Stent with self-adjusting anti-migration mechanism

Abstract

The stent may include a radially expandable tubular framework including a first end region, a second end region, an intermediate region positioned between the first end region and the second end region, and a lumen extending therethrough. The radially expandable tubular framework is configured to expand from a radially collapsed configuration to a radially expanded configuration. A plurality of covering strips are positioned along at least one of the first end region, the intermediate region, and the second end region. The plurality of covering strips are configured to completely cover the radially expandable tubular framework in the radially collapsed configuration, and to separate from each other to expose portions of the radially expandable tubular framework therebetween in the radially expanded configuration.

Description

[Technical Field]

[0001] FIELD OF THE DISCLOSURE The present disclosure relates to medical devices and methods for manufacturing medical devices. More particularly, the present disclosure relates to stents for implantation within a body lumen and related methods. [Background technology]

[0002] Implantable medical devices (e.g., expandable stents) can be designed to treat a variety of medical conditions within the body. For example, some expandable stents can be designed to expand radially to support a body lumen and / or provide a fluid pathway for digested material, blood, or other fluids to flow therethrough following a medical procedure. Some medical devices can include radially or self-expanding stents that can be implanted transluminally via various medical device delivery systems. These stents can be implanted in various body lumens, such as coronary or peripheral arteries, the esophageal tract, the gastrointestinal tract (including the intestines, stomach, and colon), the tracheobronchial tract, the urinary tract, the bile duct, the vasculature, etc.

[0003] In some instances, it may be desirable to design a stent to include sufficient flexibility while maintaining sufficient radial force to open a body lumen at the treatment site. However, in some stents, the compressibility and flexibility characteristics that aid in stent delivery may also result in the stent being prone to migration from its initially deployed position. For example, a stent designed to be positioned in the esophagus or gastrointestinal tract may be prone to migration due to peristalsis (i.e., the involuntary contraction and relaxation of the muscles of the esophagus, intestine, and colon, which expels the contents of the tract). Furthermore, the generally moist and essentially smooth environment of the esophagus, intestine, colon, etc., further contributes to the tendency of a stent to migrate when deployed therein. One method of reducing stent migration may include promoting tissue ingrowth into the uncovered or exposed portions of the stent. However, uncontrolled tissue ingrowth can reduce stent patency and lead to difficulty in removing the stent from the body lumen.

[0004] It is therefore desirable to provide alternative stent designs that include anti-migration features to reduce the susceptibility of the stent to migration. Examples of stents that include anti-migration features are disclosed herein. Summary of the Invention

[0005] The present disclosure provides design, material, manufacturing methods, and use alternatives for medical devices. An exemplary medical device may include a stent. In a first example, a stent may include a radially expandable tubular framework having a radially outer surface, a radially inner surface, a first end region, a second end region, an intermediate region positioned between the first end region and the second end region, and a lumen extending therethrough. The radially expandable tubular framework may be configured to expand from a radially collapsed configuration to a radially expanded configuration. A plurality of covering strips may be positioned along at least one of the first end region, the intermediate region, and the second end region, and the plurality of covering strips may completely cover the radially expandable tubular framework in the radially collapsed configuration and may be configured to separate from one another to expose portions of the radially expandable tubular framework therebetween in the radially expanded configuration.

[0006] Alternatively or additionally to any of the above embodiments, each of the multiple covering strips may extend longitudinally along the intermediate region of the stent, and the multiple covering strips may completely cover the intermediate region in the radially collapsed configuration, and the multiple covering strips may be configured to separate from each other in the radially expanded configuration to expose portions of the intermediate region of the radially expandable tubular framework therebetween.

[0007] Alternatively or additionally to any of the above embodiments, a first longitudinal edge of each of the plurality of covering strips may be secured to the expandable tubular framework, and a second longitudinal edge of each of the plurality of covering strips may not be secured to the expandable tubular framework.

[0008] Alternatively or additionally to any of the above embodiments, the second longitudinal edge of each of the plurality of covering strips may overlap with the first longitudinal edge of an adjacent one of the plurality of covering strips in the radially collapsed configuration.

[0009] Alternatively or additionally to any of the above embodiments, the second longitudinal edge may be located radially outward of the first longitudinal edge in the radially collapsed configuration. Alternatively or additionally to any of the above embodiments, each of the multiple covering strips may extend circumferentially around the intermediate region of the stent, and the multiple covering strips may completely cover the intermediate region in the radially collapsed configuration, and the multiple covering strips may be configured to separate from each other in the radially expanded configuration to expose a portion of the intermediate region of the radially expandable tubular framework therebetween.

[0010] Alternatively or additionally to any of the above embodiments, a first circumferential edge of each of the plurality of covering strips may be secured to the expandable tubular framework, and a second circumferential edge of each of the plurality of covering strips may not be secured to the expandable tubular framework.

[0011] Alternatively or additionally to any of the above embodiments, the second circumferential edge of each of the plurality of covering strips may overlap with the first circumferential edge of an adjacent one of the plurality of covering strips in the radially collapsed configuration.

[0012] Alternatively or additionally to any of the above embodiments, the radially expandable tubular framework may be formed from one or more interwoven filaments defining gaps therebetween, and in the radially expanded configuration, may allow tissue to grow into the gaps in the intermediate regions, and in the radially collapsed configuration, may prevent tissue from growing into the gaps in the intermediate regions.

[0013] Alternatively or additionally to any of the above embodiments, the first end region may include a polymer cover that completely covers the gap in the first end region, and the second end region may include a polymer cover that completely covers the gap in the second end region.

[0014] Alternatively or additionally to any of the above embodiments, the plurality of covering strips may be separate from the polymer cover of the first end region and the polymer cover of the second end region.

[0015] Alternatively or additionally to any of the above embodiments, multiple covering strips may be positioned along the first end region, and the multiple covering strips may completely cover the first end region in the radially collapsed configuration, and the multiple covering strips may be configured to separate from each other in the radially expanded configuration to expose portions of the first end region of the radially expandable tubular framework therebetween.

[0016] Alternatively or additionally to any of the above embodiments, one or more tie strings may be attached to the plurality of covering strips in the radially collapsed configuration, and the one or more tie strings may be removable from the plurality of covering strips to allow the first end region to radially expand to the radially expanded configuration.

[0017] Alternatively or additionally to any of the above embodiments, the one or more tie strings may include tie strings longitudinally interposed between adjacent ones of the plurality of covering strips.

[0018] In another example, a stent may include a radially expandable tubular framework having a radially outer surface, a radially inner surface, first end regions, second end regions, an intermediate region positioned between the first and second end regions, and a lumen extending therethrough. The radially expandable tubular framework may be configured to expand from a radially collapsed configuration to a radially expanded configuration. A first polymeric coating may completely cover the first end regions, and a second polymeric coating may completely cover the second end regions, and multiple coating strips may be positioned along the intermediate regions. The multiple coating strips may completely cover the intermediate region of the radially expandable tubular framework between the first and second polymeric coatings in the radially collapsed configuration, and the multiple coating strips may be configured to separate from each other to expose a portion of the intermediate region of the radially expandable tubular framework therebetween in the radially expanded configuration.

[0019] Alternatively or additionally to any of the above embodiments, multiple coating strips may extend longitudinally from the first polymer coating to the second polymer coating. Alternatively or additionally to any of the above embodiments, each of the plurality of covering strips may overlap an adjacent one of the plurality of covering strips in the radially collapsed configuration.

[0020] In another example, a method of using a stent may include implanting the stent across a stenosis in a body lumen. The stent may include a radially expandable tubular framework having a radially outer surface, a radially inner surface, first end regions, second end regions, an intermediate region positioned between the first end regions and the second end regions, and a lumen extending therethrough. A plurality of covering strips may be positioned along at least one of the first end regions, the intermediate region, and the second end regions. The method may include allowing the stent to initially expand to a first radially expanded configuration within the body lumen upon initial implantation across the stenosis, wherein the plurality of covering strips may completely cover the radially expandable tubular framework in the first radially expanded configuration. The method may further include allowing the stent to further radially expand from the first radially expanded configuration to a second radially expanded configuration within the body lumen over a period of time, and the multiple covering strips may be separated from one another in the second radially expanded configuration to expose portions of the radially expandable tubular framework therebetween.

[0021] Alternatively or additionally to any of the above embodiments, the multiple coating strips may overlap each other in the first radially expanded configuration and may be spaced apart from each other in the second radially expanded configuration.

[0022] Alternatively or additionally to any of the above embodiments, the method may include removing ties between adjacent ones of the plurality of covering strips to allow the radially expandable tubular framework to radially expand from a first radially expanded configuration to a second radially expanded configuration.

