Thin-walled scaffold

Abstract

To provide bioresorbable scaffolds for treating an anatomical lumen of the body.SOLUTION: A thin-walled scaffold includes a radiopaque marker connected to a link. In a first example, the marker is retained on a strut by a head at one or both of ends by swaging. In a second example of a thin-walled scaffold, the link is modified to avoid interference during crimping. In a third example, a distal end of the thin-walled scaffold is modified to improve deliverability of the thin-walled scaffold. These features are combined in a fourth example.SELECTED DRAWING: Figure 4D

Description

[Technical field]

[0001]

[0001] The present invention relates to bioabsorbable scaffolds, and more particularly, the present invention relates to bioabsorbable scaffolds for treating anatomical lumens in the body. [Background technology]

[0002] A radially expandable endoprosthesis is an artificial device adapted to be implanted in an anatomical lumen. An "anatomical lumen" refers to a cavity, or duct, of a tubular organ, such as a blood vessel, urinary tract, or bile duct. A stent is an example of an endoprosthesis that is generally cylindrical and holds open and possibly expands a portion of an anatomical lumen. Stents are often used in the treatment of atherosclerotic stenosis in blood vessels. "Stenosis" refers to a narrowing or constriction in the diameter of a body passageway or opening. In such treatments, stents reinforce the walls of blood vessels and prevent restenosis after angioplasty in the vascular system. "Restenosis" refers to the recurrence of stenosis in a blood vessel or heart valve after it has been treated (by balloon angioplasty, stent placement, or valvuloplasty) with apparent success.

[0003]

[0003] Treatment of a diseased area or lesion with a stent involves both introduction and deployment of the stent. "Introduction" refers to the introduction and delivery of the stent through an anatomical lumen to a desired treatment site, such as a lesion. "Deployment" corresponds to the expansion of the stent within the lumen of the treatment area. The introduction and deployment of a stent is accomplished by positioning the stent around one end of a catheter, inserting the end of the catheter through the skin into the anatomical lumen, advancing the catheter within the anatomical lumen to the desired treatment location, expanding the stent at the treatment location, and removing the catheter from the lumen.

[0004]

[0004] Scaffolds and stents are traditionally classified into two general categories: balloon-expandable and self-expandable. The latter type expands (at least partially) within the vessel to a deployed or expanded state upon removal of radial constraint, while the former utilize an externally applied force to configure itself from a crimped or retracted state to a deployed or expanded state.

[0005]

[0005] Self-expanding stents are designed to expand significantly when radial restraint is removed, and often do not require a balloon for deployment of the stent. Self-expanding stents do not undergo, or are relatively resistant to, plastic or inelastic deformation when stored in a sheath (with or without an auxiliary balloon) or expanded within a lumen. Balloon-expandable stents or scaffolds, in contrast, undergo significant plastic or inelastic deformation when crimped and later deployed by a balloon.

[0006]

[0006] In the case of a balloon-expandable stent, the stent is mounted around the balloon portion of a balloon catheter. The stent is compressed or crimped onto the balloon. Crimping can be accomplished by use of an iris-type or other form of crimper, such as the crimping machine disclosed and illustrated in U.S. Patent Application Publication No. 2012 / 0042501. A significant amount of plastic or inelastic deformation occurs both when the balloon-expandable stent or scaffold is crimped and when it is subsequently deployed by the balloon. At the treatment site within the lumen, the stent is expanded by inflating the balloon.

[0007]

[0007] A stent must be able to meet several basic functional requirements. The stent (or scaffold) must be able to sustain radial compressive forces while supporting the walls of the vessel. Thus, the stent must have adequate radial strength. After deployment, the stent must adequately maintain its size and shape throughout its useful life despite the various forces that may be exerted on the stent. In particular, the stent must adequately maintain the vessel at a specified diameter for a desired treatment period, despite these forces. The treatment period may correspond to the period required for the vessel wall to remodel, after which the stent is no longer needed.

[0008]

[0008] Examples of bioabsorbable polymer scaffolds include those described in U.S. Patent No. 8,002,817 to Limon, U.S. Patent No. 8,303,644 to Lord, and U.S. Patent No. 8,388,673 to Yang. FIG. 1 shows a distal region of a bioabsorbable polymer scaffold designed for introduction through an anatomical lumen using a catheter and plastically expanded using a balloon. The scaffold has a cylindrical shape with a central axis 2 and includes a pattern of interconnecting structural elements called bar arms or struts 4. Axis 2 extends through the center of the cylindrical shape formed by struts 4. Stresses involved during compression and deployment are distributed widely throughout struts 4 but are concentrated at bending elements, apexes or strut junctions. Struts 4 include a series of ring struts 6 connected to each other at apexes 8. Ring struts 6 and apexes 8 form sinusoidal rings 5. Rings 5 ​​are arranged longitudinally about axis 2. Struts 4 also include link struts 9 that connect rings 5 ​​to one another. Rings 5 ​​and link struts 9 collectively form a tubular scaffold 10 having an axis 2, which represents the luminal or longitudinal axis of scaffold 10. Ring 5d is located at the distal end of the scaffold. Apices 8 form a smaller angle when scaffold 10 is crimped to a balloon and a larger angle when plastically expanded by a balloon. After deployment, the scaffold is subjected to static and cyclic compressive loads from the surrounding tissue. Rings 5 ​​are configured to maintain the radially expanded state of the scaffold after deployment.

[0009]

[0009] The scaffold may be made from biodegradable, bioabsorbable, bioresorbable, or bioerodible polymers. The terms biodegradable, bioabsorbable, bioresorbable, biosoluble, or bioerodible refer to the property of a material or stent to degrade, absorb, resorb, or erode away from the implantation site. The scaffold may also be constructed of bioerodible metals and alloys. In contrast to durable metallic stents, the scaffold is intended to remain in the body only for a limited period of time. In many therapeutic applications, the presence of a stent in the body may be necessary for a limited period of time until its intended function, such as maintaining vascular patency and / or drug delivery, is accomplished. Additionally, biodegradable scaffolds have been shown to allow for improved healing of the anatomical lumen compared to metallic stents, which may lead to a reduced incidence of late thrombosis. In these cases, it is desirable to treat the vessel with a polymer scaffold, particularly a bioabsorbable or bioresorbable polymer scaffold, rather than a metallic stent, so that the presence of the prosthesis within the vessel is temporary.

[0010] In some of the following methods, the polymeric materials contemplated for use as polymeric scaffolds, such as poly(L-lactide) ("PLLA"), poly(D,L-lactide-co-glycolide) ("PLGA"), poly(D-lactide-co-glycolide) or poly(L-lactide-co-D-lactide) with less than 10% D-lactide ("PLLA-co-PDLA"), poly(L-lactide-co-caprolactone), poly(caprolactone), PLLD / PDLA stereocomplexes, and blends of the above polymers, may be described by comparison with the metallic materials used to form the stent. Polymeric materials usually have a lower strength-to-volume ratio compared to metals, which means that more material is needed to provide comparable mechanical properties. Thus, for a stent to have the necessary strength to support the lumen wall at the desired radius, the struts must be thicker and wider. Scaffolds made from such polymers also tend to be brittle or have limited fracture toughness. The inherent anisotropic and rate-dependent inelastic properties of the materials (i.e., the strength / stiffness of the material varies with temperature, degree of hydration, thermal history, as well as the rate at which the material is deformed) only exacerbates this complexity when working with polymers, especially bioabsorbable polymers such as PLLA and PLGA.

[0011]

[0011] An additional challenge with using bioabsorbable polymers (and generally polymers composed of carbon, hydrogen, oxygen and nitrogen) in scaffold construction is that the materials are radiolucent and not radiopaque. Bioabsorbable polymers tend to have x-ray absorption similar to body tissue. A known method of addressing this issue is to attach radiopaque markers to the structural elements of the scaffold, such as struts, bar arms, links, etc. For example, FIG. 1 shows link element 9d connecting distal end ring 5d to adjacent ring 5. Link element 9d has a pair of holes. Each hole holds a radiopaque marker 11. Using markers 11 with scaffold 10 presents challenges. A reliable method of attaching markers 11 to link element 9d is required so that markers 11 do not become detached from the scaffold during processing steps such as crimping the scaffold to a balloon or when the scaffold is balloon expanded from the crimped state. These two events, crimping and balloon expansion, are particularly problematic for marker attachment to the scaffold because both events induce significant plastic deformation in the scaffold body. If this deformation causes significant out-of-plane or irregular deformation of the struts that support or are near the marker, the marker may become dislodged (e.g., if the strut that holds the marker is twisted or bent during crimping, the marker may fall out of its hole). Scaffolds with radiopaque markers and methods for attaching the marker to the scaffold body are discussed in U.S. Patent Application Publication No. 2007 / 0156230.

[0012] There is a need to improve the reliability of radiopaque marker fixation to the scaffold for thin walled scaffolds. Related to this need is a need to improve the performance characteristics of scaffolds, especially thin walled scaffolds made of bioabsorbable materials that must be routed around tortuous anatomical structures. Summary of the Invention

[0013]

[0013] Disclosed is a bioabsorbable scaffold having radiopaque markers and a scaffold structure that retains such radiopaque material and allows for reduced crimp profile and / or improved catheter conformance when a catheter to which the scaffold is attached is pushed through tortuous anatomical structures.

[0014]

[0014] The scaffolds disclosed herein are suitable for meeting one or a combination of the following objectives: (i) Thinning the crimp profile of thin-walled scaffolds supporting radiopaque markers. (ii) Fixing the markers to the thin-walled scaffold. (iii) reducing strain energy storage in the marker retention structure when the thin-walled scaffold is deformed during crimping, balloon expansion at the target vascular site, or during introduction of the scaffold to the target site. (iv) reducing flaring of end rings at the distal end of the scaffold for thin walled scaffolds or scaffolds comprising PLLA and having a wall thickness greater than 125 microns (μm);

[0015]

[0015] Through testing, it has been recognized that in order to achieve thin walls, certain critical areas of the scaffold need to be modified that were not previously an issue when larger wall thicknesses were used. An example of a scaffold having a larger wall thickness of 158 microns (μm) is described in U.S. Patent Application Publication No. 2010 / 0004735. When significant reductions in wall thickness are made, compared to existing bioabsorbable scaffolds (e.g., from a wall thickness of 160 microns (μm) to a wall thickness of 100 microns (μm)), it has been found that the placement, shape and dimensions of the ring and link elements, especially at the distal end of the scaffold, require improvement.

[0016]

[0016] Thin-walled scaffolds are required because of the clinical need to maintain a low profile of exposed struts in the bloodstream. Blood compatibility, also called hemocompatibility or clot resistance, is a desirable property for scaffolds and stents. Adverse events of scaffold thrombosis, although a very low frequency event, are associated with high morbidity and mortality. To mitigate the risk of thrombosis, dual antiplatelet therapy is administered with the implantation of all coronary scaffolds and stents. This is to reduce thrombus formation from the procedure, vessel injury, and the implant itself. Scaffolds and stents are foreign bodies, and they all have some degree of thrombogenicity. Thrombogenicity of a scaffold refers to its tendency to form thrombus, which is due to several factors including strut thickness, strut width, strut shape, scaffold total surface area, scaffold pattern, scaffold length, scaffold diameter, surface roughness, and surface chemistry. Some of these factors are interrelated. A low strut profile also leads to less neointimal proliferation, as the neointimal wall will grow to the extent necessary to cover the struts, which is therefore a necessary step for complete healing. Thinner struts are also believed to result in more rapid endothelialization and healing.

[0017]

[0017] According to various aspects of the present invention, there are provided thin-walled scaffolds ("scaffolds"), medical devices, methods for making such scaffolds, methods for making markers and attaching the markers to struts, links or bar arms of the scaffold, methods for crimping, or methods for assembling a medical device with such scaffolds, having one or more of the following (1)-(15), or any combination thereof:

[0018] (1) The scaffold is crimped to the theoretical minimum crimp diameter (D-min).

[0019] (2) The scaffold wall thickness is less than 125 microns (μm), less than 100 microns (μm), about 100 microns (μm), or about 93 microns (μm).

[0020] (3) The wavelength of a ring coupled to the marker link is greater than the wavelength of another ring not coupled to the marker link, and / or the wavelengths of the rings coupled to the marker link have wavelengths of different lengths.

[0021] (4) The distance from a W vertex to the adjacent U vertex is greater than the distance from a Y vertex to the adjacent U vertex.

[0022] (5) The scaffold is made of a tube containing poly(l-lactide).

[0023] (6) A scaffold crimped to a balloon, the scaffold configuring the crimped state shown and described in connection with FIG. 4D, FIG. 6A, or FIG. 7A.

[0024] (7) A method of crimping any of the scaffolds described in connection with FIG. 3, FIG. 4, FIG. 5, FIG. 6, or FIG.

[0025] (8) A method for attaching a radiopaque marker to the scaffold.

[0026] (9) A marker link as shown and described in connection with FIG. 2C.

[0027] (10) The ring has n peaks, where n is greater than 5, or greater than 6 and less than or equal to 12.

[0028] (11) The ring has 2 wavelengths of a first size and n-3 wavelengths of a second size, the first size being greater than the second size.

[0029] (12) A ring connected to the marker link at its apex has a first width, and an adjacent ring connected to the marker link has a second width greater than the first width.

[0030] (13) The ring connected to the marker link at the W apex has a flat portion that is wider than the Y apex flat portion connected to the marker link and bonded to the first ring.

[0031] (14) A first distance between the marker link and adjacent rings is greater than a second distance between the rings joined by the marker link.

[0032] (15) A first distance between rings joined by the nonlinear marker link is greater than a second distance between rings not joined by the nonlinear marker link.

[0033] (16) D-min is about 1 mm or less than 1 mm.

[0034] (17) The aspect ratio (AR) of the marker link of the thin-walled scaffold is about 4–5, or about 4.5, where AR is defined as the maximum width of the marker link divided by the wall thickness at the marker link.

[0035] (18) A first wavelength or 1 / 2 wavelength of a first ring is greater than a second wavelength or 1 / 2 wavelength of a coupled second ring.

[0036] (19) A first wavelength or half wavelength between two peaks of a ring is different from a second wavelength between two other peaks of the same ring.

[0037] (20) The rings are sinusoidal or zigzag.

[0038] (21) For a marker link having a maximum width that is about 200% greater than the maximum width of a non-marker link, a half wavelength measured from a W apex formed between the marker link and a first ring is about 15% greater than a half wavelength measured from a Y apex formed between the marker link and a second ring coupled to the first ring.

[0039] (22) For a marker link having a maximum width that is approximately 200% greater than the maximum width of a non-marker link, a wavelength measured from a W apex formed between the marker link and a first ring is approximately 5% to 10% greater than a wavelength measured from a Y apex formed between the marker link and a second ring coupled to the first ring.

[0040] (23) For a marker link with a maximum width approximately 200% greater than the maximum width of a non-marker link, the wavelength measured from the W crest / peak formed between the marker link and the ring is approximately 5%–10% greater than the measured wavelength measured between other peaks in the ring.

[0041] (24) A top width B1 that is larger than the top width B2, for example, a top width B1 that is about 350% to 400% larger than the top width B2.

[0042] (25) A ring spacing A12 between the first ring and the second ring is larger than a ring spacing A23 between the second ring and the third ring, for example, A12 is about 40% larger than A23.

[0043] (26) The links may be linear or nonlinear links, e.g., link 20 and link 636.

[0044] (27) The length c1 is approximately 36% greater than the length c2 of the marker link.

[0045] (28) The length c1 of the nonlinear link is approximately 36% greater than the length c2 of the nonlinear link.

[0046] (29) A medical device comprising: a thin-walled scaffold having a network of rings interconnected by links, each ring having a plurality of peaks, the peaks being one of U-apexes, Y-apexes, and W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA); and a marker link extending between a first ring and a second ring of the plurality of rings, the marker link including a structure having a hole, the hole containing a radiopaque material, the marker link forming a W-apex of the first ring and a Y-apex of the second ring, the ½ wavelength of the first ring measured from the W-apex of the first ring to an adjacent U-apex of the first ring is greater than a ½ wavelength of the second ring measured from the Y-apex of the second ring to an adjacent U-apex of the second ring.

