Stents, systems, and methods for gastrointestinal treatment

Abstract

The present invention generally relates to stents, systems, and methods for gastrointestinal treatment. In some embodiments, a stent can include a tubular framework having opposing first and second ends, wherein a lumen extends between the first and second ends. The tubular framework can include a flared section and an intermediate section extending from the flared section, wherein a first diameter of the flared section is greater than a second diameter of the intermediate section. The stent can also include a liner extending partially along a surface of the tubular framework, wherein the liner is spaced apart from an anchoring region of the flared section to promote tissue ingrowth with the flared section.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims the benefit of priority under 35 U.S.C. §119 to U.S. Provisional Patent Application No. 62 / 875,267, filed on July 17, 2019, which is incorporated herein by reference in its entirety for all purposes. Technical Field

[0003] The present invention relates to implantable medical devices and, more particularly, to stents, systems and methods for gastrointestinal treatment. Background Art

[0004] Implantable medical devices, such as expandable stents, can be designed to provide access for digestive materials, blood or other fluids to flow therethrough after medical procedures. In addition, some implantable medical devices can incorporate features that facilitate fistula treatment, bypass surgery and / or anastomosis. These implantable medical devices can include radial or self-expanding stents that can be implanted via an endoscope through the lumen. Additionally, some stents can be implanted in various body cavities, such as the esophagus, gastrointestinal tract (e.g., intestines, stomach, and colon), tracheobronchial tubes, urinary tract, biliary tract, vascular system, etc.

[0005] In some stents, the compressible and flexible properties that help the stent position may also cause the stent to migrate. For example, a stent designed to be positioned in the esophagus or gastrointestinal tract may have a tendency to migrate due to peristalsis (which is the involuntary contraction and relaxation of the muscles of the esophagus, intestines and colon). Additionally, the generally moist and inherently lubricated environment of the esophagus, intestines, colon, etc. further promotes the tendency of the stent to migrate after deployment. One way to reduce stent migration includes exposing the bare metal portion of the stent to the body cavity tissue. The skeleton of the stent can provide a structure that promotes tissue ingrowth with the structure to promote a proliferative reaction.

[0006] Additionally, after deployment, some stents can be later removed from or repositioned within a body lumen. One way to reduce the force required to remove a stent includes providing a cover over a portion of the stent, thereby creating a physical barrier between the body lumen and the outer surface of the stent to reduce tissue ingrowth. However, covered stents may be more susceptible to migration than bare stents, as discussed above. Summary of the Invention

[0007] The present invention, in its various embodiments, generally relates to stents, systems, and methods for gastrointestinal treatment. In one or more embodiments, the stent may include a tubular framework having a first end opposite a second end, wherein a lumen extends between the first and second ends. The tubular framework may include a flared section; a middle section extending from the flared section, wherein the flared section has a diameter greater than a diameter of the middle section; and a liner extending partially along a surface of the tubular stent, wherein the liner is spaced apart from an anchoring region of the flared section to promote tissue ingrowth into the flared section. In some embodiments, the liner is spaced apart from an intermediate anchoring region of the middle section to promote tissue ingrowth into the middle section. In some embodiments, the intermediate anchoring region is disposed in a flared portion of the middle section, and wherein the flared portion has a third diameter greater than the diameter of the middle section. In some embodiments, the liner is spaced apart from the flared portion to promote tissue ingrowth into the flared portion. In some embodiments, the anchoring region is positioned along an inclined portion of the flared section, and wherein the inclined portion extends away from a central longitudinal axis extending through the lumen. In some embodiments, the middle section has a substantially uniform diameter. In some embodiments, the flared section has a first skeletal morphology, wherein the intermediate section has a second skeletal morphology, and wherein the first and second skeletal morphologies are different.

[0008] In one or more embodiments, a system may include a stent comprising a tubular skeleton having a first end opposite a second end, wherein a lumen extends between the first end and the second end. The tubular stent may include a flared section and an intermediate section extending from the flared section, wherein a first diameter of the flared section is greater than a second diameter of the intermediate section. The stent may further include a liner extending partially along a surface of the tubular stent, wherein the liner is spaced apart from an anchoring region of the flared section to promote tissue ingrowth with the flared section. The system may further include a sheath extending from the second end of the tubular skeleton, the sheath having a proximal end opposite a distal end, wherein the lumen extends between the proximal and distal ends. In some embodiments, the system may include a second stent coupled to the distal end of the sheath. In some embodiments, the second stent may include a second tubular skeleton and a second liner extending partially along a surface of the second tubular skeleton. In some embodiments, the second tubular skeleton may include a second flared section, and a second intermediate section extending from the second flared section, wherein the first diameter of the second flared section is greater than the second diameter of the second intermediate section, and wherein the second liner is spaced apart from the second anchoring region of the second flared section to promote tissue ingrowth with the second flared section. In some embodiments, the liner is spaced apart from the intermediate anchoring region of the intermediate section to promote tissue ingrowth with the intermediate section. In some embodiments, the anchoring region is positioned along an inclined portion of the flared section, and wherein the inclined portion extends away from a central longitudinal axis extending through the cavity. In some embodiments, the intermediate section includes an expansion portion having a third diameter greater than the diameter of the intermediate section. In some embodiments, the liner is spaced apart from the expansion portion to promote tissue ingrowth with the expansion portion. In some embodiments, the sheath includes a structural support element.

[0009] In one or more embodiments, a method may include deploying a system within a patient's gastrointestinal (GI) tract, the system comprising a stent having a tubular skeleton, the tubular skeleton having a first end opposite a second end, wherein a lumen extends between the first end and the second end. The tubular skeleton may include a flared section and an intermediate section extending from the flared section, wherein the diameter of the flared section is greater than the diameter of the intermediate section. The stent may also include a liner extending partially along a surface of the tubular stent, wherein the liner is spaced apart from an anchoring region of the flared section, and wherein the anchoring region is exposed to the GI tract to promote tissue ingrowth between the anchoring region and the GI tract. The method may also include positioning the flared section along one side of a GI tract target site and positioning the intermediate section directly adjacent to the GI tract target site. In some embodiments, the method may also include determining a location of the GI tract target site, wherein the GI tract target site corresponds to a leak in the GI tract. In some embodiments, the method may also include bypassing a portion of the GI tract using a sheath extending from the second end of the tubular skeleton, the sheath having a proximal end opposite a distal end, wherein the lumen extends between the proximal and distal ends. In some embodiments, the method can include securing a second stent within the GI tract, the second stent coupled to the distal end of the sheath.