[0023] The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The following figures and detailed description more particularly exemplify these embodiments.

[0024] The present disclosure can be more fully understood from consideration of the following detailed description in conjunction with the accompanying drawings. [Brief explanation of the drawings]

[0025] [Figure 1] FIG. 1 is a side view of an exemplary stent in a radially collapsed configuration. [Figure 1A] FIG. 1A is a cross-sectional view of the exemplary stent of FIG. 1 taken along line 1A-1A. [Figure 2] FIG. 2 is a side view of the exemplary stent of FIG. 1 in a radially expanded configuration. [Figure 2A] FIG. 2A is a cross-sectional view of the exemplary stent of FIG. 2 taken along line 2A-2A. [Figure 3] FIG. 3 is a side view of an exemplary stent in a radially collapsed configuration. [Figure 3A] FIG. 3A is a cross-sectional view of the exemplary stent of FIG. 3 taken along line 3A-3A. [Figure 4] FIG. 4 is a side view of the exemplary stent of FIG. 3 in a radially expanded configuration. [Figure 4A] FIG. 4A is a cross-sectional view of the exemplary stent of FIG. 4 taken along line 4A-4A. [Figure 5] FIG. 5 illustrates an exemplary method of an exemplary stent positioned across a stricture in a body lumen moving from an initially deployed radially expanded configuration to a post-procedure more radially expanded configuration. [Figure 6] FIG. 6 illustrates an exemplary method of an exemplary stent positioned across a stricture in a body lumen moving from an initially deployed radially expanded configuration to a post-procedure more radially expanded configuration. [Figure 7] FIG. 7 is a side view of an exemplary stent in a radially collapsed configuration. [Figure 8] FIG. 8 is a side view of the exemplary stent of FIG. 7 in a radially expanded configuration. [Figure 9]FIG. 9 is a side view of an exemplary stent in a radially collapsed configuration. [Figure 10] FIG. 10 is a side view of the exemplary stent of FIG. 9 in a radially expanded configuration. DETAILED DESCRIPTION OF THE INVENTION

[0026] While the present disclosure is susceptible to various modifications and alternative forms, specifics of which have been shown by way of example in the drawings and will be described in detail. It should be understood, however, that the intention is not to limit the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit of the disclosure.

[0027] For the following defined terms, these definitions shall be applied, unless a different definition is given in the claims or elsewhere in this specification. All numerical values ​​are assumed to be modified herein by the term "about," whether explicitly stated or not. The term "about" generally refers to a range of numbers that one of ordinary skill in the art would consider equivalent to the recited value (e.g., having the same function or result). In many instances, the term "about" may include numbers that are rounded to the nearest significant figure.

[0028] The recitation of numerical ranges by endpoints includes all numbers within that range (eg, 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5). As used in this specification 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 used generally in its sense including "and / or" unless the content clearly dictates otherwise.

[0029] It should be noted that references herein to "embodiments," "some embodiments," "other embodiments," etc., indicate that the described embodiments may include one or more particular features, structures, and / or characteristics. However, such descriptions 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 in connection with one embodiment, it should be understood that such feature, structure, and / or characteristic may also be used in connection with other embodiments, whether or not explicitly described, unless expressly stated otherwise.

[0030] The following detailed description should be read with reference to the drawings, in which like elements in different drawings are numbered the same. The drawings, which are not necessarily to scale, depict example embodiments and are not intended to limit the scope of the claims. The example embodiments shown are intended as examples only. Selected features of any example embodiment may be incorporated into additional embodiments, unless expressly stated to the contrary.

[0031] In some instances, it may be desirable to provide an intraluminal implant or stent capable of delivering luminal patency to patients with esophageal strictures or other pathologies. Such stents may sometimes be used in patients experiencing dysphagia due to esophageal cancer. Esophageal stents may allow patients to maintain nutrition via oral intake during cancer treatment or palliative care. Current gastrointestinal (GI) stent placement regimens for the treatment of strictures rely on self-expanding stents (SES) to resolve the underlying stricture within the body lumen while leaving it in place. However, this type of stent, especially fully covered designs, may have a high incidence of migration. Some stents may include protrusions (e.g., loops, quills, etc.) that protrude radially from the stent body. These raised features may interact with the walls of the body lumen and reduce device migration. However, these devices may be difficult to remove or reposition because they may be difficult to reduce to a smaller diameter. Furthermore, devices with these types of protrusions (or anti-migration features) may be indicated for permanent implantation. If it is desired that these devices be removable, retraction or repositioning of the device may be limited because the angular portions of the protrusions may cause vessel injury as the stent migrates. What is desired is an intraluminal implant or stent that includes an anti-migration mechanism to resist stent migration within the body lumen. In some instances, the stent can also be easily repositioned within and / or removed from the body lumen.

[0032] Although the embodiments disclosed herein are described with reference to esophageal stents, it is contemplated that the stents described herein may be used and sized for use in other locations, such as, but not limited to, body tissues, body organs, vascular lumens, non-vascular lumens, and combinations thereof (e.g., but not limited to, the coronary or peripheral vasculature, trachea, bronchi, colon, small intestine, bile duct, urinary tract, prostate, brain, stomach, etc.).

[0033] FIG. 1 is a side view of an exemplary stent 10, and FIG. 1A is a cross-sectional view of the exemplary stent 10 of FIG. 1 taken along line 1A-1A. In some cases, stent 10 may be formed from a radially expandable tubular framework 12 (generally referred to herein as tubular framework 12) having a radially outer surface 17 and a radially inner surface 18. Although stent 10 is described as generally tubular, it is envisioned that stent 10 may assume any desired cross-sectional shape. Tubular framework 12 may further include a first end region 11, a second end region 13, and an intermediate region 14 positioned between first end region 11 and second end region 13. Tubular framework 12 may include a lumen 15 extending therethrough from first end region 11 to second end region 13.

[0034] It is contemplated that the tubular framework 12 may be fabricated from a number of different materials, such as, but not limited to, metals, metal alloys, shape-memory alloys, and / or polymers, as desired, allowing the tubular framework 12 to expand into a shape when correctly positioned within the body. In some instances, the material may also be selected to allow the tubular framework 12 to be relatively easily removed. For example, the tubular framework 12 may be formed from alloys such as, but not limited to, Nitinol and Elgiloy®. Depending on the material selected for construction, the tubular framework 12 may be self-expanding (i.e., configured to automatically radially expand when unconstrained). In some embodiments, filaments or wires may be used to fabricate the tubular framework 12, which in some cases may be composite filaments or wires, e.g., with an outer shell fabricated from Nitinol with a platinum core. It is further contemplated that the tubular framework 12 may be formed from a polymer, including, but not limited to, polyethylene terephthalate (PET). In some embodiments, the tubular framework 12 may be self-expanding, while in other embodiments, the tubular framework 12 may be expanded by an expansion device (such as, but not limited to, a balloon inserted within the lumen 15 of the tubular framework 12). As used herein, the term "self-expanding" refers to the tendency of a stent to return to a preset diameter when unconstrained from an external biasing force (such as, but not limited to, a delivery catheter or sheath). In some examples, the tubular framework 12 may include a one-way valve, such as an elastomeric slit valve or duckbill valve, positioned within its lumen 15 to prevent the reflux of gastrointestinal fluids.

[0035] The tubular framework 12 may be configured to expand from a radially collapsed configuration 30 to a radially expanded configuration 32, as shown in FIGS. 2-2A. In some cases, the tubular framework 12 may be initially deployed within a body lumen in a partially expanded configuration between the radially collapsed configuration 30 and the radially expanded configuration 32. The stent 10 may be structured to extend across a stricture and apply radially outward pressure to the stricture within the body lumen to open the lumen and allow the passage of food, fluids, air, etc. When the tubular framework 12 is in the radially collapsed configuration 30, the outer diameter D1, as shown in FIG. 1A, is reduced compared to a partially or fully radially expanded configuration (e.g., outer diameter D2, as shown in FIG. 2A). In some cases, the tubular framework 12 is stretched to reduce the diameter of the tubular framework 12 for delivery to a target location. For example, when the tubular framework 12 is in the radially collapsed configuration 30, the tubular framework 12 may include a first length L1 and a first outer diameter D1. When the tubular framework 12 is deployed (moved from a delivery configuration or a radially collapsed configuration to a radially expanded configuration), the length of the tubular framework 12 decreases and the outer diameter increases. In some cases, the tubular framework 12 may experience a shortening (e.g., the rate at which the length of the stent decreases from its delivery configuration to its radially expanded configuration) ranging from about 20% to about 40%. It is contemplated that the change in length and / or change in diameter of the tubular framework 12 may depend, at least in part, on the size (e.g., diameter) of the tubular framework 12. In some cases, a biliary stent may have a deployed diameter ranging from about 8 millimeters to about 10 millimeters and a collapsed diameter of about 2.5 millimeters to about 3 millimeters. This may correspond to a decrease in diameter of about 60% to about 80% from the radially expanded configuration 32 to the radially collapsed configuration 30. This is merely an example. The reduction in diameter may be less than 60% or more than 80%, as desired.In another example, an endoscopic stent may have a radially expanded diameter (e.g., deployed diameter) ranging from about 18 millimeters to about 23 millimeters and a radially collapsed diameter (e.g., delivery diameter) of about 6 millimeters to about 6.5 millimeters. This may correspond to about a 60% to about 80% reduction in diameter from the radially expanded configuration 32 to the radially collapsed configuration 30. This is by way of example only. The diameter reduction may be less than 60% or more than 80%, as desired.

