Devices, systems and methods for engageable stents

Abstract

The engageable stents disclosed herein may include an outer stent including an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration. The elongate body in the unconstrained configuration may include a retention member and a cylindrical saddle region adjacent the retention member, the cylindrical saddle region defining a lumen extending along a longitudinal axis of the outer stent. The retention member of the outer stent may include a double-walled flange. The engageable stents may include an inner stent including an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration. The elongate body in the unconstrained configuration may include a retention member and a cylindrical saddle region adjacent the retention member. The retention member of the inner stent may include a double-walled flange. The retention members of the outer stent and the inner stent are releasably engageable with one another.

Description

[Technical Field]

[0001] The present disclosure relates generally to the field of medical devices. In particular, the present disclosure relates to medical devices, such as one or more stents, for promoting or restricting the flow of fluids and matter along one or more body lumens. [Background technology]

[0002] Placement of a self-expanding stent within an anatomical region (e.g., a body lumen, airway, blood vessel, secretory duct, etc.) can allow for the passage or restriction of fluid from one region to another. For example, the stent can restrict or facilitate the flow of matter across an affected sphincter.

[0003] However, available stents may have various disadvantages. For example, they may be susceptible to dislodging or migrating from a desired location, e.g., when subjected to forces caused by patient movement, or they may not provide sufficient or too much retention strength for a given use. Additionally, stents may need to be removed and / or replaced after significant ingrowth with the patient, posing a risk of trauma to the stent site during removal / replacement.

[0004] Thus, a variety of beneficial medical effects may be achieved by the devices, systems and methods of the present disclosure. Summary of the Invention

[0005] In one aspect, a stent system can include an outer stent including an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration. The elongate body in the unconstrained configuration can include a retention member and a cylindrical saddle region adjacent to the retention member. The cylindrical saddle region can define a lumen extending along a longitudinal axis of the outer stent. The retention member of the outer stent can include a double-walled flange having an axially inner wall, an axially outer wall, and a radial wall extending therebetween. The inner stent of the system can include an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration. The elongate body in the unconstrained configuration can include a retention member and a cylindrical saddle region adjacent to the retention member. The cylindrical saddle region can define a lumen. The retention member of the inner stent can include a double-walled flange having an axially inner wall, an axially outer wall, and a radial wall extending therebetween. An axially inner wall of the retention member of the inner stent can be configured to releasably engage an axially outer wall of the retention member of the outer stent.

[0006] In any of the aspects described herein or other aspects of the present disclosure, the axially inner wall of the retention member of the inner stent and the axially outer wall of the retention member of the outer stent may each have a concave surface. The axially outer wall of the retention member of the inner stent and the axially inner wall of the retention member of the outer stent may each have a convex surface. The retention member of the outer stent may be located at a distal portion of its elongate body. The retention member of the inner stent may be located at a proximal portion of its elongate body. The longitudinal cross-sectional profile of the retention member of the inner stent may substantially match the longitudinal cross-sectional profile of the retention member of the outer stent. The axially outer wall of the retention member of the inner stent may extend to a flexible sleeve that connects to the lumen of the outer stent. The diameter of the cylindrical saddle region of the inner stent may be different from the diameter of the cylindrical saddle region of the outer stent. The radial wall of the outer stent may have a diameter greater than the diameter of the cylindrical saddle region of the outer stent. The elongate body of the outer stent may include a braid. The cylindrical saddle region of the outer stent may be twisted to have a reduced diameter portion. A flexible band may be disposed around the saddle region of the outer stent at the reduced diameter portion. The radial wall of the outer stent may have a diameter greater than the diameter of the radial wall of the inner stent. A coating, such as a cylindrical coating to encourage ingrowth, may extend at least partially along the length of the elongate body of the outer stent. The retention members of the inner stent and the outer stent may each have a radiopaque marker. The inner stent may further include an element configured to reduce the profile of the inner stent and to detach the inner stent from the outer stent. A flexible sleeve may be coupled to the inner stent and may extend axially away from the retention members of the outer stent.

[0007] In one aspect, a stent can include an elongate body configured to be expandable between a constrained and an unconstrained configuration. The elongate body in the unconstrained configuration can include a proximal retention member and a cylindrical saddle region adjacent the proximal retention member. The cylindrical saddle region can define a lumen along the longitudinal axis of the stent. The proximal retention member can include a double-walled flange having an axially inner wall with a concave surface, an axially outer wall, and a radial wall extending therebetween. The proximal retention member can be configured to reversibly engage a retention member of another device.

[0008] In any of the embodiments described herein or other aspects of the present disclosure, the distal retention member can be distal to the cylindrical saddle region. The distal retention member can include a double-walled flange having an axially outer wall with a concave surface, an axially inner wall, and a radial wall extending therebetween. The lumen of the cylindrical saddle region can decrease along the cylindrical saddle region from the larger diameters of the proximal and distal retention members to smaller diameters.

