Patent Description:
A stent may be configured to be positioned in a body lumen for a variety of medical applications. For example, a stent 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. In some cases, a stent may include anti-migration features in order to help anchor the stent in place in whichever body lumen the stent is placed. In some instances, forming these ant-migration features may be difficult to do accurately and repeatedly.

<CIT> relates to a method of braiding a stent including braiding a number of elongate filaments around a mandrel using tensioned braiding carriers without spooling the filaments to the tensioned braiding carriers to form a braided stent having atraumatic ends.

<CIT> relates to a migration prevention stent comprising a hollow cylindrical body made of a metal wire, first securing elements projecting outwardly beyond the body, and second securing elements formed in the longitudinal direction of the body at a distance from the first securing elements and having a symmetrical arrangement about the vertical surface relative to the first securing elements with respect to the longitudinal direction of the body.

The invention relates to a mandrel as defined in claim <NUM> and to a method as defined in claim <NUM>. Further embodiments of the invention are defined in the dependent claims. The disclosure is directed to several alternative designs, materials and methods of manufacturing medical device structures and assemblies, and uses thereof. An example device for manufacturing a medical device structure is a mandrel to form an anti-migratory stent. The mandrel includes a mandrel body having a bore extending within the mandrel body as well as one or more apertures that are radially disposed about the mandrel body. One or more movable pins are outwardly extendable from the one or more apertures. The mandrel also includes an actuation element engagable with the bore extending within the mandrel body and including a tapered surface configured to engage the one or more movable pins, the actuation element being actuatable relative to the mandrel body such that the tapered surface supports the one or more movable pins extended from the one or more apertures.

Additionally to any embodiment above, the mandrel body may include a first stent shaping segment having a first diameter, a second stent shaping segment having a second diameter less than the first diameter, and a tapered segment disposed between the first stent shaping segment and the second stent shaping segment.

Additionally any embodiment above, the mandrel may further include a third stent shaping segment releasably securable to the second stent shaping segment, the third stent shaping segment having a third diameter greater than the second diameter.

Additionally to any embodiment above, the one or more movable pins may include a plurality of pins, and the one or more apertures may include a plurality of apertures such that there is a pin disposable within each of the plurality of apertures.

Additionally Alternatively or additionally to any embodiment above, at least some of the plurality of pins have equal lengths.

Additionally to any embodiment above, the plurality of apertures are equally spaced circumferentially about the tapered segment.

Additionally to any embodiment above, the corresponding apertures extend through the tapered segment and are configured to enable the pins to extend orthogonally to a tapered surface of the tapered segment.

Additionally to any embodiment above, the corresponding apertures extend through the tapered segment and are configured to enable the pins to extend at varying angles relative to a tapered surface of the tapered segment.

Additionally to any embodiment above, an end of each of the one or more movable pins includes a recessed slot configured to accommodate a wire of a stent being shaped on the mandrel.

Another example device is a mandrel for forming a stent with a tapered outer profile and anti-migration features, the mandrel including a mandrel body having a first stent shaping segment having a first diameter and a first threaded aperture extending within the first stent shaping segment, a second stent shaping segment having a second diameter less than the first diameter and a second threaded aperture extending within the second stent shaping segment and a tapered segment disposed between the first stent shaping segment and the second stent shaping segment, the tapered segment including a tapered surface. A plurality of apertures extend through the tapered surface. The mandrel includes a plurality of movable pins, each of the plurality of movable pins outwardly extendable from one of the plurality of apertures, the plurality of movable pins being configured to form the anti-migration features in the stent. The mandrel includes a mandrel cap that is releasably securable to the second stent shaping segment and that includes a third stent shaping segment having a third diameter greater than the second diameter. An actuation element includes a tapered end that is configured to engage the plurality of movable pins and a threaded body that is configured to threadedly engage the first threaded aperture. Rotating the actuation element causes the actuation element to advance into the first stent shaping segment such that the tapered end drives the plurality of movable pins in an outward direction.

Additionally to any embodiment above, the third diameter is equal to the first diameter.

Additionally to any embodiment above, at least some of the plurality of pins have equal lengths.

Additionally to any embodiment above, at least some of the plurality of pins have differing lengths.

Additionally to any embodiment above, an end of each of the plurality of movable pins includes a recessed slot configured to accommodate a wire of a stent being shaped on the mandrel.

Additionally to any embodiment above, the plurality of apertures extend through the tapered segment and are configured to enable the pins to extend orthogonally to a tapered surface of the tapered segment.