[0036] In some cases, the tubular framework 12 may have an interwoven filament structure fabricated from one or more interwoven filaments defining interstices 19 therebetween. In some cases, the tubular framework 12 may include a single filament braided or otherwise interwoven with itself to form the tubular framework 12, while in other cases, the tubular framework 12 may include two or more filaments (e.g., multiple filaments) interwoven (e.g., wound, braided, looped, etc.) together to form the tubular framework 12. In some cases, the radially inner surface 18 and / or the radially outer surface 17 of the tubular framework 12 may be provided by filaments. In some cases, the radially inner surface 18 and / or the radially outer surface 17 may be entirely, substantially, or partially covered with a polymeric coating, such as a first polymeric coating 16a and / or a second polymeric coating 16b, or any other suitable type of coating or covering. The first polymeric coating 16a and the second polymeric coating 16b may be generally referred to herein as a polymeric coating 16. The polymer coating 16 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 15 of the stent 10. In some cases, the polymer coating 16 may be formed from any suitable material. For example, the polymer coating 16 may be formed from silicone, polytetrafluoroethylene, polyurethane, or the like, or other materials, including those disclosed herein. In some cases, the first end region 11 and the second end region 13 may include a polymer coating 16 that completely covers the gaps 19 in the first end region 11 and the second end region 13. For example, the first polymer coating 16a may extend (both longitudinally and circumferentially) throughout the first end region 11 and span the gaps in the first end region 11, and the second polymer coating 16b may extend (both longitudinally and circumferentially) throughout the second end region 13 and span the gaps in the second end region 13.

[0037] In some cases, the tubular framework 12 may include multiple coating strips 20 positioned along the intermediate region 14 of the tubular framework 12. While the multiple coating strips 20 are shown positioned along the intermediate region 14, it is envisioned that the multiple coating strips 20 may be positioned along at least one of the first end region 11, the second end region 13, and / or the intermediate region 14. The multiple coating strips 20 may be separate from the polymer coating 16 that covers the first end region 11 and the second end region 13. In some cases, the multiple coating strips 20 may be bonded to the polymer coating 16. In some cases, the multiple coating strips 20 and the polymer coating 16 may be a monolithic structure. The multiple coating strips 20 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 15 of the stent 10. In some cases, the multiple coating strips 20 may be formed from any suitable material. For example, the multiple coating strips 20 may be formed from silicone, polytetrafluoroethylene, polyurethane, etc. In some cases, bonding the plurality of coating strips 20 to the tubular framework 12 may include adhesive bonding, thermal bonding, molding, coating, dip coating, extrusion, etc. These are merely examples.

[0038] In some cases, each of the plurality of covering strips 20 may extend longitudinally from the first polymeric coating 16a to the second polymeric coating 16b along the intermediate region 14 of the tubular framework 12. The plurality of covering strips 20 may completely cover the intermediate region 14 of the tubular framework 12 in the radially collapsed configuration 30, as shown in FIGS. 1-1A. Each of the plurality of covering strips 20 may include a first longitudinal edge 21 secured to the tubular framework 12 and a second longitudinal edge 23 not secured to the tubular framework 12. In some cases, the second longitudinal edge 23 may be located radially outward of the first longitudinal edge 21 when the tubular framework 12 is in the radially collapsed configuration 30. In such a case, the second longitudinal edge 23 of each of the plurality of covering strips 20 may be located radially outward of and overlap the first longitudinal edge 21 of an adjacent one of the plurality of covering strips 20, thereby providing complete coverage over the intermediate region 14 when the tubular framework 12 is in the radially collapsed configuration 30. Thus, tissue may be prevented from growing into the interstices 19 and into the lumens 15 of the intermediate region 14 of the tubular framework 12 when the tubular framework 12 is in the radially collapsed configuration 30.

[0039] FIG. 2 is a side view of the exemplary stent 10 of FIG. 1 in a radially expanded configuration 32, and FIG. 2A is a cross-sectional view of the exemplary stent 10 of FIG. 2 taken along line 2A-2A. As described with reference to FIGS. 1-1A, when the tubular framework 12 is initially deployed (transitioned from a delivery configuration or a radially collapsed configuration to an expanded configuration during a medical procedure), the length of the tubular framework 12 may decrease and the outer diameter may increase. In some cases, the tubular framework 12 may be positioned across a stricture in a body lumen in its initially deployed, radially expanded configuration. As the stricture resolves, the tubular framework 12 may transition from its initially deployed, radially expanded configuration to the radially expanded configuration 32 shown in FIG. 2, resulting in an increase in the diameter of the lumen through the stricture. In such cases, the tubular framework 12 may expand to a larger outer diameter as the stricture resolves. For example, the tubular framework 12 may expand to a second, shorter length L2 and a second, increased outer diameter D2.

[0040] As described with reference to FIGS. 1-1A , the tubular framework 12 may include multiple covering strips 20. When the tubular framework 12 is in the radially expanded configuration 32, the multiple covering strips 20 may be configured to separate circumferentially from one another to expose portions 22 (i.e., filaments) of the tubular framework 12 therebetween. The exposed portions 22 (e.g., bare or uncovered) of the tubular framework 12 may not include or be devoid of a polymeric covering 16, exposing gaps 19 in the intermediate region 14 of the tubular framework 12 that open into the lumen 15. Tissue may be allowed to grow into the gaps 19 in the intermediate region 14 when the tubular framework 12 is in the radially expanded configuration 32, thereby reducing migration of the stent 10.

[0041] FIG. 3 is a side view of an exemplary stent 100 in a radially collapsed configuration, and FIG. 3A is a cross-sectional view of the exemplary stent 100 of FIG. 3 taken along line 3A-3A. In some cases, stent 100 may be formed from a radially expandable tubular framework 112 (generally referred to herein as tubular framework 112) having a radially outer surface 117 and a radially inner surface 118. Although stent 100 is described as generally tubular, it is envisioned that stent 100 may assume any desired cross-sectional shape. Tubular framework 112 may further include a first end region 111, a second end region 113, and an intermediate region 114 positioned between first end region 111 and second end region 113. Tubular framework 112 may include a lumen 115 extending therethrough from first end region 111 to second end region 113.

[0042] It is contemplated that the tubular framework 112 may be fabricated from a number of different materials, such as, but not limited to, metals, metal alloys, shape memory alloys, and / or polymers, as desired, allowing the tubular framework 112 to expand into a shape when correctly positioned within the body. In some instances, the material may be selected to also allow the tubular framework 112 to be relatively easily removed. For example, the tubular framework 112 may be formed from alloys such as, but not limited to, Nitinol and Elgiloy®. Depending on the material selected for construction, the tubular framework 112 may be self-expanding (i.e., configured to automatically radially expand when unconstrained). In some embodiments, filaments or wires may be used to fabricate the tubular framework 112, which in some cases may be composite filaments or wires, e.g., with an outer shell fabricated from Nitinol with a platinum core. It is further contemplated that the tubular framework 112 may be formed from a polymer, including, but not limited to, polyethylene terephthalate (PET). In some embodiments, the tubular framework 112 may be self-expanding, while in other embodiments, the tubular framework 112 may be expanded by an expansion device (such as, but not limited to, a balloon inserted within the lumen 115 of the tubular framework 112). As used herein, the term "self-expanding" refers to the tendency of a stent to return to a preset diameter when unconstrained from an external biasing force (such as, but not limited to, a delivery catheter or sheath). In some examples, the tubular framework 112 may include a one-way valve, such as an elastomeric slit valve or duckbill valve, positioned within its lumen 115 to prevent the reflux of gastrointestinal fluids.