[0009] In one embodiment, a method for delivering a stent system can include delivering an outer stent (comprising a retention member and a lumen extending therethrough) into a body lumen of a patient. An inner stent with a retention member can be delivered into the lumen of the outer stent such that the retention member of the inner stent is positioned within and releasably engaged with the retention member of the outer stent. The inner stent is removable from the outer stent. In-growth between the outer stent and the body lumen can be tolerated because the inner stent can be removed or replaced, whereas the outer stent can remain in the patient longer than the inner stent. The outer stent can be delivered into the body lumen (pyloric sphincter), and the inner stent can extend along the duodenum. The inner stent can include a pinchable or twistable element that can constrain the inner stent for removal from engagement with the outer stent. The inner stent may be delivered through the outer stent such that a portion of the inner stent extends distally beyond the distal end of the outer stent. [Brief explanation of the drawings]

[0010] Non-limiting examples of the present disclosure will be described with reference to the accompanying drawings, which are schematic and not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is typically represented by a single numeral. For purposes of clarity, unless necessary to enable those skilled in the art to understand the disclosure, not every component is labeled in every drawing, and not every component in every embodiment of the present disclosure is shown. [Figure 1A] FIG. 1A shows a side view of an outer stent according to an embodiment of the present disclosure. [Figure 1B] FIG. 1B shows an exemplary embodiment of a cross-sectional profile of a retention member, for example, for use with the outer stent of FIG. 1A. [Figure 1C]FIG. 1C shows an exemplary embodiment of a cross-sectional profile of a retention member of an inner stent engaging an exemplary embodiment of a cross-sectional profile of a retention member of an outer stent, for example, in each case of the profile of FIG. 1B. [Figure 2A] FIG. 2A shows a cross-sectional profile of another retention member of a stent according to an embodiment of the present disclosure. [Figure 2B] FIG. 2B shows a cross-sectional profile of another retention member of a stent according to an embodiment of the present disclosure. [Figure 2C] FIG. 2C shows a cross-sectional profile of another retention member of a stent according to an embodiment of the present disclosure. [Figure 2D] FIG. 2D shows a cross-sectional profile of another retention member of a stent according to an embodiment of the present disclosure. [Figure 3] FIG. 3 illustrates a system of stents being delivered into a patient according to an embodiment of the present disclosure. [Figure 4A] FIG. 4A shows a stent that has been twisted to have a reduced diameter portion according to an embodiment of the present disclosure. [Figure 4B] FIG. 4B shows a stent with flexible bands in the smaller diameter section according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present disclosure is not limited to the specific embodiments described. The terminology used herein is intended to describe only specific embodiments and is not intended to be limiting beyond the scope of the appended claims. Unless otherwise specified, technical terms used herein have the same meaning as commonly understood by those skilled in the art to which the present disclosure belongs. The detailed description should be read with reference to the drawings, which are not necessarily to scale and illustrate embodiments to aid understanding and are not intended to limit the scope of the present invention.

[0012] As used herein, "proximal end" refers to the end of the device that is closest to a medical professional when inserting the device into a patient, and "distal end" refers to the end or object of the device that is farthest from a medical professional during implantation, placement, or delivery.

[0013] As used in this disclosure and the appended claims, the singular forms "a," "an," and "the" include plural referents unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is ordinarily employed in its sense including "and / or" unless the content clearly dictates otherwise.

[0014] It should be noted that references herein to "one embodiment," "some embodiments," and "other embodiments" indicate that the described embodiment may include one or more particular features, structures, and / or characteristics. However, such references do not necessarily imply that all embodiments include the particular feature, structure, and / or characteristic. In addition, when a particular feature, structure, and / or characteristic is described with respect to one embodiment, it should be understood that such feature, structure, and / or characteristic may also be used with respect to other embodiments, whether or not explicitly stated, unless clearly stated to the contrary.

[0015] All numerical values, whether explicitly stated or not, are assumed herein to be modified by the term "about." The term "about," in the context of the numerical values, generally indicates a range of numbers that one of ordinary skill in the art would consider equivalent to the stated value (i.e., having a similar function or result). In many instances, the term "about" may include numbers rounded to the nearest significant figure. Other uses of the term "about" (i.e., in contexts other than numerical values) may be presumed to have the ordinary and accustomed definition(s) as understood from or consistent with the context of this specification, unless otherwise specified. The recitation of numerical ranges by endpoints includes all numbers within that range, including those endpoints (e.g., recitation of 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).

[0016] Although embodiments of the present disclosure are described with specific reference to medical devices (e.g., stents) and systems for restriction or drainage of the gallbladder, pseudocyst, gastrojejunostomy, and / or the like, it should be understood that such medical devices may be used in a variety of medical procedures (e.g., external biliary drain replacement, enteroenterostomy, gastroduodenostomy, gastroileostomy, etc.) to establish and / or maintain temporary or permanent restriction or open flow paths from, along, or between various body organs, lumens, secretory ducts, blood vessels, fistulas, cysts, and cavities (e.g., the dermis, stomach, duodenum, jejunum, small intestine, gallbladder, kidney, pancreas, intrahepatic bile duct, pancreatic duct, urinary bladder, ureter, abscess, encapsulated pancreatic necrosis, extrahepatic bile duct, etc.), and may be inserted at various access points and via various approaches (e.g., percutaneously, endoscopically, laparoscopically, or some combination thereof). While the medical devices disclosed herein are self-expanding, in other embodiments, the medical devices may be expandable by other methods, including, for example, a balloon catheter, etc. Furthermore, such medical devices may facilitate access to an organ, vessel, or body lumen for other purposes, such as, but not limited to, restriction or drainage, creating a pathway for diverting or bypassing fluids or solids from one point to another, removing obstructions, and / or administering therapy (including non-invasively or minimally invasively treating tissue within an organ and / or introducing pharmacological agents through an open channel).

