The present disclosure pertains to medical devices, methods for manufacturing medical devices, and uses thereof. More particularly, the present disclosure pertains to a stent for implantation in a body lumen, and associated methods.
Implantable medical devices (e.g., expandable stents) may be designed to treat a variety of medical conditions in the body. For example, some expandable stents may be designed to radially expand and support a body lumen and/or provide a fluid pathway for digested material, blood, or other fluid to flow therethrough following a medical procedure. Some medical devices may include radially or self-expanding stents which may be implanted transluminally via a variety of medical device delivery systems. These stents may be implanted in a variety of body lumens such as coronary or peripheral arteries, the esophageal tract, gastrointestinal tract (including the intestine, stomach and the colon), tracheobronchial tract, urinary tract, biliary tract, vascular system, etc.
In some instances it may be desirable to design stents to include sufficient flexibility and elongation properties while maintaining sufficient radial force and diameter to open the body lumen at the treatment site. However, in some stents, the elongation, compressible and flexible properties that assist in stent delivery may also result in a stent that reduces in diameter and tends to migrate from its originally deployed position. For example, stents to be positioned in the gastrointestinal tract must maintain a desired diameter and be resistant to kinking when bent, particularly at angles of 90 degrees or more. Additionally, the generally moist and inherently lubricious environment of the digestive and biliary tracts further contributes to a stent's tendency to migrate when deployed therein.
Therefore, in some instances it may be desirable to design a stent with the ability to elongate while maintaining a constant diameter and to resist kinking when bending. Examples of medical devices including such features are disclosed herein.
This disclosure provides design, material, manufacturing method, and use alternatives for medical devices. An example stent configured to change in length while maintaining a constant inner diameter includes a tubular member having a proximal end, a distal end, and a longitudinal axis extending therebetween, the tubular member comprising a knitted filament forming a plurality of twisted knit stitches with rungs extending circumferentially between adjacent twisted knit stitches, wherein each twisted knit stitch is interconnected with a longitudinally adjacent twisted knit stitch forming a series of linked stitches, the tubular member configured to automatically radially expand from a constrained configuration during delivery to a radially expanded configuration, wherein when in the radially expanded configuration, the tubular member has a first length and a first inner diameter and is configured to be stretched to an elongated configuration having a second length and a second inner diameter, and wherein the first length is shorter than the second length and the first and second inner diameters are substantially the same.
Alternatively or additionally to the embodiment above, the second length is at least 200% or more of the first length.
Alternatively or additionally to any of the embodiments above, the first length is about 50 mm to about 60 mm and the second length is about 100 mm to about 160 mm.
Alternatively or additionally to any of the embodiments above, when in the radially expanded configurations the series of linked stitches defines a helix, the helix having a first angle relative to the longitudinal axis when the tubular member is at the first length and a second angle relative to the longitudinal axis when the tubular member is at the second length, wherein the first angle is larger than the second angle.
Alternatively or additionally to any of the embodiments above, when in the constrained configuration for delivery, the series of linked stitches defines longitudinal columns.
Alternatively or additionally to any of the embodiments above, each of the plurality of twisted knit stitches includes a loop portion and a crossed base region.
Alternatively or additionally to any of the embodiments above, each of the plurality of twisted knit stitches is formed by a single filament defining the loop portion and the crossed base region.
Alternatively or additionally to any of the embodiments above, the loop portion of at least some of the twisted knit stitches is wrapped around the crossed base region of the longitudinally adjacent twisted knit stitch.
Alternatively or additionally to any of the embodiments above, the stent further comprises a first suture threaded through at least some of the twisted knit stitches at the distal end and a second suture threaded through at least some of the twisted knit stitches at the proximal end of the tubular member.