[0010] One or more of the various features outlined above may be interchanged, exchanged, combined, or substituted with other features outlined above for use in conjunction with the medical systems and methods outlined above and with respect to the embodiments described in more detail below and otherwise within the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] Non-limiting embodiments of the present invention are described by way of example with reference to the accompanying drawings, which are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown is generally represented by a single numeral. For clarity, not every component is labeled in every figure, and not every component of every embodiment is shown unless a description is necessary for one skilled in the art to understand the present invention. In addition, some figures include cross-sectional views in "slice" form or "close-up" cross-sectional views, omitting certain background lines or other features that would be visible in a "true" cross-sectional view in order to achieve clarity of illustration. In the drawings:

[0012] Figures 1A to 1C is a side view of a bracket according to an embodiment of the present invention;

[0013] Figure 2 Depicts a stent within the GI tract of a patient according to an embodiment of the present invention;

[0014] Figure 3 is a side view of a bracket according to an embodiment of the present invention;

[0015] Figures 4A to 4Eis a side view of a stent having various expansion portions according to an embodiment of the present invention;

[0016] Figure 5A is a side view of a bracket including a liner having a concave portion according to an embodiment of the present invention;

[0017] Figure 5B According to an embodiment of the present invention Figure 5A Cross-sectional view of the bracket and liner;

[0018] Figure 6A is a side view of a bracket including a liner having a concave portion according to an embodiment of the present invention;

[0019] Figure 6B is similar to Figure 6A and a cross-sectional view of a bracket and liner according to an embodiment of the present invention;

[0020] Figure 6C is a side view of a bracket including a liner having a concave portion according to an embodiment of the present invention;

[0021] Figure 7 is a perspective view of a system according to an embodiment of the present invention;

[0022] Figure 8A A device placed in the GI tract during restrictive weight loss therapy according to an embodiment of the present invention is shown. Figure 7 system;

[0023] Figure 8B A device for treating a leak placed in the GI tract according to an embodiment of the present invention is shown. Figure 7 system;

[0024] Figure 9A A system is shown for placement within the GI tract during restrictive weight loss therapy according to an embodiment of the present invention;

[0025] Figure 9B A system for placement in the GI tract for treating a leak according to an embodiment of the present invention is shown;

[0026] Figure 10 A system for placement in the GI tract for treating a leak according to an embodiment of the present invention is shown;

[0027] Figure 11 is a side perspective view of a sheath according to an embodiment of the present invention;

[0028] Figure 12 is a side perspective view of a sheath according to an embodiment of the present invention;

[0029] Figure 13is a side perspective view of a system according to an embodiment of the present invention;

[0030] Figure 14A is a side perspective view of a bracket according to an embodiment of the present invention;

[0031] Figure 14B According to an embodiment of the present invention Figure 14A a side cross-sectional view of a stent;

[0032] Figure 14C According to an embodiment of the present invention Figure 14A a side cross-sectional view of a stent;

[0033] Figure 15A is a side view of a system according to an embodiment of the present invention;

[0034] Figure 15B Demonstrates the use of an embodiment of the present invention within the GI tract Figure 15A systems; and

[0035] Figure 16 is a flowchart of a method according to an embodiment of the present invention. DETAILED DESCRIPTION

[0036] The present invention is not limited to the specific embodiments described herein. The terminology used herein is intended only to describe specific embodiments and is not intended to limit the scope of the appended claims. Unless otherwise specified, all technical terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs.

[0037] As described above, self-expanding metal stents (SEMS) are widely used in a minimally invasive manner throughout the gastrointestinal (GI) tract to treat a variety of disease states, including but not limited to vascular lumen closure (e.g., stenosis due to tumor growth, surgical reasons, etc.) and GI bypass complications (e.g., post-weight loss leakage treatment). SEMS can be removable or permanent, depending on the disease state being treated, where removability is generally defined by the presence or absence of a durable coating. Permanent SEMS may not have a coating that, when placed in the GI tract, allows vascular tissue to grow inward due to stimulated vascular proliferation. Ultimately, due to tissue ingrowth, the SEMS is embedded in place.

[0038] As further described herein, embodiments of the present invention provide stents, systems, and methods for treating GI tract diseases to achieve a consistent and repeatable manner for resisting migration to treat a variety of potential conditions. In some embodiments, the stent may include a tubular backbone having a first end opposite a second end, wherein a lumen extends between the first end and the second end. The tubular backbone may include a flared section and an intermediate section extending from the flared section, wherein the diameter of the flared section is greater than the diameter of the intermediate section. The stent may also include a liner extending partially along a surface of the tubular backbone, wherein the liner is spaced apart from an anchoring region of the flared section to promote tissue ingrowth with the flared section.

[0039] Now turn Figure 1A , a stent 100 according to an embodiment of the present invention will be described in greater detail. As shown, the stent 100 can include a tubular skeleton (hereinafter referred to as "skeleton") 102 having a first end 104 opposite a second end 106. The skeleton 102 can define a lumen 105 between the first end 104 and the second end 106, such as extending along a central longitudinal axis 108. When positioned in a body lumen, such as the GI tract of a patient, the first end 104 (in this case, the proximal end) can be positioned proximate the patient's mouth.

[0040] Additionally, the stent 100 can include one or more strut members 109 forming the tubular backbone 102. The strut members 109 can extend helically, longitudinally, circumferentially, or otherwise along the stent 100. Figure 1A The strut members 109 are shown extending substantially along the entire length of the stent 100 , but in other examples, the strut members 109 may extend along only a portion of the stent 100 .