[0017] Referring to FIG. 1A, a side view of an embodiment of an outer stent 100 is illustrated in accordance with an embodiment of the present disclosure. The outer stent 100 includes an elongate body 110 that is expandable between a constrained and an unconstrained configuration. In FIG. 1A, the elongate body 110 is illustrated in an unconstrained configuration. In the unconstrained configuration, the elongate body 110 is radially expandable to form distal and proximal retention members 114, 124. The elongate body 110 includes cylindrical saddle regions 128 adjacent to the retention members 114, 124. The saddle regions 128 define a lumen extending along the longitudinal axis 1 of the outer stent 100. Each of the retention members 114, 124 includes a double-walled flange having axially inner and outer walls 114a, 124a, 114b, 124b, and radial walls 114c, 124c extending therebetween. Distal retention member 114 and proximal retention member 124 extend radially outward from longitudinal axis 1 and from the outer periphery of elongate body 110 in the unconstrained configuration, each defining a double-walled flange having an inner wall 114a, an outer wall 114b, an inner wall 124a, and an outer wall 124b. Inner wall 114a is axially inward along distal retention member 114, outer wall surface 114b is axially outward along distal retention member 114, inner wall 124a is axially inward along proximal retention member 124, and outer wall 124b is axially outward along proximal retention member 124. Radial wall 114c of the distal retention member extends between and connects inner wall 114a and outer wall 114b. A radial wall 124c of the proximal retention member 124 extends between and connects the inner and outer walls 124a, 124b. Although the outer stent 100 in FIG. 1A is shown with a distal retention member 114 and a proximal retention member 124, the stents described herein may include only one of the distal retention member 114 and the proximal retention member 124.

[0018] Referring to FIG. 1B, an exemplary cross-sectional embodiment of a stent retention member is shown, such as the distal retention member 114 of the outer stent 100 of FIG. 1A. The retention member 114 includes an outer wall 114b extending from a radial wall 114c. The outer wall 114b includes a first portion 116a and a second portion 116b. The first portion 116a is convex along the outer wall 114b, and the outer wall 114b extends to the concave second portion 116b. The radius of curvature of the first portion 116a is smaller than the radius of curvature of the second portion 116b. In various embodiments, the radii of curvature of the portions 116a and 116b of the outer wall 114b can be smaller, larger, or equal to each other, depending on the desired procedure. The inner wall 114a extends from the radial wall 114c to a first portion 118a, which is convex before further extending to a straight section in a second portion 118b, which forms an angle of less than 90° from the longitudinal axis 1. The first portion 118a has a larger radius of curvature than the first portion 116a of the outer wall 114b. The second portion 118b extends to a third portion 118c of the inner wall 114a, where the distal retention member 114 connects with the saddle region 128. The one or more convex and / or concave portions may include similar or different angles to complete the curve, similar or different circumferential radii, similar or different lengths, similar or different other features, or combinations thereof.

[0019] In various embodiments, one or more stents are configured to extend along, across, or between one or more lumens and may help to appose tissue layers (e.g., muscle layers), restrict flow, and / or temporarily or permanently facilitate flow. One or both of the first and second retention members at either end of the stent may be double-walled, as described herein, and may include one or more vertical or non-vertical surfaces that define the axially inner or axially outer wall of the retention member. These walls may be oriented relative to a cylindrical saddle region extending along the longitudinal axis between two flanges. Such a non-vertical surface configuration may help inhibit migration of the stent relative to tissue(s) or another stent (e.g., an inner stent at least partially within an outer stent), for example, when compared to a corresponding retention member with vertical surfaces. Additionally or alternatively, a retention member as a double-walled flange with one or more non-vertical surfaces may be configured to be more resistant to withdrawal to remove the device from its intended location once deployed, e.g., having a higher withdrawal force compared to a corresponding retention member with vertical surfaces.For example, a double-walled flange with a non-vertical surface may have a pull-out force of greater than about 4N, about 4.5N, about 5N, about 5.25N, about 5.5N, about 5.75N, or about 6N, such as greater than about 4.1N, about 4.2N, about 4.3N, about 4.4N, about 4.5N, about 4.6N, about 4.7N, about 4.8N, about 4.9N, about 5.0N, about 5.1N, about 5.2N, about 5.3N, about 5.4N, about 5.5N, about 5.6N, about 5.7N, about 5.75N, about 5.8N, about 5.9N, about 6.0N, about 6.1N, about 6.2N, about 6.3N, about 6.4N, about 6.5N, about 6.6N, about 6.7N, about 6.8N, about 6.9N, about 7.0N, about 7.1N, about 7.2N, about 7.3N, about 7.4N, about 7.5N, about 7.6N, about 7.7N, about 7.8N, about 7.9N, about 8.0N, about 8.1N, about 8.2N, about 8.3N, about 8.4N, about 8.5N, about 8.6N, about 8.7N, about 8.8N, about 8.9N, about 9.0N, about 9.1N, about 9.2N, about 9.3N, about 9.4N, about 9.5N, about 9.6N, about 9.7N, about 9.8N, about 9.9N, about 9.0N, about 9.1N, The pull-out force may be about 0.4 N, about 6.5 N, about 6.6 N, about 6.7 N, about 6.8 N, about 6.9 N, about 7.0 N, about 7.1 N, about 7.2 N, about 7.3 N, about 7.4 N, about 7.5 N, about 7.6 N, about 7.7 N, about 7.8 N, about 7.9 N, about 8.0 N, about 8.1 N, about 8.2 N, about 8.3 N, about 8.4 N, about 8.5 N, about 8.6 N, about 8.7 N, about 8.8 N, about 8.9 N, about 9.0 N, about 9.5 N, about 10 N, about 11 N, about 12 N, about 13 N, about 14 N, about 15 N, about 20 N, about 25 N, or thereabouts. In various embodiments, one or more non-vertical surfaces may be configured to interact less traumatically with at least one tissue wall of the first and second body lumens (e.g., by configuring the inner wall such that the contact points with the tissue have a smaller surface area), for example, compared to a vertical surface or compared to another surface having at least one tissue-engaging element (e.g., a prong, barb, hook, or other such feature).