Additionally to any embodiment above, the plurality of apertures extend through the tapered segment and are configured to enable the pins to extend at varying angles relative to a tapered surface of the tapered segment.

An example method may be found in a method of manufacturing a stent having anti-migration features. A knitted stent blank may be disposed in position over a mandrel that includes a tapered outer surface and one or more anti-migration feature forming elements. A wire of the knitted stent blank may be engaged with the one or more anti-migration feature forming elements, and the woven stent blank may be annealed while disposed on the mandrel to form a shaped stent with the anti-migration feature. The one or more anti-migration feature forming elements may be disengaged in order to remove the shaped stent from the mandrel.

The one or more anti-migration feature forming elements include pins that are configured to be driven in a radially outward direction relative to a central longitudinal axis of the mandrel, and engaging the wire with the one or more anti-migration feature forming elements includes driving the pins in the radially outward direction relative to the central longitudinal axis of the mandrel.

Additionally to any embodiment above, disengaging the one or more anti-migration feature forming elements includes permitting the pins to move in a radially inward direction relative to the central longitudinal axis of the mandrel.

Additionally to any embodiment above, disposing the knitted stent blank in position over the mandrel includes stretching the knitted stent blank over the mandrel and allowing the knitted stent blank to conform to the tapered outer surface of the mandrel.

The above summary of some example embodiments is not intended to describe each disclosed embodiment or every implementation of the aspects of the disclosure.

The aspects of 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 aspects of the disclosure are 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.

Definitions of certain terms are provided below and shall be applied, unless a different definition is given in the claims or elsewhere in this specification.

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 or otherwise refer to singular as well as plural referents, unless the content clearly dictates otherwise. As used in this specification and the appended claims, the term "or" is generally employed to include "and/or," unless the content clearly dictates otherwise.

<FIG> is a perspective view of a mandrel <NUM> for forming a stent having anti-migration features. In some instances, the stent may additionally include a tapered outer profile region with one or more flared end regions as well as anti-migration features. In some cases, the stent may be considered as having an hourglass profile, for example. However, in other instances, the stent may have a generally constant outer diameter with one or more anti-migration features extending radially outward therefrom.

As can be seen, the mandrel <NUM> includes a mandrel body <NUM>, a mandrel cap <NUM>, an actuation element <NUM> and a plurality of anti-migration feature forming pins <NUM>. <FIG> is an exploded perspective view of the mandrel <NUM>, with the anti-migration feature forming pins excluded for clarity. In some cases, the mandrel cap <NUM> may be releasably secured to the mandrel body <NUM> via a bolt <NUM>, bayonet coupling, or other securement mechanism. In some instances, the mandrel cap <NUM> may be removable from the mandrel body <NUM> in order to facilitate removal of a stent from the mandrel <NUM>. In other embodiments, the mandrel body <NUM> and the mandrel cap <NUM> may be formed as a unitary or monolithic structure, particularly if the mandrel cap <NUM> has an outer diameter roughly the same as an outer diameter of the mandrel body <NUM>. In some instances, the mandrel body <NUM> may include a cylindrical portion having an outer diameter, whereas the mandrel cap <NUM> may have an outer diameter greater than the cylindrical portion of the mandrel body <NUM>.

The mandrel body <NUM>, shown in <FIG> and <FIG>, includes a first stent shaping segment <NUM> and a second stent shaping segment <NUM>. The first stent shaping segment <NUM> may be a cylindrical portion of the mandrel body <NUM> having a first diameter, and the second stent shaping segment <NUM> may be a cylindrical portion of the mandrel body having a second diameter. In some cases, the first stent shaping segment <NUM> and/or the second stent shaping segment <NUM> may have a non-cylindrical profile. For example, the first stent shaping segment <NUM> and/or the second stent shaping segment <NUM> may instead have a polygonal cross-sectional profile such as an octagonal cross-sectional profile. This is just an example. The first diameter may be different than the second diameter. For example, the first diameter may be greater than the second diameter. A tapered segment <NUM> extends between the first stent shaping segment <NUM> and the second stent shaping segment <NUM> and defines a tapered surface <NUM> extending from a cylindrical outer surface of the first stent shaping segment <NUM> to a cylindrical outer surface of the second stent shaping segment <NUM>. The tapered segment <NUM> includes a plurality of apertures <NUM> that extend through the circumferential wall of the tapered segment from the tapered surface <NUM> to an internal bore extending axially within the mandrel body <NUM> in order to accommodate the anti-migration feature forming pins <NUM>. It will be appreciated that an angle of the tapered surface <NUM>, relative to the first stent shaping segment <NUM> and/or the second stent shaping segment <NUM>, may influence the relative angle at which the anti-migration feature forming pins <NUM> extend outwardly from the tapered surface <NUM>.