[0043] The tubular framework 112 may be configured to expand from a radially collapsed configuration 130 to a radially expanded configuration 132, as shown in FIGS. 4-4A. In some cases, the tubular framework 112 may be initially deployed within a body lumen in a partially expanded configuration between the radially collapsed configuration 130 and the radially expanded configuration 132. The stent 100 may be structured to extend across a stricture and apply radially outward pressure to the stricture within the body lumen to open the lumen and allow the passage of food, fluid, air, etc. When the tubular framework 112 is in the radially collapsed configuration 130, the outer diameter is reduced compared to the partially or fully radially expanded configuration. In some cases, the tubular framework 112 is stretched to reduce the diameter of the tubular framework 112 for delivery to a target location. For example, when the tubular framework 112 is in the radially collapsed configuration 130, the tubular framework 112 may include a first length and a first outer diameter. When the tubular framework 112 is deployed (moved from a delivery configuration or a radially collapsed configuration to a radially expanded configuration), the length of the tubular framework 112 decreases and the outer diameter increases. In some cases, the tubular framework 112 may experience a shortening (e.g., the rate at which the stent's length decreases from its delivery configuration to its radially expanded configuration) ranging from about 20% to about 40%. It is contemplated that the change in length and / or diameter of the tubular framework 112 may depend, at least in part, on the size (e.g., diameter) of the tubular framework 112. In some cases, a biliary stent may have a deployed diameter ranging from about 6 millimeters to about 10 millimeters and a collapsed diameter of about 2.5 millimeters to about 3 millimeters. This may correspond to a diameter reduction of about 60% to about 80% from the radially expanded configuration 132 to the radially collapsed configuration 130 (e.g., the delivery configuration). This is merely an example. The diameter reduction may be less than 60% or more than 80%, as desired.In another example, the endoscopic stent may have a radially expanded diameter (e.g., deployed diameter) ranging from about 18 millimeters to about 23 millimeters and a radially collapsed diameter (e.g., delivery diameter) of about 6 millimeters to about 6.5 millimeters. This may correspond to about a 60% to about 80% reduction in diameter from the radially expanded configuration 132 to the radially collapsed configuration 130. This is by way of example only. The diameter reduction may be less than 60% or more than 80%, as desired.

[0044] In some cases, the tubular framework 112 may have an interwoven filament structure fabricated from one or more interwoven filaments defining interstices 119 therebetween. In some cases, the tubular framework 112 may include a single filament braided or otherwise interwoven with itself to form the tubular framework 112, while in other cases, the tubular framework 112 may include two or more filaments (e.g., multiple filaments) interwoven (e.g., wound, braided, looped, etc.) together to form the tubular framework 112. In some cases, the radially inner surface 118 and / or the radially outer surface 117 of the tubular framework 112 may be provided by filaments. In some cases, the radially inner surface 118 and / or the radially outer surface 117 may be fully, substantially, or partially covered with a polymeric covering, such as a first polymeric covering 116a and / or a second polymeric covering 116b, or any other suitable type of covering or coating. The first polymer coating 116a and the second polymer coating 116b may be generally referred to herein as a polymer coating 116. The polymer coating 116 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 115 of the stent 100. In some cases, the polymer coating 116 may be formed from any suitable material. For example, the polymer coating 116 may be formed from silicone, polytetrafluoroethylene, polyurethane, or the like, or other materials, including those disclosed herein. In some cases, the first end region 111 and the second end region 113 may include a polymer coating 116 that completely covers the gaps 119 in the first end region 111 and the second end region 113. For example, the first polymer coating 116a may extend (both longitudinally and circumferentially) across the entire first end region 111 and span gaps within the first end region 111, and the second polymer coating 116b may extend (both longitudinally and circumferentially) across the entire second end region 113 and span gaps within the second end region 113.

[0045] In some cases, the tubular framework 112 may include a plurality of coating strips 120 positioned along the intermediate region 114 of the tubular framework 112. While the plurality of coating strips 120 is shown positioned along the intermediate region 114, it is envisioned that the plurality of coating strips 120 may be positioned along at least one of the first end region 111, the second end region 113, and / or the intermediate region 114. The plurality of coating strips 120 may be separate from the polymer coating 116 that covers the first end region 111 and the second end region 113. In some cases, the plurality of coating strips 120 may be bonded to the polymer coating 116. In some cases, the plurality of coating strips 120 and the polymer coating 116 may be a monolithic structure. The plurality of coating strips 120 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 115 of the stent 100. In some cases, the plurality of coating strips 120 may be formed from any suitable material. For example, the plurality of covering strips 120 may be formed from silicone, polytetrafluoroethylene, polyurethane, etc. In some cases, bonding the plurality of covering strips 120 to the tubular framework 112 may include adhesive bonding, thermal bonding, molding, coating, dip coating, extrusion, etc. These are merely examples.

[0046] In some cases, each of the multiple covering strips 120 may extend circumferentially around an intermediate region 114 of the tubular framework 112 between the first polymeric covering 116a and the second polymeric covering 116b. The multiple covering strips 120 may completely cover the intermediate region 114 of the tubular framework 112 in the radially collapsed configuration 130, as shown in FIGS. 3-3A. Each of the multiple covering strips 120 may include a first circumferential edge 121 secured to the tubular framework 112 and a second circumferential edge 123 not secured to the tubular framework 112. In some cases, the second circumferential edge 123 may be located radially outward of the first circumferential edge 121 when the tubular framework 112 is in the radially collapsed configuration 130. In such a case, the second circumferential edge 123 of each of the plurality of covering strips 120 may be located radially outward of and overlap the first circumferential edge 121 of an adjacent one of the plurality of covering strips 120, thereby providing complete coverage over the intermediate region 114 when the tubular framework 112 is in the radially collapsed configuration 130. Thus, tissue may be prevented from growing into the interstices 119 and into the lumens 115 of the intermediate region 114 of the tubular framework 112 when the tubular framework 112 is in the radially collapsed configuration 130.

[0047] FIG. 4 is a side view of the exemplary stent 100 of FIG. 3 in a radially expanded configuration 132, and FIG. 4A is a cross-sectional view of the exemplary stent 100 of FIG. 4 along line 4A-4A. As described with reference to FIGS. 3-3A, when the tubular framework 112 is initially deployed (transitioned from a delivery configuration or radially collapsed configuration to an expanded configuration during a medical procedure), the length of the tubular framework 112 may decrease and the outer diameter may increase. In some cases, the tubular framework 112 may be positioned across a stricture in a body lumen in its initially deployed radially expanded configuration. As the stricture resolves, the tubular framework 112 may transition from its initially deployed radially expanded configuration to the radially expanded configuration 132 shown in FIG. 4, resulting in an increase in the diameter of the lumen through the stricture. In such cases, the tubular framework 112 may expand to a larger outer diameter as the stricture resolves. For example, the tubular framework 112 may expand to a second, shorter length and a second, increased outer diameter.

[0048] As described with reference to FIGS. 3-3A , the tubular framework 112 may include multiple covering strips 120. When the tubular framework 112 is in the radially expanded configuration 132, the multiple covering strips 120 may be configured to longitudinally separate from one another to expose portions 122 (i.e., filaments) of the tubular framework 112 therebetween. The exposed portions 122 (e.g., bare or uncovered) of the tubular framework 112 may not include or be devoid of the polymer covering 116, exposing gaps 119 in the intermediate region 114 of the tubular framework 112 that open into the lumen 115. Tissue may be allowed to grow into the gaps 119 in the intermediate region 114 when the tubular framework 112 is in the radially expanded configuration 132, thereby reducing migration of the stent 100.

[0049] 5-6 illustrate an exemplary method of using an exemplary stent 200, in which the stent 200 is initially positioned across a stricture 240 in a body lumen, expanded to an initial radially expanded configuration 230 shown in FIG. 5 during a medical procedure, and then further radially expanded after implantation within the body lumen at a later time after the medical procedure (e.g., several days or more, or even weeks or more after the medical procedure) to a second, more radially expanded configuration 232 shown in FIG. 6. The stent 200 may be considered an example of the stents 10, 100, 300, and 400 described herein. The stent 200 may be formed from a radially expandable tubular framework 212 (generally referred to herein as the tubular framework 212) having a radially outer surface 217 and a radially inner surface 218. While the stent 200 is described as being generally tubular, it is envisioned that the stent 200 may assume any desired cross-sectional shape. The tubular framework 212 may further include a first end region 211, a second end region 213, and an intermediate region 214 positioned between the first end region 211 and the second end region 213. The tubular framework 212 may include a lumen 215 extending therethrough from the first end region 211 to the second end region 213.

