Tracheal stents may include a plurality of wave form structures each extending radially about the support structure, a plurality of axial loop members extending axially between adjacent wave form structures and a polymeric covering disposed thereover. Tracheal stents may include an expandable metal structure and a plurality of spacer fins extending above an outer surface of the expandable metal structure. The plurality of spacer fins may be formed of a material different than that of the expandable metal structure.

TECHNICAL FIELD

The present disclosure pertains to medical devices, and methods for manufacturing medical devices. More particularly, the present disclosure pertains to endoprostheses such as tracheal stents.

BACKGROUND

An endoprosthesis may be configured to be positioned in a body lumen for a variety of medical applications. For example, an endoprosthesis may be used to treat a stenosis in a blood vessel, used to maintain a fluid opening or pathway in the vascular, urinary, biliary, tracheobronchial, esophageal or renal tracts, or to position a device such as an artificial valve or filter within a body lumen, in some instances. Bare or partially covered endoprostheses allow tissue ingrowth through the structure of the endoprosthesis to prevent migration of the endoprosthesis. However, if it is desired to remove the endoprosthesis at some later time, the ingrown tissue must be cut away, causing significant trauma to the body lumen. Fully covered stents, on the other hand, prevent tissue ingrowth to facilitate removal. However, fully covered endoprostheses are prone to migrate through the body lumen.

Accordingly, it is desirable to provide endoprostheses that exhibit anti-migration features, while reducing the trauma to the body lumen of the patient if removal of the endoprosthesis is desired.

BRIEF SUMMARY

The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies, and uses thereof.

In one example, a medical stent, such as a tracheal stent, extends from a first end to a second end and includes a support structure extending from the first end to the second end. The support structure includes a plurality of wave form structures each extending circumferentially about the support structure and a plurality of axial loop members extending axially between adjacent wave form structures and a polymeric covering disposed over the support structure. At least some of the plurality of axial loop members are configured to include an extended configuration in which the at least some of the plurality of axial loop members extend radially outward from an outer surface defined by the plurality of wave form structures.

Alternatively, or additionally, at least some of the wave form structures extend circumferentially about 360 degrees about the support structure and form closed rings.

Alternatively, or additionally, at least some of the wave form structures include a nickel-titanium alloy.

Alternatively, or additionally, at least some of the wave form structures are formed from nitinol wire.

Alternatively, or additionally, at least some of the wave structures are defined by a wire diameter that is in the range of about 0.2 millimeters (mm) to about 0.5 mm. Alternatively, or additionally, at least some of the wave form structures are defined by a wave frequency in the range of about 0.5 to about 4 waves per centimeter (cm) and a wave amplitude in the range of about 0.25 cm to about 1 cm.

Alternatively, or additionally, at least some of the plurality of axial loop members extend from a peak, a valley or a transition region of a wave form structure of the plurality of wave form structures to a peak, a valley or a transition region of an adjacent wave form structure of the plurality of wave form structures.

Alternatively, or additionally, the plurality of axial loop members provide the only direct connection between adjacent wave form structures of the plurality of wave form structures.

In another example, a support structure for an endoprosthesis has a first end, a second end and a lumen extending therebetween. The support structure includes a first wave form structure extending circumferentially about the support structure and defining a first closed ring, the first wave form structure formed of a first wire oscillating in a wave form having a first wave frequency and a first wave amplitude. The support structure includes a second wave form structure extending circumferentially about the support structure and defining a second closed ring, the second wave form structure formed of a second wire oscillating in a wave form having a second wave frequency and a second wave amplitude. An axial loop member extends from the first wave form structure to the second wave form structure and provides a connection between the first wave form structure and the second wave form structure and is configured to include an extended configuration in which the axial loop member extends radially outward from an outer surface defined by the first and second wave form structures.

Alternatively, or additionally, the first wave form structure and the second wave form structure are formed from nitinol wire.

Alternatively, or additionally, at least some of the wave structures are defined by a wire diameter that is in the range of about 0.2 mm to about 0.5 mm.