In some cases, particularly if the first stent shaping segment <NUM> and the second stent shaping segment <NUM> have a similar or identical outer diameter, the tapered surface <NUM> may itself not be tapered, but may instead have a constant outer diameter. In some instances, at least some of the plurality of apertures <NUM> may have a major dimension that is orthogonal to the tapered surface <NUM>. In some cases, at least some of the plurality of apertures <NUM> may have a major dimension that extends at an acute angle relative to the tapered surface <NUM>. It will be appreciated that in some cases, some of the plurality of apertures <NUM> may extend at different angles relative to the tapered surface <NUM>. As shown, the plurality of apertures <NUM> may be considered as being radially aligned in a ring that extends around the tapered segment <NUM>. In some cases, it will be appreciated that some of the plurality of apertures <NUM> may be axially displaced relative to others of the plurality of apertures <NUM>. In other words, some of the plurality of apertures <NUM> may form a first ring around the tapered segment <NUM> while others of the plurality of apertures <NUM> may form a second ring around that tapered segment <NUM> that is axially displaced from the first ring around the tapered segment <NUM>.

In some cases, at least some of the plurality of apertures <NUM> may extend linearly through the tapered segment <NUM> such that each corresponding pin <NUM> extends through the aperture <NUM> orthogonally to the tapered surface <NUM>. In some cases, at least some of the apertures <NUM> may have a curved or helical shape, such that as the corresponding pin <NUM>, which may have a complementary curved or helical shape, is extended out of the aperture <NUM>, the pin <NUM> may rotate, and thus a distal end of the pin <NUM> (such as the pin end <NUM>) may move radially as well as axially.

The actuation element <NUM> may be configured to extend into the bore of the mandrel body <NUM> from one end of the mandrel body <NUM> (e.g., the end of the mandrel body opposite to the mandrel cap <NUM>) to selectively engage and actuate the pins <NUM> within the apertures <NUM>. For example, the actuation element <NUM>, shown in <FIG>, includes a tapered end <NUM> that, as will be illustrated in subsequent Figures, may be configured to engage the anti-migration feature forming pins <NUM>, as well as a threaded body <NUM> that is configured to threadedly engage a threaded aperture extending within the first stent shaping segment <NUM> of the mandrel body <NUM>. In some instances, the tapered end <NUM> may be conically, frustoconically, convexly, or concavely tapered. The actuation element <NUM> may be considered as including a handle <NUM> that may be used by an individual or a machine to rotate the actuation element <NUM> and thus advance the actuation element <NUM> into the bore of the mandrel body <NUM> by rotating in a first direction or withdraw the actuation element <NUM> from the bore of the mandrel body <NUM> by rotating in a second, opposite direction. Thus, the threaded body <NUM> may threadably engage a threaded region of the bore of the mandrel body <NUM> to threadably advance the actuation element <NUM> into the bore (e.g., toward the mandrel cap <NUM>) by rotating the actuation element <NUM> in a first rotational direction and withdraw the actuation element <NUM> from the bore (e.g., away from the mandrel cap <NUM>) by rotating the actuation element <NUM> in a second, opposite rotational direction. This may be demonstrated, for example, with respect to <FIG> and <FIG>, which are cross-sectional views showing the actuation element <NUM> fully extended into the bore of the mandrel body <NUM> (<FIG>) or partially extended (<FIG>) taken along line <NUM>-<NUM> of <FIG>. In other cases, it is contemplated that rather than the actuation element <NUM> itself including a threaded region, a threaded fastener may be configured to engage a threaded bore of the mandrel body <NUM> to actuate the actuation element <NUM> relative to the mandrel body <NUM>.