An example stent assembly includes a stent having a proximal end, a distal end, and a longitudinal axis extending therebetween, the stent comprising a knitted filament forming a plurality of twisted knit stitches with rungs extending circumferentially between radially adjacent twisted knit stitches, wherein each twisted knit stitch is interconnected with a longitudinally adjacent twisted knit stitch forming a series of linked stitches, the stent configured to automatically radially expand from a constrained configuration during delivery to a radially expanded configuration, wherein when in the radially expanded configuration, the stent has a first length and a first inner diameter and is configured to be stretched to an elongated configuration having a second length and a second inner diameter, wherein the first length is shorter than the second length and the first and second inner diameters are substantially the same, and a delivery device including an outer sleeve and an inner shaft slidable within the outer sleeve, the inner shaft having a distal tip and at least one capture element, wherein the at least one capture element is configured to move between a first configuration positioned adjacent the inner shaft when constrained within the outer sleeve, and a second configuration extending radially outward from the inner shaft when released from the outer sleeve.
Alternatively or additionally to any of the embodiments above, the at least one capture element includes at least one hook.
Alternatively or additionally to any of the embodiments above, the at least one hook includes a first distally facing hook and a second proximally facing hook.
Alternatively or additionally to any of the embodiments above, the at least one capture element includes a plurality of distally facing hooks and a plurality of proximally facing hooks.
Alternatively or additionally to any of the embodiments above, the at least one hook includes a first hook coupled to a second hook.
Alternatively or additionally to any of the embodiments above, the first hook extends through an opening in the second hook.
Alternatively or additionally to any of the embodiments above, the at least one capture element is biased in the second configuration.
Alternatively or additionally to any of the embodiments above, the at least one capture element extends radially 5 mm or more from an outer surface of the inner shaft in the second configuration.
An example method of supporting a body lumen at a stricture includes delivering a stent within the body lumen with a central region of the stent disposed across the stricture, radially expanding the stent to a radially expanded configuration in the body lumen, wherein the stent includes a tubular member having a distal end and a proximal end and a longitudinal axis extending therebetween, the tubular member comprising a knitted filament forming a plurality of twisted knit stitches with rungs extending circumferentially between adjacent twisted knit stitches, wherein each twisted knit stitch is interconnected with a longitudinally adjacent twisted knit stitch forming a series of linked stitches, the tubular member having a first length and a first inner diameter in the radially expanded configuration, and thereafter, stretching the stent within the body lumen to a radially expanded and elongated configuration having a second length, wherein the second length is greater than the first length.
Alternatively or additionally to any of the embodiments above, the stent has a second inner diameter in the radially expanded and elongated configuration, wherein the second inner diameter is substantially the same as the first inner diameter.
Alternatively or additionally to any of the embodiments above, the second length is at least 200% or more of the first length.
The above summary of some embodiments is not intended to describe each disclosed embodiment or every implementation of the present disclosure. The Figures, and Detailed Description, which follow, more particularly exemplify these embodiments.
The disclosure may be more completely understood in consideration of the following detailed description of various embodiments in connection with the accompanying drawings, in which:
While the disclosure is amenable to various modifications and alternative forms, specifics thereof 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 aspects of the disclosure to the particular embodiments described. On the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the scope of the disclosure.
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 numeric values are herein assumed to be modified by the term “about”, whether or not explicitly indicated. The term “about” generally refers to a range of numbers that one of skill in the art would consider equivalent to the recited value (i.e., having the same function or result). In many instances, the term “about” may be indicative as including numbers that are rounded to the nearest significant figure.
The recitation of numerical ranges by endpoints includes all numbers within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5).
Although some suitable dimensions, ranges and/or values pertaining to various components, features and/or specifications are disclosed, one of skill in the art, incited by the present disclosure, would understand desired dimensions, ranges and/or values may deviate from those expressly disclosed.
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 generally employed in its sense including “and/or” unless the content clearly dictates otherwise.
The following detailed description should be read with reference to the drawings in which similar elements in different drawings are numbered the same. The detailed description and the drawings, which are not necessarily to scale, depict illustrative embodiments and are not intended to limit the scope of the disclosure. The illustrative embodiments depicted are intended only as exemplary. Selected features of any illustrative embodiment may be incorporated into an additional embodiment unless clearly stated to the contrary.
A variety of self-expanding and balloon-expandable stents are available. Currently available braided and knitted stents offer good radial strength with minimal foreshortening which is desired for esophageal tracheo-bronchial, biliary, and colonic applications. However, the currently available stents often lack the desired degree of conformability for some anatomical applications. For example, braided stents do not tend to conform to bends in the anatomy and instead tend to straighten the vessel or lumen in which they are placed.