[0041] As further shown, the skeleton 102 can include a flange or flared section 110 connected to or integrally formed with the intermediate section 112. In some embodiments, the first diameter "D1" of the flared section 110 can be greater than the second diameter "D2" of the intermediate section 112. As shown, the intermediate section 112 can have a diameter that is substantially uniform along its length. The flared section 110 can include an inclined portion 114 extending away from the central longitudinal axis 108. In some embodiments, the inclined portion 114 is at the intersection between the flared section 110 and the intermediate section 112.

[0042] In some embodiments, the stent 100 can be balloon expandable or self-expanding. Examples of self-expanding stents can include a stent having one or more strut members 109 that are combined to form a rigid and / or semi-rigid stent structure. For example, the strut members 109 can be one or more wires or filaments that are braided, wrapped, wound, interwoven, braided, woven, wrapped (e.g., hexagonal mesh), etc. to form the skeleton 102. Alternatively, the stent 100 can be a unitary structure formed from a cylindrical tubular member, such as a single cylindrical tubular laser-cut nitinol tubular member, wherein the remainder of the tubular member forms the strut members 109. Openings or gaps through the wall of the stent 100 can be defined between adjacent strut members 109.

[0043] The stent 100 can be constructed from a variety of non-limiting materials. For example, when balloon expandable or self-expandable, the stent 100 can be constructed from a metal (e.g., Nitinol, Elgiloy, stainless steel, cobalt-chromium, positive temperature coefficient of resistivity, etc.). In other examples, the stent 100 can be constructed from a polymer material (e.g., polyethylene terephthalate, poly(methyl methacrylate)). In other examples, the stent 100 can be constructed from a combination of metal and polymer materials. In other examples, the stent 100 can include a bioabsorbable and / or biodegradable material (e.g., a poly(lactic-co-glycolic acid) polymer).

[0044] like Figure 1B As shown, the stent 100 can include a liner 120 extending between the first end 104 and the second end 106. The liner 120 can be provided to maintain a passage through the stent 100 and to prevent tissue ingrowth along the skeleton 102 in certain areas. In the non-limiting embodiment shown, the liner 120 can be formed on an outer surface 122 of the skeleton 102. However, the liner 120 can be formed only partially along the exterior of the skeleton 102, as will be described in more detail herein. In other embodiments, the liner 120 can be formed along an inner surface 124 of the skeleton 102. In other embodiments, the liner 120 can be formed along both the outer and inner surfaces 124 of the skeleton.

[0045] In various embodiments, the liner 120 may be a polymer material such as silicone, polyurethane, polyvinylidene fluoride (PVDF), or a similar biocompatible polymer formulation. In other embodiments, the liner 120 can include a ciliated coating along its inner surface (not shown). As shown, the liner 120 can extend between the strut members 109, thereby filling any space between adjacent strut members 109 of the skeleton 102. Reference to a liner can be understood as a coating, wherein a portion of the coating is coupled to at least a portion of the stent, and a portion of the coating can float relative to the stent.

[0046] In some embodiments, the liner 120 is spaced apart from the anchoring region 125 of the flared section 110 to promote tissue ingrowth between the GI tract and the anchoring region 125 of the flared section 110. For example, the liner 120 at the anchoring region 125 can extend radially inward toward the central longitudinal axis 108 such that the liner 120 is not substantially in contact with the inner surface 124 of the skeleton 102. As a result, the anchoring region 125 can promote or allow tissue ingrowth to anchor the flared section 110 in place within the GI tract.

[0047] In some embodiments, the liner 120 can include an elastic material component configured to stretch radially inward, for example, when tissue grows through the interstices of the framework in the anchoring region 125. The liner 120 can deflect, stretch, etc. radially inward in response to an inward force acting thereon (e.g., tissue ingrowth).

[0048] In other embodiments, it may be desirable to limit the amount of inward deflection of liner 120. For example, liner 120 may define a cavity extending therein, wherein the cavity is designed to allow food and / or other digestible matter to flow therethrough. Thus, in some cases, it may be desirable to design liner 120 to preserve the passageway defined by cavity 105. In other words, in some cases, it may be desirable to prevent or minimize the amount of radial closing of liner 120. In some cases, liner 120 may include reinforcing filaments (e.g., fibers) embedded in the material of liner 120 that can be tightened after the material of liner 120 stretches a threshold amount to prevent further stretching of liner 120. In some cases, the reinforcing filaments may be arranged longitudinally, circumferentially, helically, randomly, or in other ways.

[0049] Examples of liners and stent / liner configurations may include, but are not limited to, those shown and described in U.S. Patent Application Publication No. US2018 / 0250118, filed on March 1, 2018, and entitled “Esophageal Stent Including Liner,” and U.S. Patent Application Publication No. US2018 / 0280167, filed on March 27, 2018, and entitled “Retrievable Stent System,” both of which are incorporated herein by reference in their entirety and for all purposes.

[0050] like Figure 1CAs shown, the skeleton 102 can include multiple segments joined together. For example, the middle segment 112 can include a first component 128 coupled to a second component 130. The first and second components 128, 130 can be joined together using any type of attachment method. In the non-limiting embodiment shown, the strut members 109 of the first component 128 can be arranged in a first configuration, e.g., woven, while the strut members 109 of the second component 130 can be arranged in a second configuration, e.g., braided. In some embodiments, the first component 128 and the second component 130 can have the same or different braid patterns. The embodiments herein are not limited in this context.

[0051] Figure 2 A depiction of a stent 100 in use within a patient's GI tract 132, according to an embodiment of the present invention. In this non-limiting example, the GI tract 132 may include sutures 131, for example, as a result of a sleeve gastrectomy. As shown, the stent 100 can be deployed to a GI tract target site 134, which can correspond to a leak, perforation, or tear along the sutures 131. As shown, the flared section 110 can be positioned within a proximal section of the GI tract 132, in this case, the patient's esophagus, while the intermediate section 112 can extend further down into the GI tract 132, in this case, the gastric remnant. An anchoring region 125 of the flared section 110 can be positioned adjacent to the GI tract 132 to promote tissue ingrowth between the GI tract 132 and the flared section 110. Simultaneously, the liner 120 along the intermediate section 112 can be positioned directly adjacent to the GI tract target site 134 to prevent or minimize leaks.

