Patent Application
20180133034
The present invention relates to bioresorbable scaffolds; more particularly, this invention relates to bioresorbable scaffolds for treating an anatomical lumen of the body.
Radially expandable endoprostheses are artificial devices 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, and bile duct. Stents are examples of endoprostheses that are generally cylindrical in shape and function to hold open and sometimes expand a segment of an anatomical lumen. Stents are often used in the treatment of atherosclerotic stenosis in blood vessels. “Stenosis” refers to a narrowing or constriction of the diameter of a bodily passage or orifice. In such treatments, stents reinforce the walls of the blood vessel and prevent restenosis following angioplasty in the vascular system. “Restenosis” refers to the reoccurrence of stenosis in a blood vessel or heart valve after it has been treated (as by balloon angioplasty, stenting, or valvuloplasty) with apparent success.
The treatment of a diseased site or lesion with a stent involves both delivery and deployment of the stent. “Delivery” refers to introducing and transporting the stent through an anatomical lumen to a desired treatment site, such as a lesion. “Deployment” corresponds to expansion of the stent within the lumen at the treatment region. Delivery and deployment of a stent are accomplished by positioning the stent about one end of a catheter, inserting the end of the catheter through the skin into the anatomical lumen, advancing the catheter in the anatomical lumen to a desired treatment location, expanding the stent at the treatment location, and removing the catheter from the lumen.
The following terminology is used. When reference is made to a “stent”, this term will refer to a permanent structure, usually comprised of a metal or metal alloy, generally speaking, while a scaffold will refer to a structure comprising a bioresorbable polymer, or other resorbable material such as an erodible metal, and capable of radially supporting a vessel for a limited period of time, e.g., 3, 6 or 12 months following implantation. It is understood, however, that the art sometimes uses the term “stent” when referring to either type of structure.
Scaffolds and stents traditionally fall into two general categories—balloon expanded and self-expanding. The later type expands (at least partially) to a deployed or expanded state within a vessel when a radial restraint is removed, while the former relies on an externally-applied force to configure it from a crimped or stowed state to the deployed or expanded state.
Self-expanding stents are designed to expand significantly when a radial restraint is removed such that a balloon is often not needed to deploy the stent. Self-expanding stents do not undergo, or undergo relatively no plastic or inelastic deformation when stowed in a sheath or expanded within a lumen (with or without an assisting balloon). Balloon expanded stents or scaffolds, by contrast, undergo a significant plastic or inelastic deformation when both crimped and later deployed by a balloon.
In the case of a balloon expandable stent, the stent is mounted about a balloon portion of a balloon catheter. The stent is compressed or crimped onto the balloon. Crimping may be achieved by use of an iris-type or other form of crimper, such as the crimping machine disclosed and illustrated in US 2012/0042501. A significant amount of plastic or inelastic deformation occurs both when the balloon expandable stent or scaffold is crimped and later deployed by a balloon. At the treatment site within the lumen, the stent is expanded by inflating the balloon.
The stent must be able to satisfy a number of basic, functional requirements. The stent (or scaffold) must be capable of sustaining radial compressive forces as it supports walls of a vessel. Therefore, a stent must possess adequate radial strength. After deployment, the stent must adequately maintain its size and shape throughout its service life despite the various forces that may come to bear on it. In particular, the stent must adequately maintain a vessel at a prescribed diameter for a desired treatment time despite these forces. The treatment time may correspond to the time required for the vessel walls to remodel, after which the stent is no longer needed.
Examples of bioresorbable polymer scaffolds include those described in U.S. Pat. No. 8,002,817 to Limon, No. 8,303,644 to Lord, and No. 8,388,673 to Yang.
Scaffolds may be made from a biodegradable, bioabsorbable, bioresorbable, or bioerodable polymer. The terms biodegradable, bioabsorbable, bioresorbable, biosoluble or bioerodable refer to the property of a material or stent to degrade, absorb, resorb, or erode away from an implant site. Scaffolds may also be constructed of bioerodible metals and alloys. The scaffold, as opposed to a durable metal stent, is intended to remain in the body for only a limited period of time. In many treatment applications, the presence of a stent in a body may be necessary for a limited period of time until its intended function of, for example, maintaining vascular patency and/or drug delivery is accomplished. Moreover, it has been shown that biodegradable scaffolds allow for improved healing of the anatomical lumen as compared to metal stents, which may lead to a reduced incidence of late stage thrombosis. In these cases, there is a desire to treat a vessel using a polymer scaffold, in particular a bioabsorable or bioresorbable polymer scaffold, as opposed to a metal stent, so that the prosthesis's presence in the vessel is temporary.