[0047] (30) The medical device according to (29) in combination with one or more of the following items (a) to (g), or any combination thereof: (a) The length of the marker link is greater than the length of the link connecting the second ring to a third ring coupled to the second ring. (b) the marker link includes a first link portion extending from the structure to a W apex of the first ring and a second link portion extending from a Y apex of the second ring to the structure, the width of the first link portion being less than the length of the second link portion. (c) the length of the first link portion is less than the length of the second link portion. (d) the structure includes a first hole and a second hole each including a radiopaque material, the first hole and the second hole being disposed parallel to the axis AA; (e) the first ring includes a first peak, a second peak and a third peak, the first peak corresponds to a W apex of the first ring, the second peak is adjacent to the first peak, the third peak is adjacent to the second peak, and a second wavelength extending from the second peak to the third peak is smaller than a first wavelength extending from the first peak to the second peak. (f) a flat portion of the W apex of the first ring is larger than a flat portion of a W apex of a third ring coupled to the second ring and / or a flat portion of a W apex of a fourth ring of the first ring. (g) the wavelength of the first ring forming the W apex of the first ring is longer than the wavelength of the second ring forming the Y apex of the second ring;

[0048] (31) A medical device, comprising: a thin-walled scaffold having a proximal end portion and a distal end portion formed by a network of a plurality of rings interconnected by links, each ring having a plurality of peaks, the peaks being one of U-apexes, Y-apexes, and W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA); and a marker link extending between a first ring and a second ring of the plurality of rings, the marker link extending between the thin-walled scaffold and a first ring and a second ring of the plurality of rings. and a marker link, the marker link including a structure having a hole within which a radiopaque material is contained, the marker link forming a first ring and a W apex of the first ring and a second ring and a Y apex of the second ring, the W apex of the first ring corresponding to a first peak, and a first wavelength of the first ring measured from the first peak to a second peak of the first ring adjacent to the first peak is greater than a second wavelength of the first ring measured from the second peak to a third peak adjacent to the first ring.

[0049] (32) The medical device according to (31) in combination with one or more of the following items (a) to (c), or any combination thereof: (a) a first ring has n crests and n-1 wavelengths, where n is at least 6 and not more than 12, the first wavelength and the second wavelength are measured above and below the first crest, respectively, and the first crest is greater than the remaining n-3 wavelengths measured between the n-1 crests; (b) The remaining n-3 wavelengths all have the same length. (c) The length of the marker link is approximately equal to the length of the link connecting the second ring to the third ring.

[0050] (33) A medical device, comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; a thin-walled scaffold crimped onto the balloon, the thin-walled scaffold being formed by a network of a plurality of rings interconnected by links, the thin-walled scaffold having a proximal end portion and a distal end portion, each ring having a plurality of peaks, the peaks being one of U-apexes, Y-apexes, and W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA); and a marker link extending between a first ring and a second ring of the plurality of rings, the marker link having a hole. and a marker link, the marker link including a first ring and a W apex of the first ring and a second ring and a Y apex of the second ring, the W apex of the first ring corresponding to a first crest, a first wavelength of the first ring measured from the first crest to a second crest adjacent to the first crest is greater than a second wavelength of the first ring measured from the second crest to a third crest adjacent to the second crest, the thin walled scaffold having an outer diameter of about D-min, where D-min=(1 / π)×[(n×strut_width)+(m×link_width)]+2*t.

[0051] (34) The medical device according to (33) in combination with one or more of the following items (a) to (d), or any combination thereof: (a) The maximum width of the structure measured along axis BB is greater than the maximum width of a link extending between the second ring and a third ring coupled to the second ring. (b) the marker link includes a first link portion extending from the structure to the W apex and a second link portion extending from the Y apex to the structure, the width of the first link portion being greater than the width of the second link portion. (c) the length of the first link portion is less than the length of the second link portion. (d) the structure includes a first hole and a second hole containing a radiopaque material, the first hole and the second hole being oriented parallel to the axis AA;

[0052] (35) A method for making a medical device, comprising the steps of using a tube comprising poly(L-lactide) and forming a thin-walled scaffold pattern from the tube, the thin-walled scaffold being formed by a network of a plurality of rings interconnected by links, each ring having a proximal end portion and a distal end portion, each ring having a plurality of crests, the crests being one of U-apexes, Y-apexes and W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA), the thin-walled scaffold having at least one crest extending between a first ring and a coupled second ring of the plurality of rings. forming a thin-walled scaffold pattern including marker links of the first dimension, the marker links including structures having holes; disposing radiopaque material in the marker holes, the holes having a first size before material disposition and a second size after material disposition that is larger than the first size, the structures having a width measured along an axis BB; and crimping the thin-walled scaffold onto a balloon catheter, wherein the thin-walled scaffold is crimped to about a theoretical minimum crimp diameter (D-min) and none of the apexes adjacent above or below the structures overlap the structures.

[0053] (36) The medical device according to (35) in combination with one or more of the following items (a) to (c), or any combination thereof: (a) The marker links form a first ring and a W apex of the first ring and a Y apex of the second ring, the W apex of the first ring corresponds to a first crest, and a first wavelength of the first ring measured from the first crest to a second crest adjacent to the first crest is greater than a second wavelength of the first ring measured from the second crest to a third crest adjacent to the first crest. (b) the marker links form a first ring and a W apex of the first ring and a second ring and a Y apex of the second ring, the first U apex and the second U apex are adjacent above and below the W apex of the first ring, respectively, a first strut extends from the W apex of the first ring to the first U apex, and a second strut extends from the W apex of the first ring to the second U apex, and a distance between the first U apex and the second U apex, or the distance from the second strut to the first strut, is greater than or equal to a maximum width of the marker structure measured along axis BB. (c) The width of the marker structure is greater than the maximum width of the link connecting the second ring to an adjacent third ring.

[0054] (37) A medical device, comprising a thin-walled scaffold having a proximal end portion and a distal end portion formed by a network of a plurality of rings interconnected by thin-walled scaffold links, each ring having a plurality of apexes including a U apex and at least one of a Y apex and a W apex, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA), the proximal end portion being connected to a first proximal link by a first proximal link. the distal end portion includes an outermost proximal ring coupled to the first distal ring by a first distal link, the first distal ring coupled to the second distal ring by a second distal link, the first proximal link including a proximal marker link with a proximal hole containing radiopaque material, the first distal link being devoid of a link retaining the radiopaque material.

[0055] (38) The medical device according to (37) in combination with one or more of the following items (a) to (i), or any combination thereof: (a) The outermost proximal ring is connected to the first proximal ring only by first proximal links, two of which extend parallel to the axis AA and have a constant moment of area. (b) The outermost distal ring is connected to the first distal ring only by first distal links, each of which is a non-linear link strut. (c) The proximal marker link has a first end and a second end, the first end forming one of the W apex and Y apex with the outermost proximal ring and forming the other of the W apex and Y apex with the first proximal ring. (d) The first distal ring and the second distal ring are connected by a distal marker link. (e) the distal marker link includes a structure surrounding the two holes, and the first distal ring and the second distal ring are further coupled by one or more marker links. (f) the distal marker link has a first end and a second end, the first end forming one of a W-apex and a Y-apex with the first distal ring and forming the other of the W-apex and the Y-apex with the second distal ring, the W-apex being wider than the Y-apex. (g) the proximal marker link further comprises a periphery generally surrounding the hole and defining a hole wall and a strut periphery, the distance between the wall and the periphery being D, and a radiopaque marker disposed in the hole, the radiopaque marker including a head having a flange disposed on the periphery, the flange having a radial length less than ½D to D, and the thin-walled scaffold thickness (t) is related to the length (L) of the marker measured between the abluminal and luminal sides of the marker by 1.1≦(L / t)≦1.8. (h) the distal marker link forms one of a W apex and a Y apex with a first distal ring and a second distal ring, and a ½ wavelength of the ring having the W apex is greater than a ½ wavelength of the ring having the Y apex, measured from the first adjacent apex; (i) the length of the first proximal link is less than the length of the first distal link, and / or the length of the second distal link is less than the length of the first distal link.

[0056] (39) A medical device comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; and a thin-walled scaffold crimped to the balloon, the thin-walled scaffold being formed by a network of rings interconnected by links of the thin-walled scaffold, the thin-walled scaffold having a proximal end portion and a distal end portion, each ring having a plurality of apices including U-apexes and at least one of Y-apexes and W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA), the proximal end portion being crimped to the proximal balloon end and including an outermost proximal ring coupled to a first proximal ring by a first proximal link; 11. A medical device comprising: a first proximal ring coupled to a second proximal ring by a second proximal link; a distal end portion crimped to the distal balloon end, comprising an outermost distal ring coupled to the first distal ring by a first distal link; the first distal ring coupled to the second distal ring by a second distal link; the first proximal link comprising a proximal marker link with a proximal hole comprising radiopaque material; the first distal link lacking a link retaining the radiopaque material; the first distal link comprising a nonlinear link; and wherein the thin walled scaffold has an outer diameter of about D-min, where D-min=(1 / π)×[(n×strut_width)+(m×link_width)]+2*t.

[0057] (40) The medical device according to (39) in combination with one or more of the following items (a) to (i), or any combination thereof: (a) The outermost proximal ring is connected to the first proximal ring only by first proximal links, each of which extends parallel to the axis AA and has a constant moment of area. (b) The nonlinear link is a U-shaped link. (c) a proximal marker link having a first end and a second end, the first end forming one of the W apex and Y apex with the outermost proximal ring and forming the other of the W apex and Y apex with the first proximal ring, the marker link including structure surrounding the hole; (d) a first link portion of the proximal marker link extends from the W apex to the structure and a second link portion of the proximal marker link extends from the Y apex to the structure, the length of the first link portion being greater than the length of the second link portion. (e) The length of the first link portion is approximately equal to twice the ring width plus the length of the strut extending between the U apex and the U apex, Y apex, or W apex of the ring. (f) the nonlinear link has a first end and a second end, the first end forming one of a W apex and a Y apex with the outermost proximal ring and forming the other of the W apex and the Y apex with the first proximal ring, the nonlinear link including a U-shaped structure between the W apex and the Y apex. (g) a first link portion of the proximal U-shaped link extends from the W apex to the U-shaped structure and a second link portion of the proximal marker link extends from the Y apex to the structure, the length of the first link portion being greater than the length of the second link portion. (h) The length of the first link portion is approximately equal to twice the ring width plus the length of the strut extending between the U apex and the U apex, Y apex, or W apex of the ring. (i) The distal marker link has a first end and a second end, the first end forming one of the W apex and Y apex with the first distal ring and forming the other of the W apex and Y apex with the second distal ring.

[0058] (41) A medical device, comprising a thin-walled scaffold having a proximal end portion and a distal end portion formed by a network of a plurality of rings interconnected by thin-walled scaffold links, each ring having a plurality of apexes including a U apex and at least one of a Y apex and a W apex, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA), the proximal end portion including an outermost proximal ring coupled to a first proximal ring by a first proximal link, the first proximal link being a first proximal link. The ring is coupled to a second proximal ring by a second proximal link, the distal end portion includes an outermost distal ring coupled to the first distal ring by a first distal link, the first distal ring coupled to the second distal ring by a second distal link, the first proximal link includes a proximal marker link with a pair of proximal holes containing radiopaque material, the proximal holes being disposed along axis AA, and the first distal link includes a distal marker link with a pair of distal holes containing radiopaque material, the distal holes being disposed along axis BB.

[0059] (42) The medical device according to (41) in combination with one or more of the following items (a) to (i), or any combination thereof: (a) The outermost proximal ring is connected to the first proximal ring only by first proximal links, two of which extend parallel to the axis AA and have a constant moment of area. (b) The outermost distal ring is connected to the first distal ring only by the first distal marker link and the nonlinear link strut. (c) The proximal marker link has a first end and a second end, the first end forming one of the W apex and Y apex with the outermost proximal ring and forming the other of the W apex and Y apex with the first proximal ring. (d) a width of the W-apex formed by the first end is greater than a width of the Y-apex formed by the second end, such that the wavelength of the ring forming the W-apex is longer than the wavelength of the ring forming the Y-apex. (e) The distal marker link has a first end and a second end, the first end forming one of the W apex and Y apex with the outermost distal ring and forming the other of the W apex and Y apex with the first distal ring. (f) the distal marker link includes a first link portion extending from the hole to the W apex and a second link portion extending from the hole to the Y apex, the first link portion having a length greater than the length of the second link portion. (g) the proximal marker link further comprises a periphery generally surrounding the hole and defining a hole wall and a strut periphery, the distance between the wall and the periphery being D, and a radiopaque marker disposed in the hole, the radiopaque marker including a head having a flange disposed on the periphery, the flange having a radial length less than ½D to D, and the thin-walled scaffold thickness (t) is related to the length (L) of the marker measured between the abluminal and luminal sides of the marker by 1.1≦(L / t)≦1.8. (h) A radiopaque material is contained within the hole, the radiopaque material having a frustum shape. (i) the hole has a first opening and a second opening located on a first side and a second side of the marker link, respectively, the first opening being larger than the second opening, and the frustum being generally coplanar with the first opening and the second opening.

[0060] (43) A medical device comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; and a thin-walled scaffold crimped to the balloon, the thin-walled scaffold being formed by a network of rings interconnected by links of the thin-walled scaffold, the thin-walled scaffold having a proximal end portion and a distal end portion, each ring having a plurality of apices including U-apexes and at least one of Y-apexes and W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (BB) perpendicular to a longitudinal axis (AA), the proximal end portion being crimped to the proximal balloon end and including an outermost proximal ring coupled to a first proximal ring by a first proximal link, the first proximal ring being coupled to a second proximal link. 16. A medical device comprising: a first distal link coupled to a second proximal ring by a first distal link; a distal end portion crimped to the distal balloon end; an outermost distal ring coupled to the first distal ring by a first distal link; the first distal ring coupled to the second distal ring by a second distal link; (1) the first proximal link comprises a proximal marker link comprising a structure, the structure extending parallel to an axis AA and comprising a radiopaque material; and (2) the first distal link comprises a distal marker link comprising a structure, the structure extending parallel to an axis BB and comprising a radiopaque material; and the thin-walled scaffold has an outer diameter of about D-min, where D-min=(1 / π)×[(n×strut_width)+(m×link_width)]+2*t.

[0061] (44) The medical device according to (43) in combination with one or more of the following items (a) to (i), or any combination thereof: (a) The outermost proximal ring is connected to the first proximal ring only by first proximal links, each of which extends parallel to the axis AA and has a constant moment of area. (b) the first distal link includes a nonlinear link; (c) a proximal marker link having a first end and a second end, the first end forming one of the W apex and Y apex with the outermost proximal ring and forming the other of the W apex and Y apex with the first proximal ring, the marker link including structure surrounding the hole; (d) a first link portion of the proximal marker link extends from the W apex to the structure and a second link portion of the proximal marker link extends from the Y apex to the structure, the length of the first link portion being greater than the length of the second link portion. (e) The length of the first link portion is approximately equal to twice the ring width plus the length of the strut extending between the U apex and the Y apex, U apex, or W apex of the ring. (f) the first distal link comprises a nonlinear link having a first end and a second end, the first end forming one of a W apex and a Y apex with the outermost proximal ring and forming the other of the W apex and Y apex with the first proximal ring, the nonlinear link including a U-shaped structure between the W apex and the Y apex. (g) a first link portion of the nonlinear link extends from the W apex to the U-shaped structure and a second link portion of the nonlinear link extends from the Y apex to the U-shaped structure, the length of the first link portion being greater than the length of the second link portion. (h) The length of the first link portion is approximately equal to twice the ring width plus the length of the strut extending between the U apex and the Y apex, U apex, or W apex of the ring. (i) The holes in the distal marker links are between, without overlapping or underlapping, the U apex next to the W apex of the outermost distal ring and the U apex next to the Y apex of the first distal ring.