Additionally, currently available braided and knitted stents are often manufactured to span a specified diameter and length. For example, 20 mm diameter stents may be available in lengths of 60 mm, 80 mm, 100 mm, 120 mm, and 150 mm. Stents with other diameters may also be provided in a similar number of lengths. This variety of sizes of stents may create increased operational overhead based on the need for specific tooling to cover many stent sizes, increased clinical storage requirements for individual stent sizes often without regard to how popular or requested a particular size may be. As the matrix of available stent sizes is large, often physicians and/or hospitals will purchase select sizes. For example, a hospital might stock large, medium and small stent sizes for a particular application, with the physicians choosing from this reduced matrix when treating their patients. This may result in a stricture that would ideally require a different sized stent being treated with a larger or smaller device because it is available. This may occur in hospitals in order to reduce the costs of stocking the entire matrix of stent sizes and may result in less than desirable results when the physician selects a stent size based on availability rather than the specific needs of the patient and procedure.
An example where stent size selection is of particular importance is in biliary applications. The biliary tree has many side ducts and/or branches which the physician generally wishes to avoid blocking with a stent. At the same time, the physician requires the stent to be long enough to fully span and relieve the stricture with the ends of the stent appropriately positioned, such as for the proximal end of the stent to protrude through the ampulla into the duodenum while the distal end of the stent is positioned distal of the stricture. Correct sizing of the stent in such a procedure is important to the successful outcome of the procedure.
An alternative knitted self-expanding stent is desired that is capable of delivery via a coaxial delivery system to a torturous anatomical bend or other anatomical location, having similar conformability, radial forces, and foreshortening as previous parallel knitted stent configurations, but resists migration and kinking. While the embodiments disclosed herein are discussed with reference to biliary and intestinal 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: bodily tissue, bodily organs, vascular lumens, non-vascular lumens and combinations thereof, such as, but not limited to, in the coronary or peripheral vasculature, trachea, bronchi, urinary tract, prostate, brain, stomach and the like.
The stent 10 may be fabricated from at least one filament 24 defining open cells 25 and twisted knit stitches 22. In some examples, the stent 10 may be formed from only a single filament 24 intertwined with itself to form open cells 25 and twisted knit stitches 22. In some cases, the filament 24 may be a monofilament, while in other cases the filament 24 may be two or more filaments wound, braided, or woven together. In some instances, an inner and/or outer surface of the stent 10 may be entirely, substantially or partially, covered with a polymeric covering or coating. The covering or coating may extend across and/or occlude one or more, or a plurality of the open cells 25 and twisted knit stitches 22 defined by the filament 24. The covering or coating may help reduce tissue ingrowth.
It is contemplated that the stent 10 can be made from a number of different materials such as, but not limited to, metals, metal alloys, shape memory alloys and/or polymers, as desired, enabling the stent 10 to be expanded into shape when accurately positioned within the body. In some instances, the material may be selected to enable the stent 10 to be removed with relative ease as well. For example, the stent 10 can be formed from alloys such as, but not limited to, Nitinol and Elgiloy®. Depending on the material selected for construction, the stent 10 may be self-expanding (i.e., configured to automatically radially expand when unconstrained). In some embodiments, fibers may be used to make the stent 10, which may be composite fibers, for example, having an outer shell made of Nitinol having a platinum core. It is further contemplated the stent 10 may be formed from polymers including, but not limited to, polyethylene terephthalate (PET). In some instances, the filaments of the stent 10, or portions thereof, may be bioabsorbable or biodegradable, while in other instances the filaments of the stent 10, or portions thereof, may be biostable. The stent 10 may be self-expanding. As used herein the term “self-expanding” refers to the tendency of the stent to return to a preprogrammed diameter when unrestrained from an external biasing force (for example, but not limited to a delivery catheter or sheath). In some instances, in the expanded configuration as shown in
In some embodiments, the stent 10 may have a uniform outer diameter from the distal end 14 to the proximal end 16 when in the relaxed, expanded configuration, as shown in
The distal end 14 of the stent 10 may be defined by a series of free loop portions 30. In some embodiments, a first tether or suture 27 may be threaded through at least some of the free loop portions 30 at the distal end 14 and a second suture 27 may be coupled to the proximal end to facilitate elongation of the stent 10. The suture 27 coupled to the proximal end of the stent 10 may also be used for removing the stent, if so desired. The size of the free loop portions 30 at the proximal end may be increased or decreased to increase or decrease, respectively, the amount of tissue ingrowth at the proximal end achieved upon implantation of the stent 10.