Alternatively, or additionally, at least some of the wave form structures are defined by a wave frequency in the range of about 0.5 to about 4 waves per cm and a wave amplitude in the range of about 0.25 cm to about 1 cm.

Alternatively, or additionally, in another example, the axial loop member extends from a peak, a valley or a transition region of the first wave form structure to a peak, a valley or a transition region of the second wave form structure.

In another example, a method of forming a support structure for an endoprosthesis having a first end, a second end and a lumen extending therebetween includes forming a first wave form structure from a first wire, the first wave form structure undulating side to side while extending circumferentially around to form a first closed ring. A second wave form structure is formed from a second wire, the second wave form structure undulating side to side while extending circumferentially around to form a second closed ring. An axial loop member having a first end and a second end is secured, the first end secured to the first wave form structure and the second end secured to the second wave form structure.

Alternatively, or additionally, the first wave form structure is formed on a mandrel.

Alternatively, or additionally, the second wave form structure is formed on a mandrel.

Alternatively, or additionally, the method further includes forming a plurality of additional wave form structures from a plurality of wires, each of the plurality of additional wave form structures undulating side to side while extending circumferentially around to form a plurality of additional closed rings.

Alternatively, or additionally, the method further includes securing a plurality of axial loop members between adjacent wave form structures of the plurality of additional wave form structures.

Alternatively, or additionally, the first wire and the second wire include a nitinol wire.

Alternatively, or additionally, the first end of the axial loop member is secured to the first wave form structure via welding.

In another example, a medical stent, such as a tracheal stent, extending from a distal end to a proximal end includes an expandable metal structure extending from the distal end to the proximal end, the expandable metal structure convertible between a compressed configuration for delivery and an expanded configuration once deployed, the expandable metal structure including an inner surface defining a stent lumen and an outer surface. A plurality of spacer fins extends above the outer surface of the expandable metal structure and are formed of a material different than that of the expandable metal structure.

Alternatively, or additionally, the plurality of spacer fins are formed of a biodegradable or bioabsorbable material.

Alternatively, or additionally, the plurality of spacer fins are formed from a filament that is interlaced within the expandable metal structure.

Alternatively, or additionally, the plurality of spacer fins are separately formed each having an end, and the ends of the plurality of spacer fins are encapsulated in a polymeric coating that is disposed over the expandable metal structure.

Alternatively, or additionally, the plurality of spacer fins include a cap secured to high spots formed within the expandable metal structure.

Alternatively, or additionally, at least some of the plurality of spacer fins are triangular in shape, with a base secured relative to the expandable metal structure and an apex extending above the base.

Alternatively, or additionally, the expandable metal structure comprises a laser cut expandable metal structure.

Alternatively, or additionally, the expandable metal structure includes a woven or braided expandable metal structure.

In another example, a medical stent, such as a tracheal stent, extending from a distal end to a proximal end includes an expandable metal structure extending from the distal end to the proximal end, the expandable metal structure convertible between a compressed configuration for delivery and an expanded configuration once deployed, the expandable metal structure including an inner surface defining a stent lumen and an outer surface. A biodegradable filament is interwoven through the expandable metal structure to form a plurality of biodegradable spacer fins extending above the outer surface of the expandable metal structure.

Alternatively, or additionally, the expandable metal structure includes a laser cut expandable metal structure.

Alternatively, or additionally, the expandable metal structure includes a woven or braided expandable metal structure.

Alternatively, or additionally, the biodegradable filament includes square or round shaped protruding caps.

Alternatively, or additionally, the biodegradable filament has a diameter in the range of about 0.1 cm to about 1 cm.

Alternatively, or additionally, at least some of the plurality of spacer fins are triangular in shape.