[0062] [Incorporated by reference]

[0018] All publications and patent applications mentioned in this specification are incorporated herein by reference to the same extent as if each individual publication or patent application was specifically and individually indicated to be incorporated by reference. To the extent there is a conflicting usage of words and phrases between the incorporated publications or patents and this specification, those words have the meaning consistent with the usage of those words in this specification. [Brief description of the drawings]

[0063] [Figure 1] FIG. 1 is a perspective view of a portion of a prior art scaffold, where the scaffold is shown in a crimped state (balloon not shown). [Diagram 2] FIG. 13 is a top partial view of the scaffold showing marker links connecting adjacent rings with holes for holding radiopaque material. [Figure 2A] FIG. 3 is a replica of FIG. 2 showing additional dimensional and / or characteristics of the link for holding the two markers. [Figure 2B] FIG. 13 illustrates an alternative embodiment of a marker link. [Figure 2C] FIG. 3 is another replica of FIG. 2 in which the markers are attached to the links. [Diagram 3] 3 illustrates distal and proximal end portions of a scaffold according to one embodiment including marker links of the connection ring of FIG. [Figure 3A] FIG. 4 shows section IIIA of the scaffold of FIG. 3. [Figure 3B] FIG. 4 shows section IIIB of the scaffold of FIG. 3. [Figure 3C] FIG. 4 illustrates the scaffold of FIG. 3 in a crimped state. [Figure 3D] FIG. 4 illustrates the scaffold of FIG. 3 crimped onto a balloon of a balloon catheter. [Figure 4] FIG. 13 illustrates an end portion of a scaffold according to another embodiment, the end portion including links connecting adjacent rings and including markers, the rings having W-apexes formed in part by the marker links, the W-apexes modified to accommodate the marker structures. [Figure 4A] FIG. 5 shows a section IV surface of the scaffold of FIG. 4. [Figure 4B]FIG. 5 shows the distal end ring of the scaffold of FIG. 3 with the distal end ring of the scaffold of FIG. 4 shown in dotted lines to show the difference between the two rings. [Figure 4C] FIG. 5 shows section IVC of the scaffold of FIG. 4. [Figure 4D] FIG. 5 illustrates the scaffold of FIG. 4 in a crimped state. [Diagram 5] FIG. 13 is a partial view of a distal end portion of a scaffold according to another embodiment. [Figure 6] FIG. 13 illustrates an end portion of a scaffold according to another embodiment, where the distal end portion differs from the proximal end portion, where non-linear link struts connect the outermost distal ring to the inner rings, and where marker links are between the inner rings at the distal end portion. [Figure 6A] FIG. 7 is a partial view of the scaffold of FIG. 6 in a crimped state. [Figure 6B] 13 is an image of the distal end of the catheter in a bent configuration showing the distal rings of the scaffold flaring or protruding outward from the balloon distal end. [Figure 6C] FIG. 7 is an image of the catheter distal end in a bent configuration showing the distal ring of the scaffold according to FIG. 6, where the distal end ring no longer flares out when the catheter is placed in a bent state. [Figure 7] FIG. 13 illustrates an end portion of a scaffold according to another embodiment, where the proximal end portion differs from the distal end portion and where non-linear link struts and modified marker links connect the outermost distal ring to the inner ring. [Figure 7A] FIG. 8 is a partial view of the scaffold of FIG. 7 in a crimped state. [Figure 7B] FIG. 8 is a partial view of the scaffold of FIG. 7 taken at section VII of FIG. [Figure 7C] FIG. 8 is an image of the distal end of a catheter in a bent configuration showing the distal rings of a scaffold according to FIG. 7, where the distal end rings do not flare outward when the catheter is placed in a bent state. [Figure 8A] FIG. 13 is a side view of a marker according to another embodiment. [Figure 8B] Top view of the marker according to another embodiment. [Figure 9] Cross-sectional view of a link having holes with the markers of FIGS. 8A-8B embedded therein. [Figure 10] Side cross-sectional view of a first die for forming a rivet marker from radiopaque beads. [Figure 11A] Side view of a rivet marker formed using the die of FIG. 10. [Figure 11B] Side cross-sectional view of a scaffold strut after deforming the marker to create a peripheral edge and a lower peripheral edge for holding the marker within the hole, with the marker of FIG. 11A engaged with the hole of the strut, during the forming process. [Figure 12] Side cross-sectional view of a second die for forming a rivet marker from radiopaque beads. [Figure 13] Side view of a rivet marker formed using the die of FIG. 12. [Figure 14A] Perspective view showing one aspect of a process for deforming a rivet inserted into a scaffold hole to strengthen its engagement with the hole in order to resist the dropout force associated with crimping or balloon expansion. [Figure 14B] Perspective view showing another aspect of a process for deforming a rivet inserted into a scaffold hole to strengthen its engagement with the hole in order to resist the dropout force associated with crimping or balloon expansion. [Figure 14C] Perspective view showing yet another aspect of a process for deforming a rivet inserted into a scaffold hole to strengthen its engagement with the hole in order to resist the dropout force associated with crimping or balloon expansion. [Figure 15A] Side cross-sectional view of the deformed rivet marker and scaffold hole after the process described in connection with FIGS. 14A-14C. [Figure 15B] View of the deformed marker shown in FIG. 15A. [Figure 15C]FIG. 15B is a side cross-sectional view of the rivet and marker hole of FIG. 15A after a heating step. [Figure 16A] 13 illustrates steps associated with removing the formed rivet marker from the die and placing the rivet marker into a hole in the scaffold. [Figure 16B] 13 illustrates steps associated with removing the formed rivet marker from the die and placing the rivet marker into a hole in the scaffold. [Figure 16C] 13 illustrates steps associated with removing the formed rivet marker from the die and placing the rivet marker into a hole in the scaffold. [Figure 17A] 1A-1D illustrate a process for crimping a thin-walled scaffold according to the present disclosure. [Figure 17B] 1A-1D illustrate a process for crimping a thin-walled scaffold according to the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0064]

[0056] In this specification, like reference numbers in the drawings and specification designate corresponding or similar elements in the different views.

[0065]

[0057] The following terms and definitions apply to this disclosure.

[0066] The terms "about," "approximately," "generally," or "substantially" mean 30%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1.5%, 1%, 1-2%, 1-3%, 1-5%, or 0.5-5% less or more than a stated value, range, or each endpoint of a stated range, or 1 sigma, 2 sigma, or 3 sigma variance (Gaussian distribution) from a stated average or expected value. For example, d1 is about d2 means that d1 differs from d2 by 30%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0%, or 1-2%, 1-3%, 1-5%, or 0.5-5%. If d1 is a mean value, then d2 being about d1 means that d2 is within 1 sigma, 2 sigma, or 3 sigma variance or standard deviation from d1.

[0067]

[0059] Any numerical value, range, or range endpoint preceded by the words "about," "approximately," "generally," or "substantially" in this disclosure (including, for example, "approximately nothing," "almost nothing," "almost all," etc.) is understood to also describe or disclose the same numerical value, range, or range endpoint without the words "about," "approximately," "generally," or "substantially."

[0068]

[0060] "Glass transition temperature", TG, is the temperature at which the amorphous domains of a polymer change from a brittle glassy state to a solid deformable or ductile state at atmospheric pressure. In this application, the method of finding the TG, or TG-low (lower limit of the TG range) of a polymer is defined in the same manner as in U.S. Patent Application Serial No. 14 / 857635 (Docket No. 62571.1216).

[0069]

[0061] A "stent" generally refers to a permanent, durable, or non-degradable structure comprised of a non-degradable metal or alloy structure, whereas a "scaffold" refers to a temporary structure that includes a bioabsorbable or biodegradable polymer, metal, alloy, or combination thereof and is capable of radially supporting a vessel for a limited period of time, e.g., 3, 6, or 12 months after implantation. However, it should be understood that the art often uses the term "stent" to refer to either type of structure.

[0070]

[0062] "Inflated diameter" or "expanded diameter" refers to the inner or outer diameter a scaffold attains when its support balloon inflates the scaffold from its crimped configuration to implant the scaffold in a vessel. Inflated diameter may refer to a post-expanded balloon diameter that exceeds the nominal balloon diameter, for example, a 6.5 mm balloon (i.e., a balloon having a nominal diameter of 6.5 mm when inflated to a nominal balloon pressure such as 6 times atmospheric pressure) has a post-expanded diameter of about 7.4 mm, and a 6.0 mm balloon has a post-expanded diameter of about 6.5 mm. The nominal to post-expanded ratio of the balloon may range from 1.05 to 1.15 (i.e., the post-expanded diameter may be 5% to 15% larger than the nominal inflated balloon diameter). After the scaffold attains its expanded diameter by the balloon pressure, it will decrease in diameter to some extent due to a recoil effect that is primarily related to any or all of the manner in which the scaffold was manufactured and processed, the material of the scaffold, and the design of the scaffold.

[0071]

[0063] When referring to diameter, it is intended to mean either the inner diameter or the outer diameter, unless otherwise specified or suggested otherwise by the context of the description.

[0072]

[0064] When we say scaffold strut, it also applies to the links and bar arms.

[0073]

[0065] The "post-expanded diameter" (PDD) of a scaffold refers to the inner diameter of the scaffold after it has increased to its expanded diameter and the balloon has been removed from the patient's vasculature. The PDD takes into account the recoil effect. For example, acute PDD refers to the scaffold diameter taking into account acute recoil in the scaffold.

[0074]

[0066] "Pre-crimp diameter" refers to the outer diameter (OD) of the scaffold before it is crimped into a tube (e.g., cut from a tube that has been dip coated, injection molded, extruded, radially expanded, die drawn, and / or annealed) or balloon from which the scaffold is made. Similarly, "crimp diameter" refers to the OD of the scaffold when it is crimped into a balloon. The "pre-crimp diameter" can be about 2-2.5, 2-2.3, 2.3, 2, 2.5, 3.0 times the crimp diameter, about 0.9, 1.0, 1.1, 1.3, and about 1-1.5 times the expanded diameter, nominal balloon diameter, or expanded diameter. Crimping, in this disclosure, refers to a diameter reduction of a scaffold characterized by significant plastic deformation, i.e., greater than 10%, or greater than 50% diameter reduction attributable to plastic deformation, such as at the apexes in the case of a stent or scaffold having a wavy ring pattern, e.g., FIG. 1. When a scaffold is deployed or expanded by a balloon, the inflated balloon plastically deforms the scaffold from its crimped diameter. Methods for crimping scaffolds made according to this disclosure are described in U.S. Patent Application Publication No. 2013 / 0255853 (Docket No. 62571.628).

[0075] A material "comprising" or "comprises" poly(L-lactide) or PLLA includes, but is not limited to, a PLLA polymer, a blend or mixture comprising PLLA and another polymer, and a copolymer of PLLA and another polymer. Thus, a strut comprising PLLA means that the strut can be made from a material that comprises any of a PLLA polymer, a blend or mixture comprising PLLA and another polymer, and a copolymer of PLLA and another polymer.

[0076]

[0068] Bioabsorbable scaffolds made of biodegradable polyester polymers are radiolucent. Radiopaque markers are placed on the scaffold to allow for fluoroscopic visualization. For example, the scaffold described in U.S. Pat. No. 8,388,673 (the '673 patent) has two platinum markers 206 fixed to each end of the scaffold 200, as shown in FIG. 2 of the '673 patent.

[0077]

[0069] When we say a direction perpendicular to or parallel to the axis AA (e.g., as shown in FIG. 3), we mean perpendicular to or parallel to the axial direction of the scaffold or tube. Similarly, when we say a direction perpendicular to or parallel to the axis BB (e.g., as shown in FIG. 3), we mean perpendicular to or parallel to the circumferential direction of the scaffold or tube. Thus, the sinusoidal rings of the scaffold (periodically) run parallel to the circumferential direction or parallel to the axis BB and perpendicular to the axis AA, while the links, in one embodiment, run parallel to the axial direction or axis AA and perpendicular to the axis BB of the scaffold or tube.

[0078]

[0070] Whenever the same element number is used in multiple drawings, it should be understood that the same description first used for the element in the first drawing applies to the embodiment depicted in the subsequent drawing, unless otherwise specified.

[0079]

[0071] The thickness dimension (e.g., thickness of a wall, strut, ring or link) refers to the dimension measured perpendicular to both axis AA and axis BB. The width dimension is measured in the plane of axis AA and axis BB. More specifically, width is the cross-sectional width from one side of a continuous structure to the other, thus clevis link 636 has a constant link width over its length just as link 334 has a constant link width. Furthermore, it should be understood that the so-called plane of axis AA and axis BB is not technically a plane since it describes the surface of a tubular structure having a central lumen axis parallel to axis AA. Thus, axis BB may alternatively be considered as an angular component if the scaffold position were described using a cylindrical coordinate system (i.e., axis AA is the Z axis and the luminal / abluminal positions of the apexes, links, rings, etc. are found by angular and radial coordinate constants).

[0080]

[0072] "Thin wall thickness", "thin wall scaffold", "thin wall" refers to a strut, ring, link, or bar arm made of a polymer, including poly(L-lactide), having a wall thickness of less than 125 microns (μm). Discussed herein are challenges faced in working with thin wall scaffolds, including retaining markers with the same volume of radiopaque material.

[0081]

[0073] Figure 2 is a top view of a portion of a polymer scaffold, e.g., a polymer scaffold having a pattern of rings interconnected by links. Marker link 20 ("link 20") extends between rings 312a, 312b in Figure 2. Link 20 forms left and right structures or strut portions 21b, 21a, respectively, for holding radiopaque markers. The markers can be held in holes 22 formed by structures 21a, 21b. Surface 22a corresponds to the abluminal side of the scaffold.

[0082]

[0074] Figure 2A is a reproduction of Figure 2 showing additional dimensional features, in particular the characteristic dimensional features D0, D1 and D2. The diameter of the holes 22 is D0. The distance between adjacent holes 22 is greater than or equal to D1. The width of the edge of either or both of the holes 22, i.e., the distance from the inner wall surface surrounding either or both of the holes 22 to the edge of the link 20, is greater than or equal to D2.

[0083]

[0075] Figure 2B illustrates the dimensional features described in connection with Figure 2A for a marker link 720 oriented such that structures 21a, 21b are offset along axis BB rather than axis AA. Marker 720 connects ring 312a and ring 312b. A scaffold embodying this marker is shown in Figure 7.

[0084]

[0076] In Figure 2C, a rivet type marker 127' / 137' is shown secured to hole 22. The indicated dimensions refer to parameters that may be used to test the marker link (after the radiopaque material is coupled) to evaluate the ability of the marker link to resist forces that tend to cause the rivet 127' / 137' to fall out of hole 22. These forces may result from the pressurized balloon surface or deformation of nearby scaffold structures that tend to deform hole 22 when the scaffold is crimped or balloon expanded. According to one embodiment, the rivet head and / or rivet tip of the rivet 127' / 137' pair may be tested to determine if the minimum distances δ1, δ2 and δ3 (Figure 2C) are met. Distances δ1, δ2, and δ3 reflect either or both the minimum size of the head and / or tip of the rivet pressed into the hole, which dictates both that the rivet should be retained within the hole 22 (too small a head or tip diameter would not be able to resist dislodgement forces) and that excess rivet material would not cause issues such as balloon puncture or vessel irritation when the scaffold is implanted in the vessel. According to embodiments, the minimum distance from the end of the marker head / tip to the edge of the strut (or link) portion 21a / 21b, i.e., δ2, can be about 10%, 25% and up to 50% of D2. Above 50% means the head or tip is too small to hold the rivet in place. For heads / tips above D2, the head may or will extend beyond the edge of the strut / link, which can lead to issues such as forming relatively sharp edges that can damage the balloon or irritate adjacent tissue. The minimum distance between marker heads / tips, i.e., δ1, is 0% or up to 25% of distance D1. If the marker edges or heads overlap each other, this may exceed the maximum height required for the struts (approximately 160 microns (μm)). The minimum length of the heads / tips extending to the right or left of hole 22, i.e., δ3, is greater than 50% of D2.