<FIG> shows the actuation element <NUM> fully extended into the bore of the mandrel body <NUM> with the threaded body <NUM> threadably engaged with the threaded region of the bore of the mandrel body <NUM>. In particular, the bore of the mandrel body <NUM> includes a first threaded region <NUM> extending into the first stent shaping segment <NUM> of the mandrel body <NUM> from a first end of the mandrel body <NUM> that is configured, in diameter, depth and thread pitch, to threadedly engage the threaded body <NUM> of the actuation element <NUM>. In some instances, as illustrated, the mandrel body <NUM> also includes a second threaded bore or region <NUM> extending into the second stent shaping segment <NUM> of the mandrel body <NUM> from the second, opposite end of the mandrel body that is configured, in diameter depth and thread pitch, to threadedly engage threads on the threaded fastener (e.g., bolt or screw) <NUM> in order to releasably secure the mandrel cap <NUM> in position relative to the mandrel body <NUM> at the second end of the mandrel body <NUM>. In some cases, it is contemplated that rather than utilizing a separate threaded fastener <NUM>, that the mandrel cap <NUM> itself may include a threaded protuberance that is configured to engage the second threaded bore <NUM>. Alternatively, it is also contemplated that the second end of the mandrel body <NUM> may include a threaded protuberance, and the mandrel cap <NUM> may include a threaded bore or aperture to engage the threaded protuberance of the mandrel body <NUM>, or a through hole for passing the threaded protuberance through to be threadedly engaged with a mating threaded fastener (e.g., nut) on an opposite side of the mandrel cap <NUM>. In either event, the mandrel cap <NUM> may be secured to or removed from the mandrel body <NUM>, particularly for aid in removing a formed stent from the mandrel <NUM>. In some cases, the mandrel cap <NUM> may be permanently secured to the mandrel body <NUM>, particularly in cases where the mandrel <NUM> has a profile in which an outer diameter of each successive stent shaping segment is equal to or less than an outer diameter of a preceding stent shaping segment and a formed stent may simply be slid off the mandrel <NUM> without removing the mandrel cap <NUM>. In some cases, the mandrel body <NUM> may include a locating or centering aperture <NUM> that is configured to accommodate a locating or centering feature <NUM> extending from the mandrel cap <NUM>, but this is not required in all cases. In some cases, rather than using the fastener <NUM> to secure the mandrel cap <NUM> to the mandrel body <NUM>, the locating or centering feature <NUM> may itself threadedly engage the locating or centering aperture <NUM>.

As seen in <FIG>, the actuation element <NUM> is fully extended into the first threaded region <NUM> of the bore of the mandrel body <NUM>. As a result, the anti-migration feature forming pins <NUM> can be seen as being extended radially outwardly through the corresponding apertures <NUM>. In some cases, depending on the particular dimensions of the various components forming the mandrel <NUM>, the anti-migration feature forming pins <NUM> may be considered as being extended radially outwardly as far as they can go before the actuation element <NUM> is fully extended into the first threaded region <NUM> of the bore of the mandrel body <NUM>. A base <NUM> of each pin <NUM> may be seen as engaging the tapered end <NUM> of the actuation element <NUM>. This can be contrasted with <FIG>, in which the actuation element <NUM> is only partially extended into the first threaded region <NUM> of the bore of the mandrel body <NUM>. Accordingly, while the base <NUM> of each pin <NUM> (only <NUM> pins are shown for clarity) is still engaged with the tapered end <NUM> of the actuation element <NUM>, it can be seen that the pins <NUM> do not extend radially outwardly through the corresponding apertures <NUM> as far as the pins <NUM> extend in <FIG>. In some cases, as shown in <FIG> and <FIG>, the base <NUM> of each pin <NUM> may be larger in at least one dimension than a diameter of the corresponding aperture <NUM>. Thus, the extent that the pins <NUM> can be extended radially outward through the apertures <NUM> may be limited when the base <NUM> of the pin <NUM> abuts a peripheral edge of the aperture <NUM>. As a result, the pins <NUM> are retained within the apertures <NUM>, and won't fall out. The pins <NUM> can, in some instances, be removed completely by withdrawing the actuation element <NUM> from the bore of the mandrel body <NUM>, permitting the pins <NUM> to move radially inward of the apertures <NUM> and then fall into the bore of the mandrel body <NUM>.