[0052] Figure 3 A stent 300 is shown according to an embodiment of the present invention. The stent 300 may be the same as or similar to the stent 100 described above in many aspects. Therefore, for the sake of brevity, only certain aspects of the stent 300 are described below.

[0053] As shown, stent 300 may include a backbone 302 having opposing first and second ends 304, 306. Backbone 302 may define a cavity 305 extending between first and second ends 304, 306, such as along a central longitudinal axis 308. Backbone 302 may include a flared section 310 connected to or integrally formed with a middle section 312. Flared section 310 may include an angled portion 314 extending away from central longitudinal axis 308. In some embodiments, angled portion 314 couples flared section 310 to middle section 312.

[0054] As shown, the middle section 312 can include a middle anchoring region 335, which is an exposed portion of the skeleton 302 for promoting tissue ingrowth between the middle section 312 and the GI tract. As shown, the liner 320 extending along the skeleton 302 can be spaced apart from the middle anchoring region 335 to promote tissue ingrowth. In some embodiments, the liner 320 at the middle anchoring region 335 can extend radially inward toward the central longitudinal axis 308. The liner 120 can also be spaced apart from the anchoring region 325 of the flared section 310 to promote tissue ingrowth between the GI tract and the flared section 310. In some embodiments, the anchoring region 325 is positioned along the inclined portion 314. Once inserted into the patient, the anchoring region 325 of the flared section 310 can be positioned along one side (e.g., above) a GI tract target site (not shown), while the middle anchoring region 335 of the middle section 312 can be positioned adjacent to and / or below the GI tract target site to isolate leakage at the GI tract target site.

[0055] Figure 4A A stent 400 is shown according to an embodiment of the present invention. Stent 400 may be the same or similar in many respects to stents 100 and / or 200 described above. Therefore, for the sake of brevity, only certain aspects of stent 400 are described below.

[0056] As shown, the stent 400 may include a skeleton 402 having opposing first and second ends 404, 406. The skeleton 402 may define a cavity 405 extending between the first and second ends 404, 406, such as along a central longitudinal axis 408. A liner 420 may be disposed along the skeleton 402. The skeleton 402 may include a flared section 410 connected to or integrally formed with a middle section 412. In some embodiments, the first diameter "D1" of the flared section 410 may be greater than the second diameter "D2" of the middle section 412. The flared section 410 may include an inclined portion 414 extending away from the central longitudinal axis 408. In some embodiments, the inclined portion 414 couples the flared section 410 to the middle section 412.

[0057] As shown, the middle section 412 can include an intermediate anchoring region 435, which can be a bare spot / area along the backbone 402 to promote tissue ingrowth between the middle section 412 and the GI tract. In some embodiments, the intermediate anchoring region 435 can be disposed at a flared portion 440 of the middle section 412. As shown, the flared portion 440 can have a third diameter "D3" that is greater than D2 of the middle section 412. The flared portion 440 can have a curvature, for example, flaring radially outward from the middle section 412 such that the third diameter D3 is the maximum diameter of the curvature. In some embodiments, D3 can also be greater than D1 of the flared section 410. In other embodiments, D3 is equal to or less than D1. The embodiments herein are not limited in this context.

[0058] As further shown, the liner 420 extending along the skeleton 402 can be spaced apart from the flared portion 440 to promote tissue ingrowth along certain portions of the middle section 412, such as at the middle anchoring region 435. In some embodiments, the liner 420 positioned radially inward from the flared portion 440 can bend or extend toward the central longitudinal axis 408. In other embodiments, as shown, the liner 420 can be generally straight at the flared portion 440. Once inserted into the patient, the anchoring region 425 of the flared section 410 can be positioned along one side (e.g., above) of a GI tract target site (not shown), while the flared portion 440 of the middle section 412 can be positioned at or below the GI tract target site. The anchoring region 425 can secure the flared section 410 within the GI tract, while the flared portion 440 can interact with the GI tract target site to promote a proliferative response from GI tract tissue. In some embodiments, the distal portion 442 of the intermediate section 412 can extend from the dilation portion 440 to act as a conduit around a target site in the GI tract.

[0059] It should be understood that the expansion portion 440 can take on a variety of different forms. For example, Figure 4A The expansion portion 440 may have a generally spherical cross-section, Figure 4B The expansion portion 440B may have a generally trapezoidal cross-section, Figure 4C The expansion portion 440C may have a substantially pentagonal cross-section, and Figure 4D The expansion portion 440D may have a generally chord-shaped cross-section. The embodiments herein are not limited in this context.

[0060] Furthermore, it should be understood that the length of each expansion portion 440A to 440E can be modified to affect the amount of interaction between the intermediate anchoring region 435 and the GI tract. Figure 4EAs shown, the length "L1" of the expanded portion 440E can be increased relative to the overall length "L2" of the intermediate section 412. As will be appreciated, tissue ingrowth of the GI tract generally increases with increasing length L1.

[0061] Now turn Figures 5A to 5B , the liner 520 of the stent 500 according to an embodiment of the present invention will be described in more detail. As shown, the liner 520 can have a non-circular cross-section to promote tissue ingrowth between the skeleton 502 of the stent 500 and the GI tract. In this embodiment, the liner 520 can include a concave section 550 spaced from the inner surface 524 of the skeleton 502. The concave section 550 can provide a middle anchoring region 535 of the skeleton 502. In some embodiments, the middle anchoring region 535 can be disposed at the expanded portion 540 of the middle section 512. In other embodiments, the middle section 512 can have a generally uniform diameter along its length.

[0062] exist Figures 6A to 6B In the embodiment of the present invention, the liner 620 of the stent 600 may include a plurality of recessed sections 650 spaced apart from the inner surface 624 of the skeleton 602 of the stent 600. The recessed sections 650 may be spaced apart circumferentially along the liner 620 (at Figure 6A and Figure 6B 6 (shown as non-limiting examples in various configurations) can provide a plurality of intermediate anchoring regions 635 along the backbone 602 to promote tissue ingrowth between the backbone 602 and the intermediate section 612. In some embodiments, the intermediate anchoring regions 635 can be disposed at the flared portion 640 of the intermediate section 612. In other embodiments, the intermediate section 612 can have a generally uniform diameter along its length.