[0085]

[0077] Methods for inserting radiopaque markers into holes generally utilize cylindrical holes to hold the marker. Most of the retention force comes from friction between the wall and the marker material. The marker material has been reliably held in the scaffold hole in this manner when the scaffold has a wall thickness of 150 microns (μm) or more. However, when the wall thickness is reduced to 100 microns (μm) or less, it becomes much more difficult to hold the marker material in the hole. Coating materials for carrying drugs may help hold the marker in place, but coatings such as everolimus / PDLLA tend to be very thin, on the order of 3 microns (μm), which limits the out-of-plane shear strength to resist detachment of the marker from the hole.

[0086]

[0078] There are several desirable properties or capabilities that result from the reduction in the wall thickness of the scaffold struts. Advantages of using a thinner wall thickness include a lower profile and therefore better introduceability, reduced acute thrombogenicity, and potentially improved healing. In some embodiments, it is desirable to use the same size markers in scaffolds with thinner struts so that there is no difference, i.e., reduction, in radiopacity between the two types of scaffolds. However, reducing the strut thickness while keeping the marker holes 22 the same size may result in the markers protruding above and / or below the strut surface due to reduced hole volume. It is desirable to keep the abluminal and luminal sides 25a and 25b of the marker flush with the corresponding abluminal and luminal sides of the strut, in which case the hole 22 diameter (d) may be increased to partially compensate for the reduced hole volume as a result of the thinner struts.

[0087]

[0079] Paragraphs

[0073] to

[0083] of commonly owned US patent application Ser. No. 14 / 738,710 describe factors that affect the ability of the scaffold to retain the marker in the hole and the special challenges faced when the wall thickness is less than 160 microns (μm) or less than 125 microns (μm). According to some embodiments, it has been found that when the wall thickness is less than 125 microns (μm), i.e., when the scaffold is thin-walled, the marker cannot be reliably retained in the hole essentially by friction alone. In a preferred embodiment where the wall thickness is less than 100 microns (μm), the marker material is retained in the hole using a rivet-shaped marker, briefly described above in connection with Fig. 2C and described in more detail in connection with Figs. 8 to 16.

[0088]

[0080] Described below are embodiments of scaffold patterns suitable for meeting one or a combination of the following objectives: (i) Thinning the crimp profile of thin-walled scaffolds supporting radiopaque markers. (ii) Fixing radiopaque markers within the thin-walled scaffold. (iii) reducing strain energy storage in the marker retention structure when the thin-walled scaffold is deformed during crimping, balloon expansion at the target vascular site, or introduction of the scaffold to the target site. (iv) For thin-walled scaffolds, or scaffolds comprising PLLA and having a wall thickness greater than 125 microns (μm), avoiding protruding or flaring end rings at the distal end of the scaffold.

[0089]

[0081] It will be appreciated that the above objectives are interrelated and that a single modification can address multiple objectives. For example, by making the marker link more flexible, both objectives (iii) and (iv) can be met. The scaffolds according to these embodiments may be made from thin-walled tubes or sheets of material including poly(L-lactide) (PLLA), which are laser cut from the tubular body to generate the patterns shown in Figures 3-7. Methods for making the tubes may include one or more of extrusion, injection molding, solid state processing, and biaxial expansion as described in US Patent Application Serial No. 14 / 810,344 (62571.1212).

[0090]

[0082] A scaffold according to an embodiment, such as scaffold 300, 400, 500, 600 or 700, is preferably crimped onto a balloon catheter as shown in Figure 3D. The scaffold may be attached to a balloon using any of the crimping methods described in US Patent Application No. 2013 / 0255853, specifically any of the crimping methods and crimping devices described in paragraphs

[0068] to

[0073] ,

[0077] to

[0099] ,

[0111] to

[0126] ,

[0131] to

[0146] and Figures 1A, 1B, 4A, 4B, 5A, 5B, 8A and 8B of US Patent Application No. 2013 / 0255853, to ensure a desired crimp diameter, such as D-min (defined below).

[0091]

[0083] Figure 3 shows a partial plan view of an end portion of a scaffold, i.e., scaffold 300, according to one embodiment. The left or distal end portion 302 (i.e., left side of Figure 3) includes sinusoidal rings 312a, 312b, and 312c, with ring 312a being the outermost ring. Rings 312a and 312b are connected by two links 334 and a marker link 20. Rings 312c and 312d are connected by three links 334 that extend parallel to axis AA. Links 334 extend parallel to axis AA and have a constant moment of inertia over their length, meaning that they have a constant width and thickness, and the location of the center of gravity or geometric center (or longitudinal axis) of the links is everywhere parallel to axis AA. The right or proximal end portion 304 (i.e., the right side of FIG. 3) includes sinusoidal rings 312d, 312e, and 312f, with ring 312f being the outermost ring. Ring 312d and ring 312e are connected by three links 334. Ring 312e and ring 312f are connected by two links 334 and a marker link 20. Thus, the scaffold 300 has a marker link 20 extending between and connecting the outermost link to the adjacent inner ring. The scaffold 300 can have 15, 18, or 20 rings 312 interconnected to each other by links 334.

[0092]

[0084] Ring 312, for example ring 312b, is sinusoidal, meaning that the curvature of the ring along axis BB is best described by a sine wave with the wavelength of the sine wave equal to the distance between adjacent peaks 311a of the ring. The ring has a constant width at both the apices 307, 309, 310 and at the struts 330 connecting the apices to adjacent apices.

[0093]

[0085] Each inner ring 312b-312e has three types of apexes: U-apex, Y-apex, and W-apex. The outermost ring has only Y-apex type or W-apex type and U-apex type. The mountain or peak 311a (or valley or valley 311b) can correspond to U-apex, Y-apex, or W-apex. The outermost ring 312a has only U-apex type and W-apex type. The outermost ring 312f has only U-apex type and Y-apex type. The marker link 20 joins the rings by forming a W-apex with the first ring (e.g., ring 312e) and a Y-apex with the second ring (e.g., ring 312f).

[0094] Link 334 connects to ring 312f at Y apex 310. A "Y apex" refers to an apex where the angle extending between strut 330 of ring 312 and link 334 is an obtuse angle (greater than 90 degrees). Link 334 connects to ring 312a at W apex 309. A "W apex" refers to an apex where the angle extending between strut 330 and link 334 is an acute angle (less than 90 degrees). A U apex 307 is an apex where no link is connected. Marker link 20 connects to the ring at W apex 314 and Y apex 316.

[0095]

[0087] In scaffold 300, there are six peaks or crests 311a and six valleys or crests 311b per ring 312. A peak 311a is always followed by a valley 311b. Ring 312b has 12 apexes: three W apexes 309, three Y apexes 310, and six U apexes 307.

[0096]

[0088] Figures 3A and 3B show close-up views of a portion of scaffold 300. Figure 3A shows section IIIA of Figure 3, and Figure 3B shows section IIIB of Figure 3. The following description is provided with respect to Figures 3A-3B and applies equally to portions 302 and 304 of scaffold 300, with the understanding that link 20 connects to outermost ring 312f at Y apex 316 and to adjacent ring 312e at W apex 314.

[0097]

[0089] Referring to FIG. 3A, the successive wavelengths of the outermost ring 312a have length L1 and length L2, i.e., the distance (along axis BB) from apex 314 to U apex 307 is L1, and the distance from U apex 307 to Y apex 309 is L2. The same distances apply to ring 312b, L1 and L2 from apex 316 to W apex 309 and from W apex 309 to Y apex 310, respectively. In scaffold 300, L1=L2=constant for rings 312a, 312b. That is, the distance or wavelength from one crest to another is the same. Also, in scaffold 300, L1+L2 is constant everywhere. That is, for all rings, the distance between W apex and Y apex is the same as the distance between adjacent crests of rings 312a-312f. Distance X in Figure 3A refers to a half cycle or half length of a sine wave, i.e., 1 / 2 L1. Distance X is equal to the distance from apex 314 to the U apex 307 of the adjacent apex 312a. X is the same for ring 312b. In other embodiments, L1 is not equal to L2 and X is different for the outermost ring 312a and the adjacent ring 312b.

[0098] In alternative embodiments including scaffold 400, scaffold 500 or scaffold 700 described below, the rings may be zigzag rather than sinusoidal ring shaped. An example of a zigzag shaped ring is shown in US Patent Application Publication No. 2014 / 0039604, FIGS. 5A and 6A. A zigzag ring may be described as non-curved strut elements converging at apices shaped to have an inner apex radius and an outer apex radius. The same description applies, i.e., the rings may be described in terms of wavelengths, struts and apices, except that the shape is zigzag rather than sinusoidal. The term "wavy" refers to both zigzag and sinusoidal ring types.

[0099]

[0091] Referring to Figure 3B, the distance along axis AA from the peak or crest of ring 312a to the peak or crest of adjacent ring 312b, i.e., the length of marker 20 (plus width t1), is A12. The distance along axis AA from the peak or crest of ring 312b to the peak or crest of adjacent ring 312c, i.e., the length of marker 334 between these rings (plus width t2), is A23. For scaffold 300, A12 = A23. The width of left link 20 of marker structure 21a is tm1, and the width of right link 20 of structure 21b is tm2. The width of link 334 is tl1. The apexes 307, 310, 309, 314 and struts 330 of ring 312a have a constant width t1. Apices 307, 310, 309, 314 and struts 330 of ring 312b have a constant width t2. Apices 307, 310, 309, 314 and struts 330 of ring 312c have a constant width t3. In scaffold 300, t1 is less than t2, so t2=t3. Dimensions B1 and B2 are the top surfaces of rings 312a and 312c that extend parallel to axis BB, or the non-curved, i.e., flat, top surface portions. In scaffold 300, B1=B2.

[0100]

[0092] Referring to Figure 3C, a scaffold 300 is shown with markers 20 in a crimped state. The crimp diameter implemented on the scaffold 300 is the theoretical minimum crimp diameter where struts converging to the same apex touch each other when the scaffold is fully crimped, i.e., when the scaffold is removed from the crimping device or placed in a constraining sheath immediately after crimping. The formula for the theoretical minimum crimp diameter (D-min) under these conditions is given below: D-min=(1 / π)×[(n×strut_width)+(m×link_width)]+2*t where: "n" is the number of struts in the ring (12 struts for scaffold 300); "strut_width" is the width of the strut (170 microns (μm) for scaffold 300); "m" is the number of links connecting adjacent rings (3 for scaffold 300); "link_width" is the width of the link (127 microns (μm) for scaffold 300); "t" is the wall thickness (93 microns (μm) for scaffold 300).

[0101]

[0093] Therefore, for scaffold 300, D-min = (1 / π) x [(12 x 170) + (3 x 127)] + 2 x (93) = 957 microns (μm).

[0102]

[0094] In the bonded ring pairs 312a, 312b at the distal end 302 and 312e, 312f at the distal end, the marker links 20 are wider (along axis BB) than the links 334 to accommodate the markers. As a result, adjacent struts 330 can often overlap the links 20 to achieve the same D-min all the way around. This condition is shown in FIG. 3C. Such a condition in the crimped scaffold raises concerns about the local strength of the rings and links that hold the markers. As shown in FIG. 3C, there is overlap (struts pushing against the abluminal side of the marker) or underlap (struts pushing against the luminal surface of the marker) by the struts 330a, 330b and / or the associated U-apexes associated with these struts. It is preferable to eliminate this overlap / underlap when the scaffold is crimped.

[0103]

[0095] Scaffold struts, especially the struts and links of thin-walled scaffolds, are not designed to twist or to support large twists. Twisting occurs when struts meet and overlap each other. If the aspect ratio of the width to thickness of the scaffold struts is higher, there is a greater tendency for the struts to twist when they meet adjacent structures, such as structure 21a of marker link 20 (thin-walled scaffolds have a higher aspect ratio, strut width, for the same vascular tissue coverage compared to thicker scaffolds). As can be seen from the deformation state in FIG. 3C compared to FIG. 3, twisting is introduced into the ring structure and possibly even the marker link struts. This type of abnormal deformation can lead to crack propagation or reduced fatigue life of the ring and / or link 20 during balloon expansion in a vessel.

[0104] 3D shows a medical device comprising a balloon catheter and a scaffold 300 crimped to a balloon 15. The distal end 302 of the scaffold 300 is closest to the distal end 17b of the balloon 15 and the proximal end 304 is closest to the balloon proximal end 17a. The tip or most distal end 12 of the balloon catheter is shown. A guidewire or mandrel 8 extends from the tip 12 and exits the lumen of the catheter shaft 2. The scaffold crimped to the balloon (according to D-min or other minimum crimp diameter) can be scaffold 300 or scaffold 400 discussed below. Scaffold 500, scaffold 600, and scaffold 700 may be used in place of scaffold 300.

[0105]

[0097] As mentioned above, when compared to scaffolds with relatively thicker wall thicknesses, such as those described in US Patent Application Publication No. 2010 / 0004735 and the ABSORB GT1 bioabsorbable scaffold, thin walled scaffolds with similar scaffold patterns were found to exhibit significantly higher incidence of strut overlap or underwrap (hereafter referred to as MBOL) as shown in Figure 3C. Higher incidence of MBOL is likely when the width of the links containing the markers is increased to accommodate the same total volume of marker material used in scaffolds with thicker struts. MBOL can also be higher when more aggressive crimps are used, e.g., D-min crimp profiles.

[0106]

[0098] Furthermore, if the same volume of marker beads is attached to both thin and thick scaffolds and the markers are to be flush with the abluminal and luminal sides of the links, a flatter, wider shape must be used in the marker bead region, which forces structures 21a and 21b to deform and increase the propensity for strut overlap in the marker bead region, as the marker structures will have a higher aspect ratio to accommodate the markers and / or may retain strain from the marker upsetting process, making marker structure 21 more susceptible to out-of-plane twisting. Table 1 summarizes these findings. [Table 1]

[0107]

[0099] Paragraphs

[0073] -

[0083] of commonly owned U.S. patent application Ser. No. 14 / 738,710 describe factors that affect the ability of a scaffold to retain a marker in a hole and the special challenges faced when the wall thickness is less than 160 microns (μm) or less than 125 microns (μm). In addition, the '710 application also describes how the width of the marker retention structure must be increased for a reduced wall thickness and the same volume of radiopaque material if the marker is to remain flush with the abluminal side of the strut, if necessary (hence the higher aspect ratio and more prone to twisting and overlap during crimping). A wider and flatter marker structure increases the aspect ratio (AR) of the link width to wall thickness, which increases the likelihood that the link will twist when it contacts an adjacent strut or apex.

[0108]

[0100] In one example, the aspect ratio (AR) of a marker link of a thin-walled scaffold with a wall thickness of 93 microns (μm) is about 4.5 (AR=ts / t=419 microns (μm) / 93 microns (μm)=4.5) when the same volume of marker material is retained in both the 93 micron marker structure and the 158 micron marker structure, as described in, for example, U.S. Patent Application Publication No. 2010 / 0004735. For a scaffold with an overall thickness of 158 microns (μm), the AR is about 2 (AR=ts / t=322 / 158). Thus, for the same volume of marker material, the AR increases by a factor of 2.5 when the wall thickness is reduced from 158 microns (μm) to 93 microns (μm). Given this significant increase in aspect ratio, it will be appreciated that there may be a tendency for the marker link to twist and / or for the strut to overlap / underlap the marker link as it contacts an adjacent strut or apex during crimping.

