon expansion, each of the cells in the second plurality of cells lacking a cross member, wherein the first and second plurality of cells are interleaved with each other.

2. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are arranged in a plurality of circular bands, and within one of the circular bands every second, third, or fourth cell is from the second plurality of cells, with the remaining cells from the first plurality of cells.

3. The stent of claim 2, wherein at least one of the plurality of circular bands has an arrangement of cells that is different than the arrangement in at least one other of the plurality of circular bands.

4. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are arranged in a plurality of circular bands, and within one of the circular bands every other cell is from the second plurality of cells, with the remaining cells from the first plurality of cells.

5. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are interleaved to form a pattern.

6. The stent of claim 5, wherein the pattern is a spiral pattern.

7. The stent of claim 1, wherein each cell of the second plurality of cells is smaller than each cell of the first plurality of cells.

8. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are arranged to impart uniform flexibility along the stent.

9. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are arranged to impart flexibility at a first location along the stent which differs from flexibility at a second location along the stent.

10. The stent of claim 9, wherein, in the longitudinal, axial direction, the stent is defined by a first end, a second end, and a middle section between the first and second ends, wherein the middle section has a flexibility that is lower than the flexibility present in the first end, the second end, or both the first end and the second end.

11. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are arranged to impart uniform expansion along the stent.

12. The stent of claim 1, wherein the first plurality of cells and the second plurality of cells are arranged to impart maximum expansion at a first location a long the stent which differs from maximum expansion at a second location along the stent.

13. The stent of claim 1, wherein the cells are defined by cell walls, and wherein the cross members adjoin the cell walls at acute angles.

14. The stent of claim 13, wherein the acute angles are 20-60 degrees.

Images