Polymeric materials considered for use as a polymeric scaffold, e.g. poly(L-lactide) (“PLLA”), poly(D,L-lactide-co-glycolide) (“PLGA”), poly(D-lactide-co-glycolide) or poly(L-lactide-co-D-lactide) (“PLLA-co-PDLA”) with less than 10% D-lactide, poly(L-lactide-co-caprolactone), poly(caprolactone), PLLD/PDLA stereo complex, and blends of the aforementioned polymers may be described, through comparison with a metallic material used to form a stent, in some of the following ways. Polymeric materials typically possess a lower strength to volume ratio compared to metals, which means more material is needed to provide an equivalent mechanical property. Therefore, struts must be made thicker and wider to have the required strength for a stent to support lumen walls at a desired radius. The scaffold made from such polymers also tends to be brittle or have limited fracture toughness. The anisotropic and rate-dependent inelastic properties (i.e., strength/stiffness of the material varies depending upon the rate at which the material is deformed, in addition to the temperature, degree of hydration, thermal history) inherent in the material, only compound this complexity in working with a polymer, particularly, bioresorbable polymers such as PLLA or PLGA.
One additional challenge with using a bioresorbable polymer (and polymers generally composed of carbon, hydrogen, oxygen, and nitrogen) for a scaffold structure is that the material is radiolucent with no radiopacity. Bioresorbable polymers tend to have x-ray absorption similar to body tissue. A known way to address the problem is to attach radiopaque markers to structural elements of the scaffold, such as a strut, bar arm or link. For example,
There needs to be a reliable way of attaching the markers 11 to the link element 9d so that the markers 11 will not separate from the scaffold during a processing step like 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 adherence 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 struts supporting, or near to markers the marker can dislodge (e.g., if the strut holding the marker is twisted or bent during crimping the marker can fall out of its hole). A scaffold with radiopaque markers and methods for attaching the marker to a scaffold body is discussed in US20070156230.
There is a continuing need to improve upon the reliability of radiopaque marker securement to a scaffold; and there is also a need to improve upon methods of attaching radiopaque markers to meet demands for scaffold patterns or structure that render prior methods of marker attachment in adequate or unreliable.
What is disclosed are scaffolds having non-circular radiopaque markers and methods for attaching non-circular radiopaque markers to a strut, link or bar arm of a polymeric scaffold.
According to one aspect markers are re-shaped to facilitate a better retention within a marker hole. Examples include a marker shaped as a rectangle and having at least one pair of concave or convex surfaces, or an X-shaped marker having four flanges extending radially outward from a center. Each of these marker shapes may be made from a variety of well-known processes, such as by drawing a radiopaque wire through a die.
According to another aspect a marker is held within a hole of the link, or bar arm by a tongue and groove connection. The tongue and groove connection is formed in a preferred embodiment by applying a lateral constraint to the scaffold element when the marker is being inserted into the element. The hole for the marker has a rectangular opening, as opposed to a circular opening as in
According to another embodiment a rectangular radiopaque marker is inserted into a hole of a link, strut or bar arm without lateral restraining. This embodiment may also produce a tongue and groove engagement by virtue of resistance to bulging of side walls by; e.g., the link element made substantially thicker and/or wider surrounding the hole to increase its flexural stiffness near the hole.
According to another aspect a marker is inserted into the hole of a scaffold element, such as a link or strut, by a cold forged or swaging process.
According to another aspect of the invention a scaffold structure for holding a marker and method for making the same addresses a need to maintain a low profile for struts exposed in the bloodstream, while ensuring the marker will be securely held in the strut. Low profiles for struts mean thinner struts or thinner portions of struts. The desire for low profiles addresses the degree thrombogenicity of the scaffold, which can be influenced by a strut thickness overall and/or protrusion from a strut surface. Blood compatibility, also known as hemocompatibility or thromboresistance, is a desired property for scaffolds and stents. The adverse event of scaffold thrombosis, while a very low frequency event, carries with it a high incidence of morbidity and mortality. To mitigate the risk of thrombosis, dual anti-platelet therapy is administered with all coronary scaffold and stent implantation. This is to reduce thrombus formation due to the procedure, vessel injury, and the implant itself. Scaffolds and stents are foreign bodies and they all have some degree of thrombogenicity. The thrombogenicity of a scaffold refers to its propensity to form thrombus and this is due to several factors, including strut thickness, strut width, strut shape, total scaffold surface area, scaffold pattern, scaffold length, scaffold diameter, surface roughness and surface chemistry. Some of these factors are interrelated. Low strut profile also leads to less neointimal proliferation as the neointima will proliferate to the degree necessary to cover the strut. As such coverage is a necessary step to complete healing. Thinner struts are believed to endothelialize and heal more rapidly.