[0109]

[0101] It is known that during crimping, the angle of the scaffold bar arm decreases and the adjacent bar arm strut naturally moves towards the w-apex link. In this crimping event, the "outer radius" of the w-apex and its center point (usually located on the outside of the link) play an important role in guiding how the scaffold strut crimps. In fact, this center point of the outer radius tends to act as a pivot point that guides the initial behavior of the strut and limits the degree of strut movement towards the marker link mechanism. In this second respect, the MBOL that occurs between the strut and the marker link mechanism is closely related to the location of this outer radius and pivot point. In the case of the w-apex with the marker link 20 and thin-walled scaffold design, the center point of the w-apex was initially positioned within the marker structure 21 area. Therefore, during crimping, the closing behavior of the strut was not kinematically restricted, which resulted in frequent overlap / underlap with the marker link. To reduce the incidence of MBOL, the center point of the W-apex with the marker structure 21 can be moved to an area outside of the marker structure 21. Thus, as the struts of the W-apex move towards the marker structure 21 during crimping, the struts should avoid being squeezed and slipping into an overlap or underlap condition that induces twisting of the W-apex and / or the link.

[0110]

[0102] Figure 4 shows a partial plan view of an end portion of a scaffold according to another embodiment, namely, scaffold 400. The left or distal end portion 402 (i.e., left side of Figure 4) includes sinusoidal rings 412a, 312b and 312c, where ring 412a is the outermost ring. Ring 412b and ring 312c are connected by two links 334 and marker link 20. Ring 312c and ring 312d are connected by three links 334 that extend parallel to axis AA. The right or proximal end portion 404 (i.e., right side of Figure 4) includes sinusoidal rings 312d, 412b and 312f, where ring 312f is the outermost ring. Ring 312d and ring 412b are connected by three links 334. Rings 412b and 312f are connected by two links 334 and a marker link 20. Thus, the scaffold 400 has a marker link 20 that extends between the outermost link and the adjacent ring and connects the outermost ring to the adjacent ring. The scaffold 400 can have 15, 18, or 20 rings 312 interconnected to each other by links 334.

[0111] Scaffold 400 has the same features as described above for scaffold 300, except that rings 412a and 412b are sinusoidal and are joined to adjacent rings by W apexes 414 and Y apexes 416 (as in rings 312a and 312e), but the ring structure of rings 412a and 412b near marker 20 has been modified to avoid strut overlap when the scaffold is crimped to the minimum theoretical crimp diameter (D-min), as described above.

[0112]

[0104] Referring to Figures 4A and 4C, there are shown close-up views of the scaffold 400 at sections IVA and IVB of Figure 4, respectively. To avoid the overlap as described above, the spacing between the strut portions of the w apexes at the markers of rings 412a and 412b has been increased. This modification is shown in the drawings as w apexes 414. The extended apexes (along axis BB) provide more spacing between the struts 430 and the marker structures 21a, 21b to avoid the overlap (the resulting crimp shape with this modification is shown in Figure 4D). The w apexes 414, in contrast to the apexes 309 not associated with the marker links 20, modify the scaffold structure near the markers 20 in at least one of the following ways (1), (2) and (3): (1) The flat, i.e., non-curved, surface portion B1 of the apex increases in the direction BB over the flat surface portion B2 of the other apex 309, for example, by about 350% to about 400% increase relative to the maximum width (ts) of the marker link, which is about 200% greater than the non-marker link width (tL). (2) The distance from the w apex 414 (peak) to the adjacent u apex 407 (valley) is increased compared to the distance from the y apex 316 (peak) to the adjacent u apex 307 (valley) of ring 312b and / or the distance from the w apex 309 (peak) or y apex 310 (peak) to the adjacent u apex 307 (valley) of either ring 312. This is shown in the figure by comparing distance X412, measured from the center of the peak to the center of the valley, to distance X312 of ring 412 and ring 312, respectively. Distance X412 is approximately 15% greater than X312 of the maximum marker link width (ts), which is approximately 200% greater than the non-marker link width (tL). (3) The distance from peak 414 to the adjacent peak 407 is greater than the distance from peak 407 to peak 409, i.e., L1 is greater than L2 in FIG. 4A, e.g., L1 is about 10% greater than L2, and / or L1 is about 5% greater than the distance between any adjacent peak of rings 312a, 312b, 312d, 312f and any adjacent peak of a marker link maximum width (ts) that is about 200% greater than the non-marker link width (tL).

[0113]

[0105] The characteristics of ring 412a apply equally to ring 412b in the vicinity of marker link 20. FIG. 4B shows a view of portion 302 where ring 412a is shown in dotted lines on ring 312a from scaffold 300. The added spacing between marker link 20 and strut 430 is represented by "spacing increase" in the drawing. In this drawing, the difference in half period of the sinusoidal ring portion (X412, X312) that extends between y and w apexes of the marker link, respectively, can also be seen. Also, the characteristics of ring 412a are symmetrical about w apex 414. Thus, at least one of the modifications (1), (2), and (3) described above apply to both sides of w apex 414.

[0114]

[0106] According to another aspect of scaffold 400 related to the "increased spacing" shown for scaffold 400 that avoids MBOL or overlap, in some embodiments where scaffold marker links are made to avoid overlap and connect rings, it is also beneficial to take into account deformation of structures 21a, 21b when marker elements, rivets or beads are swaged into the holes.

[0115] FIG. 4D shows a portion of scaffold 400 in a crimped state where the scaffold is crimped to D-min. As shown, the added spacing between strut portions 430a, 430b of the w-apexes 414 in the marker link 20 results in no overlap or underlap when the scaffold is crimped to the theoretical minimum crimp diameter, D-min. Specifically, FIG. 4D shows that by modifying the ring 412 with the W-apexes 414 connection to the marker link 20, adjacent struts and / or U-apexes above and below the marker structure are separated by a distance that is equal to or greater than the maximum width (ts) of the marker structure when the scaffold is crimped to D-min. There is no overlap when the scaffold with the ring 412 is crimped to D-min. The marker link is between the apices and struts everywhere when the scaffold is crimped to about D-min.

[0116]

[0108] It has been found that when a thin-walled scaffold similar to scaffold 300 follows a simulated calcified serpentine anatomical model, distortion of the distal ring due to struts lifting and catching on obstacles along the path was observed. In addition, the marker structure 21 and holes 22 could deform / stretch, resulting in possible shedding of the marker material. To address this concern of marker material separation from the thin-walled scaffold, the marker link can be made more flexible in bending by lengthening the marker link and / or narrowing the width of the link portion connecting the structure 21 to the adjacent Y or W apex. As a result of this change, the hinge area next to the marker structure 21 becomes more flexible, thereby localizing the deformation to a point away from the structure 21 and protecting the marker hole 22 from significant deformation. This modification also allows the distal and / or proximal ends of the scaffold to be more flexible and balloon compliant, thereby reducing the chance of the struts lifting and catching on obstacles during delivery to the target site.

[0117]

[0109] Figure 5 shows a close-up view of another embodiment of a scaffold, namely, scaffold 500. The view in Figure 5 is the same as section IVC in Figure 4, and scaffold 500 has all the features of scaffold 400, except that the marker link connecting ring 412a to ring 312b and the marker link connecting ring 412b to ring 312f are modified. Marker link 520 differs from marker link 20 in that an additional link 520b is added, i.e., the existing link (see marker link 20) ​​on the right side of marker structure 21b is extended. This additional or extended marker link portion results in an increase in distance A12 compared to when marker 20 is used. Also, distance A12 is longer than distance A23 that separates rings not connected by marker links, e.g., ring 312b to ring 312c in Figure 5. The same modified marker link 520 that replaces marker link 20 is made to the marker link extending between ring 412b and ring 312f. Marker link 520 may also replace marker link 20 of scaffold 300 (at both the proximal and distal ends). In such a case, the same features discussed with respect to scaffold 400 with link 520 also apply to scaffold 300 with link 520.

[0118]

[0110] It has been found that by replacing links 20 with marker links 520, the radiopaque material retained by marker structures 21 is less prone to shed or separate from the scaffold as the scaffold is crimped, balloon expanded, or follows a tortuous vessel. The reason for improved retention can be understood by considering the strain energy distribution on the links as the scaffold is deformed or as the y apexes 316 of ring 312b move relative to the w apexes of ring 412a.

[0119]

[0111] If the apex 316 of ring 312b moves radially outward or inward relative to the apex 414 of ring 412a, or if the apex moves in the opposite direction along axis BB, the marker link 20 will deform. A significant portion of the strain energy of the link 20 resulting from this deformation is stored in the marker structures 21a, 21b because the left and right link portions of the structures 21 are relatively short and thick (so there is little deformation in this portion of the marker link and therefore less strain energy stored there). Since the load must be reacted somewhere along the marker link when ring movement is forced (i.e., because ring movement occurs due to forced displacement or overwhelming force, e.g., by the closing of the crimper jaws on the scaffold, the rings will move relative to each other by a prescribed amount regardless of link stiffness), most of the strain energy is stored in the marker structure 21 which is more deformable than the short and thick link portions near the apex. This deformation may change the shape of the hole in which the marker material is located, resulting in loss of retention. By lengthening the link portion of the marker 20, or by adding a link 520b that is significantly longer than the link 520a that represents the length of the link portion of the link 20 between the left and right sides of the structure 21, less strain energy is retained in the structure 21, and more strain energy is retained by the link 520b. As a result, the marker material is less likely to fall off during crimping or bending of the scaffold, since the marker hole 22 retains its shape during these loading events. In other words, most of the deformation of the link occurs in the elongated portion 520b, so the hole 22 can retain its shape. In addition, the link 520b increases the flexibility of the link, which allows the ring 312b or ring 312f to move more easily relative to the ring 412a and ring 412b, respectively. This embodiment is advantageous in avoiding the problem of the distal end ring flaring or protruding from the balloon as the catheter is routed around dense vasculature (objective (iv) above). Note also that marker 720, discussed in connection with FIG. 7, similarly addresses objectives (iv) and (iii).

[0120] According to one example, link 520b forming y apex 316 has a thickness (tm2) that is approximately 60% less than the thickness (tm1) of link portion 520a forming w apex 414. In addition, length A12 is approximately 27% longer than length A23 to accommodate link 520 having additional link portion 520b.

[0121]

[0113] When a thin-walled scaffold crimped into a delivery system was made to follow a simulated calcified serpentine anatomical model, distortion of the distal ring due to the struts getting stuck on obstacles along its path was observed. To understand the possible cause of the struts getting stuck, a thin-walled scaffold was crimped into the same configuration of delivery system and placed in a bend similar to that present in the anatomical model viewed under a microscope. The balloon was observed to be compressed at the inner curve of the bend and under tension at the outer curve of the bend. Under tension, the balloon stretched and conformed to the curve. If the w-apex associated with the marker link was accidentally positioned at the outer curve of the bend, the w-apex would flare outward (see FIG. 6B) rather than conforming to the underlying curved balloon material at the distal end 15a. The w-apex portion of the scaffold would remain straight due to the rigidity of the marker material and structure 21.

[0122]

[0114] Figure 6 shows a partial plan view of an end portion of a scaffold according to another embodiment, namely, scaffold 600. The left or distal end portion 602 (i.e., left side of Figure 6) includes sinusoidal rings 312a, 412b and 312c, with ring 312a being the outermost ring. The right or proximal end portion 604 (i.e., right side of Figure 6) includes sinusoidal rings 312d, 412b and 312f, with ring 312f being the outermost ring. As can be seen from Figure 6, distal end portion 602 is different than proximal end portion 604. This modification to scaffold 300 or scaffold 400 is made to address the occurrence of a non-compliant distal outermost end ring when the scaffold mounted on a balloon catheter is routed around sharp turns in the vasculature.

[0123]

[0115] Proximal end portion 604 of scaffold 600 is the same as proximal end portion 304 or proximal end portion 404 associated with scaffold 300 and scaffold 400, respectively. Distal end portion 602 is modified from distal end portion 302 or distal end portion 402 as follows.

[0124]

[0116] The (distal) marker link 20 or 520 is located between the inner distal end ring 412a and the inner distal end ring 312c, as opposed to the (proximal) marker link 20 or 520, which is located between the outermost distal ring 312f and the inner ring 412b. This modification to the distal end 602 is desirable for at least one of the following reasons (a) and (b). (a) Improved compliance with the distal balloon: Marker link 20 has a higher bending stiffness than link 634, or for that matter link 334, which may result in separation of the distal outermost ring from the balloon distal end. If it is undesirable or not feasible to modify the marker link structure (e.g., because the structure is required to provide sufficient surface area to hold the desired volume of radiopaque material), a significant reduction in bending stiffness of the link connecting the outermost ring 312a to the inner ring 412a may be achieved by moving marker link 20 between the inner rings. In this way, the bending stiffness between the two outermost rings 312a can be dramatically reduced (objective (iv)) and addressed. (b) Reduced strain on marker retention structure: When the scaffold is routed around a sharp turn, it is the outermost ring that experiences the greatest strain as the scaffold bends. In scaffold embodiments where it is not desirable to reduce the bending stiffness of the outermost ring relative to the adjacent inner ring (e.g., where it is important to avoid reducing the radial stiffness of the outermost ring, which can occur if the connecting links are lengthened to make either more flexible, or to avoid increasing the spacing between the rings for drug coating or vessel support), by moving the marker link 20 to a position between the inner rings, bending strain on the link 20 that could cause the marker material to fall off is avoided or reduced. That is, because the bending strain of the scaffold (which occurs when the catheter makes a sharp turn) is greater between the outermost ring and the adjacent inner ring than between the inner rings, placing the link 20 between the inner rings reduces the bending strain on the marker structure 21 (without having to modify the marker link structure). Objectives (ii) and (iii) are met.

[0125]

[0117] Scaffold 600 also differs from scaffolds 300 and 400 by the link type used to connect the outermost ring to the inner ring, i.e., link 634 connecting ring 312a to ring 412a. Outermost distal ring 312a is connected to ring 412a with three non-linear link struts 634 that are significantly more flexible in bending than the link struts 334 connecting the inner rings. This also contributes to reason (a) for using the scaffold 600 pattern at the distal end.

[0126]

[0118] The non-linear link struts can take a variety of shapes, with some constraints, such as providing sufficient clearance for crimping, such as a D-min crimp profile. The type shown in Figure 6 has a U-shaped intermediate section 636 connected to each y and w apex by a short and long straight link section, respectively. The link section 632a connecting section 636 to the w apex is longer than the link section 632b connecting to the y apex, to provide sufficient clearance for the ring strut during crimping (as will be explained later). Because of this clearance, the w apex 309 formed by the link section 632a can be crimped to D-min without the U-shaped section 636 interfering with the strut 330 or the strut 330 overlapping the U-shaped section 636 in the crimped state.

[0127] 6A, a crimped side profile of scaffold 600 is shown. Long straight link portion 632a and short straight link portion 632b of link 634 are shown along with a U-shaped intermediate portion 636. Length A12 (measured relative to axis AA) exceeds length A23 by approximately the length of U-shaped portion 636, or the sum of the lengths of portions 632a and 632b is approximately equal to A23 minus the strut width of the ring. In one example, length A12 is approximately 40% longer than length A23.

[0128]

[0120] In other embodiments, the U-shaped portion 636 may be replaced with a link having a smaller moment of inertia in the area between portions 632a and 632b, an S-shaped cutout portion replacing the U-shaped portion, or a narrowed portion. Examples of these link types are described in US Patent Application Publication No. 2014 / 0039604, Figures 14B, 14C, 14D, 14E, and 14F, and accompanying paragraphs

[0223] -

[0229] . By "non-linear" link strut we mean any of these links.

[0129]

[0121] FIG. 6B is an image showing a deformed distal end of a medical device including a balloon catheter with a shaft 2 and a scaffold 10 crimped to a balloon 15. As can be seen from this figure, when the catheter is navigated around a sharp turn (as it is tracked over a guidewire), the distal end of the balloon and shaft accommodate the angle of the turn, but the distal end 7 of the scaffold does not. More specifically, the outermost ring 5 flares or protrudes outward from the distal end. This protruding structure 5 can catch on the wall of the vasculature. The most immediate concern with this orientation of the scaffold relative to the distal end of the balloon is the damage that can be caused by the ring 5 getting caught on the vasculature (due to excessive bending strain) and damaging the scaffold. The possible damages were discussed above. First, the marker link structure can be deformed, resulting in the shedding of the marker material. Secondly, the strain may result in the fracture of the ring 5 or in fracture or crack propagation within the ring 5 .