In another example, a medical stent, such as a tracheal stent, extending from a distal end to a proximal end includes an expandable metal structure extending from the distal end to the proximal end, the expandable metal structure convertible between a compressed configuration for delivery and an expanded configuration once deployed, the expandable metal structure including an inner surface defining a stent lumen and an outer surface. A polymeric coating is disposed over the expandable metal structure and a plurality of biodegradable spacer fins are secured relative to the polymeric coating, the plurality of biodegradable spacer fins extending above the outer surface of the expandable metal structure.

Alternatively, or additionally, at least some of the plurality of spacer fins are triangular in shape, with a base secured relative to the expandable metal structure and an apex extending above the base.

Alternatively, or additionally, the plurality of biodegradable spacer fins are separately formed each having an end, and the ends of the plurality of biodegradable spacer fins are encapsulated in the polymeric coating.

Alternatively, or additionally, the plurality of biodegradable spacer fins are formed of a biodegradable material comprising poly-1-lactide acid (PLLA) and/or poly(lactide-co-Glycoside 8515) (PLGA 8515).

Alternatively, or additionally, the plurality of biodegradable spacer fins have an average height, relative to the outer surface of the expandable metal structure, ranging from about 0.1 cm to about 0.5 cm.

Alternatively, or additionally, the polymeric coating includes silicone.

DETAILED DESCRIPTION

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. It will be appreciated that while the disclosure describes an airway or trachea stent, the features and elements described herein may be applied to any variety of endoprosthesis.

FIG. 1provides a schematic illustration of the torso of a patient10. The patient10includes a trachea12, a left main bronchus14and a right main bronchus16(relative to the patient's perspective). An endoprosthesis18may be seen in phantom, disposed within the right main bronchus16. It will be appreciated that this placement is merely for illustrative purposes, as the endoprosthesis18may be deployed elsewhere in the trachea12or even down into the bronchia (not illustrated). It will also be appreciated that while the endoprosthesis18is described herein as an airway stent, the endoprosthesis18may be deployed in a variety of other bodily lumens, including but not limited to the vascular, urinary, biliary, tracheobronchial, esophageal or renal tracts. Although illustrated as a stent, the endoprosthesis10may be any of a number of devices that may be introduced endoscopically, subcutaneously, percutaneously or surgically to be positioned within an organ, tissue, or lumen, such as a heart, artery, vein, urethra, esophagus, trachea, bronchus, bile duct, or the like.

A difficulty in placing an endoprosthesis in the trachea12is that the patient10may have a tendency to try and cough out the endoprosthesis18. The human respiratory system is designed, when encountering an obstacle or other foreign object, to try to move the obstacle out of the way. This may mean pushing the object farther down, to a position of relative safety. This may also mean trying to cough it out. The human body may try to forcibly eject the object. Accordingly, and in some embodiments, the endoprosthesis18may be configured to help hold the endoprosthesis18in place within the trachea12.

Another difficulty in placing an endoprosthesis in the trachea12is that the presence of a foreign object such as an endoprosthesis triggers an inflammatory response that produces mucus. Mucus can become trapped between the body of an endoprosthesis and the wall of the trachea12. Trapped mucus can stimulate or facilitate the growth of bacteria. Accordingly, and in some embodiments, the endoprosthesis18may be configured to provide air channels or voids by spacing at least a part of the endoprosthesis18away from the wall of the trachea12.

FIG. 2provides an illustration of a trachea stent20that may be deployed as shown with respect to the endoprosthesis18ofFIG. 1. InFIG. 2, the trachea stent20is shown on a mandrel30. The trachea stent20may include a support structure22extending from a first end24to a second end26. The support structure22may include one or more (a plurality are illustrated) wave form structures28that extend circumferentially about the support structure22. In some embodiments, the wave form structures28extend about 360 degrees about the support structure22and thus each of the wave form structures28may form closed loops. In some embodiments, each wave form structure28is formed independently of any other wave form structure28. The wave form structures28may be arranged axially adjacent one another along the length of the support structure22. In some embodiments, each wave form structure28may be formed on the mandrel30, by forming a wire into the sinusoidal pattern shown, having peaks oriented toward the first end24of the support structure22and valleys oriented toward the second end26of the support structure22.

