STENT

TECHNICAL FIELD

[001] The present invention relates, generally, to medical devices and, particularly but not exclusively, to medical devices for deployment in a lumen such as blood vessels or ducts to maintain the patency thereof.

5

BACKGROUND

[002] A stent is a tubular support structure made of a biocompatible metal, biostable polymer, biodegradable material, non-metals, bio-resorbable material or shape-memory alloys. The stent may be used in the lumen of humans as well as 10 non-human animals, such as primates, horses, cows, pigs, and sheep. Physiologically, the stent may be placed inside the lumen of any space, such as an artery, vein, bile duct, urinary tract, alimentary tract, tracheobronchial tree, cerebral aqueduct, or genitourinary system to prevent the lumen, duct, or tract from collapsing. Also, the stents are either balloon-expandable or self-expandable and 15 accordingly a suitable type of catheter is used for deployment in the lumen. Therefore, in an example, the stent may be used in arteries, such as coronary, superficial femoral, and iliac, at a narrowed site to expand the vessel and to circumferentially support the vessel wall, to remedy blockages and/or narrowing of arteries that may otherwise cause obstruction of blood flow.

20 [003] The stents are deployed at a target site using catheter-based procedures or similar interventional procedures into the intravascular region. The stent arrives at the target site in an initial crimped state and expands or is expanded to a final state for deployment. In the process, the stent securely fixes inside the lumen against a wall of the lumen and provides the radial support to the lumen. For example, in case of a blood vessel, the stent expands the vessel from a clogged condition, thereby facilitating the recovery of blood flow in the clogged blood vessel and preventing elastic recoil and collapsing of the blood vessel. To achieve the objectives of stent deployment at targeted lesion; it is important that the stent has adequate vessel or lumen scaffolding (artery to metal ratio) for maintaining the patency and it should also have the required flexibility to provide ease to the operators in manoeuvring the stent through angulated lumens, tortuous anatomy, kinked lesions and at the same time conform to the lumen in as much natural manner as possible. [004] Generally, stents are designed to have certain inherent properties for effective operation. For example, the stents should be highly flexible to navigate through tortuous route inside the lumen and it should have sufficient stiffness and rigidity in the crimped state to be easily pushed through calcified lesions in the lumen. In addition, the stent should be able to conform to the shape of the artery during deployment, and at the same time, should have sufficient radial strength and rigidity to provide adequate radial support to the artery to avoid prolapse after deployment. Further, the design of the stent should be such that it allows the stent to be crimped without compromising with the design of the stent.

[005] In addition, stents are designed such that the design either restricts or accommodates the stresses generated in the stent due to different mechanical forces applied on it at the time of deploying the stent or after the deployment. Most commonly, these mechanical forces are elongation, compression, torsional movement, bending movement and other physiological conditions e.g., blood flow (after the deployment). The combined effect of these forces, beyond a safe value, leads to fracturing of the joints in deployed stent and the fractured joints give rise to many clinical complications e.g., recoiling, overlapping of adjacent ringlets, collapsing of the stent structure and restenosis. Hence, fracture resistance is a major safety aspect of stent designing.

[006] Conventionally, to meet the abovementioned criteria, the stents have different constructions, designs, and properties each of which attempt to address different properties or a combination of the properties as mentioned above. However, due to design compromises, most of the stents meet only limited no. of properties and objectives outlined above, resulting in restricted utility and effectiveness.

[007] In a conventional medical device, a tubular support structure of the stent is formed of multiple rings arranged and connected along a longitudinal axis. A ring or is formed by struts which are of a specific design and are sequentially arranged and joined in an endless manner to form a ring or ringlet along the tubular shape of the stent. Further, these ringlets are joined longitudinally through connectors or connecting ties. The connectors made of biodegradable polymers that degrade over a period and may slowly change the scaffolding behaviour of the stent after deployment. Further, yet another conventional medical device disclose stent having ringlets that induce stress variations in the stent and therefore lack bending stiffness in specific zones. Further, still another conventional medical device disclose stent having flexibility and radial strength, however, such conventional design compromises on bending stiffness of the stent. [008] Therefore, there is still a need for medical device that address or overcomes one or more aforementioned problems.