[0020] Delivering a stent into a patient's body can result in stent fixation and / or placement along the patient's tissue. Removal or replacement of such a stent can undesirably injure the tissue. Therefore, it may be desirable to extend the duration of the stent within the patient's body and instead remove or replace a second stent configured to engage with the first stent. For example, an outer stent may be delivered into the patient so as to substantially engage and interface with the patient's tissue, and an inner stent may be delivered at least partially within the outer stent so that the inner stent engages with the outer stent. Such a configuration allows the inner stent to be removed from engagement with the outer stent or replaced with minimal trauma to the tissue compared to removal or replacement of the outer stent.

[0021] Referring to Figure 1C, the inner stent 102 is shown engaged with the outer stent 100 of Figures 1A and 1B. The inner stent 102 includes an elongate body 132 configured to be expandable between a constrained and an unconstrained configuration. In Figure 1C, the elongate body 132 of the inner stent 102 is in an unconstrained configuration, which includes a retention member 134 and a cylindrical saddle region 138 adjacent to the retention member 134. The cylindrical saddle region 138 extends within the lumen of the saddle region 128 of the outer stent 100 and defines a fluid-communicating lumen. The retention member 134 of the inner stent 100 includes a double-walled flange having an axially inner wall 134a, an axially outer wall 134b, and a radial wall 134c extending therebetween. An axially inner wall 134 a of the retention member 134 of the inner stent 102 is releasably engaged with an axially outer wall 114 b of the distal retention member 114 of the outer stent 100 .

[0022] In various embodiments of a stent system including an inner stent engaged within an outer stent, one or more walls of the outer stent's retention member can aid in engaging with the inner stent's retention member. For example, referring to FIG. 1C , the engagement between the concave axially outer wall 114b of the distal retention member 114 of the outer stent 100 and the concave axially inner wall 134a of the retention member 134 of the inner stent 102 increases the resistance and further increases the threshold force at which the inner stent 102 separates from the outer stent 100, compared to walls perpendicular (relative to the longitudinal axis 1). In various embodiments, one or more portions of the retention member 134 of the inner stent 102 can match (e.g., complementarily, align, engage, mimic, match, mate, or the like) one or more portions (e.g., at least a portion of the cross-sectional profile) of the distal retention member 114 of the outer stent 102. For example, the axially inner wall 134a matches the axially outer wall 114b. Additionally, a portion of the retention member (e.g., portion 118c of distal retention member 114) can disengage from distal retention member 114 to resist radially inward movement of the retention member (e.g., retention member 134), e.g., by engaging (e.g., by securing or bonding) with at least a portion (e.g., portion 139) of retention member 134. Additionally, an axial wall of the retention member (e.g., axially inner wall 114a of distal retention member 114) may, for example, allow and provide room for flexibility for the retention member (e.g., retention member 134) to engage with the distal retention member 114. Once engaged, retention member 114 and retention member 134 can fit together such that surfaces of retention member 114 and retention member 134 are in full or substantially full contact with each other, e.g., resisting movement and / or sliding relative to each other.

[0023] In various embodiments, the inner stent may include one or more retention members. In embodiments of an inner stent including a single retention member, the elongate body of the stent may extend away from the single retention member to form a lumen within the flexible sleeve and / or saddle region (e.g., along a body lumen such as the duodenum). This sleeve may be everted after or during delivery of the inner stent within the outer stent, for example, by delivering the inner stent to engage a distal retention member of the outer stent and everting the sleeve over the outer stent so that it extends proximally from the outer stent (e.g., in the colon or small intestine).

[0024] In various embodiments, the diameter of the retention member can be in the range of about 5 mm to about 40 mm. Other exemplary retention member diameters can be about 15 mm to about 40 mm, about 15 mm to about 35 mm, or any range thereof. In various embodiments, the diameter of the retention member can be configured to have a specific offset from the diameter of the cylindrical saddle region in the unconstrained configuration. For example, a stent can be configured to have a difference between the diameter of the cylindrical saddle region and the diameter of the first and / or second retention member in the unconstrained configuration of about 3 mm to about 20 mm. In other examples, the first and / or second retention member can be configured to have a diameter in the unconstrained configuration that is about 1 to 5 times larger than the diameter of the cylindrical saddle region. For example, in a device having a cylindrical saddle region with a diameter of about 10 mm in the unconstrained configuration, the first and / or second retention member can have a diameter of about 13 mm to about 30 mm, about 15 mm to about 25 mm, or about 16 mm to about 20 mm. In another example, a stent having a cylindrical saddle region with a diameter of about 20 mm in the unconstrained configuration may have one or more retention members with a diameter of about 23 mm to about 40 mm. It will be understood that some embodiments may include a significant or slight offset between the diameter of the cylindrical saddle region and the larger diameter of the first retention member and / or second retention member. In various embodiments, a retention member may have an axial width that is substantially similar or different from another retention member of a similar or different stent. The axial width of a retention member is measured as the distance along the longitudinal axis between the axially inner and axially outer walls of the respective retention member, including the radial wall. In various embodiments, the width of a retention member in the unconstrained configuration may be about 0.5 mm to about 10.0 mm. Other embodiments may include one or more retention members with smaller and / or larger widths, e.g., about 0.5 mm to about 6 mm, about 2 mm to about 6 mm, or about 3 mm to about 7 mm. In some embodiments, a retention member may have a constant width. In other embodiments, the width of the retention member may vary along a vertical plane (i.e., a plane perpendicular to the longitudinal axis of the elongate body of the stent). Various embodiments may include, for example, a total stent length in the unconstrained configuration ranging from about 5 mm to about 60 mm.For example, an exemplary deployed stent can have a length of about 10 mm to about 50 mm, about 10 mm to about 35 mm, or so. If it is desired to require a large pull-out force to remove the stent, the diameter ratio between the retention member and the adjacent saddle region or elongate body can be large, and if it is desired to require a small pull-out force to remove the stent, the diameter ratio between the retention member and the adjacent saddle region or elongate body can be small.