The wave form structures28are joined together via connectors, such as one or more axial loop members32. In some embodiments, the axial loop members32(two are illustrated inFIG. 2) are the only physical connection between adjacent wave form structures28. It will be appreciated that, while not illustrated, the trachea stent20may include a polymeric coating or covering to prevent tissue ingrowth into the interior of the trachea stent20. The polymeric coating or covering, if present, may be disposed about an exterior of the support structure22, for example. The axial loop members32are shown in an extended configuration in which they extend radially outward from an outer surface34that is defined by the wave form structures28and the polymeric coating or covering, if present. While not illustrated, it will be appreciated that the support structure22may have a compressed configuration for delivery in which the axial loop members32flatten against the outer surface34.

The connectors or axial loop members32may be configured to engage a wall of a body lumen in the expanded state to inhibit migration of the endoprosthesis18subsequent to implanting the endoprosthesis18in the body lumen. For example, the connectors or axial loop members32may engage the tissue between cartilage rings within the tracheal anatomy to provide anti-migration support for the endoprosthesis18.

A space or opening may be defined between the connectors or axial loop member32and the outer circumference of the wave form structures28and/or overlaying polymeric coating or covering as viewed along the central longitudinal axis of the support structure22, as a result of the connectors or axial loop members32extending radially outward of or above the outer circumference of the wave form structures28and/or overlaying polymeric coating or covering. The space or opening may be unobstructed by any other structure of the endoprosthesis18. Accordingly, tissue ingrowth through these spaces or openings subsequent to implanting the endoprosthesis18may further secure the endoprosthesis18in place in the anatomy and prevent migration of the endoprosthesis18.

The support structure22may be formed of any suitable material. In some embodiments, the support structure22may be formed of a nickel-titanium alloy such as nitinol. In some embodiments, at least some of the wave form structures28may be formed of a nitinol or other wire having a wire diameter that is in the range of about 0.2 mm to about 0.5 mm. In some embodiments, at least some of the axial loop members32may be formed of a nitinol or other wire having a wire diameter that is in the range of about 0.25 mm to about 0.4 mm, which may be the same or different from the wire diameter used to form at least some of the wave form structures28.

FIG. 3provides an illustration of a portion of a wave form structure28. In some embodiments, at least some of the wave form structures28may be considered as undulating back and forth in a sinusoidal pattern. A sinusoidal pattern may be defined, at least in part, by a frequency and an amplitude. As illustrated, the wave form structure28may be considered as having a frequency that is in the range of about 0.5 to about 4 waves per cm. A wave may be defined as the distance or wavelength F between adjacent peaks. The wave form structure28may be considered as having an amplitude A, measured as the distance between peak and valley. In this, it will be appreciated that peaks and valleys are a matter of perspective. What appears as a peak from one side looks like a valley if viewing from the opposite side.

FIG. 4provides an illustration of two adjacent wave form structures28. One of the wave form structures (i.e., the first wave form structure) is labeled as28aand the adjacent wave form structure (i.e., the second wave form structure) is labeled as28b. To avoid confusion, each wave form structure28a,28bare labeled as having peaks P and valleys V. It will be appreciated that in connecting the axial loop members32to adjacent wave form structures28, there are a variety of different relative locations at which the axial loop members32may be connected. Each axial loop member32may be considered as having a first end36connected to the first wave form structure28aand a second end38connected to the adjacent second wave form structure28b.

InFIG. 4, an axial loop member32ais shown having its first end36secured to a peak P on the wave form structure28aand its second end38secured to a peak P on the wave form structure28b. An axial loop member32bis shown extending from an intermediate position I on the wave form structure28ato an intermediate position I on the wave form structure28b. An axial loop member32cis shown extending from a valley V on the wave form structure28ato a valley V on the wave form structure28b. An axial loop member32dis shown extending from a peak P on the wave form structure28ato a valley V on the wave form structure28b. It will be appreciated that these axial loop members32a,32b,32cand32d, are illustrative only, and are intended merely to illustrate the variety of available connection points. In alternative embodiments, the first end36of the axial loop member32may be secured at any desired location along the first wave form structure28awhile the second end38of the axial loop member32may be secured at any desired location along the second wave form structure28b.