In the expanded configuration, the rungs 26 define an outer surface 40 of the stent 10 and the crossed base regions 32 of the twisted knit stitches 22 extend radially outward from the outer surface 40, as shown in
The space between the raised helical ridges 34 may define channels 38 extending between crests 36 of adjacent raised helical ridges 34. The channels 38 may provide a drainage feature for the stent 10. The raised helical ridges 34 may engage the tissue wall, while leaving at least a portion of the channels 38 spaced from the tissue wall, providing for drainage of fluid along the entire length of the stent 10. A covering or graft disposed over the stent or within the lumen may aid in defining the channels 38.
When migration forces (arrow 44), such as peristalsis when the stent 10 is disposed within the esophagus or intestine, are exerted in a distal direction on the stent 10, the wave crest 36 provides resistance by pushing into the vessel wall 46, and the pocket 37 engages a portion of the vessel wall 46, as seen in
The twisted knit stitches 22, and in particular, the loop portions 30 may be configured to match the level of tissue ingrowth desired and/or required. For example, increased tissue ingrowth may be achieved by increasing the number of loop portions 30 around the circumference of the stent 10. The pitch and/or angle of the helices may also be increased, and the size of the loop portions 30 may be altered. The configuration of the loop portions 30 may have a more pronounced effect on the tissue ingrowth in stents having a bare metal composition, devoid of any covering or graft.
The peristaltic motion in the esophagus and intestines occurs along the longitudinal surface of the vessel wall. Existing parallel knitted stents have raised loops in a straight formation along the entire length of the stent. The forces transferred to such stents by peristalsis is thus constantly exerted on the entire length of the stent. However, due to the helical ridges 34 of the stent 10, there is no direct transfer of force along the entire length of the stent. Instead, the vessel wall 46 exhibits force on the raised ridge 34 of the stent 10, but the force is intermittent, because no force is transferred to the outer surface 40 defined by the rungs 26 of the stent 10.
The configuration of the knit pattern as shown in
Elongation of the disclosed knitted pattern, as shown in
Another stent 10 with a length profile at the larger end of the spectrum often medically desired may be provided, such as a stent with a first length L1 of 120 mm in a radially expanded, relaxed configuration and an elongated (or stretched) length L2 of 300 mm in a radially expanded, elongated configuration, where the stent may have a constant inner diameter in both configurations. Providing the stent 10 in multiple diameters would further increase the variety of sizes covered by only a few stent sizes.
The inner diameter D1/D2 may be defined by an inner surface of the rungs 26. The stent 10 may thus have a first longitudinal length L1 and a first inner diameter D1 in the radially expanded, axially relaxed configuration (
The elongation characteristics of the stent 10 may allow the physician to vary the length of the stent in situ while maintaining the expanded diameter and the radial force of the stent constant. Namely, the stent 10 may be radially expanded in a body lumen, and thereafter, medical personnel may elongate or stretch the expanded stent 10 to a desired elongated length from its initial length when first expanded in the body lumen.
In addition to the biliary tract, the flexibility of the stent 10 may provide advantages for use in the enteral anatomy. As shown in
Stenting of the colonic flexures with conventional stents has been recognized as problematic due to issues in correct stent placement. A conventional stent, if placed incorrectly, may be susceptible to migration due to non-symmetry of the stent across the stricture or the use of a stent that is too short and offers insufficient scaffold on one or both sides of the stent. Additionally, stent end stenosis often occurs with conventional stents placed in these regions as the stent is placed at an approximately 90-degree angle which may cause the stent to attempt to straighten out, causing abrasion of the contacting vessel wall. The ability of the physician to vary the length of the stent 10 without compromising the radial characteristics of the stent 10 makes the stent 10 particularly suitable for use in these locations with an improved outcome. The stent 10 is very flexible, which also is beneficial for this application.