Markers attached to a scaffold having thinner struts, however, may not hold as reliably as a scaffold having thicker struts since there is less surface contact area between the strut and marker. Embodiments of invention address this need.
According to another aspect a thickness of the combined marker and strut is kept below threshold values of about 150 microns while reliably retaining the marker in the hole.
According to other aspects of the invention, there is a scaffold, medical device, method for making such a scaffold, method of making a marker, attaching a marker to a strut, link or bar arm of a scaffold, or method for assembly of a medical device comprising such a scaffold having one or more, or any combination of the following things (1) through (26):
All publications and patent applications mentioned in the present specification are herein incorporated 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 are any inconsistent usages of words and/or phrases between an incorporated publication or patent and the present specification, these words and/or phrases will have a meaning that is consistent with the manner in which they are used in the present specification.
In the description like reference numbers appearing in the drawings and description designate corresponding or like elements among the different views.
For purposes of this disclosure, the following terms and definitions apply:
The terms “about,” “approximately,” “generally,” or “substantially” mean 30%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1.5%, 1%, between 1-2%, 1-3%, 1-5%, or 0.5%-5% less or more than, less than, or more than a stated value, a range or each endpoint of a stated range, or a one-sigma, two-sigma, three-sigma variation from a stated mean or expected value (Gaussian distribution). For example, d1 about d2 means d1 is 30%, 20%, 15%, 10%, 5%, 4%, 3%, 2%, 1.5%, 1%, 0% or between 1-2%, 1-3%, 1-5%, or 0.5%-5% different from d2. If d1 is a mean value, then d2 is about d1 means d2 is within a one-sigma, two-sigma, or three-sigma variance or standard deviation from d1.
It is understood that any numerical value, range, or either range endpoint (including, e.g., “approximately none”, “about none”, “about all”, etc.) preceded by the word “about,” “approximately,” “generally,” or “substantially” in this disclosure also describes or discloses the same numerical value, range, or either range endpoint not preceded by the word “about,” “approximately,” “generally,” or “substantially.”
A “stent” means a permanent, durable or non-degrading structure, usually comprised of a non-degrading metal or metal alloy structure, generally speaking, while a “scaffold” means a temporary structure comprising a bioresorbable or biodegradable polymer, metal, alloy or combination thereof and capable of radially supporting a vessel for a limited period of time, e.g., 3, 6 or 12 months following implantation. It is understood, however, that the art sometimes uses the term “stent” when referring to either type of structure.
“Inflated diameter” or “expanded diameter” refers to the inner diameter or the outer diameter the scaffold attains when its supporting balloon is inflated to expand the scaffold from its crimped configuration to implant the scaffold within a vessel. The inflated diameter may refer to a post-dilation balloon diameter which is beyond the nominal balloon diameter, e.g., a 6.5 mm balloon (i.e., a balloon having a 6.5 mm nominal diameter when inflated to a nominal balloon pressure such as 6 times atmospheric pressure) has about a 7.4 mm post-dilation diameter, or a 6.0 mm balloon has about a 6.5 mm post-dilation diameter. The nominal to post dilation ratios for a balloon may range from 1.05 to 1.15 (i.e., a post-dilation diameter may be 5% to 15% greater than a nominal inflated balloon diameter). The scaffold diameter, after attaining an inflated diameter by balloon pressure, will to some degree decrease in diameter due to recoil effects related primarily to, any or all of, the manner in which the scaffold was fabricated and processed, the scaffold material and the scaffold design.
When reference is made to a diameter it shall mean the inner diameter or the outer diameter, unless stated or implied otherwise given the context of the description.
When reference is made to a scaffold strut, it also applies to a link or bar arm.