FIG. 5provides a perspective illustration of a trachea stent40having a first end42and a second end44. The trachea stent40has an inner surface46defining a lumen48and an outer surface50. In some embodiments, as illustrated, the outer surface50includes a plurality of spacer fins52that extend above the outer surface50. In some embodiments, the spacer fins52are formed of a different material. In some embodiments, the spacer fins52are formed of a biodegradable or bioabsorbable material that will break down or dissolve over time once implanted. Accordingly, the spacer fins52may provide migration resistance upon implantation of the trachea stent40within a body lumen. Over time, the spacer fins52, which are formed of a biodegradable or bioabsorbable material, will break down or dissolve once implanted. Thereafter, if it is desired to remove the trachea stent40at a later time, the degradation or absorption of the spacer fins52will reduce the trauma experienced by the patient in removing the trachea stent40from the body lumen.

In some embodiments, the spacer fins52could also provide drug elution. The terms “therapeutic agents,” “drugs,” “bioactive agents,” “pharmaceuticals,” “pharmaceutically active agents”, and other related terms may be used interchangeably herein and include genetic therapeutic agents, non-genetic therapeutic agents, and cells. Therapeutic agents may be used singly or in combination. A wide range of therapeutic agent loadings can be used in conjunction with the devices of the present invention, with the pharmaceutically effective amount being readily determined by those of ordinary skill in the art and ultimately depending, for example, upon the condition to be treated, the nature of the therapeutic agent itself, the tissue into which the dosage form is introduced, and so forth.

Numerous additional therapeutic agents useful for the practice of the present invention may be selected from those described in paragraphs [0040] to [0046] of commonly assigned U.S. Patent Application Pub. No. 2003/0236514, the entire disclosure of which is hereby incorporated by reference.

While the spacer fins52are illustrated as being generally aligned along an axial length of the trachea stent40(i.e., generally parallel to a central longitudinal axis of the trachea stent40), it will be appreciated that in some embodiments, the spacer fins52could be aligned perpendicular or at an acute angle relative to an axial length of the trachea stent40(i.e., generally non-parallel to a central longitudinal axis of the trachea stent40, such as perpendicular to or at an acute angle to the central longitudinal axis of the trachea stent40), in order to limit migration in a particular direction, for example. Moreover, while the spacer fins52are shown as being generally triangular in shape, it will be appreciated that in some cases the spacer fins52may have other shapes, such as round or square.

FIG. 6provides a schematic cross-sectional view of the trachea stent40, illustrating that the trachea stent40may, in some embodiments, include an expandable metal structure54and a polymeric coating or sleeve56disposed over the expandable metal structure54. The expandable metal structure54is generically illustrated, as the expandable metal structure54may have any desired design and configuration. For example, in some embodiments, the expandable metal structure54may represent a laser cut structure that can be laser cut from a tube. In some embodiments, the expandable metal structure54may represent a wound metal structure. In some embodiments, the expandable metal structure54may represent a braided metal structure. In some embodiments, as shown inFIG. 6, the spacer fins52may be secured relative to the trachea stent40by encapsulating the spacer fins52within the polymeric coating or sleeve56. In some embodiments, the spacer fins52may have a base and an opposing apex positioned radially outward from the base, and the base of each of the spacer fins52may be encapsulated within the polymeric coating or sleeve56and the apex of each of the spacer fins is exposed from and extends radially outward from the polymeric coating or sleeve56such that the biodegradable material forming the spacer fins52are exposed after implantation.