[0050] The tubular framework 212 may include a plurality of covering strips 220 positioned along the intermediate region 214 of the tubular framework 212. While the plurality of covering strips 220 is shown positioned along the intermediate region 214, it is envisioned that the plurality of covering strips 220 may be positioned along at least one of the first end region 211, the second end region 213, and / or the intermediate region 214. The plurality of covering strips 220 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 215 of the stent 200. In some cases, the plurality of covering strips 220 may be formed from any suitable material. For example, the plurality of covering strips 220 may be formed from silicone, polytetrafluoroethylene, polyurethane, etc. In some cases, bonding the plurality of covering strips 220 to the tubular framework 212 may include adhesive bonding, thermal bonding, molding, coating, dip coating, extrusion, etc. These are merely examples.

[0051] In some cases, the plurality of covering strips 220 may completely cover the intermediate region 214 of the stent 200 in the initially deployed, first radially expanded configuration 230, as shown in FIG. 5 . In some cases, the plurality of covering strips 220 may completely cover the first end region 211 of the stent 200 in the initially deployed, first radially expanded configuration 230, and / or the plurality of covering strips 220 may completely cover the second end region 213 of the stent 200, although not explicitly shown. The plurality of covering strips 220 may each include a first edge 221 secured to the tubular framework 212 and a second edge 223 not secured to the tubular framework 212. In some cases, the second edge 223 may be located radially outward of the first edge 221 when the stent 200 is in the first radially expanded configuration 230. In such a case, the second edge 223 of each of the plurality of coating strips 220 may be radially outward of and overlap the first edge 221 of an adjacent one of the plurality of coating strips 220, thereby providing complete coverage over the intermediate region 214, the first end region 211, or the second end region 213 when the stent 200 is in its initially deployed, first radially expanded configuration 230. Thus, tissue may be prevented from growing into the gaps 219 in the intermediate region 214 (or first end region 211 / second end region 213) of the stent 200 when the stent 200 is in its first radially expanded configuration 230.

[0052] In some cases, the plurality of covering strips 220 may be positioned along the first end region 211, and the plurality of covering strips 220 may completely cover the first end region 211 while the stent 200 is in the first radially expanded configuration. In some cases, the plurality of covering strips 220 may include one or more tie strings attached to the plurality of covering strips 220. In some cases, the one or more tie strings may include tie strings longitudinally interposed between adjacent ones of the plurality of covering strips 220. The tie strings may hold the plurality of covering strips 220 in abutting and / or overlapping relationship and may be configured to be pulled from the plurality of covering strips 220 to allow the covering strips 220 to separate from and move away from adjacent covering strips 220.

[0053] In some cases, when the stent 200 is in the second, more radially expanded configuration 232, such as after being implanted across the stenosis 240 for a period of time, the multiple coating strips 220 may be configured to be spaced apart (e.g., separated from one another) to expose the portions 222 of the tubular framework 212 therebetween. The exposed portions 222 (e.g., bare or uncovered) of the tubular framework 212 may not include or be devoid of the polymer coating 216, exposing gaps 219 in the intermediate region 214 of the tubular framework 212 that open into the lumen 215. Tissue may be allowed to grow into the gaps 219 in the intermediate region 214 when the tubular framework 212 is in the second, more radially expanded configuration 232, thereby reducing migration of the stent 200.

[0054] In some cases, the method may include implanting stent 200 across stricture 240 within body lumen 245 during a medical procedure. For example, in some cases, body lumen 245 may include, but is not limited to, a body tissue, a body organ, a vascular lumen, a non-vascular lumen, and combinations thereof (e.g., but not limited to, the coronary or peripheral vasculature, esophagus, trachea, bronchi, colon, small intestine, bile duct, urinary tract, prostate, brain, stomach, etc.). Stent 200 may be structured to extend across stricture 240 and apply radially outward pressure to stricture 240 within body lumen 245 to open body lumen 245 and allow the passage of food, fluid, air, etc. The method may include allowing the stent 200 to initially expand to a first radially expanded configuration 230 within the body lumen 245 when the stent 200 is initially implanted across the stenosis, with the plurality of coating strips 220 completely covering the tubular framework 212 throughout the intermediate region 214 of the tubular framework 212. In other words, when the stent 200 is initially implanted across the stenosis 240 in the body lumen 245, the tubular framework 212 may be completely covered (i.e., all of the interstices of the tubular framework 212 are covered with either the coating 216 on the first end region 211 and the second end region 213 or the coating strips 220 on the intermediate region 214), such that tissue is prevented from growing into the interstices between the tubular framework 212 and into the lumen 245. The method may include allowing the stent 200 to further radially expand within the body lumen 245 from the first radially expanded configuration 230 to a second radially expanded configuration 232 as the stenosis resolves over a period of time after implantation of the stent 200 (e.g., over a period of days and / or weeks after the surgical procedure in which the stent 200 is implanted), with the plurality of covering strips 220 separated from one another in the second, further radially expanded configuration 232 to expose portions 222 of the tubular framework 212 therebetween, as shown in FIG. 6 . The exposed portions 222 may include uncovered or open gaps 219 between the filaments of the tubular framework 212 to permit tissue ingrowth therethrough.Thus, portions of the intermediate region 214 of the tubular framework 212 may transition from being covered by the covering strip 220 in a first, initially deployed, radially expanded configuration upon implantation within a body lumen, as shown in FIG. 5, to being uncovered at a subsequent post-operative time (e.g., days and / or weeks after implantation of the stent 200) to defining an exposed portion 222 of the tubular framework 212 in a further radially expanded configuration, as shown in FIG. 6.

[0055] It should be noted that upon initial implantation when intermediate region 214 is positioned at stenosis 240, stenosis 240 may prevent or inhibit full radial expansion of intermediate region 214 such that the initial expanded diameter of intermediate region 214 of stent 200 may be smaller than the initial expanded diameter of first end region 211 and / or the initial expanded diameter of second end region 213. The enlarged first end region 211 and / or enlarged second end region 213 relative to intermediate region 214 may prevent migration of stent 200 within body lumen 245 upon initial implantation of stent 200. However, over time, as stenosis 240 resolves, intermediate region 214 may continue to radially expand to a more radially expanded configuration shown in FIG. 6, which has an outer diameter larger than the outer diameter of the initial radially expanded configuration of intermediate region 214 shown in FIG. 5. In instances where stent 200 remains fully covered, stent 200 may be prone to migration within the body lumen once intermediate region 214 may be further expanded. However, as shown in Figure 6, uncovering or exposing exposed portions 222 of tubular framework 212 allows tissue ingrowth into gaps 219 of exposed portions 222, providing stent 200 with anti-migration capabilities.

[0056] In some cases, the method may include removing one of the tie strings between adjacent ones of the covering strips 220 to allow the tubular framework 212 to further radially expand from the first, initially radially expanded configuration 230 to a second, further radially expanded configuration 232. Other removable structures that may be selectively removed from the covering strips 220 to allow the tubular framework 212 to expand and expose portions of the tubular framework 212 between adjacent covering strips 220 are also envisioned.

[0057] In some cases, the length of the tubular framework 212 may decrease and the outer diameter may increase as the stent 200 moves from a first, initially deployed, radially expanded configuration 230 to a second, post-procedure, more radially expanded configuration 232. The tubular framework 212 may move from the first radially expanded configuration 230 to the second radially expanded configuration 232 as the stenosis 240 resolves, resulting in an increase in the diameter of the lumen through the stenosis 240, as shown in FIG. 6 . In such cases, the tubular framework 212 (e.g., intermediate region 214) may expand to a larger outer diameter over time as the stenosis 240 resolves. For example, the intermediate region 214 of the tubular framework 212 may expand from a first, initially deployed outer diameter to a second, larger outer diameter after a period of time (e.g., days and / or weeks) after initial implantation.

[0058] FIG. 7 is a side view of an exemplary stent 300 in a radially collapsed configuration, and FIG. 8 is a side view of the exemplary stent 300 of FIG. 7 in a radially expanded configuration 332. In some cases, the stent 300 may be formed from a radially expandable tubular framework 312 (generally referred to herein as the tubular framework 312) having a radially outer surface 317 and a radially inner surface 318. Although the stent 300 is described as generally tubular, it is envisioned that the stent 300 may assume any desired cross-sectional shape. The tubular framework 312 may further include a first end region 311, a second end region 313, and an intermediate region 314 positioned between the first end region 311 and the second end region 313. The tubular framework 312 may include a lumen 315 extending therethrough from the first end region 311 to the second end region 313.