“Post-dilation diameter” (PDD) of a scaffold refers to the inner diameter of the scaffold after being increased to its expanded diameter and the balloon removed from the patient's vasculature. The PDD accounts for the effects of recoil. For example, an acute PDD refers to the scaffold diameter that accounts for an acute recoil in the scaffold.
A “before-crimp diameter” means an outer diameter (OD) of a tube from which the scaffold was made (e.g., the scaffold is cut from a dip coated, injection molded, extruded, radially expanded, die drawn, and/or annealed tube) or the scaffold before it is crimped to a balloon. Similarly, a “crimped diameter” means the OD of the scaffold when crimped to a balloon. The “before-crimp diameter” can be about 2 to 2.5, 2 to 2.3, 2.3, 2, 2.5, 3.0 times greater than the crimped diameter and about 0.9, 1.0, 1.1, 1.3 and about 1-1.5 times higher than an expanded diameter, the nominal balloon diameter, or post-dilation diameter. Crimping, for purposes of this disclosure, means a diameter reduction of a scaffold characterized by a significant plastic deformation, i.e., more than 10%, or more than 50% of the diameter reduction is attributed to plastic deformation, such as at a crown in the case of a stent or scaffold that has an undulating ring pattern, e.g.,
A material “comprising” or “comprises” poly(L-lactide) or PLLA includes, but is not limited to, a PLLA polymer, a blend or mixture including PLLA and another polymer, and a copolymer of PLLA and another polymer. Thus, a strut comprising PLLA means the strut may be made from a material including any of a PLLA polymer, a blend or mixture including PLLA and another polymer, and a copolymer of PLLA and another polymer.
An undeformed, deformed or swaged marker, or a hole of a scaffold link element has a “convex” or “concave” sidewall surface when the average curvature of the hole side wall or marker side wall is substantially convex or concave, respectively. For example, the marker shown in
A marker inserted into a hole of a scaffold link element (or strut) forms a “tongue-and-groove” or “tongue/groove” connection with the hole when a medial portion of the wall of the marker or adjoining wall of the (link element or strut) hole extends into the adjoining medial portion of the wall of the hole or marker, respectively. For example, the medial portions (between the upper and lower edges) of the hole walls 24A, 24B in
A “lateral restraint” or “laterally restraining” means a physical or mechanical restraint or restraining of a scaffold element (of a scaffold element such as a link, strut or crown having a marker hole) that prevents or resists the width of the element from changing when a radiopaque marker is being forced into a marker hole formed in the element during a swaging or forging process. Without the restraint side walls of the element will bulge laterally outward to accommodate the marker. The direction of bulging is circumferentially in respect to the circumferential direction of a tubular scaffold body.
Bioresorbable scaffolds comprised of biodegradable polyester polymers are radiolucent. In order to provide for fluoroscopic visualization, radiopaque markers are placed on the scaffold. For example, the scaffold described in U.S. Pat. No. 8,388,673 ('673 patent) has two platinum markers 206 secured at each end of the scaffold 200, as shown in FIG. 2 of the '673 patent.
Additional scaffold structure considered within the scope of this disclosure is the alternative scaffold patterns having the marker structure for receiving markers as described in FIGS. 11A, 11B and 11E and the accompanying description in paragraphs [0177]-[0180] of the '871 Pub. In these embodiments the values D0, D1 and D2 would apply to the relevant structure surrounding the holes 512, 518 and 534 shown in the '871 Pub., as will be readily understood.
In the discussion that follows when the same element numbering is used the same description applies, except in those circumstances where it is readily apparent that the identical description does not apply. Also, reference is made to a radiopaque marker and marker hole before and after inserting the marker into the marker hole using a swaging process. The deformed vs. undeformed markers are distinguished by use of the prime symbol. Thus, for example, a marker undeformed is marker 40, whereas the same marker in a deformed state is marker 40′. In the examples below the marker is inserted into a link 20 of a scaffold. However, the disclosure is not limited to a link or link element adapted to receive radiopaque markers. The marker and methods for insertion according to the disclosure equally applies to markers inserted into struts, crowns, or other scaffold structure capable of having a rectangular marker hole formed therein without departing from the scope of invention.
The apparatus is elongate, extending along the longitudinal axis of the scaffold and includes a frame 106 holding members 102A, 102B and a strip 104. Preferably these members are bosses, and more preferably triangular bosses that have a length about equal to the length of the link 20 and adjacent rings 5. The bosses are made of a relatively rigid material, such as a steel or alloy of steel, stainless steel, tool steel or tungsten carbide. The effective compressive stiffness of the bosses (i.e., when fixed in the recesses and opposing outward movement of the side walls of the link 20) may be 100 times, 1000 times or at least 100 times higher than the compressive or flexural stiffness of the link 20 side walls.