[0130]

[0122] One solution to this problem is to increase the bending stiffness of the end rings to allow space for flared or protruding scaffold ends due to vascular occlusion. For example, the end rings could be made thicker or the number of connecting links between the outermost and inner rings could be increased. However, what is preferred is to instead reduce the stiffness of the rings so that the scaffold ends are more compliant with the balloon distal end. It is also preferred to limit the load on the marker links for the reasons discussed above. Scaffold 600 (or scaffold 700 below) fills this need.

[0131]

[0123] Figure 6C is an image of the scaffold distal end 602 attached to the distal end 15a of the balloon 15 as the catheter makes a similar turn in the vasculature. As shown, the end ring 312a conforms to the shape of the balloon distal end 15a by reducing the bending stiffness of the ring 312a relative to the inner ring (ring 312b). The end ring 312a does not flare or protrude as in the case of scaffold 5. The link 632 acts as a hinge to accommodate the compression and tension that the bend would exert on the distal end ring when the crimped scaffold is placed into the bend.

[0132]

[0124] Distal end scaffold compliance with the balloon distal section may also be achieved by modifying the marker link structure to be more flexible in bending. In fact, the w-apex formed by the marker links according to the present discussion may significantly reduce the stiffness at the w-apex associated with marker link 314. A thin-walled scaffold design may then couple the marker links to the outermost ring without the flaring issues discussed above.

[0133]

[0125] Figure 7 shows a partial plan view of an end portion of a scaffold according to another embodiment, namely scaffold 700. The left or distal end portion 702 (i.e., left side of Figure 7) includes sinusoidal rings 312a, 312b and 312c, with ring 312a being the outermost ring. The right or proximal end portion 704 (i.e., right side of Figure 7) includes sinusoidal rings 312d, 412b and 312f, with ring 312f being the outermost ring. As can be seen from Figure 7, distal end portion 702 is different than proximal end portion 704. This modification to scaffold 300 or scaffold 400 is again made to address the occurrence of a non-compliant distal outermost end ring when the scaffold mounted on a balloon catheter is routed around sharp turns in the vasculature.

[0134]

[0126] Proximal end portion 704 of scaffold 700 is the same as proximal end portions 304 or 404 associated with scaffolds 300 and 400, respectively. Additionally, distal end portion 702 shares some of the characteristics of scaffold 600 at distal end portion 602, with the following exceptions.

[0135]

[0127] In contrast to the marker link 20 or 520 of scaffold 600, which is located between the inner links, marker link 720 (FIG. 2B) is located between the outermost ring 312a and the inner ring 312b. The marker link of scaffold 700 also differs from the marker links of the previous embodiment. Marker link 720 has marker structures 21 oriented vertically, rather than horizontally as in the case of marker link 20 or link 520. That is, marker structure 21a is offset from marker structure 21b along axis BB, rather than axis AA. There is a long straight link portion 732a that connects structures 21 at one end to form w apex 314, and a short link 732b at the opposite end that forms y apex 316.

[0136]

[0128] The outermost ring 312a of the scaffold distal end portion 702 is connected to the inner ring 312b by one marker link 720 and two nonlinear links 634 used in the scaffold 600. The combined inner rings are not connected by marker link 720 or by link 634. Link 334 is used. Marker link 720, in contrast to marker link 20, is more flexible in bending due to the length of portion 732a, and is conveniently located between the outermost ring and the adjacent inner ring so that the end of the scaffold can be more easily positioned under fluoroscopy. In addition, when marker 720 is used, there are one or more of the following advantages function oriented. First, the marker is more flexible so that the outermost ring can more easily conform to the balloon when the catheter is sent around a sharp bend in the vasculature. In this sense, marker 720 has some of the same advantages as marker 520 (objectives (ii) and (iii)). Also, no modifications to the ring structure are required to allow for crimping of the ring with the w-apex formed by the marker link. Ring 312a can be crimped to D-min (objective (i)) since structure 21 does not interfere with ring structure 21.

[0137] 6A and 7A show the crimped state of scaffold 700 near marker 720 and link 634, and the lengths A12, A23 between the rings. As can be seen in these figures, portion 732a and portion 632a of the marker and link, respectively, have lengths that allow outer ring 312a to crimp to D-min without interference from U-shaped portion 636 or marker structure 21. As can be seen in these figures, structure 21 with hole 22 and U-shaped structure 636 is between the U apex next to the W apex of the left ring and the U apex next to the Y apex of the right ring.

[0138]

[0130] Referring to Figure 7B, an enlarged view of section VII of Figure 7 is shown. As shown, the lengths of portions 732a and 732b are c1 and c2, respectively. The lengths of portions 632a and 632b are also c1 and c2. The lengths A12 and A23 of scaffold 700 are also shown (lengths A12, A23, c1 and c2 also apply to the lengths and ring spacing of portions 632a and 632b of scaffold 600). The sum of lengths c1 and c2 is equal to A12 minus the length and width of the apex of U-shaped portion 636. In some embodiments, A12 is about 40% greater than A23, and c1 is about 36% greater than c2. Length c1 is approximately equal to the distance between the valley of the adjacent apex and the W apex formed by portion 732a or portion 632a minus the width of apex 314 or strut 330 when the scaffold is in a crimped state (see FIGS. 6A-7A). The marker structure is located to the right of the U apex next to the W apex formed by the marker link.

[0139] 7C is an image of the scaffold distal end 702 attached to the distal end 15a of the balloon 15 as the catheter makes a similar turn in the vasculature. As shown, the end ring 312a conforms to the shape of the balloon distal end 15a by reducing the bending stiffness of the ring 312a relative to the inner ring (ring 312b). The end ring 312a does not flare or protrude as in the case of scaffold 5.

[0140]

[0132] Table 2 shows dimensions associated with example scaffolds that were fabricated corresponding to the illustrated scaffold embodiment. (An entry of "-" means the same value as the adjacent column to the left. Thus, the value of tm2 for scaffold 400 is 217, and the length B1 for scaffold 500 and scaffold 700 are 374 and 78, respectively.) [Table 2]

[0141]

[0133] With reference to Table 2, as understood from the above examples and as previously described with respect to scaffold 300 compared to scaffolds 400, 500, 600, 700, the wavelength, 1 / 2 wavelength, marker link thickness, length, and orientation, non-marker link type and length, ring spacing, and apex width at the marker links are modified as needed in connection with crimping and / or introduction of the scaffold through a tortuous artery, respectively. These relationships apply to thin-walled scaffolds, whether in a crimped state or prior to the crimp configuration. Thus, when referring to a crimped scaffold, the above relationships also apply. It should also be understood that features of scaffold 400 and / or scaffold 500 that are different from scaffold 300 can be incorporated into scaffold 600 and scaffold 700. Alternatively, features of scaffold 400 and / or scaffold 500 may not be included in the patterns of scaffold 600 and scaffold 700.

[0142]

[0134] The following discussion is primarily directed to meeting objective (ii): securing radiopaque material in the scaffold holes provided by marker structures 21a, 21b. As previously mentioned, it has been discovered that thin-walled scaffolds do not allow the marker material to be reliably held in the marker holes by frictional engagement with the walls of the cylindrical holes. To meet objective (ii), in preferred embodiments, the radiopaque material is secured to either the scaffold 300, 400, 500, 600 or 700 by swaging a rivet-like body of marker material into the marker structure 20, 520 or 720 without interfering with any of the other objectives (i), (iii) or (iv). The attachment and securing of the marker, in some embodiments, does not include the addition of any polymer, adhesive or reshaping of the cylindrical holes (other than the deformations that occur in the swaging process). In preferred embodiments, a drug-polymer coating is applied after the marker is placed in the hole.

[0143]

[0135] Instead of the spherical marker 25 for the cylindrical hole, a rivet-shaped marker is used. Figures 8A and 8B show side and top views of the rivet-shaped marker 27. The head 28 can include the abluminal side 27a or the luminal side 27b of the rivet 27. In the drawings, the head 28 includes the abluminal side 27a. It would be preferable to make the head 28 the luminal side part of the rivet 27 for assembly, because then the scaffold can be placed over the mandrel and the tip part of the rivet deformed by a tool (such as a pin) applied externally to the abluminal side of the scaffold. The rivet 27 has a head diameter d1, and a diameter d2 of the shank 27c is approximately equal to the hole 22 diameter. The height of the head 28 is h2, which is the amount that the head 28 will extend beyond the abluminal side 22a of the strut portion 21a. Although not desirable, protrusion of the head 28 from about 5-10 microns (μm) to about 25 microns (μm) from the abluminal side 22a, or an amount of about 25% or less of the thickness of the strut, may also be tolerated. A similar degree of protrusion beyond the luminal side 22b may also be tolerated for deformation of the tip of the rivet.

[0144]

[0136] Referring to Figure 9, there is shown a rivet in hole 22. The deformed tip 27b' secures the rivet 27 in hole 22. The overall height h1 is preferably about 40% or about 10%-40% or less of the strut thickness (t), and the tip height is about the same as the head height h2 or within 5-20 microns (μm) of the head height h2.

[0145]

[0137] The rivet 27 may be attached to the hole 22 of the strut portion 21a by first inserting the rivet 27 into the hole 22 from the luminal side of the scaffold so that the head 28 rests on the luminal side 22b of the strut portion 21a. The scaffold is then slid over an interference fit mandrel. With the mandrel surface pressed against the head 28, a tool (such as a pin) is used to deform the tip 27b resulting in the deformed tip 27b' of FIG. 9. In some embodiments, the rivet 27 may be inserted into the hole 22 from the abluminal side first so that the head 28 rests on the abluminal side 22a of the strut portion 21a. With the head 28 held in place by a tool or flat surface applied against the abluminal side, the tip 27b is deformed by a tool, pin, or mandrel inserted into the lumen or piercing the scaffold pattern from an adjacent location on the abluminal side. In some embodiments, the rivet 27 may be solid (FIGS. 8A-8B) or hollow, for example, the shank is a hollow tube with an opening extending through the head 28 of the rivet.

[0146]

[0138] In some embodiments, the rivet is a hollow or solid cylindrical tube, without a prefabricated head 28. In these embodiments, a tube (solid or hollow) may first be fitted into the hole, and then a clamping tool may be used to form the head and tip of the rivet. According to a preferred embodiment, there is a method for making a radiopaque marker as a rivet and attaching the rivet to a scaffold, and a scaffold with such marker attached. First, a method is described for making a rivet-shaped marker from a bead.

[0147] As mentioned above, the head and tip portions of the markers help hold the markers in place when external forces are applied to the rivet, when the link structure is deformed during crimping or balloon expansion, when the scaffold makes a sharp turn in the vasculature, etc. However, in some embodiments, the tip portions of the rivet 27' in FIG. 9, such as tip 27b', are not present. Instead, the shank portion of the rivet is deformed to have a trapezoidal or frustoconical shape or an enlarged end (e.g., rivet 137' shown in FIG. 15A). It has been found that this type of marker provides additional resistance to being pushed out of the strut or link hole when the scaffold is subjected to an external force that deforms the link or strut that holds the marker.

[0148]

[0140] It is desirable to select the appropriate size of the bead to form the rivet. According to some embodiments, the bead size to be used, i.e., the bead volume, depends on the strut thickness (t), hole diameter (D2), distance between holes (D1) and perimeter thickness (D2) of the scaffold structure to which the rivet is attached (e.g., link strut with holes 22 in FIG. 2A or FIG. 2B). The raw material may be spherical or cylindrical. The raw material made of radiopaque material can be obtained from a commercial source.

[0149]

[0141] In accordance with the present disclosure, raw material beads are used to create rivet markers for attachment to scaffold holes 22. In a preferred embodiment, the rivet markers are attached or engaged to scaffold holes in thin walled struts or links, preferably having a thickness (t) of less than about 100 microns (μm). The rivet creation process and attachment to the scaffold can be summarized as a six step process.

[0150] Step 1: From the raw material, select marker beads having diameters or volumes within the desired range, i.e., diameters or volumes suitable for attachment to the scaffold according to the dimensions D0, D1, D2 and t (FIG. 2B). Selection of marker beads having the desired diameter or volume, or removal of beads that are too small from the lot, can be done using a mesh sieve. A set of beads is sieved on the mesh sieve. Beads that do not have the minimum diameter or volume fall through the openings of the mesh sieve. Alternative methods known in the art may be used to remove unwanted beads or select beads of appropriate size.

[0151] Step 2: The beads selected from step 1 are placed on a die plate.

[0152]

[0144] Step 3: Cold form a rivet from the bead by forcing it into a die plate. Forcing the bead through a die (e.g., using a plate, mandrel head, pin or tapered ram head) at near ambient temperature reshapes the bead into a rivet defined by the shape of the die and the volume of the bead relative to the volume of the die that receives the bead.

[0153]

[0145] Step 4: Remove the formed rivet from the die plate. The formed rivet has an overall length of about 190-195 microns (μm) and a diameter of about 300-305 microns (μm) and is removed using a tool with a vacuum tube. Air pressure is adjusted to grip the rivet or to pull the rivet away from the tip. The rivet is removed from the die by placing the opening of the vacuum tube over the head of the rivet and reducing the air pressure in the tube to cause the head to adhere or be sucked (by pressure difference) to the tube tip and lift the rivet off the die.

[0154]

[0146] Step 5: With the rivet still attached to the tip of the tube, the rivet is moved to position over the hole in the scaffold and the same tool is used to place the rivet in the hole, then the air pressure in the tool is increased to ambient air pressure. The rivet is released from the tool.

[0155]

[0147] Step 6: Deform the rivet and / or hole to enhance engagement or resistance to the marker falling out of the hole, eg, FIGS. 14A-14C.

[0156]

[0148] It will be appreciated that steps 1-6 overcome the problem of handling non-spherical beads. For example, steps 1-6 above overcome the problem of orienting a spherical bead so that it can be aligned and placed in a hole without having to be reoriented after a rivet is formed from the spherical bead.

[0157] 16A, 16B and 16C, there are shown steps associated with transferring the formed rivet 127′ (or 137′) from the die 200 (or 205) into the scaffold strut hole 22 using a vacuum tool 350. As can be appreciated, the formed radiopaque marker 127′ is extremely small, i.e., less than 1 millimeter in its largest dimension, and thus handling and orienting the marker 127′ for placement in the hole 22 is complicated (as opposed to placing a ball in a hole) due to the need to properly orient the shank relative to the hole. Thus, the upsetting or forging process is combined with the removal of rivet 127′ from hole 200 with tool 250, FIG. 16A, maintaining the orientation of rivet 127′ while it remains attached to the tool, FIGS. 16B-16C, and then placing rivet 127′ into hole 22a, FIG. 16C, into the scaffold hole.

[0158]

[0150] Referring to Figures 10 and 11A, a first embodiment of a die 200 and a marker 127 formed using the die 200 are shown, respectively, according to the present disclosure. The die is a flat plate having an upper surface 201 and a through hole extending from the upper end 201 to the lower end. The hole has an upper diameter dp2 and a lower diameter dp1 that is less than dp2. The hole 202 is preferably circular throughout, but in other embodiments the hole may be rectangular or hexagonal throughout a thickness tp, in which case dp1 and dp2 are lengths or dimensions across the hole (rather than diameters). The plate 200 also has a height tp. The taper angle is related to dp2 and dp1 by the formula tan Φ = (1 / 2 (dp2 - dp1) / tp), and in preferred embodiments Φ is 1-5 degrees, 5-10 degrees, 3-5, or 2-4 degrees. The shape of the die 200 produces a frustoconical shank, as shown in FIG. 18A. A feed bead (not shown) is placed at the top of the opening 202 such that the bead is partially located within the hole 202. A flat plate, mandrel or pin ("ram head") is then forced onto the top of the bead such that the bead is forced into the hole 202. The bead is forced into the hole until the ram head is a distance of about HH from the surface 201. The rivet 127 formed from the above forming process has a taper angle Φ over all or a substantial portion of the shank height SH, and the shank shape is frustoconical. The overall rivet height is HR, the head thickness is HH, and the head diameter is HD. In some embodiments, the angle Φ may be small enough such that the shank is treated as a cylinder, or Φ is approximately zero.