[0059] It is contemplated that the tubular framework 312 may be fabricated from a number of different materials, such as, but not limited to, metals, metal alloys, shape memory alloys, and / or polymers, as desired, allowing the tubular framework 312 to expand into a shape when correctly positioned within the body. In some instances, the material may be selected to also allow the tubular framework 312 to be relatively easily removed. For example, the tubular framework 312 may be formed from alloys such as, but not limited to, Nitinol and Elgiloy®. Depending on the material selected for construction, the tubular framework 312 may be self-expanding (i.e., configured to automatically radially expand when unconstrained). In some embodiments, filaments or wires may be used to fabricate the tubular framework 312, which in some cases may be composite filaments or wires, e.g., with an outer shell fabricated from Nitinol with a platinum core. It is further contemplated that the tubular framework 312 may be formed from a polymer, including, but not limited to, polyethylene terephthalate (PET). In some embodiments, the tubular framework 312 may be self-expanding, while in other embodiments, the tubular framework 312 may be expanded by an expansion device (such as, but not limited to, a balloon inserted within the lumen 315 of the tubular framework 312). As used herein, the term "self-expanding" refers to the tendency of a stent to return to a preset diameter when unconstrained from an external biasing force (such as, but not limited to, a delivery catheter or sheath). In some examples, the tubular framework 312 may include a one-way valve, such as an elastomeric slit valve or duckbill valve, positioned within its lumen 315 to prevent the reflux of gastrointestinal fluids.

[0060] The tubular framework 312 may be configured to expand from a radially collapsed configuration 330 shown in FIG. 7 to a radially expanded configuration 332 shown in FIG. 8 . In some cases, the tubular framework 312 may initially be deployed within a body lumen in a partially expanded configuration between the radially collapsed configuration 330 and the radially expanded configuration 332. The stent 300 may be structured to extend across a stricture and apply radially outward pressure to the stricture within the body lumen to open the lumen and allow the passage of food, fluids, air, etc. When the tubular framework 312 is in the radially collapsed configuration 330, the outer diameter is reduced compared to the partially or fully radially expanded configuration. In some cases, the tubular framework 12 is stretched to reduce the diameter of the tubular framework 312 for delivery to a target location. For example, when the tubular framework 12 is in the radially collapsed configuration 30, the tubular framework 12 may include a first length L1 and a first outer diameter D1. As the tubular framework 312 is deployed (moved from a delivery configuration or a radially collapsed configuration to a radially expanded configuration), the length of the tubular framework 312 decreases and the outer diameter increases. In some cases, the tubular framework 312 may experience a shortening (e.g., the rate at which the stent's length decreases from its delivery configuration to its radially expanded configuration) ranging from about 20% to about 40%. It is contemplated that the change in length and / or diameter of the tubular framework 312 may depend, at least in part, on the size (e.g., diameter) of the tubular framework 312. In some cases, a biliary stent may have a deployed diameter ranging from about 8 millimeters to about 10 millimeters and a collapsed diameter of about 2.5 millimeters to about 3 millimeters. This may correspond to about a 60% to about 80% reduction in diameter from the radially expanded configuration 332 to the radially collapsed configuration 330. This is merely an example. The diameter reduction may be less than 60% or more than 80%, as desired.In another example, the endoscopic stent may have a radially expanded diameter (e.g., deployed diameter) ranging from about 18 millimeters to about 23 millimeters and a radially collapsed diameter (e.g., delivery diameter) of about 6 millimeters to about 6.5 millimeters. This may correspond to about a 60% to about 80% reduction in diameter from the radially expanded configuration 332 to the radially collapsed configuration 330. This is by way of example only. The diameter reduction may be less than 60% or more than 80%, as desired.

[0061] In some cases, the tubular framework 312 may have an interwoven filament structure fabricated from one or more interwoven filaments defining interstices 319 therebetween. In some cases, the tubular framework 312 may include a single filament braided or otherwise interwoven with itself to form the tubular framework 312, while in other cases, the tubular framework 312 may include two or more filaments (e.g., multiple filaments) interwoven (e.g., wound, braided, looped, etc.) together to form the tubular framework 312. In some cases, the radially inner surface 318 and / or the radially outer surface 317 of the tubular framework 312 may be provided by filaments. In some cases, the radially inner surface 318 and / or the radially outer surface 317 may be entirely, substantially, or partially covered with a polymeric covering 316 or any other suitable type of covering or coating. The polymeric covering 316 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 315 of the stent 300. In some cases, the polymer coating 316 may be formed from any suitable material. For example, the polymer coating 316 may be formed from silicone, polytetrafluoroethylene, polyurethane, or the like, or other materials, including those disclosed herein. In some cases, as shown in Figures 7-8, the first end region 311, the second end region 313, and the intermediate region 314 may include the polymer coating 316, spanning gaps 319 within the first end region 111, the second end region 313, and the intermediate region 314.

[0062] In the radially collapsed configuration 330, the stent 300 may include one or more tie strings 340 attached to and extending along a portion of the polymeric covering 316, such as along the first end region 311. The one or more tie strings 340 may include a retrieval tether 345 or a suture secured to or otherwise provided with the one or more tie strings 340. As discussed herein, the tie strings 340 may be selectively removed from the polymeric covering 316, such as by medical personnel grasping the retrieval tether 345 and pulling the retrieval tether 345 and attached tie string 340 from the polymeric covering 316. As shown in FIG. 8 , removing the tie string 340 may allow portions of the polymeric covering 316 (e.g., covering strips 320) to move away from one another, exposing portions of the tubular framework 312 therebetween.

[0063] In some cases, the tubular framework 312 may include a plurality of covering strips 320 (shown in FIG. 8 ) positioned along the first end region 311 of the tubular framework 312, with one or more tie strings interposed between adjacent ones of the plurality of covering strips 320. While the plurality of covering strips 320 is shown positioned along the first end region 311, it may be envisioned that the plurality of covering strips 320 may be positioned along at least one of the first end region 311, the second end region 313, or the intermediate region 314. The plurality of covering strips 320 may be an integral part of the polymer covering 316, or the covering strips 320 may be separate from the polymer covering 316 that covers the tubular framework 312.

[0064] In some cases, each of the plurality of covering strips 320 may extend longitudinally along the first end region 311 of the tubular framework 312. In some cases, the plurality of covering strips 320 may completely cover the first end region 311 of the tubular framework 312 in a radially collapsed configuration 330, as shown in FIG. 7. In some cases, the plurality of covering strips 320 may be separated from one another when the tie cords 340 are removed to allow the tubular framework 312 (e.g., the first end region 311 of the tubular framework 312) to radially expand to a radially expanded configuration 332, as shown in FIG. 8. In the radially expanded configuration, each of the plurality of covering strips 320 may include a first longitudinal edge 321 and a second longitudinal edge 323, with a portion 322 of the tubular framework 312 located therebetween exposed. Ties 340 may be attached to the plurality of covering strips 320 in the radially collapsed configuration 330 or may otherwise hold the plurality of covering strips 320 joined together in the radially collapsed configuration 330. In some cases, one or more ties 340 may include a tie interposed between adjacent ones of the plurality of covering strips 320. In some cases, when the tubular framework 312 is in the radially collapsed configuration 330, the second longitudinal edge 323 may abut the first longitudinal edge 321 of an adjacent covering strip 320 to completely cover the first end region 311 of the tubular framework 312. In some cases, the second longitudinal edge 323 of each of the plurality of covering strips 320 may overlap the first longitudinal edge 321 of an adjacent one of the plurality of covering strips 320, thereby providing complete coverage over the first end region 311 when the tubular framework 312 is in the radially collapsed configuration 330. Thus, when the tubular framework 312 is in the radially collapsed configuration 330, tissue may be prevented from growing into the gaps 319 in the first end region 311 where the multiple covering strips are located.

[0065] In some cases, the stent 300 may be positioned across a stricture in a body lumen. When it is desired to expose a portion of the tubular framework 312 for tissue ingrowth therein, the retrieval tether 345 may be pulled, like a drawstring, which may pull on one or more tie strings 340. The one or more tie strings 340 may be embedded within the polymer coating 316, such as the plurality of coating strips 320, so that when the retrieval tether 345 is pulled, the one or more tie strings 340 may be removed from the polymer coating 316, thereby allowing portions of the polymer coating 316 (e.g., the plurality of coating strips 320) to separate from one another and expose portions of the first end region 311 of the tubular framework 312 therebetween. The exposed portions 322 may then allow tissue ingrowth therein, providing the stent 300 with anti-migration capabilities. The exposed portions 322 (e.g., bare or uncovered) of the tubular framework 312 may not include or may lack the polymer coating 316, exposing gaps 319 in the first end region 311 of the tubular framework 312. Tissue may be allowed to grow into the gaps 319 in the first end region 311, thereby reducing migration of the stent 300.