The apparatus is used to restrain the link 20 while the radiopaque marker 40 is pressed into the rectangular hole 22.
The marker 40 shown in
Referring again to
This lateral restraint provided by the members and frame is intended to force a tongue/groove connection between the deformed marker and walls of the marker hole 22, or alternatively form a concave/convex engagement between surfaces of the hole and marker. In the preferred embodiment, to achieve either of these results, the marker 40 is arranged so that its concave walls 43A and 43B face the respective members 102A and 102B. The head 108 is brought down to engage the top surface 42. The head 108 continues to press down until both surfaces 42, 44 of the deformable marker 40 are flush or nearly flush with the upper/abluminal and lower/luminal surfaces of the link 20.
In other embodiments a lateral restraint to outward bulging may be provided by increasing the wall thickness or width of the link, thereby effectively increasing the flexural rigidity of the link's side walls. According to these embodiments a rectangular hole receives a rectangular marker without applying a mechanical or physical restraint, but which may also produce the desired tongue and groove connection by virtue of the link element having relatively high wall stiffness.
In other embodiments the link wall may be made more thick, which has the effect of increasing the frictional force for holding the marker in the rectangular hole. The rectangular hole may have a thickness of between about 125 microns and about 160 microns. It has been found that within this range of wall thickness there is an acceptable level of retention force (due to the added friction) even in those cases where there is no significant, or no tongue/groove connection present.
The walls of the marker 40′ are concave, as mentioned above. The corresponding walls 24A, 24B of the hole 22 may be deformed into convex shapes, and/or may only form a tongue portion of a tongue/groove connection. Surfaces of the left and right sides of the hole's deformed side walls 24A, 24B proximal centerline C and distal the top and lower surfaces are closer to each other than are the surfaces proximal the upper and lower edges and distal the centerline C.
In some embodiments the concave marker shape may be maintained, while in other embodiments the concave shape is altered, yet there is retained the tongue/groove connection. In some embodiments a marker has concave sidewalls and after being pressed into a hole the marker sidewalls may form the tongue or groove portion of the tongue/groove connection.
In
The shape of the marker may be affected by using swaging or forging heads with differing coefficients of friction. For example, using an upper swaging head with higher coefficient of friction than the opposing bottom swaging surface can produce greater lateral flow near the bottom surface.
Referring again to
The walls of the marker 50′/60′ are convex, as mentioned above. The corresponding walls 24A, 24B of the hole 22 may be deformed into concave shapes, or may only form the groove portion of a tongue/groove connection. Surfaces of the left and right sides of the hole wall 24A, 24B proximal centerline C and distal the top and lower surfaces are further apart from each other than are the surfaces proximal the upper and lower surface and distal the centerline C.
In some embodiments the convex marker shape may be maintained, while in other embodiments the convex shape is altered, yet there is retained the tongue/groove connection. In some embodiments a marker has convex sidewalls and after being pressed into a hole the marker sidewalls may form the tongue or groove portion of the tongue/groove connection.
Referring to
Referring to
During the Swaging process the head is brought down upon the surfaces 72 and continues pressing downward until the head 108 comes into contact with the top surfaces of the members 102A, 102B. The process is preferably down at room or ambient temperatures thus it may be regarded as a cold-forging process (the same cold-forging process applies when markers 40, 50 and 60 are swaged using the apparatus).
As compared to the rectangular-like markers of 50, 60 and 40 the deformed X-shape marker is forced into the rectangular shape of the hole by plastic deformation of the flanges 73A-73D. Additionally, the material will not completely flow to re-form the X-shaped marker into a rectangular form like that of marker 40-60. This is indicated by the marker 70′ having the recess 77 at the top surface 72′, bottom surface 74′. Additionally, in some embodiments it is expected there will be a gap between the side walls 73A′, 73B′ and side walls 24A, 24B respectively, near the centerline C of the link 20. The material between a side recess and top (or bottom) recess represents the material from a respective flange (compare
A medial portion of the marker 70′ has a width (L1) measured between the left and right surfaces 73A′, 73B′. The width measured between the left and right sides of the upper and/or lower edges (L2) is greater than L1. Stated differently, a portion of each of the wall surfaces 73A′, 73B′ distal of the top surface 72′ and lower surface 74′ and proximal the centerline “C” passing through the marker 70′ in
The walls of the marker 70′ are concave, as mentioned above. The corresponding walls 24A, 24B of the hole 22 may be deformed into convex shapes, and/or may only form a tongue portion of a tongue/groove connection. Surfaces of the left and right sides of the hole's deformed side walls 24A, 24B proximal centerline C and distal the top and lower surfaces are closer to each other than are the surfaces proximal the upper and lower edges and distal the centerline C.