As shown in
As an alternative to the grasper or forceps 170 used to elongate the stent, another grasping instrument is incorporated into a stent delivery system. The stent delivery system includes an engagement element configured to engage the sutures, or other structure, on the distal and/or proximal ends of the stent 10, as illustrated in
The capture element 120 may include any desired structure configured to engage the suture 27 and/or other structure of the stent 10. In some embodiments, the capture element 120 may include at least one hook 129. In one embodiment, the capture element 120 includes both a first distally facing hook 129 and a second proximally facing hook 129, as shown in
In other embodiments, the capture element 120 may include a plurality of distally facing hooks 121 and/or a plurality of proximally facing hooks 122, as shown in
The stents, delivery systems, and the various components thereof, as described above, may be made from a metal, metal alloy, polymer (some examples of which are disclosed below), a metal-polymer composite, ceramics, combinations thereof, and the like, or other suitable material. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, 304L, and 316LV stainless steel; mild steel; nickel-titanium alloy such as linear-elastic and/or super-elastic 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, and the like; cobalt-chromium alloys; cobalt-chromium-molybdenum alloys; platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material.
Some examples of suitable polymers for the stents or delivery systems may include polytetrafluoroethylene (PTFE), ethylene tetrafluoroethylene (ETFE), fluorinated ethylene propylene (FEP), polyoxymethylene (POM, for example, DELRIN® available from DuPont), polyether block ester, polyurethane (for example, Polyurethane 85A), polypropylene (PP), polyvinylchloride (PVC), polyether-ester (for example, ARNITEL® available from DSM Engineering Plastics), ether or ester based copolymers (for example, butylene/poly(alkylene ether) phthalate and/or other polyester elastomers such as HYTREL® available from DuPont), polyamide (for example, DURETHAN® available from Bayer or CRISTAMID® available from Elf Atochem), elastomeric polyamides, block polyamide/ethers, polyether block amide (PEBA, for example available under the trade name PEBAX®), ethylene vinyl acetate copolymers (EVA), silicones, polyethylene (PE), Marlex high-density polyethylene, Marlex low-density polyethylene, linear low density polyethylene (for example REXELL®), polyester, polybutylene terephthalate (PBT), polyethylene terephthalate (PET), polytrimethylene terephthalate, polyethylene naphthalate (PEN), polyetheretherketone (PEEK), polyimide (PI), polyetherimide (PEI), polyphenylene sulfide (PPS), polyphenylene oxide (PPO), poly paraphenylene terephthalamide (for example, KEVLAR®), polysulfone, nylon, nylon-12 (such as GRILAMID® available from EMS American Grilon), perfluoro(propyl vinyl ether) (PFA), ethylene vinyl alcohol, polyolefin, polystyrene, epoxy, polyvinylidene chloride (PVdC), poly(styrene-b-isobutylene-b-styrene) (for example, SIBS and/or SIBS 50A), polycarbonates, ionomers, biocompatible polymers, other suitable materials, or mixtures, combinations, copolymers thereof, polymer/metal composites, and the like.
In at least some embodiments, portions or all of the stents or delivery systems may also be doped with, made of, or otherwise include a radiopaque material. Radiopaque materials are generally understood to be materials which are opaque to RF energy in the wavelength range spanning x-ray to gamma-ray (at thicknesses of <0.005″). These materials are capable of producing a relatively dark image on a fluoroscopy screen relative to the light image that non-radiopaque materials such as tissue produce. This relatively bright image aids the user of the stents or delivery systems in determining its location. Some examples of radiopaque materials can include, but are not limited to, gold, platinum, palladium, tantalum, tungsten alloy, polymer material loaded with a radiopaque filler, and the like. Additionally, other radiopaque marker bands and/or coils may also be incorporated into the design of the stents or delivery systems to achieve the same result.
It should be understood that this disclosure is, in many respects, only 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 that it is appropriate, the use of any of the features of one example embodiment being used in other embodiments. The disclosure's scope is, of course, defined in the language in which the appended claims are expressed.
This application claims the benefit of U.S. Provisional Patent Application Ser. No. 63/254,683, filed Oct. 12, 2021, which is incorporated herein by reference.
Number | Date | Country | |
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63254683 | Oct 2021 | US |