<FIG> is a side view of the mandrel body <NUM> and <FIG> is a cross-sectional view thereof, taken along the <NUM>-<NUM> line in <FIG>. As can be seen, the first stent shaping segment <NUM> has a first diameter D1 and the second stent shaping segment <NUM> has a second diameter D2 that is less than the first diameter D1. In other cases, the second diameter D2 may be equal to the first diameter D1, or the second diameter D2 may be greater than the first diameter D1. In some cases, while a first stent shaping segment <NUM> and a second stent shaping segment <NUM> are shown, it will be appreciated that the mandrel body <NUM> may include a third stent shaping segment, a fourth stent shaping segment, and so on, depending on the desired profile of the final stent product. As will be appreciated, in the illustrated embodiment, the tapered segment <NUM> has a diameter (not labeled) that tapers smoothly from D1 to D2. In some cases, it is contemplated that the tapered segment <NUM> may instead have one or more step-wise changes in diameter. Furthermore, it can be seen that the plurality of apertures <NUM> may be uniformly spaced circumferentially around the perimeter (e.g., circumference) of the tapered segment <NUM>. However, in other instances at least some of the plurality of apertures <NUM> may be non-uniformly spaced circumferentially around the perimeter (e.g., circumference) of the tapered segment <NUM>. In some cases, at least some of the plurality of apertures <NUM> may be axially displaced relative to others of the plurality of apertures <NUM>.

<FIG> is a side view of the mandrel cap <NUM> and <FIG> is a cross-sectional view thereof, taken along the <NUM>-<NUM> line of <FIG>. In some cases, the mandrel cap <NUM> includes a mandrel cap body <NUM> and a tapered section <NUM>. The mandrel cap <NUM> may be considered as providing a third stent shaping segment <NUM> having a third diameter D3. In some cases, the diameter D3 may be the same as the diameter D1 (of the first stent shaping segment <NUM>). In some instances, the diameter D3 may be either larger or smaller than the diameter D1, depending on the desired properties and dimensions of the stent to be produced using the mandrel <NUM>. In some cases, the tapered section <NUM> varies smoothly in diameter between the diameter D3 and the diameter D2 (of the second stent shaping segment <NUM>). In other cases, it is contemplated that the tapered section <NUM> may instead have one or more step-wise changes in diameter. In some instances, as shown for example in <FIG>, the mandrel cap <NUM> may include an aperture <NUM> that is dimensioned to accommodate the fastener <NUM>, as well as a larger aperture <NUM> that accommodates the fastener head <NUM> of the fastener <NUM>. In some cases, the fastener head <NUM> of the fastener <NUM> may be configured to accommodate a tool such as but not limited to an Allen wrench, and thus may include a six or eight sided aperture <NUM>.

<FIG> is a perspective view of one example of an anti-migration feature forming pin <NUM>. In some cases, the pin <NUM> may include a pin body <NUM> extending between the base <NUM> (which may have an enlarged cross-section relative to the pin body <NUM>) and a pin end <NUM> opposite the base <NUM>. As noted, the base <NUM> may be larger in diameter than the pin body <NUM>, but this is not required in all cases. In some cases, the pin end <NUM> may be curved to facilitate a portion of a wire of a stent to be formed in a curved shape. In some cases, the curved shape may be a simple curve. In some instances, the curved shape may be a compound curve, such as an undulating or wave-like shape. In some instances, the pin end <NUM> may include a recessed slot <NUM> that may be configured to accommodate a wire or wires of the stent being shaped on the mandrel <NUM>. In some cases, the recessed slot <NUM> may itself have a simple or compound curve shape to instill a corresponding simple or compound curve shape to a stent wire extending through the recessed slot <NUM>. For example, in some embodiments the recessed slot <NUM> may be a curved slot <NUM> providing a wire placed therein with a curved region. In some cases the recessed slot <NUM> may include two converging portions converging at a point at the pen end <NUM> to provide a wire with a sharp bend for an anti-migration feature. In some cases, the stent being formed is a knitted stent, and a constant diameter knitted stent blank may be stretched over the mandrel <NUM>, with a particular wire of the knitted stent blank disposed within the recessed curved slot <NUM> in order to form an anti-migration feature extending radially outward from a knitted tubular wall of the stent. In some cases, the stent being formed is a braided stent, and may be braided in place on the mandrel <NUM>, with a particular wire forming an anti-migration feature braided within the recessed curved slot <NUM> and extending radially outward from the braided tubular wall of the stent.

While the pin end <NUM> is illustrated as a curved profile and being no larger in dimension than the pin body <NUM>, in some cases it is contemplated that the pin end <NUM> may extend laterally beyond the pin body <NUM> and form an arcuate surface. In some cases, for example, the arcuate surface of each of the pin ends <NUM> may align end to end, and essentially form a raised ring extending around the mandrel <NUM>. The individual arcuate surfaces of each of the pin ends <NUM> maybe driven outward by extending the actuation element <NUM> into the mandrel body <NUM> by rotating the actuation element <NUM> in a first rotational direction in order to form a raised ring anti-migration feature in the stent. Rotating the actuation element <NUM> in a second, opposing rotational direction, allows the pins <NUM> to retract, and allow removal of the stent from the mandrel <NUM>.