[0066] FIG. 9 is a side view of an exemplary stent 400 in a radially collapsed configuration 430, and FIG. 10 is a side view of the exemplary stent 400 of FIG. 9 in a radially expanded configuration 432. In some cases, the stent 400 may be formed from a radially expandable tubular framework 412 (generally referred to herein as the tubular framework 412) having a radially outer surface 417 and a radially inner surface 418. Although the stent 400 is described as generally tubular, it is envisioned that the stent 400 may assume any desired cross-sectional shape. The tubular framework 412 may further include a first end region 411, a second end region 413, and an intermediate region 414 positioned between the first end region 411 and the second end region 413. The tubular framework 412 may include a lumen 415 extending therethrough from the first end region 411 to the second end region 413.

[0067] It is contemplated that the tubular framework 412 may be fabricated from a number of different materials, such as, but not limited to, metals, metal alloys, shape memory alloys, and / or polymers, as desired, allowing the tubular framework 412 to expand into a shape when correctly positioned within the body. In some instances, the material may also be selected to allow the tubular framework 412 to be relatively easily removed. For example, the tubular framework 412 may be formed from alloys such as, but not limited to, Nitinol and Elgiloy®. Depending on the material selected for construction, the tubular framework 412 may be self-expanding (i.e., configured to automatically radially expand when unconstrained). In some embodiments, filaments or wires may be used to fabricate the tubular framework 412, which in some cases may be composite filaments or wires, e.g., with an outer shell fabricated from Nitinol with a platinum core. It is further contemplated that the tubular framework 412 may be formed from a polymer, including, but not limited to, polyethylene terephthalate (PET). In some embodiments, the tubular framework 412 may be self-expanding, while in other embodiments, the tubular framework 412 may be expanded by an expansion device (such as, but not limited to, a balloon inserted within the lumen 415 of the tubular framework 412). As used herein, the term "self-expanding" refers to the tendency of a stent to return to a preset diameter when unconstrained from an external biasing force (such as, but not limited to, a delivery catheter or sheath). In some examples, the tubular framework 412 may include a one-way valve, such as an elastomeric slit valve or duckbill valve, positioned within its lumen 415 to prevent the reflux of gastrointestinal fluids.

[0068] The tubular framework 412 may be configured to expand from a radially collapsed configuration 430 shown in FIG. 9 to a radially expanded configuration 432 shown in FIG. 10 . In some cases, the tubular framework 412 may initially be deployed within a body lumen in a partially expanded configuration between the radially collapsed configuration 430 and the radially expanded configuration 432. The stent 400 may be structured to extend across a stricture and apply radially outward pressure to the stricture within the body lumen to open the lumen and allow the passage of food, fluid, air, etc. When the tubular framework 412 is in the radially collapsed configuration 430, the outer diameter is reduced compared to the partially or fully radially expanded configuration. In some cases, the tubular framework 412 is stretched to reduce the diameter of the tubular framework 412 for delivery to a target location. For example, when the tubular framework 412 is in the radially collapsed configuration 430, the tubular framework 412 may include a first length and a first outer diameter. As the tubular framework 412 is deployed (moved from a delivery configuration or a radially collapsed configuration to a radially expanded configuration), the length of the tubular framework 412 decreases and the outer diameter increases. In some cases, the tubular framework 412 may experience a shortening (e.g., the rate at which the stent's length decreases from its delivery configuration to its radially expanded configuration) ranging from about 20% to about 40%. It is contemplated that the change in length and / or diameter of the tubular framework 412 may depend, at least in part, on the size (e.g., diameter) of the tubular framework 412. In some cases, a biliary stent may have a deployed diameter ranging from about 8 millimeters to about 10 millimeters and a collapsed diameter of about 2.5 millimeters to about 3 millimeters. This may correspond to about a 60% to about 80% reduction in diameter from the radially expanded configuration 432 to the radially collapsed configuration 430. This is merely an example. The diameter reduction may be less than 60% or more than 80%, as desired.In another example, the endoscopic stent may have a radially expanded diameter (e.g., deployed diameter) ranging from about 18 millimeters to about 23 millimeters and a radially collapsed diameter (e.g., delivery diameter) of about 6 millimeters to about 6.5 millimeters. This may correspond to about a 60% to about 80% reduction in diameter from the radially expanded configuration 432 to the radially collapsed configuration 430. This is by way of example only. The diameter reduction may be less than 60% or more than 80%, as desired.

[0069] In some cases, the tubular framework 412 may have an interwoven filament structure fabricated from one or more interwoven filaments defining interstices 419 therebetween. In some cases, the tubular framework 412 may include a single filament braided or otherwise interwoven with itself to form the tubular framework 412, while in other cases, the tubular framework 412 may include two or more filaments (e.g., multiple filaments) interwoven (e.g., wound, braided, looped, etc.) together to form the tubular framework 412. In some cases, the radially inner surface 418 and / or the radially outer surface 417 of the tubular framework 412 may be provided by filaments. In some cases, the radially inner surface 418 and / or the radially outer surface 417 may be wholly, substantially, or partially covered with a polymeric coating, such as a first polymeric coating 416a and / or a second polymeric coating 416b, or any other suitable type of coating or covering. The first polymer coating 416a and the second polymer coating 416b may be generally referred to herein as a polymer coating 416. The polymer coating 416 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 415 of the stent 400. In some cases, the polymer coating 416 may be formed from any suitable material. For example, the polymer coating 416 may be formed from silicone, polytetrafluoroethylene, polyurethane, or the like, or other materials, including those disclosed herein. In some cases, the first end region 411 and the second end region 413 may include a polymer coating 416 that completely covers the gaps 419 in the first end region 411 and the second end region 413. For example, the first polymer coating 416a may extend (both longitudinally and circumferentially) across the entire first end region 411 and span gaps within the first end region 411, and the second polymer coating 416b may extend (both longitudinally and circumferentially) across the entire second end region 413 and span gaps within the second end region 413.

[0070] In some cases, the tubular framework 412 may include a covering strip 420 positioned along the intermediate region 414 of the tubular framework 412. While the covering strip 420 is shown positioned along the intermediate region 414, it is envisioned that the covering strip 420 may be positioned along at least one of the first end region 411, the second end region 413, and / or the intermediate region 414. The covering strip 420 may be separate from the polymer covering 416 that covers the first end region 411 and the second end region 413. In some cases, the covering strip 420 may be bonded to the polymer covering 416. In some cases, the covering strip 420 and the polymer covering 416 may be one monolithic structure. The covering strip 420 may be configured to help reduce food impingement and / or tumor or tissue ingrowth into the lumen 415 of the stent 100. In some cases, the covering strip 420 may be formed from any suitable material. For example, the covering strip 420 may be formed from silicone, polytetrafluoroethylene, polyurethane, etc. In some cases, bonding the covering strip 420 to the tubular framework 412 may include adhesive bonding, thermal bonding, molding, coating, dip coating, extrusion, etc. In some cases, the covering strip 420 is positioned on the tubular framework 412 similar to a sleeve. These are merely examples.

[0071] In some cases, the covering strip 420 may extend circumferentially around the tubular framework 412 and extend along the intermediate region 414 of the tubular framework 412 from the first polymeric covering 416a to the second polymeric covering 416b. As described herein, in some cases, the covering strip 420 may be part of the polymeric covering 416 that covers the intermediate region 414 of the tubular framework 412. The covering strip 420 may completely cover the intermediate region 414 of the tubular framework 412 in the radially collapsed configuration 430, as shown in FIG. 9 . The covering strip 420 may include a plurality of slits 424 within the covering strip 420. When the tubular framework 412 is in the radially collapsed configuration 430, the plurality of slits 424 may remain closed, thereby keeping the intermediate region 414 of the tubular framework 412 completely covered. Thus, when the tubular framework 412 is in the radially collapsed configuration 430, tissue may be prevented from growing into the gaps 419 in the intermediate region 414 of the tubular framework 412. Thus, the first edge 421 of the slit 424 may abut or be juxtaposed with the second edge 423 of the slit when the tubular framework 412 is in the radially collapsed configuration 430.

[0072] As shown in FIG. 10 , as the tubular framework 412 is deployed (moved from a delivery configuration or radially collapsed configuration to a radially expanded configuration), the length of the tubular framework 412 may decrease and the outer diameter may increase. In some cases, the tubular framework 412 may be positioned across a stricture in a body lumen. The tubular framework 412 may move from the radially collapsed configuration 430 to the radially expanded configuration 432 as the stricture resolves, resulting in an increase in the diameter of the lumen through the stricture. In such cases, the intermediate region 414 of the tubular framework 412 may further expand from its initial deployed diameter to a more radially expanded diameter over a period of time (e.g., days and / or weeks after implantation).