[0063] In other embodiments, Figure 6C As shown, the expanded portion 640 of the middle section 612 may not include the liner 620. Instead, the expanded portion 640 remains exposed to promote hyperplastic tissue growth 627 between the body cavity (not shown) and the exposed portion of the scaffold 602. The hyperplastic tissue growth 627 can act as a seal to form a continuous passage through the interior of the scaffold 602.

[0064] Now turn Figure 7 , a system 701 according to an embodiment of the present invention will be described in greater detail. As shown, system 701 can include a stent 700 having a tubular skeleton (hereinafter referred to as "skeleton") 702. Stent 700 can be the same as or similar to stents 100, 300, 400, 500, and 600 described above in many aspects. Therefore, for the sake of brevity, only certain aspects of stent 700 will be described below.

[0065] As shown, the stent 700 can include a first flared section 710 at a first end 704 and a second flared section 711 at a second end 706. An intermediate section 712 is located between the first flared section 710 and the second flared section 711. As shown, the intermediate section 712 can have a reduced diameter compared to the diameters of the first and second flared sections 710, 711. As further shown, the stent 700 can include a lining 720 disposed along a surface of the framework 702.

[0066] In some embodiments, a sheath 760 can be coupled to the second end 706 of the stent 700. The sheath 760 can be a flexible tube having a proximal end 762 and a distal end 764, the sheath 760 defining a lumen extending between the proximal end 762 and the distal end 764. Although non-limiting, the sheath 760 can be silicone, UE, PTFE, ePTFE, Chronoflex, PMMA, PVDF, etc.

[0067] As further shown, the system 701 can include a second stent 765 coupled to the distal end 764 of the sheath 760. In some embodiments, the second stent 765 can include a second tubular skeleton (hereinafter referred to as the "second skeleton") 768 defined by a plurality of stent members 769 arranged in any of a variety of configurations. The second skeleton 768 of the stent 765 can have a constant diameter or a varying diameter. For example, in the latter case, the second skeleton 768 can include a first flared section 770 connected to or integrally formed with a second intermediate section 772. In some embodiments, the second tubular skeleton 768 can include a second flared section 773 extending from opposite sides of the second intermediate section 772. In some embodiments, the diameters of the first and second flared sections 770, 773 of the second skeleton 768 are greater than the diameter of the second intermediate section 772. The embodiments herein are not limited in this context.

[0068] Although not shown, a second liner can extend along a surface (e.g., interior and / or exterior) of the second skeleton 768. In some embodiments, the second liner can be spaced apart from the second skeleton 768 in one or more second anchoring regions to promote tissue ingrowth between the second skeleton 768 and the patient's GI tract. In other embodiments, no liner is present along the second skeleton 768.

[0069] Figures 8A to 8B An example use of system 701 within a patient's GI tract 732 is shown, although not limiting, according to an embodiment of the present invention. Figure 8A System 701 is shown for restrictive bariatric treatment positioned within GI tract 732. As shown, sheath 760 can bypass a portion of GI tract 732. Figure 8BA system 701 for treating a gastrocutaneous fistula is shown. As shown, a stent 700 can be positioned within a proximal segment of a GI tract 732, while a sheath 760 extends further down into the GI tract 732. An anchoring region 725 of a flared segment 710 can be positioned directly adjacent to the interior of the GI tract 732 to promote tissue ingrowth between the GI tract 732 and the flared segment 710.

[0070] A second stent 765 coupled to sheath 760 can also be positioned within GI tract 732, e.g., beneath its pyloric region 780. In some embodiments, second stent 765 can include one or more second anchoring regions (not shown) to promote tissue growth between GI tract 732 and second scaffold 768.

[0071] In some embodiments, system 701 may not include a second stent coupled to sheath 760. For example, Figures 9A to 9B As shown, the stent 700 can be positioned within the proximal section of the GI tract 732, while the sheath 760 can extend further down into the GI tract 732. In some embodiments, the sheath 760 can extend beyond the pyloric region 780 of the GI tract 732. Although non-limiting, Figure 9A A system 701 is shown for placement within the GI tract 732 for restrictive weight loss therapy. Figure 9B A system 701 is shown for treating a leak, such as an enterocutaneous fistula, an enterocutaneous fistula, a complex fistula, etc. Figure 9A As shown, the sheath 760 can be extended further along the GI tract 732, for example, into the duodenum 782 (also known as a gastrojejunal bypass (GJ bypass)).

[0072] Now turn Figure 10 , a system 701 will be described for use in a patient according to an embodiment of the present invention. Although non-limiting, the system 701 may be particularly effective during restrictive weight loss treatment using, for example, a gastro-jejunal bypass. As shown, the stent 700 can be positioned within a proximal segment of the GI tract 732, and the sheath 760 can extend through the patient's stomach 781. A second stent 765 coupled to the sheath 760 can also be positioned within the GI tract 732, for example, between the stomach 781 and the duodenum 782 extending from the stomach 781. As shown, the second backbone 768 of the second stent 765 can be positioned such that the first flared section 770 is located within the stomach 781 and the second flared section 773 is located within the duodenum 782. The second intermediate section 772 can extend between the first flared section 770 and the second flared section 773, thereby creating a bypass between the stomach 781 and the duodenum 782. Although not shown in Figure 10770, the second liner 775 may extend through the second intermediate section 772. Additionally, one or more anchoring regions may be positioned along the first flared section 770, the second flared section 773, and / or the second intermediate section 772 to secure the second stent 765 in place between the stomach 781 and the duodenum 782.

[0073] exist Figure 11 , a sheath 1160 is shown in accordance with an embodiment of the present invention. The sheath 1160 can include a structural support element 1183 extending along the length of the sheath 1160, for example, between the proximal end 1162 and the distal end 1164. In some embodiments, the structural support element 1183 can be a spiral or helical rib extending along the sheath 1160. The structural support element 1183 can be disposed along the inner and / or outer surface of the sheath 1160, or can be embedded within the sheath 1160, for example, between one or more layers thereof. The structural support element 1183 can provide rigidity to the sheath 1160. In a non-limiting embodiment, the structural support element 1183 can be made of a reinforced, thickened, or tubular hollow, tubular solid natural polymer, or a denser polymer strip. Additionally or alternatively, the structural support element can include sections of a more rigid material, for example, nitinol, stainless steel, or the like.