[0159]

[0151] Referring to Figures 12 and 13A, a second embodiment of a die 205 and a marker 137 formed using the die 205 are shown, respectively, according to the present disclosure. The die is a flat plate having an upper surface 206 and a hole extending from the upper end 301 to the lower end. The hole has a constant diameter dcb1 throughout. A counterbore is formed at the upper end 206. The counterbore diameter is dcb2. The hole 207 is preferably circular throughout, but in other embodiments the hole 207 may be rectangular or hexagonal, in which case dcb1 is the length or size across the hole (rather than the diameter). The shape of the die 205 produces a rivet with a stepped cylindrical shape or a cylindrical shank with a head, as shown in Figure 13A. A raw bead (not shown) is placed at the top of the opening 207 so that the bead is partially located within the hole 207. The ram head is then forced onto the top of the bead so that the bead is forced into the hole 207. The bead is forced into the hole until the ram head is approximately a distance HH from surface 206. The formed rivet 137 from the above forming process takes the shape shown in Figure 13A. The overall rivet height is SH+HH, the head thickness is HH, the shank height is SH, and the head diameter is HD.

[0160]

[0152] Tables 3 and 4 below provide example rivet dimensions for a rivet for fastening in link hole 22 as shown in Figure 2A. In this example, the link has a thickness of 100 microns (μm) and the values ​​of D0, D1 and D2 in microns (μm) are 241, 64 and 64, respectively.

[0161]

[0153] The values ​​of dimensions tp, dp2 and dp1 of die 200 are 178, 229 and 183. The dimensions of the formed rivet obtained using die 200 are shown in Table 3. As can be seen from the results, the shank length (or height) is greater than 150% of the link thickness and the rivet head diameter (HD) is significantly greater than the hole 22 diameter. The lower portion of the shank is utilized to form the tip portion of the rivet. The average and standard deviation of HD, SD and SL are based on "n" sample rivets each measured. [Table 3]

[0162]

[0154] The values ​​of dimension dcb2 and dimension dcb1 for die 205 are 305 and 203. The dimensions of the formed rivets obtained using die 300 are shown in Table 4. The averages and standard deviations for HD, SD, HH and SL are based on "n" sample rivets each measured. [Table 4]

[0163]

[0155] In Tables 3 and 4, "OD rivet head diameter after swaging" refers to the outside diameter of the rivet marker head after the rivet marker is forced into the scaffold hole.

[0164]

[0156] Consider now an example process for installing either rivet 127, 137 in a scaffold hole 22. According to some embodiments, the rivet shank is placed in the hole 22 from the abluminal or exterior side of the scaffold so that the head is located on the abluminal side 22a. The rivet may alternatively be placed from the luminal side of the hole. The rivet is pressed firmly into the hole such that the greatest portion of the shank extends from the luminal or abluminal side, respectively.

[0165] After the rivet 127 is placed in the hole 22, the opposite side of the head is subjected to a swaging process. Referring to FIG. 11B, a cross section of the deformed rivet 127' in the hole 22 is shown. The rivet 127' has a head 127a' that extends from the surface 22a by an amount h2. The length h2 may be about 25 microns (μm), 25-50 microns (μm), or 5-50 microns (μm). The same dimensions apply to the tip 127b' that extends from the opposite surface (e.g., the luminal side) of the link. The diameter of the head 127a' may be larger than the tip, and the tip 127b' diameter may be larger than the head 127a' diameter. The tip portion is formed from an extended shank length that protrudes from the link surface by swaging. The tip 127b' is formed by swaging. For example, rivet 127 is placed from surface 22a (abluminal) such that a significant portion of the shank length, e.g., 50% of the strut thickness, extends from the luminal side. A cylindrical mandrel (not shown) is placed through the lumen of the scaffold. The mandrel has an outer diameter slightly smaller than the inner diameter of the scaffold and provides an upsetting surface that forms tip 127b'. The mandrel is rolled back and forth over the portion of the shank that extends from the luminal side. This action flattens the shank material around the hole to create tip 127b'. The resulting rivet 127' is held in place, at least in part, by the resistance of tip 127b' pushing the rivet toward the abluminal side of the hole and the resistance of head 127a' pushing the rivet toward the luminal side of hole 22. As shown, deformation of the shank creates tip 127b' with a flange disposed on surface 22b. The flange may be circular like the head and may have a flange radial length greater or less than the flange radial length of the head 127a'.

[0166]

[0158] Referring to Figures 15A and 15B, a stepped mandrel is used with a ram head to produce rivet 137' from rivet 137. The rivet has a shank 137' that is reformed from a generally cylindrical shape, for example when using die 205 of Figure 12, to the shape shown in Figures 15A-15C. This shank shape may be characterized by a taper angle θ of about 5-15 degrees, 5-9 degrees, or about 3-8 degrees. The shank of some embodiments of the rivet in hole 22 is frusto-conical in shape, with the shank end opposite or distal to head 137a', i.e., end 137b', being larger or having a larger diameter than the shank portion proximal to or closest to head 137a'. The deformed shank 22' may have a shank diameter S2 closest to one of the luminal or abluminal openings of the hole 22' that is larger than the shank diameter S1 closest to the other of the luminal or abluminal openings, i.e., S2>S1. According to some embodiments, the cylindrical hole 22 is also deformed to a hole 22' with an opening on surface 22b that is larger than the hole opening on surface 22a, as shown in FIG. 15A. According to some embodiments, the hole 22 and the rivet 137 are deformed when the rivet 137 is attached to the scaffold.

[0167]

[0159] The structure shown in Fig. 15A can be made by a second step of attaching a rivet marker to the scaffold hole 22. In contrast to the first step, the tool is not rolled over the entire surface where the shank tip portion protrudes from the hole opening. Instead, the shank tip is pressed directly into a non-compliant surface, which can be the surface of a metal mandrel. The rivet is deformed by the compressive force between the surface of the mandrel and the head of the ram 234, which presses the rivet into the mandrel surface. The first step of producing the deformed rivet 127' is, in contrast, formed by a combination of rolling a hard surface into the shank and a constraint on the head 127a, which holds the rivet head against the surface 22a while the tip 127b is swaged. Under the second step, the line of action of the force is entirely along the axis of the rivet or perpendicular to the rivet head. This results in the shank portion being smoothed or widened and the hole being distorted with little or no flange or rim formed from the tip of the shank.

[0168]

[0160] The second step will now be described in more detail with reference to Figures 14A-14C. The scaffold 400 is placed on a stepped mandrel 230. The mandrel has a first outer diameter and a second outer diameter smaller than the first outer diameter. The scaffold portion carrying the marker 137 is placed over the smaller diameter portion of the mandrel 230. The larger diameter portion of the mandrel 230 carries an adjacent portion of the scaffold. The smaller diameter portion of the mandrel 230 has a surface 230a and the larger diameter portion has a surface 230b. As shown in Figures 14B-14C, the ram 234 presses the scaffold portion 230a carrying the marker 137 against the mandrel surface 230a with a force F (Figure 14B), which deflects the scaffold end a distance "d" toward the surface 230a (Figure 14A). After the scaffold reaches surface 230a, ram 234 continues to press (by directly pushing head 137a) into the scaffold portion holding the marker to create a deformed marker 137' and hole 22' as shown in FIG. 15A. The selected surface 230a may be smooth or free of grooves, pits, dents, or other surface irregularities (other than the surface of a cylinder) that would impede material flow during upsetting. In a preferred embodiment, the mandrel surface is smooth compared to the surface of head 234 pressed into the rivet marker 137. That is, the coefficient of friction (Mu) between head 234 and surface 137a' is greater than Mu between surface 230a and surface 137b' of mandrel 230.

[0169]

[0161] The deformed shank 137' and hole 22' configuration shown in Figure 15B resulted in a greater push-out force (by "push-out force" we mean the force required to remove the marker from the hole) than previously thought. Indeed, it was unexpectedly discovered that the deformed rivet 137' and hole 22', with or without head 137a', had a greater resistance to back-out than a marker fitted to a link having a 50% greater thickness. For example, testing of the minimum pull-out force required to push rivet 137' out of side 22a of a 100 micron (μm) thick strut hole 22' was higher than the pull-out force required to push out a marker attached to a strut hole having a thickness of about 50% greater (158 μm vs. 100 μm) according to U.S. Patent Application Publication No. 2007 / 0156230 (FIGS. 8A, 8B, or when the sphere deforms more cylindrically upon storage, increasing surface-to-surface contact to a maximum), as shown in Table 4. [Table 5]

[0170]

[0162] Scaffold B has a higher push-out force even though scaffold A has more surface area for contact with the markers and therefore more frictional force resisting shedding. This result shows that the deformation caused by the upsetting process resulting in the deformed rivet markers and holes in FIG. 15A has a large effect on the push-out force (Note: the force in grams of push-out force reported in Table 4 was applied to the luminal side 22b of scaffold B). Considering the 50% larger wall thickness, scaffold A should have had a higher pull-out force (same bead material, bead volume and poly(L-lactide) scaffold material for scaffold A and scaffold B). The higher pull-out force can be explained by the deformed shank and hole geometry that essentially creates a lower portion 137b' that is significantly larger than the opening 22a of the strut 22. Thus, the dislodgement force must be large enough to deform opening 22a' and / or shank portion 137b' to dislodge the marker from the 22a side of hole 22' (not just essentially overcoming the frictional forces between the material and the wall of the hole).

[0171]

[0163] The shape 137' of Figure 15B may be formed by a swaging process that deforms the rivet while it is inside the hole 22. The rivet may have the shape and / or characteristics of rivet 27, rivet 127 or rivet 137 prior to swaging. The rivet material flows laterally (shear flow) during swaging near tip portion 137b', causing the rivet material to expand and the strut hole to move closer (widen) to aperture 22b'. This creates a trapezoid-like or frusto-conical shape of the rivet shank and hole. The swaging process of Figures 14A-14C applies equal and opposite forces approximately collinear with the axis of symmetry of the rivet (rather than a rolling motion on one side). If instead a cylinder or ball (rather than a rivet) was placed in the hole 22 and there was a coefficient of friction (COF) between the upsetting surface 230a and the tip 137b similar to that between the upsetting surface 234 and the head 137a, but otherwise the same upsetting process as in Figures 14A-14C, the result would have been a more symmetrically deformed marker, such as the shape shown in US Patent Application Publication No. 2007 / 0156230, e.g., a cylindrical or barrel shaped marker that was squashed according to the COF. This result can be understood by reading Kajtoch, J Strain in the Upsetting Process, Metallurgy and Foundry Engineering, Vol.33, 2007, No.1 (discussing the effect of the coefficient of friction between the ram and the ingot on the resulting shape for slenderness ratios greater than 2). The shape of the radiopaque material forced into the hole, e.g., rivet 137 vs. ball (Scaffold A), is also a factor. The presence of the head on one side causes the shank to form an asymmetric shape about the strut midplane axis. It is believed that the combination of the rivet shape and the friction coefficient difference produced favorable results.

[0172] In a preferred embodiment, the smooth mandrel 230 surface 230a presses against surface 137b, compared to the rougher surface of head 234 pressing against surface 137a. In a preferred embodiment, the friction coefficient on the abluminal side was greater than 0.17, i.e. Mu>0.17, while the friction coefficient on the luminal side was less than 0.17, i.e. Mu<0.17. As discussed above, the effect of the difference in friction coefficients can be explained by the constraint on shear flow or subsequent material flow near the ends that meet the respective swage heads. If the friction coefficient is low enough, the surface area expands laterally, rather than remaining relatively constant. Thus, since Mu is smaller on the luminal side, there is more lateral flow than on the abluminal side. The result, when combined with the use of a rivet shape, would be the disclosed frustoconical shape, as shown in Figures 15A-15B, which could be thought of as a shank with a fixed angle θ, for example.

[0173]

[0165] There may be a heating step for the scaffold after marker placement. In some embodiments, this heating step may correspond to a healing process for the scaffold polymer before crimping, which removes the aging effects of the polymer.

[0174]

[0166] Thermal recovery prior to the crimping process (including heat treatment of the bioabsorbable scaffold above the TG but below the melting temperature (Tm) of the polymer scaffold) can reverse or eliminate physical aging of the polymer scaffold and may reduce the incidence of crimp damage (e.g., at the peaks of the scaffold) and / or marker loss.

[0175] According to some embodiments, just prior to crimping the scaffold into the balloon and after placement of the markers, the scaffold is heat treated, mechanically strained, or solvent treated to induce recovery or elimination of polymer aging. Recovery negates or reverses the changes in physical properties caused by physical aging by returning the polymer to a less aged or even unaged state. Physical aging brings the polymer closer to thermodynamic equilibrium, and recovery moves the material away from thermodynamic equilibrium. Thus, recovery can change the properties of the polymer in a direction opposite to that caused by physical aging. For example, recovery can decrease the density of the polymer (increase the specific volume), increase the elongation at break of the polymer, decrease the modulus of the polymer, increase the enthalpy, or any combination thereof.

[0176] According to some embodiments, recovery is desirable to reverse or erase physical aging of previously processed polymers. However, recovery is not intended to remove, reverse, or erase the memory of previous processing steps. Thus, recovery does not train or impart memory to the scaffold or tube. Memory may refer to the transient polymer chain structure and transient polymer properties provided by the previous processing step. This includes the processing step of radially strengthening the tube to form the scaffold by inducing biaxial stretching of the polymer chains in the tube described herein.

[0177]

[0169] With regard to the integrity of the marker scaffold during crimping or resistance to shedding, a heating step has been found to help reduce instances where the crimping causes the marker to shedding. According to some embodiments, any of the above-described embodiments of the marker retained in the scaffold hole 22 can include a heating step after the marker is placed in the hole and immediately prior to crimping, for example within 24 hours after crimping. It has been found that the scaffold can better retain the marker in the hole 22 after heating. Mechanical strain, such as limited radial expansion, or thermal recovery (which raises the scaffold temperature above the glass transition temperature (TG) of the load-bearing portion of the scaffold polymer for a short period of time) can have a beneficial effect on the structural integrity of the scaffold after crimping and / or after balloon expansion from the crimped state.

[0178]

[0170] In particular, these strain-inducing processes tend to beneficially affect the dimensions of the hole 22 surrounding the marker when the hole is deformed as described above in connection with Figures 15A-15B.

[0179] According to some embodiments, the scaffold after marker placement is heated to a temperature of about 20 or 30 degrees above the glass transition temperature of the polymer for 10-20 minutes. More preferably, the load-bearing structure of the scaffold (e.g., the portion made from a polymer tube or sheet of material) is a polymer that includes poly(L-lactide) and its temperature is raised to about 80-85°C for 10-20 minutes after marker placement.

[0180]

[0172] According to some embodiments, it has been found that increasing the temperature of the scaffold after placement of the marker reshapes portions of the hole 22 to improve the fit of the marker within the hole. Referring to FIG. 15C, after the rivet marker 137 is placed in the hole 22 according to the second step, the hole shape deforms to create a lip or edge 140 at the end 137b" that may create a greater resistance to shedding than a scaffold marker structure that is not treated with a healing step. The surface 140a of the lip 140 better resists shedding of the marker when force is directed toward the end 22b'.

[0181] In accordance with the aforementioned objective of achieving a desired crimp profile for a thin-walled scaffold, there is a method for crimping such a scaffold onto a balloon that meets the following needs: Structural Integrity: Avoiding damage to the structural integrity of the scaffold when it is crimped onto or expanded by the balloon. Safe introduction to the implantation site: Avoid dislodging or detaching the scaffold from the balloon during transport to the implantation site. Uniformity of Expansion: Avoid uneven expansion of the scaffold rings, which can lead to structural failure and reduced fatigue life.

[0182]

[0174] As previously reported in US Patent Application Publication No. 2014 / 0096357, scaffolds are not as resilient as more ductile metallic stents, and therefore there is a need to meet all of the above needs, especially for thin-walled scaffolds that may break more easily during crimping or balloon expansion.