<FIG> shows a portion of a knitted stent <NUM> disposed on the mandrel <NUM>, while <FIG> shows the knitted stent <NUM> removed from the mandrel <NUM>. As shown in <FIG>, one of the wires of the knitted stent may extend radially outward from the knitted tubular wall of the stent <NUM> and along the recessed slot <NUM> of the pin <NUM> to form one or more of the anti-migration features <NUM> of the stent <NUM>. In some cases, a knitted stent such as the knitted stent <NUM> may be formed by first knitting a constant diameter stent blank (not illustrated), then stretching the constant diameter stent blank over the mandrel <NUM> prior to a shaping process and/or an annealing process. It can be seen that the knitted stent <NUM> has a first enlarged diameter portion <NUM> proximate a first end of the knitted stent <NUM> that corresponds to the first stent shaping segment <NUM>, a second enlarged diameter portion <NUM> proximate a second end of the knitted stent <NUM> that corresponds to the third stent shaping segment <NUM>, and a (relatively) reduced diameter portion <NUM> (e.g., a cylindrical body region intermediate the first and second enlarged diameter portions <NUM>, <NUM>) that corresponds to the second stent shaping segment <NUM>. The knitted stent <NUM> includes anti-migration features <NUM> that correspond to the pins <NUM> which are arranged circumferentially around the knitted stent <NUM> at a transition region between the first enlarged dimeter portion <NUM> and the reduced diameter portion <NUM>. However, it is contemplated that the anti-migration features <NUM> may be arranged at a different location along the length of the knitted stent <NUM>, if desired. The pins <NUM> may be actuated radially outward with the wires disposed in the recessed slots <NUM> after the knitted stent black has been placed on the mandrel <NUM> to cause the portions of the wires engaged with the pins <NUM> to be urged radially outward from the knitted tubular wall of the stent to form the anti-migration features <NUM>.

<FIG> is an end view of the knitted stent <NUM>, showing the anti-migration features <NUM> extending radially outward from the knitted tubular wall of the knitted stent <NUM>. As illustrated, each of the anti-migration features <NUM> are loops of the filament(s) or wire(s) forming the knitted stent <NUM> extending between adjacent anchor points <NUM>, each loop being roughly equal in shape and dimension. Anchor points <NUM> may be location in which portions of the filament(s) or wire(s) cross or loop around another portion of the filament(s) or wire(s). In other cases, some of the anti-migration features <NUM> may vary in shape and/or dimension, or may not be equally spaced, for example. While the anti-migration features <NUM> are shown as being curved, in some cases the anti-migration features <NUM> may be pointed, or include a flattened region, for example.

<FIG>, for example, shows a knitted stent 70a that includes a number of anti-migration features 78a. The anti-migration features 78a each extend between adjacent anchor points <NUM>, and are each roughly equal in shape and dimension. However, by comparing <FIG> with <FIG>, it can be seen that the anti-migration features <NUM> shown in <FIG>extend radially outward further than the anti-migration features 78a shown in <FIG>. The anti-migration features 78a may be formed, for example, by using anti-migration feature forming pins <NUM> that are shorter in length, or by not advancing the actuation element <NUM> as far into the mandrel body <NUM>, thus not advancing the pins <NUM> radially outward as far from the surface of the tapered segment <NUM> of the mandrel body <NUM>. The anti-migration features 78a may be pointed, for example, or have other shapes as well.

It will be appreciated that the relative dimensions of the anti-migration features <NUM> and the anti-migration features 78a may be a function of the ultimate end-use of the knitted stent <NUM> (or 70a). Relatively larger anti-migration features <NUM>, 78a may be useful in situations where the knitted stent <NUM> (or 70a) will be placed in anatomical locations where the knitted stent <NUM> (or 70a) may be subjected to relatively stronger migration forces and/or anatomical locations where the dimensions of the patient's anatomy are more variable. Relatively smaller anti-migration features <NUM>, 78a may be useful in situations where the knitted stent <NUM> (or 70a) may be subjected to relatively weaker migration forces and/or anatomical locations where the dimensions of the patient's anatomy are less variable. In some cases, the overall dimensions of the knitted stent <NUM> (or 70a) may play a part as well. In some cases, for example, a larger diameter knitted stent <NUM> (or 70a) may have relatively larger anti-migration features <NUM>, 78a while a smaller diameter knitted stent <NUM> (or 70a) may have relatively smaller anti-migration features <NUM>, 78a.