[0074] exist Figure 12 , a sheath 1260 according to an embodiment of the present invention is shown. Sheath 1260 can include a flexible section 1284 disposed between a proximal end 1262 and a distal end 1264. In some embodiments, flexible section 1284 comprises a length of corrugated material arranged as a series of ridges 1285 and grooves 1286. Flexible section 1284 can provide flexibility to sheath 1260. In some embodiments, flexible section 1284 can include one or more structural support members. In a non-limiting embodiment, the series of ridges 1285 and grooves 1286 of the corrugated material can correspond to the plurality of corrugations formed in sheath 1260. The series of ridges 1285 and grooves 1286 can also be formed by placing strips of alternating density or thickness adjacent to each other. Alternatively or additionally, the series of ridges 1285 and grooves 1286 can be formed by placing alternating strips of polymer layers and strips of different elastic layers adjacent to each other. Alternatively or additionally, the series of ridges 1285 and grooves 1286 may be formed from embedded ribs made of a material such as Nitinol, stainless steel, or the like.

[0075] Now turn Figure 13 , a system 1301 according to an embodiment of the present invention will be described. System 1301 can be the same as or similar to system 701 described above in many aspects. Therefore, for the sake of brevity, only certain aspects of system 1301 are described below.

[0076] As shown, system 1301 may include a first stent 1300 and a second stent 1365 coupled together by a first sheath 1360. For example, a first end 1362 of first sheath 1360 may be coupled to first stent 1300, while a second end 1364 of first sheath 1360 may be coupled to second stent 1365. In some embodiments, first sheath 1360 may be a flexible conduit defining a lumen. Although not limiting, first sheath 1360 may also include one or more structural support elements and / or flexible segments.

[0077] System 1301 can also include a second sheath 1388 extending from second stent 1365. Second sheath 1388 can include a proximal end 1389 coupled to second stent 1365 and a distal end 1390 extending further into the patient's GI tract. Second sheath 1388 can be the same as or similar to first sheath 1360. In other embodiments, second sheath 1388 can differ from first sheath 1360, for example, depending on the intended location of use within the patient's GI tract. Although not shown, it should be understood that additional stents can be connected to second sheath 1388, for example, at its distal end 1390.

[0078] As shown, first stent 1300 may include a first flared section 1310 at first end 1304 and a second flared section 1311 at second end 1306. An intermediate section 1312 is located between first flared section 1310 and second flared section 1311. As shown, intermediate section 1312 may have a reduced diameter compared to the diameters of first and second flared sections 1310, 1311. A first sheath 1360 may extend from and be coupled to second end 1306 of first stent 1300.

[0079] In some embodiments, the first stent 1300 can include a lining 1320 disposed along a surface of the backbone 1302. The lining 1320 can also be spaced apart from anchoring regions 1325 along the backbone 1302 to promote tissue ingrowth with the GI tract. Although not limiting, the anchoring regions 1325 can be disposed along the first flared section 1310, the second flared section 1311, and / or the intermediate section 1322.

[0080] As further shown, in some embodiments, the second stent 1365 can be the same as or similar to the first stent 1300. For example, the second backbone 1368 of the second stent 1365 can include a first flared section 1370 and a second flared section 1373 connected by a second intermediate section 1372. In some embodiments, the second liner 1375 can extend along a surface (e.g., interior and / or exterior) of the second backbone 1368. The second liner 1375 can be spaced apart from the second backbone 1368 in one or more second anchoring regions 1379 to promote tissue ingrowth between the second backbone 1368 and the GI tract. Although not limiting, the second anchoring regions 1379 can be provided along the first flared section 1370, the second flared section 1373, and / or the second intermediate section 1372.

[0081] Now turn 14A to 14C , a stent 1400 according to an embodiment of the present invention will be described in more detail. As shown, a skeleton 1402 of the stent 1400 can have opposing first and second ends 1404, 1406, wherein the skeleton 1402 defines a cavity extending between the first and second ends 1404, 1406, such as along a central longitudinal axis 1408.

[0082] Stent 1400 may include one or more strut members 1409 forming a tubular skeleton 1402 ( Figure 14A ). The strut members 1409 can extend helically, longitudinally, circumferentially, or otherwise along the stent. As further shown, the backbone 1402 can include a first flared / flange section 1410 and a second flared / flange section 1411 connected to or integrally formed with the intermediate section 1412. In some embodiments, the diameter of the first and / or second flared sections 1410, 1411 can be greater than the diameter of the intermediate section 1412. As shown, the intermediate section 1412 can generally have a uniform diameter along its length.

[0083] In some embodiments, the stent 1400 can be balloon expandable or self-expanding. Examples of self-expanding stents can include a stent having one or more strut members 1409 that are combined to form a rigid and / or semi-rigid stent structure. For example, the strut members 1409 can be wires or filaments that are braided, wrapped, wound, interwoven, braided, woven, wrapped (e.g., hexagonal mesh), etc. to form the stent structure. Alternatively, the stent 1400 can be a unitary structure formed from a cylindrical tubular member, such as a single cylindrical tubular laser-cut nitinol tubular member, with the remainder of the tubular member forming the strut members 1409. Openings or gaps through the wall of the stent 1400 can be defined between adjacent strut members 1409.

[0084] The stent 1400 in the examples disclosed herein can be constructed from a variety of materials. For example, when balloon expandable or self-expandable, the stent 1400 can be constructed from a metal (e.g., Nitinol, Elgiloy, etc.). In other examples, the stent 1400 can be constructed from a polymer material (e.g., PET). In other examples, the stent 1400 can be constructed from a combination of metal and polymer materials. In other examples, the stent 1400 can include a bioabsorbable and / or biodegradable material.