According to another aspect of the disclosure there is a heating step for a scaffold following marker placement. In some embodiments this heating step may correspond to a rejuvenation step of the scaffold polymer, prior to crimping, to remove aging effects of the polymer.
Thermal rejuvenation (including thermal treatment of a bioresorbable scaffold above Tg, but below melting temperature (Tm) of the polymer scaffold) prior to a crimping process may reverse or remove the physical ageing of a polymeric scaffold, which may reduce crimping damage (e.g., at the crests of a scaffold) and/or instances of dislodgment of a marker.
According to some embodiments a scaffold is thermally treated, mechanically strained, or solvent treated to induce a rejuvenation or erasure of ageing in a polymer shortly before crimping the scaffold to a balloon and after marker placement. Rejuvenation erases or reverses changes in physical properties caused by physical ageing by returning the polymer to a less aged or even an un-aged state. Physical ageing causes the polymer to move toward a thermodynamic equilibrium state, while rejuvenation moves the material away from thermodynamic equilibrium. Therefore, rejuvenation may modify properties of a polymer in a direction opposite to that caused by physical ageing. For example, rejuvenation may decrease density (increase specific volume) of the polymer, increase elongation at break of the polymer, decrease modulus of the polymer, increase enthalpy, or any combination thereof.
According to some embodiments, rejuvenation is desired for reversal or erasure of physical ageing of a polymer that was previously processed. Rejuvenation is not however intended to remove, reverse, or erase memory of previous processing steps. Therefore, rejuvenation also does not educate or impart memory to a scaffold or tube. Memory may refer to transient polymer chain structure and transient polymer properties provided by previous processing steps. This includes processing steps that radially strengthen a tube from which a scaffold is formed by inducing a biaxial orientation of polymer chains in the tube as described herein.
In reference to a marker—scaffold integrity or resistance to dislodgment during crimping, it has been found that a heating step can help reduce instances where crimping causes dislodgment of a marker. According to some embodiments, any of the foregoing embodiments for a marker held within the scaffold hole 22 can include, after the marker has been placed in the hole, a heating step shortly before crimping, e.g., within 24 hours of crimping. It has been found that the scaffold is better able to retain the marker in the hole 22 following heating. A mechanical strain, e.g. a limited radial expansion, or thermal rejuvenation (raise the scaffold temperature above the glass transition temperature (Tg) of the load-bearing portion of the scaffold polymer for a brief time period) can have a beneficial effect on scaffold structural integrity following crimping and/or after balloon expansion from a crimped state.
In particular, these strain-inducing processes tend to beneficially affect the hole 22 dimensions surrounding the marker when the hole is deformed in the manner discussed earlier in connection with
According to some embodiments the scaffold after marker placement is heated to about 20 degrees, or 30 degrees above the glass transition temperature of the polymer for a period of between 10-20 minutes; more preferably the scaffold load bearing structure (e.g., the portion made from a polymer tube or sheet of material) is a polymer comprising poly(L-lactide) and its temperature is raised to between about 80 and 85 Deg. C. for 10-20 minutes following marker placement.
According to some embodiments it has been found that raising the temperature of the scaffold after marker placement re-shapes portions of the hole 22 to improve the fit of the marker with the hole, especially for marker 70. With reference to
The above description of illustrated embodiments of the invention, including what is described in the Abstract, is not intended to be exhaustive or to limit the invention to the precise forms disclosed. While specific embodiments of, and examples for, the invention are described herein for illustrative purposes, various modifications are possible within the scope of the invention, as those skilled in the relevant art will recognize.
These modifications can be made to the invention in light of the above detailed description. The terms used in claims should not be construed to limit the invention to the specific embodiments disclosed in the specification.
| Number | Date | Country | |
|---|---|---|---|
| Parent | 14885926 | Oct 2015 | US |
| Child | 15854665 | US |