[0025] In various embodiments, the length of the cylindrical saddle region may be measured as (i) the length along the elongate body between the beginning of the axially inner wall(s) of one or more retention members, (ii) the length along the body at the smallest distance between retention members at any point along the inner wall of the retention members when the stent is unconstrained and not deployed along tissue, (iii) the length along the body at the smallest distance between retention members at any point along the inner wall of the retention members when the stent is unconstrained and deployed along tissue, or (iv) the length along the body from a point along the inner wall of a single retention member of the stent to the opposite end of the elongate body. In various embodiments, the cylindrical saddle region, including those under conditions (i)-(iv) above, may have a length of about 5 mm to about 150 mm in the unconstrained configuration, a length of about 5 mm to about 35 mm in the unconstrained configuration, or a length therebetween. Exemplary lengths of the cylindrical saddle region of a stent for gastrointestinal function in the unconstrained configuration can include lengths of about 10 mm to about 30 mm, about 15 mm to about 20 mm, about 10 mm to about 20 mm, about 10 mm to about 15 mm, about 5 mm to about 10 mm, or so. In many embodiments, the diameter of the cylindrical saddle region in the unconstrained configuration can be larger than the diameter of the elongate body in the constrained configuration. For example, the diameter of the cylindrical saddle region in the unconstrained configuration can be about 3 mm to about 40 mm. In some embodiments, the diameter of the cylindrical saddle region in the unconstrained configuration can be about 5 mm to about 25 mm, about 5 mm to about 20 mm, about 5 mm to about 15 mm, about 10 mm to about 20 mm, or so. In various embodiments, the diameter of the cylindrical saddle region can be about 3 to 5 times, about 3 to 10 times, or so, larger than the corresponding diameter of its elongate body in the constrained configuration.

[0026] In various embodiments, the elongate body of the stent may be partially or fully coated, uncoated, coated, or a combination thereof. The elongate body may include a constrained configuration (e.g., an unexpanded or delivery configuration), an unconstrained configuration (e.g., a reduced length configuration, an expanded configuration, or a deployed configuration), and a partially constrained / unconstrained transition state between the constrained and unconstrained configurations.

[0027] The non-vertical surfaces of the retention members, comprising the axially inner and outer walls of the double-walled flange, may include one or more curved, straight, angled, concave, or convex portions, or any combination thereof. Each portion may have a substantially equal or different length, angle, radius of curvature, orientation, angle, or other characteristic relative to another portion. The surfaces of the first and second retention members may be similar or different. For example, each end of the medical device may be designed to enhance the strength (e.g., pullout strength or retention strength, or radial or radial strength) of the stent or a portion of the stent, thereby providing a desired amount of linear apposition force when positioned across a tissue plane and / or engaging another stent. The shape of the retention members may include one or more rolls and / or structural folds, for example, to create a double-walled flange structure. In various embodiments, the retention member may include multiple inflection points, which may be points of curvature where a change in direction of curvature occurs.

[0028] 2A-2D, various cross-sectional profiles of retention members of a stent are illustrated in accordance with embodiments of the present disclosure. Retention member configurations such as those described with respect to FIGS. 2A-2E may be substituted for or applied to any of the embodiments described herein. For example, distal retention member 114 as described with respect to FIG. 1A, proximal retention member 124 as described with respect to FIG. 1A, retention members as described with respect to FIG. 1C, and / or other retention members described herein may have configurations such as those described with respect to FIGS. 2A-2E. Thus, embodiments may include multiple retention members with similar or different configurations.

[0029] Referring to FIG. 2A , elongate body 210 includes retention member 202. Retention member 202 includes a first wall 204, a second wall 206 axially offset from first wall 204 along longitudinal axis 1, and a radial wall 208 extending therebetween. A cylindrical saddle region 228 is adjacent to and extends from first wall 204. Second wall 206 includes three portions (portion 206a, portion 206b, and portion 206c). Cylindrical saddle region 228 may extend to a concave surface of portion 206a, which in turn extends to portion 206b. Portion 206b includes a substantially straight section extending at an angle of less than 90° from longitudinal axis 1. Portion 206c includes a convex curvature extending between portion 206b and radial wall 208. Radial wall 208 includes a portion substantially parallel to longitudinal axis 1. Radial wall 208 extends to first wall 204, which includes portion 204a and portion 204b. Portion 204a includes a convex surface having a variable radius along its length. One or more of the convex and / or concave surfaces may include similar or different angles to complete the curve, similar or different circumferential radii, similar or different lengths, similar or different other features, or combinations thereof. Portion 204b is concave and connects to the remainder of elongate body 210.

[0030] Referring to FIG. 2B , another exemplary embodiment is illustrated in which retention member 202 may include similar portions 206a, 206b, and 206c as described with respect to FIG. 2A . However, portion 204a as illustrated in FIG. 2B may have a larger radius of curvature than portion 204a as illustrated in FIG. 2A . In FIG. 2B , portion 204b may include a substantially straight section extending rearward from radial wall 208 and portion 204a toward cylindrical saddle region 228. Portion 204b may extend to portion 204c, which is illustrated in FIG. 2B as including a concave portion. Portion 204c extends to the remainder of elongate body 210. The angle of retention member 202 defined by portions 204b and 206b with respect to longitudinal axis 1 is less than 90°.