<FIG> shows a knitted stent 70b that includes a number of anti-migration features 78b. In contrast to the knitted stents <NUM> and 70a shown in <FIG> and <FIG>, the anti-migration features 78b are unequally spaced about the periphery of the knitted stent 78b. Each of the anti-migration features 78b extend between adjacent anchor points <NUM>, although some anchor points <NUM> are not attached to an anti-migration feature 78b. As illustrated, each of the anti-migration features 78b are roughly equal in shape and dimension. The anti-migration features 78b may be formed, for example, by only placing anti-migration feature forming pins <NUM> into some of the apertures <NUM>. In some cases, it is contemplated that some of the anti-migration features 78b may be smaller or larger in dimension, and/or may vary in shape, relative to others of the anti-migration features 78b.

<FIG> shows a knitted stent 70c that includes a number of anti-migration features 78c and a number of anti-migration features 78d, each extending between adjacent anchor points <NUM>. It will be appreciated that as illustrated, each of the anti-migration features 78c are roughly equal in shape and dimension, and each of the anti-migration features 78d are roughly equal in shape and dimension, albeit not extending radially outward as far as the anti-migration features 78c. The anti-migration features 78c and 78d may be formed, for example, by using a longer length pin <NUM> to form each of the anti-migration features 78c and a shorter length pin <NUM> to form each of the anti-migration features 78d. It will be appreciated that the particular anti-migration features <NUM>, 78a, 78b, 78c and 78d are merely illustrative, and may be mixed or matched in any desired pattern.

<FIG> is a flow diagram showing a method <NUM> of forming a knitted stent having a non-uniform profile and one or more anti-migration features. In some cases, a constant diameter knitted stent blank may be positioned over a mandrel having a tapered outer surface and one or more anti-migration feature forming elements, as generally indicated at block <NUM>. The mandrel may be the mandrel <NUM>, for example. In some cases, disposing a constant diameter knitted stent blank in position over a mandrel includes stretching the constant diameter knitted stent blank over the mandrel and allowing the constant diameter knitted stent blank to conform to the varied diameter outer surface of the mandrel, such conforming to the various constant diameter regions and/or tapered diameter regions of the mandrel.

The one or more anti-migration feature forming elements (such as but not limited to the pins <NUM>) may be engaged, as noted at block <NUM>, in order to provide a desired shape prior to annealing, as indicated at block <NUM>. In some cases, the one or more anti-migration feature forming elements are pins that are configured to be driven in a radially outward direction relative to the outer surface of the mandrel, and engaging the one or more anti-migration feature forming elements includes driving the pins in radially outward direction relative to the mandrel to urge the wire(s) or filament(s) engaged with the end of each of the pins in a radially outward direction relative to the knitted tubular structure of the stent. The mandrel and the stent thereon, with the anti-migration features formed, may then be subjected to an annealing or shape setting process. As seen at block <NUM>, after the annealing or shape setting process, the one or more anti-migration feature forming elements may be disengaged in order to remove the shaped stent from the mandrel. In some cases, disengaging the one or more anti-migration feature forming elements comprises permitting the pins to move in an inward direction relative to the mandrel.

<FIG> is a flow diagram showing a method <NUM> of forming a knitted stent having a non-uniform profile and one or more anti-migration features. In some cases, the knitted stent may have a metallic component and a non-metallic or even biodegradable component. The metallic component and the non-metallic component may individually be shaped, and then combined to form a stent. In some cases, each of the metallic component and the non-metallic or even biodegradable component may each include anti-migration features, where the anti-migration features of the non-metallic or even biodegradable component complement the anti-migration features of the metallic component. In cases where the non-metallic component is biodegradable, the biodegradable anti-migration features may provide additional resistance to migration upon initial implantation of the stent, but dissolve away over time.

In some cases, a constant diameter metallic knitted stent blank may be positioned over a mandrel having a tapered outer surface and one or more anti-migration feature forming elements, as generally indicated at block <NUM>. The mandrel may be the mandrel <NUM>, for example. In some cases, disposing a constant diameter metallic knitted stent blank in position over a mandrel includes stretching the constant diameter metallic knitted stent blank over the mandrel and allowing the constant diameter metallic knitted stent blank to conform to the varied diameter outer surface of the mandrel, such conforming to the various constant diameter regions and/or tapered diameter regions of the mandrel.