[0085] As further shown, the stent 1400 can include a lining 1420 that extends partially along the skeleton 1402. In the non-limiting embodiment shown, the lining 1420 can be formed along an inner surface 1424 of the skeleton 1402. In other embodiments, the lining 1420 can be formed along an outer surface 1422 of the skeleton 1402. In other embodiments, the lining 1420 can be formed along both the outer surface 1422 and the inner surface 1424 of the skeleton 1402.

[0086] In addition, the liner 1420 can include one or more layers bonded together, wherein the liner 1420 is positioned along the skeleton 1402 to prevent or minimize tissue ingrowth. In some examples, the liner 1420 can be an elastomeric or non-elastomeric material. As shown, the liner 1420 can extend between the strut members 1409, thereby filling any space between adjacent strut members 1409 of the skeleton 1402.

[0087] In some embodiments, the liner 1420 is connected to the backbone 1402 along the first flared / flange section 1410 and the second flared / flange section 1411 and is spaced apart from the anchoring region 1425 of the middle section 1412 to promote tissue ingrowth between the GI tract and the backbone 1402 of the middle section 1412. For example, the liner 1420 at the anchoring region 1425 can extend radially inward toward the central longitudinal axis 1408 such that the liner 1420 does not substantially contact the inner surface 1424 of the backbone 1402 along the middle section 1412. Figure 14B As shown, the anchoring region 1425 can extend substantially along the entire length of the intermediate section 1412. Figure 14C As shown, the anchoring region 1425 can extend along only a portion of the middle section 1412. It will be appreciated that the dimensions of the anchoring region 1425 can be selected to increase or decrease the amount of tissue ingrowth between the middle section 1412 and the GI tract. The embodiments herein are not limited in this context.

[0088] Now turn FIG. 15A to FIG. 15B, a system 1501 according to an embodiment of the present invention will be described. As shown, the system 1501 can include a stent 1500 coupled to a sheath 1560. The stent 1500 can be the same or substantially the same as the stent 1400 described above. Figure 15B As shown, stent 1500 can be used to connect a patient's stomach 1581 and duodenum 1582, with sheath 1560 extending further into duodenum 1582. More specifically, backbone 1502 of stent 1500 can be positioned such that first flared section 1510 is located within stomach 1581, while second flared section 1511 is located within duodenum 1582. Intermediate section 1512 can extend between first flared section 1510 and second flared section 1511, thereby creating a bypass between stomach 1581 and duodenum 1582.

[0089] Lining 1520( Figure 15A ) can extend through the middle section 1512. The liner 1520 can be spaced apart from the inner surface 1522 of the skeleton 1502 to create one or more anchoring regions 1525 along the middle section 1512. The anchoring regions 1525 can promote tissue growth to secure the stent 1500 in place between the stomach 1581 and the duodenum 1582, for example, across the pyloric valve 1587, as shown. Figure 15B What is shown.

[0090] In some embodiments, the sheath 1560 can be a length of corrugated material that extends through the duodenum 1582. The corrugated material can be defined by a series of ridges 1585 and grooves 1586, wherein the corrugated material can provide flexibility to the sheath 1560 to traverse the duodenum 1582. In some embodiments, the corrugated material can also act as a lining to inhibit nutrient absorption, such as for treating diabetes and / or promoting weight loss.

[0091] Figure 16 is a flow chart of a method 1600 according to an embodiment of the present invention. At block 1601, method 1600 may include determining a location of a GI tract target site, wherein the GI tract target site corresponds to a defect of the GI tract.

[0092] At box 1603, method 1600 may include deploying a system within the GI tract of a patient, wherein the system includes a stent having a tubular skeleton, the tubular skeleton including a flared section and an intermediate section extending from the flared section, wherein the tubular skeleton may further include a liner extending partially along a surface of the tubular skeleton, wherein the liner is spaced apart from an anchoring region of the flared section, and wherein the anchoring region is exposed to the GI tract to promote tissue ingrowth between the anchoring region and the GI tract.

[0093] At box 1605, method 1600 may include positioning the flared section along one side of the GI tract target site and positioning the intermediate section directly adjacent to the GI tract target site. In some embodiments, mucosal stripping at the insertion site within the GI tract is used to promote tissue ingrowth between one or more regions or sections of the stent, such as the anchoring region and the GI tract, such as to mitigate migration of the stent from the target site. In some embodiments, method 1600 may further include bypassing a portion of the GI tract using a sheath extending from a second end of the tubular stent, the sheath having a proximal end opposite the distal end, wherein a lumen extends between the proximal and distal ends. In some embodiments, method 1600 may further include securing a second stent within the GI tract, the second stent being coupled to the distal end of the sheath. In some embodiments, mucosal stripping at the insertion site within the GI tract is used to promote tissue ingrowth between one or more regions or sections of the second stent, such as the anchoring region and the GI tract, such as to mitigate migration of the second stent from the target site.

[0094] The stents described herein can be made of 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 polymers can include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, e.g., available from DuPont), ), polyether block esters, polyurethanes (e.g., polyurethane 85A), polypropylene (PP), polyvinyl chloride (PVC), polyether esters (e.g., available from DSM Engineering Plastics), ), ether or ester based copolymers (e.g., butylene / poly(alkylene ether) phthalate and / or other polyester elastomers such as those available from DuPont ), polyamide (e.g., available from Bayer Or available from Elf Atochem ), elastomeric polyamides, block polyamide / ethers, polyether block amides (PEBA, for example, available under the trade name commercially available), ethylene vinyl acetate copolymer (EVA), silicone, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low-density polyethylene (e.g., ), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polypropylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS)), polyphenylene oxide (PPO), polyparaphenylene terephthalamide (e.g., ), polysulfone, nylon, nylon-12 (such as available from EMS American Grilon ), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefins, polystyrene, epoxy resins, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (e.g., SIBS and / or SIBS 50A), polycarbonate, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers, polymer / metal composites, etc. In some embodiments, the sheath can be blended with a liquid crystal polymer (LCP). For example, the blend can contain up to about 6% LCP.

[0095] 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 (e.g., UNS: N06625, such as 625, UNS:N06022, such as UNS:N10276, such as other alloys, etc.), nickel-copper alloys (e.g., UNS: N04400, such as 400, 400, 400, etc.), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035, such as etc.), nickel-molybdenum alloys (e.g., UNS: N10665, such as ALLOY ), 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, etc.; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys (e.g., UNS: R30003, such as etc.); platinum-rich stainless steel; titanium; combinations thereof; etc.; or any other suitable material.