[0031] 2C , another exemplary embodiment is shown in which retention member 202 includes portion 206a having a concave curvature that extends to a substantially straight section of portion 206b. Portion 206b extends to a convex curvature of portion 206c, which then extends to radial wall 208. Radial wall 208 extends to portion 204a having a convex curvature. Portion 204a extends to a substantially straight section of portion 204b, which then extends to portion 204c having a concave curvature. Portion 204b and the substantially straight section of portion 206b form an angle of less than 90° with respect to longitudinal axis 1. Portion 204c extends to the remainder of elongate body 210. However, one or more of portions 206a, 206c, 204a, and / or 204c may have a smaller radius of curvature than that shown (e.g., as illustrated with respect to concavely curved portion 204c in FIG. 2A compared to concavely curved portion 204c in FIG. 2C). However, other sections may additionally or alternatively be substituted for one or more sections of the retention members of other embodiments described herein. In various embodiments, at least a portion of the concave or convex curvature may have a radius of curvature small enough to contain creases or other folds.

[0032] Referring to FIG. 2D , another exemplary embodiment is illustrated in which retention member 202 includes portions 206a, 206b, and 206c similar to those described with respect to at least one of FIGS. 2A-2C. Portion 206a as illustrated in FIG. 2D has a larger radius of curvature than portion 206a as illustrated in FIG. 2A. For example, portion 206a as illustrated in FIG. 2D may have a radius of curvature between about 1 mm and about 3 mm. In various embodiments, portion 206a and / or portion 206c may have a radius of curvature between about 1.5 mm and about 2.1 mm. In FIG. 2D , portion 206a may include a varying radius of curvature along its length. As illustrated in FIG. 2D , portion 206a extends radially away from saddle region 228 toward longitudinal axis 1 such that a section of portion 206a is closer to longitudinal axis 1 than cylindrical saddle region 228. Portion 206d extends between saddle region 228 and portion 206a. In various embodiments, portion 206a or other portions 206b, 206c, and 206d may include an uneven and / or otherwise wavy curvature. Portion 204b of first wall 204 includes a straight portion that is substantially perpendicular to longitudinal axis 1, as shown in FIG. 2D . Portion 204c includes a concave surface that extends to the remainder of elongate body 210.

[0033] While various retention member profiles are described with reference to Figures 2A-2D, it should be understood that various embodiments may include one or more similarities and / or differences from the illustrated examples. For example, first wall 204 or second wall 206 may be comprised of additional or fewer portions, any of which may include concave sections, convex sections, substantially straight sections, or any combination thereof. A portion may extend toward the first or second end of its elongate body perpendicular to the longitudinal axis, parallel to the longitudinal axis, at another angle relative to the longitudinal axis, or any combination thereof. Furthermore, any dimension and / or orientation of a portion described with reference to Figures 2A-2D may apply alternatively or in combination with other portions described therewith, or may otherwise apply with portion profiles and / or retention member profiles within the scope of this disclosure.

[0034] In various embodiments, a smaller radius of curvature of such a portion may contribute to a corresponding higher retention strength and / or resistance of the retention member. For example, the retention member configuration illustrated in FIG. 1B may have greater resistance to deformation than the respective configuration in FIG. 2A. Thus, embodiments may be configured to comply with various retention member strength and / or resistance requirements, as dictated by at least one particular procedure, anatomy, stent engagement, stent function, or other considerations.

[0035] In various embodiments, a stent may be formed from one or more filaments and / or surfaces. In various embodiments, a stent may be formed from one or more metal wires, one or more wire braids, polymer filaments, sheets, or combinations thereof. A stent may include one or more structural elements (e.g., struts, hoops, meshes, tessellating cells, or other units). In many embodiments, a stent may include mesh, woven, and / or knit surfaces. In various embodiments, a stent may be formed from a shape-memory material (e.g., nitinol). Features (e.g., retention members, saddle regions, etc.) on portions or throughout the stent may include radiopaque markers to allow a user to identify the location of one or more features across one or more stents. For example, any portion of the retention member of an inner stent may be radiopaque along with any portion of the retention member of an outer stent, allowing a user to identify their relative positions during delivery and deployment and ensure a desired engagement / configuration between the two.

[0036] Various stent embodiments described herein may include a full or partial coating, covering, or other film that covers the interior of the device, covers the exterior of the device, extends between structural elements, or any combination thereof. For example, the coating, covering, or other film may include silicone, polymer, or a combination thereof. For example, the coating may include polyurethane, polytetrafluoroethylene, expanded polytetrafluoroethylene, polyvinylidene fluoride, aromatic polycarbonate-based thermoplastic polyurethane, and / or other such materials. The coating may include an ingrowth-promoting material for tissue interfacing. The coating may be applied by dip coating, roll coating, painting, spraying, other known processing methods, or a combination thereof. The coating, covering, or other film may inhibit tissue growth and / or minimize fluid leakage from within and / or from the stent. The first retention member, the second retention member, the saddle region extending between the first and second retention members, or a combination thereof, can comprise a solid coating, a porous coating, or other coating configuration. In various embodiments, the circumferential coating or covering can be applied to cover the entire length of the stent or a partial length of the stent. For example, a partial coating can cover the entire length of the saddle region but not the flange, or vice versa.