In some cases, once the shaped metallic stent has been removed from the mandrel, a constant diameter biodegradable knitted stent blank may be positioned over a mandrel having a tapered outer surface and one or more anti-migration feature forming elements, as generally indicated at block <NUM>. In some cases, disposing a constant diameter biodegradable knitted stent blank in position over a mandrel includes stretching the constant diameter biodegradable knitted stent blank over the mandrel and allowing the constant diameter biodegradable knitted stent blank to conform to the varied diameter outer surface of the mandrel, such conforming to the various constant diameter regions and/or tapered diameter regions of the mandrel. The one or more anti-migration feature forming elements may be engaged, as noted at block <NUM>, in order to provide a desired shape prior to annealing, as indicated at block <NUM>.

In some cases, the annealing process for the biodegradable knitted stent blank may involve lower temperatures than that used for the metallic knitted stent blank. The mandrel and the stent thereon, with the anti-migration features formed, may then be subjected to an annealing or shape setting process. As seen at block <NUM>, after the annealing or shape setting process, the one or more anti-migration feature forming elements may be disengaged in order to remove the shaped biodegradable stent from the mandrel. In some cases, disengaging the one or more anti-migration feature forming elements comprises permitting the pins to move in an inward direction relative to the mandrel. In some cases, while not illustrated, the shaped biodegradable stent may be disposed about or within the shaped metallic stent.

In some embodiments, the knitted stent <NUM> may be formed from any desired material, such as a biocompatible material including biostable, bioabsorbable, biodegradable or bioerodible materials. For instance, the knitted stent <NUM> may be formed of a metallic material. Some suitable metallic materials include, but are not necessarily limited to, stainless steel, tantalum, tungsten, nickel-titanium alloys such as those possessing shape memory properties commonly referred to as nitinol, nickel-chromium alloys, nickel-chromium-iron alloys, cobalt-chromium-nickel alloys, or other suitable metals, or combinations or alloys thereof. In some cases, the mandrel <NUM> may be formed of a material that is thermally stable and does not materially expand at the temperatures used in annealing the knitted stent <NUM>. In some cases, for example, the mandrel <NUM> may be formed of a metallic material such as stainless steel, titanium or a nickel-titanium alloy. In some cases, the mandrel <NUM> may be formed of a ceramic material.

In some embodiments, the knitted stent <NUM> may include one or more metals. Some examples of suitable metals and metal alloys include stainless steel, such as 304V, <NUM>, 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 (e.g., UNS: N06625 such as INCONEL® <NUM>, UNS: N06022 such as HASTELLOY® C-<NUM>®, UNS: N10276 such as HASTELLOY® C276®, other HASTELLOY® alloys, and the like), nickel-copper alloys (e.g., UNS: N04400 such as MONEL® <NUM>, NICKELVAC® <NUM>, NICORROS® <NUM>, and the like), nickel-cobalt-chromium-molybdenum alloys (e.g., UNS: R30035 such as MP35-N® and the like), nickel-molybdenum alloys (e.g., UNS: N10665 such as HASTELLOY® ALLOY B2®), 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 (e.g., UNS: R30003 such as ELGILOY®, PHYNOX®, and the like); platinum enriched stainless steel; titanium; combinations thereof; and the like; or any other suitable material.

Instead, in the linear elastic and/or non-super-elastic nitinol, as recoverable strain increases, the stress continues to increase in a substantially linear, or a somewhat, but not necessarily entirely linear relationship until plastic deformation begins or at least in a relationship that is more linear that the super elastic plateau and/or flag region that may be seen with super elastic nitinol.

Both of these materials can be distinguished from other linear elastic materials such as stainless steel (that can also can be distinguished based on its composition), which may accept only about <NUM> to <NUM> percent strain before plastically deforming.

of Kanagawa, Japan. Some examples of nickel titanium alloys are disclosed in <CIT> and <CIT>.

Claim 1:
A mandrel (<NUM>) comprising:
a mandrel body (<NUM>) including:
a bore extending within the mandrel body (<NUM>); and
one or more apertures (<NUM>) radially disposed about the mandrel body (<NUM>);
one or more movable pins (<NUM>) outwardly extendable from the one or more apertures (<NUM>); and
an actuation element (<NUM>) engagable with the bore extending within the mandrel body (<NUM>) and including a tapered surface configured to engage the one or more movable pins (<NUM>), the actuation element (<NUM>) being actuatable relative to the mandrel body (<NUM>) such that the tapered surface supports the one or more movable pins (<NUM>) extended from the one or more apertures (<NUM>) to form an anti-migratory stent (<NUM>).