[0096] In at least some embodiments, part or all of the stent and other components of the stent described herein may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are understood to be capable of producing a relatively bright image on a fluoroscopic screen or with another imaging technique during a medical procedure. This relatively bright image helps the user determine the position of the stent. Some examples of radiopaque materials may include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloys, polymer materials loaded with radiopaque fillers, and the like. Additionally, other radiopaque marker bands and / or coils may also be incorporated into the design of the stent to achieve the same result.

[0097] In some embodiments, a degree of magnetic resonance imaging (MRI) compatibility is imparted to the stents described herein. For example, the stent and other components of the stent or portions thereof can be made of materials that do not substantially distort images and create substantial artifacts (e.g., gaps in the image). The stent can also be made of materials that can be imaged by an MRI machine. Some materials that exhibit these properties include, for example, tungsten, cobalt-chromium-molybdenum alloys (e.g., UNS: R30003, such as etc.), nickel-cobalt-chromium-molybdenum alloys (e.g. UNS: R30035, such as etc.), Nitinol, etc.

[0098] The expressions "coupled" and "connected," and their derivatives, may be used to describe some embodiments. These terms are not intended to be synonymous with each other. For example, some embodiments may be described using the terms "connected" and / or "coupled" to indicate that two or more elements are in direct physical or electrical contact with each other. However, the term "coupled" may also mean that two or more elements are not in direct contact with each other, but still cooperate or interact with each other.

[0099] As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will also be understood that when used herein, the terms "comprises" and / or "includes" or "includes" and / or "includes" specify the presence of stated features, regions, steps, elements and / or components, but do not preclude the presence or addition of one or more other features, regions, integers, steps, operations, elements, components and / or groups.

[0100] In addition, the terms "substantially" or "substantially" and the terms "approximately" or "approximately" can be used interchangeably in some embodiments and can be described using any relevant measurement value acceptable to a skilled person. For example, these terms can be used as a comparison to a reference parameter to indicate a deviation that will still provide the intended function. Although not limiting, the deviation from the reference parameter can be, for example, less than 1%, less than 3%, less than 5%, less than 10%, less than 15%, less than 20%, etc.

[0101] Although specific embodiments have been shown and described herein, it should be understood that any arrangement calculated to achieve the same purpose may be substituted for the specific embodiments shown. The present invention is intended to cover any and all adaptations or modifications of the various embodiments. It should be understood that the above description is provided in an illustrative manner, not a restrictive manner. Upon reviewing the above description, combinations of the above embodiments and other embodiments not specifically described herein will be apparent to those skilled in the art. Therefore, the scope of the various embodiments includes any other applications in which the above compositions, structures, and methods are used.

[0102] Furthermore, although the illustrative method 1600 is described above as a series of actions or events, unless otherwise specified, the present invention is not limited by the illustrated ordering of these actions or events. For example, according to the present invention, some actions may occur in a different order and / or concurrently with other actions or events other than those shown and / or described herein. Furthermore, not all illustrated actions or events are required to implement a method according to the present invention.

[0103] Although the subject matter has been described in language specific to structural features and / or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

1. A system for gastrointestinal treatment, comprising: A stent comprising a tubular skeleton having a longitudinal extension, the tubular skeleton having opposite first and second ends and an anchoring region along the longitudinal extension, and defining a lumen extending between the first and second ends, the tubular skeleton comprising: a flared section; and an intermediate section extending from the flared section; wherein the shape of the anchoring region is different from the shape of the region of the tubular skeleton proximal to the anchoring region and the shape of the region of the tubular skeleton distal to the anchoring region; and the diameter of the flared section is larger than the diameter of the middle section; and a liner extending at least partially along the tubular framework, wherein a portion of the liner co-located along the longitudinal extension of the tubular framework with an anchoring region of the tubular framework is spaced from and positioned within the anchoring region to promote tissue ingrowth between the anchoring region and regions of the tubular framework proximal and distal to the anchoring region; and A sheath extends from the second end of the tubular framework, the sheath having opposing proximal and distal ends with a lumen extending therebetween. 2 . The system of claim 1 , further comprising a second stent coupled to the distal end of the sheath.

3. The system of claim 2, wherein the second bracket comprises: a second tubular skeleton; as well as A second liner extends partially along a surface of the second tubular skeleton.

4. The system of claim 3, wherein the second tubular skeleton comprises: a second flared section; as well as A second intermediate section extends from the second flared section, wherein the first diameter of the second flared section is greater than the second diameter of the second intermediate section, and wherein the second liner is spaced apart from the second anchoring region of the second flared section to promote tissue ingrowth with the second flared section.

5. The system of any one of claims 1 to 4, wherein the liner is spaced apart from a middle anchoring region of the middle section to promote tissue ingrowth with the middle section.

6. The system of any one of claims 1 to 4, wherein the anchoring region is located along an inclined portion of the flared section, and wherein the inclined portion extends radially away from a central longitudinal axis extending through the lumen.

7. The system of any one of claims 1 to 4, wherein the intermediate section includes a flared portion having a third diameter greater than the second diameter of the intermediate section.

8. The system of claim 7, wherein the liner is spaced apart from the expansion portion to promote tissue ingrowth with the expansion portion.

9. The system of any one of claims 1 to 4, wherein the sheath comprises a structural support element.

10. The system of claim 9, wherein the structural support elements are helical fins extending along the jacket.

11. The system of any one of claims 1 to 4, the sheath comprising a flexible section comprising a series of ridges and grooves.

12. The system of any one of claims 1 to 4, wherein the liner includes one or more recessed sections spaced circumferentially along the liner.

13. The system of any one of claims 1 to 4, wherein the intermediate section comprises a first component coupled to a second component.

14. The system of any one of claims 1 to 4, wherein the flared section of the tubular skeleton is a flange extending radially from the intermediate section.

15. The system of claim 1, wherein the intermediate section has a substantially constant diameter along its length.

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