[0037] Various embodiments described herein may include one or more additional features designed to engage at least one tissue layer. For example, embodiments may include textured surfaces, prongs, or other tissue-engaging elements along one or more retention members.

[0038] Various embodiments herein may include retention elements and alternative configurations at opposite ends or portions of the stent. For example, various embodiments may include flanges with walls perpendicular to the longitudinal axis, flared retention elements, bulbous retention elements, ramped retention elements, curled retention elements, folded retention elements, or other configurations. Some embodiments may include one or more structures for managing the flow of matter therethrough. For example, various embodiments may include valves, barrier elements, funnels, tubes, reducers, or other structures useful for managing flow therethrough.

[0039] In various embodiments of the medical device, at least a portion of one or more walls of the retention member can include at least one curved section, a straight section, a section angled with respect to the longitudinal axis, a section perpendicular to the longitudinal axis, a section horizontal to the longitudinal axis, a radius of curvature, or any combination thereof. Although the cross-sectional profiles of the retention members are illustrated and described herein in particular orientations, it should be understood that any retention member can be inverted, flipped, or mirrored in orientation (e.g., across the "x" (horizontal) or "y" (vertical) axis of the drawings of the present disclosure) depending on the procedure (e.g., endoscopic procedure, colonoscopic procedure, desired engagement between retention member(s) and tissue or other retention member(s), atraumatic concerns during delivery, placement, or removal, or the like).

[0040] Referring to Figure 3, a stent system is shown being delivered into a patient's body in accordance with an embodiment of the present disclosure. The outer stent 300 may be positioned along patient tissue 350 and extend across an opening in a tissue wall or an apposing tissue wall (e.g., a sphincter 352, such as the pyloric sphincter). The outer stent 300 may be delivered in a constrained configuration along a guidewire 360 ​​while being constrained by a retractable sheath 362, which may include a radiopaque marker 364 at its distal end. The sheath 362 may be retracted to position the outer stent 300 along the tissue 350 in an unconstrained configuration, allowing the distal retention member 314 and the proximal retention member 324 to engage the tissue 350. 3, a guidewire 360 ​​and sheath 362 may be passed through the outer stent 300 to deliver the inner stent 302 in a constrained configuration, over the guidewire 360 ​​and constrained by the sheath 362 (although the inner stent 302 may be delivered and positioned using a separate guidewire and / or sheath). The distal end of the guidewire 360 ​​and the sheath 362 are extended distally beyond the outer stent 300 to deploy the inner stent 302. The inner stent 302 is partially unconstrained by retracting the sheath 362 proximally relative to the guidewire 360. A distal portion 302d of the inner stent 302 is unconstrained, while a proximal portion of the stent 302 is constrained by and within the sheath 362. The proximal portion of the stent, including the retention members, may be free within the outer stent 300 such that the retention members engage the distal retention members 314 of the outer stent 300 (e.g., as shown in FIG. 1C , such that the retention members 134 of the inner stent 102 engage the distal retention members 114 of the outer stent 100). While FIG. 3 shows / described inner stent 302 positioned to engage only the distal retention member 314 of the outer stent 300, in various embodiments inner stent 302 may include two retention members, one each engaging the distal retention member 314 and the proximal retention member 324 of the outer stent.Although FIG. 3 illustrates / describes the inner stent 302 as being partially positioned distally beyond the outer stent 300, the inner stent 302 may be positioned at least partially proximal to the outer stent 300 (e.g., within the large or small intestine), or the inner stent 302 may be positioned entirely within the outer stent 300 (e.g., so as to engage both the distal retention member 314 and the proximal retention member 324 of the outer stent 300).

[0041] 4A , in accordance with an embodiment of the present disclosure, stent 400 is illustrated as including a twist 430 along its saddle region 428. Saddle region 428 reduces in diameter from each of distal retention member 414 and proximal retention member 424 along longitudinal axis 1 toward twist 430. Stent 400 is illustrated in an unconstrained configuration. Twist 430 may be expandable, for example, such that another device (e.g., a guidewire, catheter, and / or another stent) or the like passes through twist 430 of unconstrained stent 400, while saddle region 428 partially untwists or otherwise expands to accommodate the diameter of additional device(s). Twist 430 may substantially return to the illustrated configuration upon removal of the device(s) from within saddle region 428. Additionally or alternatively, twist 430 may function as a reducer / restrictor for flow along longitudinal axis 1 and may include a coating and / or covering. It should be understood that stent 400 may be an outer stent or an inner stent as described herein. For example, stent 400 may be placed along tissue and an inner stent may be placed within stent 400, or stent 400 may be placed within an outer stent. The reduced diameter portion of saddle region 428 may be larger or smaller depending on the flow reduction, obstruction, body lumen patency, size of the device to be passed therethrough, or fit of saddle region 428 around the device.

[0042] Referring to FIG. 4B, the saddle region 428 of the stent 400 may similarly be reduced in diameter with the use of a band 432 rather than the twist 430 of FIG. 4A. As illustrated in FIG. 4B, the saddle region 428 reduces in diameter along the longitudinal axis 1 from each of the distal and proximal retention members 414, 424 toward the band 432. While the stent 400 is shown in an unconstrained configuration, the band 432 constrains a portion of the saddle region 428. The band 432 may be flexible so that another instrument may penetrate the saddle region 428, expanding the saddle region 428 and the band 432 around the instrument. The band 432 and saddle region 428 may substantially return to the configuration illustrated in FIG. 4B upon removal of the instrument from within the saddle region 428. Additionally or alternatively, the band 432 may function as a reducer / restrictor for flow along the longitudinal axis 1 and may include a coating and / or covering. It should be understood that stent 400 can be an outer stent or an inner stent as described herein. For example, stent 400 can be placed alongside tissue and an inner stent can be placed within stent 400, or stent 400 can be placed within an outer stent. The reduced diameter portion of saddle region 428 can be larger or smaller depending on the flow reduction, obstruction, body lumen patency, size of the device to be passed therethrough, or the fit of saddle region 428 around the device.