[0183] 17A-17B show steps associated with a crimping process for crimping a thin-walled scaffold 300, 400, 500, 600 or 700 according to the present disclosure onto a balloon catheter (FIG. 3D). This crimping process has been found to be capable of meeting all of the above needs for a scaffold crimped to D-min. In this example, a crimping process for crimping a 3.5 mm scaffold onto a 3.0 mm semi-compliant PEBAX balloon is described. FIG. 17B shows the crimping portion of the process of FIG. 17A in graph form, i.e., a graph of scaffold diameter versus time when a balloon pressure of about 20-70 psi (or 1 atm up to a fully inflated or over-inflated balloon pressure) is applied throughout most of the crimping process. For example, the balloon pressure is maintained at 70 psi for steps A through G, and then the pressure is reduced (or deflated) to 50 psi (or 1 atmosphere) over a period G through H. The balloon pressure is removed at point H. No balloon pressure is used in steps H through J in order to achieve a low transverse profile or crimp to D-min and avoid damaging the balloon.

[0184]

[0176] In Fig. 17A, three possible methods of crimping are shown, depending on the need. First, two balloons are used, balloon A and balloon B. Balloon B is used for the pre-crimp step(s) and balloon A (used with the delivery system) is used for the final crimp. Second, only one balloon is used (balloon A) for the entire crimping process including alignment check. In this case, the scaffold inner diameter is larger than the fully inflated or over-inflated balloon A. Thus, slippage can occur on the balloon before crimping. Third, only one balloon is used (balloon A) for the entire crimping process without the final alignment check. In this case, the balloon for the delivery system has a fully inflated or over-inflated state that is approximately equal to the inner diameter of the scaffold inner diameter.

[0185] Stage I: The scaffold supported on a fully inflated balloon of a balloon catheter is placed into the crimp head. The balloon when inflated and supporting the scaffold in this state has substantially all folds removed. In a preferred embodiment, the balloon of the catheter (i.e., the balloon used in the final product, stent delivery system) is used for Stages I-II. In other embodiments, it may be preferable to use a second, larger balloon for Stages I and II (as described in more detail below). The blades of the crimper are heated to raise the temperature of the scaffold to the crimp temperature. In a preferred embodiment, the crimp temperature is between the lower limit of the glass transition temperature (TG) of the polymer and 15 degrees between the TG.

[0186] After the scaffold reaches the crimp temperature, the crimper iris closes, reducing the scaffold inner diameter (ID) to a diameter slightly smaller than the outer diameter (OD) of the fully inflated or over-inflated balloon (e.g., 3.45 mm to about 3.05 mm for a PEBAX 3.0 mm semi-compliant balloon inflated to a diameter of about 3.2 mm). In this example, balloon B would be used for diameter reduction to the 3.0 mm balloon size, or balloon A size (e.g., 3.0 mm balloon).

[0187]

[0179] Stage II: The crimper jaws are held at a diameter of 3.05 mm and maintained at this diameter for a second rest period at the crimp temperature. After Stage II, the scaffold has approximately 90% of its pre-crimp diameter.

[0188]

[0180] In steps I-II above, the scaffold diameter is reduced to the size of the fully inflated balloon (i.e., balloon A) of the stent delivery system. During the initial alignment check (before crimping), the scaffold inner diameter was larger than the fully inflated diameter of the balloon (e.g., the scaffold diameter is about 109%-116% of the fully inflated diameter of a balloon having a diameter of 3.0 mm-3.2 mm), so there is a possibility that the scaffold may shift longitudinally (relative to the balloon) while being crimped to the balloon size. With this possibility in mind, the scaffold is removed from the crimper and the alignment of the scaffold on the balloon is inspected relative to the proximal and distal balloon markers.

[0189]

[0181] "Verify Final Alignment" Step: When the scaffold needs to be adjusted on the balloon, the technician makes manual adjustments to move the scaffold into place. However, it has proven difficult to make these minor adjustments while the scaffold is resting on the fully inflated balloon and has an inner diameter slightly smaller than the outer diameter of the balloon. To address this need, the balloon pressure is slightly reduced or the balloon is temporarily deflated to make realignment easier. Once the scaffold is properly realigned between the balloon markers, the scaffold and fully inflated balloon are returned to the crimper. Now that the scaffold inner diameter and balloon size are approximately equal, the final crimping of the scaffold onto the balloon of the catheter can begin. It is preferable to make the scaffold diameter slightly smaller than the fully inflated diameter of the balloon before the start of Stage III to prevent further longitudinal movement of the scaffold relative to the balloon. As mentioned above, if two balloons are used, balloon B is replaced with balloon A, alignment is made to balloon A, and the scaffold is crimped to the final diameter of balloon B.

[0190] Stage III: The scaffold and balloon are returned to the crimper. The jaws close to a diameter approximately equal to or slightly larger than that of Stage II (to account for recoil that occurs during alignment testing). The crimper jaws are held at this diameter for a third rest period, which may be the time required for the scaffold to return to the crimping temperature.

[0191]

[0183] The iris diameter is then reduced to an ID approximately equal to or slightly smaller than the OD of the balloon if it was not pressurized and had randomly distributed folds. That is, the scaffold is crimped to approximately the OD of the balloon if it was pressurized and then deflated so that nearly all pre-formed folds are replaced with random folds. For example, the iris diameter is reduced to about 1.78 mm for a 3.5 mm scaffold. After this diameter reduction, the scaffold OD is about 60% of its diameter in Stage III and about 50% of its starting OD or pre-crimp OD.

[0192] Stage IV: After the scaffold OD is reduced to approximately 50% of its starting diameter, the crimper jaws are held at this diameter for a third pause. In a preferred embodiment, the balloon pressure is slightly reduced during this pause. For example, for a 3.0 mm semi-compliant PEBAX balloon, the pressure is reduced from 70 psi to 50 psi during the Stage IV pause. This reduction is preferred to achieve a lower transverse profile and / or protect the balloon material from overstretching.

[0193]

[0185] After the rest period of Stage IV, the balloon is deflated, or allowed to return to atmospheric pressure, and the iris of the crimper is reduced to the final crimp OD, e.g., 1.01 mm, or about 30% of its pre-crimp OD. This balloon deflation can be accomplished by opening a valve supplying pressurized gas to the balloon while or just before the iris diameter is reduced to the final crimp diameter.

[0194] The crimper jaws are then held at the final crimp diameter for a dwell period of about 170 seconds, or 100-200 seconds, with or without maintaining the crimp temperature (i.e., scaffold temperature is between 15 degrees below TG and about TG). This final dwell period is intended to reduce the amount of scaffold recoil when the crimped scaffold is removed from the crimper. Immediately after the 170 second dwell, the scaffold is removed and a retaining sheath is placed over it to further reduce recoil. A leak test may be performed after the final stage crimp.

[0195]

[0187] It may be necessary to provide a secondary pressure source for the balloon to maintain a relatively constant pressure throughout the diameter reduction and dwell periods (as shown in the example above). Indeed, in one embodiment, it was found that a pressure drop occurred in the balloon during diameter reduction. To address this pressure drop, a secondary pressure source was used to maintain the same pressure during diameter reduction as during the dwell periods.

[0196]

[0188] The above example of a preferred crimping process that selectively pressurizes the balloon throughout the crimping step is expected to provide three advantages while minimizing possible overstretching of the balloon. The first advantage is increased scaffold balloon retention. By maintaining a relatively high pressure on the balloon throughout the majority of the crimping step, more of the balloon material will be forced into the scaffold than if the crimping were performed without balloon pressurization or only after the scaffold diameter has been substantially reduced, so more of the balloon material should be located between the struts of the scaffold. In addition, by substantially removing the folds prior to diameter reduction, the balloon material is also expected to be more compliant. Thus, more of the balloon material can extend between the struts rather than being forced between the scaffold and the catheter shaft as the scaffold is being crimped.

[0197]

[0189] A second benefit of balloon pressurization is a more uniform expansion of the crimped scaffold as the balloon is expanded. If the balloon is inflated from the start, and there is maximum space available for the balloon to unfold within the attached scaffold before the crimping occurs, the balloon material will be more uniformly distributed around the catheter shaft after crimping. In a preferred embodiment, the balloon is fully inflated and held in this inflated state for at least 10 seconds before crimping to ensure that all pre-made folds are removed. If the balloon is only partially expanded and the fold lines or balloon memory are not removed by balloon pressure, such as when the scaffold is partially crimped and then the balloon is inflated (thus leaving less space available for the balloon to fully unfold), it is believed that the folds or partial folds will cause a shift or displacement of the balloon material during crimping, which will result in a more uneven distribution of the balloon material around the catheter shaft after crimping.

[0198]

[0190] A third advantage is the avoidance of out-of-plane twisting or overlapping of the scaffold struts, which can result in loss of strength, cracking or breakage of the struts. As mentioned above, it is believed that supporting the scaffold in the crimper with an inflated balloon inhibits or minimizes the tendency of the struts to move out of alignment.

[0199]

[0191] The aforementioned advantages may be achieved without the risk of overstretching the balloon material during the crimping process where the balloon pressure is selectively controlled. Referring to FIG. 3B, the pressure range provided is 20-70 psi. The upper end of this pressure range, which for the balloon used in the example, would form a fully inflated balloon and may be maintained for the first three stages. The balloon pressure is then reduced to 50 psi and 20 psi in stage IV. Several tests have shown that maintaining a constant, consistent, fully inflated balloon pressure until the beginning of stage IV or after the crimped scaffold reaches approximately 1 / 2 the original scaffold diameter followed by a slight reduction in pressure provides a good balance of stent retention, uniform expansion, low transverse profile, uniform crimp and avoidance of damage to the balloon material.

[0200]

[0192] As mentioned above, there are three possible methods for crimping: Using two balloons, balloon A and balloon B. Balloon B is used for step (a) before crimping, and balloon A (used with the delivery system) is used for the final crimp. Second, using only one balloon (balloon A) for the entire crimping process including alignment verification check. In this case, the scaffold inner diameter is larger than the fully inflated or over-inflated balloon A. Thus, deviations can occur on the balloon before crimping. Third, using only one balloon (balloon A) for the entire crimping process without the final alignment verification check. In this case, the balloon for the delivery system has a fully inflated or over-inflated state that is approximately equal to the inner diameter of the scaffold inner diameter. These different embodiments are further described below.

[0201] In some embodiments, the process is described above by way of example in FIGS. 17A-17B, with the following exceptions: Two balloons are used; that is, a sacrificial or secondary balloon (balloon B) is used in addition to the balloon of the catheter (balloon A) rather than just balloon A as in the above example of the preferred embodiment. Balloon B is a balloon that has a nominal inflated balloon diameter larger than balloon A or that can be overinflated to a diameter larger than balloon A. Balloon B is used for Stage I and Stage II. Balloon B is selected to have a fully inflated diameter that is the same as or slightly larger than the original inner diameter of the scaffold. One advantage of this alternative embodiment is that the scaffold is supported by the balloons throughout the crimping process (as opposed to the example above where balloon A is unable to provide little or no radial support for the scaffold due to the gap in Stage I). After Stage II, the scaffold is removed from the crimper and balloon B is replaced with balloon A. The crimping process then continues as described above.

[0202]

[0194] The above description of illustrated embodiments of the present invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise form disclosed. While specific embodiments of, and examples for, the present invention have been described herein for illustrative purposes, those skilled in the art will recognize that various modifications are possible within the scope of the present invention.

[0203]

[0195] These modifications can be made to the invention in light of the above detailed description. The terms used in the claims should not be construed to limit the invention to only the specific embodiments disclosed in the specification.

Claims

1. A medical device, comprising:

1. A thin-walled scaffold having proximal and distal ends formed by a network of rings interconnected by links, each ring having a plurality of apices including U-apexes and at least one of Y-apexes or W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (B-B) perpendicular to a longitudinal axis (A-A); the proximal end includes an outermost proximal ring connected to a first proximal ring by a plurality of first proximal links, the first proximal ring being connected to a second proximal ring by a plurality of second proximal links; the distal end includes an outermost distal ring connected to a first distal ring by a plurality of first distal links, the first distal ring being connected to a second distal ring by a plurality of second distal links; (1) the plurality of first proximal links includes a proximal marker link having a pair of proximal holes containing radiopaque material, the proximal holes being aligned along the longitudinal axis (A-A); (2) the plurality of first distal links includes a distal marker link having a pair of distal holes containing radiopaque material, the distal holes being aligned along the vertical axis (B-B); the distal marker link has a first end and a second end, the first end forming one of a W apex or a Y apex with the outermost distal ring and the second end forming the other of the W apex or the Y apex with the first distal ring, the distal marker link including structure surrounding the pair of distal holes; the distal marker link having a first link portion extending from the structure to the W apex and a second link portion extending from the structure to the Y apex; a length of the first link portion is greater than a length of the second link portion, and a width of the first link portion and a width of the second link portion are each less than a width of the structure; the outermost proximal ring is connected to the first proximal ring only by the plurality of first proximal links, the plurality of first proximal links extending parallel to the longitudinal axis (A-A), and the first proximal links other than the proximal marker link have a constant moment of area; Medical tools.

2. 2. The medical device of claim 1, wherein the outermost distal ring is connected to the first distal ring only by the distal marker links and non-linear link struts.

3. 2. The medical device of claim 1, wherein the proximal marker link has a first end and a second end, the first end forming one of a W apex or a Y apex with the outermost proximal ring and the second end forming the other of the W apex or the Y apex with the first proximal ring.

4. 4. The medical device of claim 3, wherein the width of the W apex formed by the first end is greater than the width of the Y apex formed by the second end, such that the wavelength of the ring forming the W apex is longer than the wavelength of the ring forming the Y apex.

5. A medical device, comprising: a balloon catheter having a balloon with a distal balloon end and a proximal balloon end; a thin-walled scaffold crimped to the balloon, the thin-walled scaffold having proximal and distal ends formed by a network of rings interconnected by links, each ring having a plurality of apices including U-apexes and at least one of Y-apexes or W-apexes, each ring extending circumferentially in an undulating manner along a vertical axis (B-B) perpendicular to a longitudinal axis (A-A); the proximal end crimped to the proximal balloon end includes an outermost proximal ring connected to a first proximal ring by a plurality of first proximal links, the first proximal ring being connected to a second proximal ring by a plurality of second proximal links; the distal end crimped to the distal balloon end includes an outermost distal ring connected to a first distal ring by a plurality of first distal links, the first distal ring being connected to a second distal ring by a plurality of second distal links; (1) the plurality of first proximal links includes a proximal marker link having a pair of proximal holes containing radiopaque material, the proximal holes being aligned along the longitudinal axis (A-A); (2) the plurality of first distal links includes a distal marker link having a pair of distal holes containing radiopaque material, the distal holes being aligned along the vertical axis (B-B); the proximal marker link has a first end and a second end, the first end forming one of a W apex or a Y apex with the outermost proximal ring and the second end forming the other of the W apex or the Y apex with the first proximal ring, the proximal marker link including structure surrounding the pair of proximal holes; a first link portion of the proximal marker link extends from the W apex to the structure and a second link portion of the proximal marker link extends from the Y apex to the structure; a length of the first link portion is greater than a length of the second link portion, and a width of the first link portion and a width of the second link portion are each less than a width of the structure; the thin-walled scaffold has an outer diameter of about D-min, D-min=(1 / π)×[(n×strut_width)+(m×link_width)]+2×t, "n" is the number of struts in the ring; "strut_width" is the width of the strut, "m" is the number of links connecting adjacent rings, "link_width" is the width of the link, "t" is the wall thickness, and no apex adjacent above or below said structure overlaps said structure; Medical tools.

6. The medical device of claim 5 , wherein the first plurality of distal links comprises non-linear links.

7. 6. The medical device of claim 5, wherein the outermost proximal ring is connected to the first proximal ring only by the plurality of first proximal links, each of the plurality of first proximal links extending parallel to the longitudinal axis (A-A), and the first proximal links other than the proximal marker link have a constant moment of area.

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