[0073] When the tubular framework 412 expands to the radially expanded configuration 432, the multiple slits 424 in the covering strip 420 may be configured to separate from one another to expose the portions 422 of the tubular framework 412 therebetween. In other words, the first edges 421 of the slits 424 may move away from the second edges 423 of the slits 424 to expose the portions of the tubular framework 412 therebetween. The exposed portions 422 (e.g., bare or uncovered) of the tubular framework 412 may not include or be devoid of the polymer coating 416, exposing gaps 4419 in the intermediate region 414 of the tubular framework 412. Tissue may be allowed to grow into the gaps 419 in the intermediate region 414 when the tubular framework 412 is in the radially expanded configuration 432, thereby reducing migration of the stent 400.

[0074] The stent, delivery system, and various components thereof may be made from metals, metal alloys, polymers (some examples of which are disclosed below), metal-polymer composites, ceramics, combinations thereof, or other suitable materials. Some examples of suitable metals and metal alloys include stainless steels such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloys such as linear elastic and / or superelastic nitinol; other nickel alloys such as nickel-chromium-molybdenum alloys, nickel-copper alloys, nickel-cobalt-chromium-molybdenum alloys, nickel-molybdenum alloys, other nickel-chromium alloys, other nickel-molybdenum alloys, other nickel-cobalt alloys, other nickel-iron alloys, other nickel-copper alloys, other nickel-tungsten or tungsten alloys; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys; platinum-strengthened stainless steels; titanium; combinations thereof; the like; or any other suitable material.

[0075] Some examples of polymers suitable for stents or delivery systems include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, e.g., DELRIN® available from DuPont), polyether block esters, polyurethanes (e.g., Polyurethane 85A), polypropylene (PP), polyvinyl chloride (PVC), polyetheresters (e.g., ARNITEL® available from DSM Engineering Plastics), ether or ester-based copolymers (e.g., butylene / poly(alkylene ether) phthalates and / or other polyester elastomers such as HYTREL® available from DuPont), polyamides (e.g., DURETHAN® or Elf® available from Bayer), and the like. CRISTAMID™ available from Atochem), elastomeric polyamides, block polyamide / ethers, polyether block amides (PEBA, e.g., available under the trade name PEBAX®), ethylene vinyl acetate copolymer (EVA), silicone, polyethylene (PE), MARLEX® high density polyethylene, MARLEX® low density polyethylene, linear low density polyethylene (e.g., REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyether ether ketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (e.g., KEVLAR®), polysulfone, nylon, nylon 12 (EMS AmericanSuch materials may include, but are not limited to, GRILAMID® available from Grillon, perfluoro(propyl vinyl ether) (PFA), ethyl vinyl alcohol, polyolefins, polystyrene, epoxies, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (e.g., SIBS and / or SIBS50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers, polymer / metal composites, and the like.

[0076] In at least some embodiments, portions or all of the stent or delivery system may also be doped with, made from, or otherwise include a radiopaque material. Radiopaque materials are generally understood to be materials that are opaque to RF energy in the wavelength range extending from X-rays to gamma rays (thickness less than 0.005 inches). These materials can produce a relatively dark image on a fluoroscopy screen compared to the bright image produced by non-radiopaque materials such as tissue. This relatively bright image aids the user of the stent or delivery system in determining its location. Some examples of radiopaque materials include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloys, polymeric materials loaded with radiopaque fillers, and the like. Additionally, other radiopaque marker bands and / or coils may also be incorporated into the stent or delivery system design to achieve the same results.

[0077] It will be understood that this disclosure is, in many respects, merely illustrative. Changes may be made in details, particularly in matters of shape, size, and arrangement of steps, without exceeding the scope of the disclosure. This may include, to the extent appropriate, the use of any of the features of one illustrative embodiment used in other embodiments. The scope of the disclosure is, of course, defined in the language in which the appended claims are expressed.

Claims

1. a radially expandable tubular framework having a radially outer surface, a radially inner surface, a first end region, a second end region, an intermediate region positioned between the first end region and the second end region, and a lumen extending through the radially expandable tubular framework, the radially expandable tubular framework being configured to expand from a radially collapsed configuration to a radially expanded configuration; a plurality of covering strips positioned along at least one of the first end region, the intermediate region, and the second end region, the covering strips configured to completely cover the radially expandable tubular framework in the radially collapsed configuration and to separate from one another to expose portions of the radially expandable tubular framework therebetween in the radially expanded configuration; A stent comprising:

2. 2. The stent of claim 1, wherein each of the plurality of covering strips extends longitudinally along the intermediate region of the stent, the plurality of covering strips completely covering the intermediate region in the radially collapsed configuration, and the plurality of covering strips are configured to separate from one another in the radially expanded configuration to expose portions of the intermediate region of the radially expandable tubular framework therebetween.

3. 3. The stent of claim 2, wherein a first longitudinal edge of each of the plurality of covering strips is secured to the expandable tubular framework and a second longitudinal edge of each of the plurality of covering strips is not secured to the expandable tubular framework.

4. The stent of claim 3 , wherein the second longitudinal edge of each of the plurality of covering strips overlaps the first longitudinal edge of an adjacent one of the plurality of covering strips in the radially collapsed configuration.

5. The stent of claim 4 , wherein the second longitudinal edge is located radially outward of the first longitudinal edge in the radially collapsed configuration.

6. 2. The stent of claim 1, wherein each of the plurality of covering strips extends circumferentially around the intermediate region of the stent, the plurality of covering strips completely covering the intermediate region in the radially collapsed configuration, and the plurality of covering strips are configured to separate from one another in the radially expanded configuration to expose portions of the intermediate region of the radially expandable tubular framework therebetween.

7. 7. The stent of claim 6, wherein a first circumferential edge of each of the plurality of covering strips is secured to the expandable tubular framework and a second circumferential edge of each of the plurality of covering strips is not secured to the expandable tubular framework.

8. 8. The stent of claim 7, wherein the second circumferential edge of each of the plurality of covering strips overlaps the first circumferential edge of an adjacent one of the plurality of covering strips in the radially collapsed configuration.

9. 9. The stent of claim 1, wherein the radially expandable tubular framework is formed from one or more interwoven filaments defining gaps therebetween, such that in the radially expanded configuration, tissue is allowed to grow into the gaps in the intermediate regions, and in the radially collapsed configuration, tissue is prevented from growing into the gaps in the intermediate regions.

10. 10. The stent of claim 9, wherein the first end region includes a polymer covering that completely covers the gap in the first end region and the second end region includes a polymer covering that completely covers the gap in the second end region.

11. The stent of claim 10, wherein the plurality of covering strips are separate from the polymer covering of the first end region and the polymer covering of the second end region.

12. 2. The stent of claim 1, wherein the plurality of covering strips are positioned along the first end region, the plurality of covering strips completely covering the first end region in the radially collapsed configuration, and the plurality of covering strips are configured to separate from one another in the radially expanded configuration to expose portions of the first end region of the radially expandable tubular framework therebetween.

13. 13. The stent of claim 12, further comprising one or more tie strings attached to the plurality of covering strips in the radially collapsed configuration, the one or more tie strings being removable from the plurality of covering strips to allow the first end regions to radially expand to the radially expanded configuration.

14. a radially expandable tubular framework having a radially outer surface, a radially inner surface, a first end region, a second end region, an intermediate region positioned between the first end region and the second end region, and a lumen extending through the radially expandable tubular framework, the radially expandable tubular framework being configured to expand from a radially collapsed configuration to a radially expanded configuration; a first polymer coating completely covering the first end region; a second polymer coating completely covering the second end region; and a plurality of covering strips positioned along the intermediate region, the covering strips being configured to, in the radially collapsed configuration, completely cover the intermediate region of the radially expandable tubular framework between the first polymeric coating and the second polymeric coating, and to separate from one another in the radially expanded configuration to expose a portion of the intermediate region of the radially expandable tubular framework therebetween; A stent comprising:

15. Implanting a stent across a stricture in a body lumen, said stent comprising: a radially expandable tubular framework having a radially outer surface, a radially inner surface, a first end region, a second end region, an intermediate region positioned between the first end region and the second end region, and a lumen extending through the radially expandable tubular framework; a plurality of covering strips positioned along at least one of the first end region, the intermediate region, and the second end region; implanting a stent; allowing the stent to initially expand to a first radially expanded configuration within the body lumen when initially implanted across the stenosis, the plurality of covering strips completely covering the radially expandable tubular framework in the first radially expanded configuration; allowing the stent to further radially expand within the body lumen from the first radially expanded configuration to a second radially expanded configuration over a period of time, the plurality of covering strips separating from one another in the second radially expanded configuration to expose portions of the radially expandable tubular framework therebetween; A method of using a stent comprising:

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