[0043] An embodiment of a method for delivering a stent system disclosed herein may include delivering an outer stent (comprising a retention member and a lumen extending therethrough) into a body lumen of a patient. An inner stent including a retention member may be delivered into the lumen of the outer stent such that the retention member of the inner stent is disposed within and removably engages the retention member of the outer stent. The inner stent is removable from the outer stent. In-growth between the outer stent and the body lumen may be tolerated because the inner stent may be removed or replaced, whereas the outer stent may remain in the patient longer than the inner stent. The outer stent may be delivered into the body lumen (pyloric smooth muscle), and the inner stent may extend along the duodenum. The inner stent may include elements (e.g., bands, sutures, strings, wires, or the like) that can be pinched or twisted to constrain the inner stent (e.g., to separate the inner stent from the retention member(s) of the outer stent prior to removal). The inner stent may be removed from the outer stent in a variety of ways, such as by pinching the inner stent or elements connected to it (e.g., sutures, loops, wires, etc.) with an instrument (e.g., forceps, graspers, clamps, etc.) and pulling, pushing, and / or twisting the instrument to separate the inner stent from the outer stent. The inner stent may be delivered through the outer stent.

[0044] All of the apparatus and / or methods disclosed and claimed herein can be made and executed without undue experimentation in light of the present disclosure. While the apparatus and methods of the present disclosure have been described in terms of preferred embodiments, it will be apparent to those skilled in the art that variations can be applied to the apparatus and / or methods and to the steps or sequence of method steps described herein without departing from the concept, spirit and scope of the present disclosure. All such similar substitutes and modifications apparent to those skilled in the art are deemed to be within the spirit, scope and concept of the present disclosure as defined by the appended claims.

Claims

1. 1. A stent system comprising: The outer stent is an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration, the elongate body in the unconstrained configuration including a retention member and a cylindrical saddle region adjacent the retention member, the cylindrical saddle region defining a lumen extending along a longitudinal axis of the outer stent; the outer stent, wherein the retention member of the outer stent includes a double-walled flange having an axially inner wall, an axially outer wall, and a radial wall extending therebetween; The inner stent an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration, the elongate body in the unconstrained configuration including a retention member and a cylindrical saddle region adjacent the retention member, the cylindrical saddle region defining a lumen; the retention member of the inner stent includes a double-walled flange having an axially inner wall, an axially outer wall, and a radial wall extending therebetween; an inner stent configured to releasably engage the axially inner wall of the retention member of the inner stent with the axially outer wall of the retention member of the outer stent by engaging the retention member of the inner stent with the retention member of the outer stent to engage the inner stent to the outer stent; The system.

2. The system of claim 1 , wherein the axially inner wall of the retention member of the inner stent and the axially outer wall of the retention member of the outer stent each include a concave surface.

3. The system of claim 1 or claim 2, wherein the axially outer wall of the retention member of the inner stent and the axially inner wall of the retention member of the outer stent each include a convex surface.

4. The system of claim 1 or claim 2, wherein the retention member of the outer stent is located at a distal portion of the elongate body and the retention member of the inner stent is located at a proximal portion of the elongate body.

5. 3. The system of claim 1 or claim 2, wherein the longitudinal cross-sectional profile of the retention member of the inner stent substantially matches the longitudinal cross-sectional profile of the retention member of the outer stent.

6. 3. The system of claim 1 or claim 2, wherein the axially outer wall of the retention member of the inner stent extends to a flexible sleeve that connects to the lumen of the outer stent.

7. 3. The system of claim 1 or claim 2, wherein the diameter of the cylindrical saddle region of the inner stent is different from the diameter of the cylindrical saddle region of the outer stent.

8. 3. The system of claim 1 or claim 2, wherein the radial wall of the outer stent has a diameter greater than a diameter of the cylindrical saddle region of the outer stent.

9. 3. The system of claim 1 or claim 2, wherein the elongate body of the outer stent comprises a braid, and the cylindrical saddle region of the outer stent is twisted to have a reduced diameter portion.

10. 3. The system of claim 1 or claim 2, wherein the radial wall of the outer stent comprises a diameter greater than a diameter of the radial wall of the inner stent.

11. The system of claim 1 or claim 2, further comprising a coating extending at least partially along the elongate body of the outer stent.

12. The system of claim 1 or claim 2, further comprising a radiopaque marker on each of the retention members of the inner stent and the outer stent.

13. 3. The system of claim 1 or claim 2, wherein the inner stent further comprises elements configured for reducing the profile of the inner stent and for detaching the inner stent from the outer stent.

14. The system of claim 1 or claim 2, further comprising a flexible sleeve coupled to the inner stent and extending axially away from the retention member of the outer stent.

15. 1. A stent comprising: an elongate body configured to be expandable between a constrained configuration and an unconstrained configuration, the elongate body including a proximal retention member and a cylindrical saddle region adjacent the proximal retention member in the unconstrained configuration, the cylindrical saddle region defining a lumen along a longitudinal axis of the stent; the proximal retention member includes a double-walled flange having an axially inner wall including a concave surface, an axially outer wall, and a radial wall extending therebetween; the proximal retention member is configured to reversibly engage a retention member of another instrument to engage the elongate body to the other instrument. Stent.

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