In some embodiments, the spacer fins52may be formed by placing a biodegradable cap directly on a portion of the expandable metal structure54. As schematically illustrated inFIG. 7, an expandable metal structure54amay include high spots54b, such as an apex of a stent strut. A spacer fin52amay be formed by securing a biodegradable cap52bonto the high spot54bor protruding portion of the expandable metal structure54a. In some embodiments, while not illustrated, a polymeric covering or sleeve could cover the expandable metal structure54aprior to securing the biodegradable cap52bonto the high spot54bor protruding portion.

Another method for creating the spacer fins52is illustrated inFIG. 8, which shows a schematic cross-sectional view of an expandable metal structure54c. As discussed above with respect to the expandable metal structure54, the expandable metal structure54cmay generically represent a laser cut structure, a wound structure or a braided metal structure. A filament58may be wrapped around the expandable metal structure54c, in and out of apertures formed within the expandable metal structure54csuch that the filament58forms high spots60or radially outwardly protruding portions. The high spots60or protruding portions may form spacer fins. While a single filament58is shown, it will be appreciated that a plurality of filaments58may be wrapped around the expandable metal structure54c. The filament58may be formed of any desired biodegradable or bioabsorbable material, as discussed above with respect to the spacer fins52, and may have any desired diameter such as about 0.5 cm.

In some embodiments, as noted, the expandable metal structure54,54band54cmay be cut from a metal tube using any desired technique, including but not limited to micro-machining, saw-cutting (e.g., using a diamond grit embedded semiconductor dicing blade), electron discharge machining, grinding, milling, casting, molding, chemically etching or treating, or other known methods, and the like. Some example embodiments of appropriate micromachining methods and other cutting methods, and structures for tubular members including slots and medical devices including tubular members are disclosed in U.S. Pat. Publication Nos. 2003/0069522 and 2004/0181174-A2; and U.S. Pat. Nos. 6,766,720; and 6,579,246, the entire disclosures of which are herein incorporated by reference. Some example embodiments of etching processes are described in U.S. Pat. No. 5,106,455, the entire disclosure of which is herein incorporated by reference.

In at least some embodiments, a laser cutting process may be used. The laser cutting process may include a suitable laser and/or laser cutting apparatus. For example, the laser cutting process may utilize a fiber laser. Utilizing processes like laser cutting may be desirable for a number of reasons. For example, laser cutting processes may allow for a number of different cutting patterns in a precisely controlled manner. Furthermore, changes to the cutting pattern can be made without the need to replace the cutting instrument (e.g., blade).

The materials that can be used for the expandable metal structure54,54b,54cmay include those commonly associated with medical devices. For simplicity purposes, the following discussion makes reference to the expandable metal structure54. However, this is not intended to limit the devices and methods described herein, as the discussion may be applied to other similar structures.

In some embodiments, the exterior surfaces of the expandable metal structures22,52may be sandblasted, beadblasted, sodium bicarbonate-blasted, electropolished, etc. In these as well as in some other embodiments, a coating, for example a lubricious, a hydrophilic, a protective, or other type of coating may be applied thereover portions. Alternatively, the expandable metal structures22,52may include a lubricious, hydrophilic, protective, or other type of coating. Hydrophobic coatings such as fluoropolymers provide a dry lubricity which improves guidewire handling and device exchanges. Lubricious coatings improve steerability and improve lesion crossing capability. Suitable lubricious polymers are well known in the art and may include silicone and the like, hydrophilic polymers such as high-density polyethylene (HDPE), polytetrafluoroethylene (PTFE), polyarylene oxides, polyvinylpyrrolidones, polyvinylalcohols, hydroxy alkyl cellulosics, algins, saccharides, caprolactones, and the like, and mixtures and combinations thereof. Hydrophilic polymers may be blended among themselves or with formulated amounts of water insoluble compounds (including some polymers) to yield coatings with suitable lubricity, bonding, and solubility. Some other examples of such coatings and materials and methods used to create such coatings can be found in U.S. Pat. Nos. 6,139,510 and 5,772,609, which are incorporated herein by reference.