SUMMARY [009] This summary is provided to introduce concepts related to a medical device for deployment in a lumen. This summary is neither intended to identify essential features of the present invention nor is it intended for use in determining or limiting the scope of the present invention.

[0010] Accordingly, an aspect of the present invention discloses a medical device comprising a plurality of ringlets located sequentially along a common longitudinal axis, the plurality of ringlets having at least one cylindrical ringlet formed of a plurality of crowns connected along a circumferential direction, peaks of the crowns have a common cross-sectional plane perpendicular to a longitudinal axis of the medical device; at least one helical ringlet having a helical structure formed of a plurality of crowns connected along a circumferential direction; and a plurality of hybrid connectors connecting the at least one cylindrical ringlet adjacent to the at least one helical ringlet.

BRIEF DESCRIPTION OF ACCOMPANYING DRAWINGS [0011] The above and other aspects, features, and advantages of certain exemplary embodiments of the present invention will be more apparent from the following description taken in conjunction with the accompanying drawings in which: [0012] Figure 1 illustrates a magnified and detailed view of a section of a medical device in a two-dimensional and in a nominal diameter state, according to an aspect of the present invention;

[0013] Figure 2 illustrates the magnified and the detailed view of the section of the medical device in the two-dimensional, nominal diameter state, focusing various type of connectors, according to the embodiment of the present invention; [0014] Figure 3 illustrates the magnified and the detailed view of the section of the medical device in the two-dimensional, nominal diameter state, focusing struts of constant and varying lengths in various ringlets or sections of the said medical device, according to the embodiment of the present invention;

[0015] Figure 4 illustrates a magnified and a detailed longitudinally cross- sectional view of the section of the medical device in a three-dimensional, and in a crimped state, according to the embodiment of the present invention; and [0016] Figure 5 illustrates a magnified and a detailed cross-sectional view of the section of the medical device in the three-dimensional, and in an expanded state, according to the embodiment of the present invention.

[0017] Persons skilled in the art will appreciate that elements in the figures are illustrated for simplicity and clarity and may have not been drawn to scale. For example, the dimensions of some of the elements in the figure may be exaggerated relative to other elements to help to improve understanding of various exemplary embodiments of the present disclosure. Throughout the drawings, it should be noted that like reference numbers are used to depict the same or similar elements, features, and structures. DETAILED DESCRIPTION

[0018] In the following description, for the purpose of explanation, specific details are set forth in order to provide an understanding of the present invention. It will be apparent, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known structures are shown in diagram form to facilitate describing the invention. One skilled in the art will recognize that embodiments of the present invention, some of which are described below, may be incorporated into several applications. [0019] In general, the present invention claims a plurality of ringlets located sequentially along a common longitudinal axis, the plurality of ringlets having at least one cylindrical ringlet formed of a plurality of crowns connected along a circumferential direction, peaks of the crowns have a common cross-sectional plane perpendicular to a longitudinal axis of the medical device; at least one helical ringlet having a helical structure formed of a plurality of crowns connected along a circumferential direction; and a plurality of hybrid connectors connecting the at least one cylindrical ringlet adjacent to the at least one helical ringlet.

[0020] Accordingly, various embodiments of the present disclosure provide a medical, such as a stent, that is designed to have a high degree of flexibility, significant radial strength, good vessel scaffolding and controlled flair at the ends after deployment. At the same time, torsional forces in the medical device are balanced which is helpful in trackability and makes the medical device safe. In the present invention, the design of the connectors and their positioning between two adjoining ringlets substantially affects the design and performance of the stent either during the deploying of stent or post-deployment of the stent or both. Flexural and strength related properties of the stent are customized by customizing design, numbers, and type of ringlets and by customizing design, numbers and type of connectors and their arrangement along the length of the stent. Increased number of connectors bring bending stiffness. However, some connector designs, specifically longer in length, bring flexibility as well. The ringlets provide radial support while the helical ringlets provide conformance and scaffolding. The properties of the stent, such as radial strength, fracture resistance, flexibility, bending strength, and stability, are achieved by selecting combinations of connectors and ringlets and by customizing the density of connectors and ringlets along the length of the stent.

[0021] While this invention is susceptible of embodiments in many different forms, there is shown in the drawings and will herein be described in detail, a preferred embodiment of the invention with the understanding that the present disclosure is to be considered as an exemplification of the principles of the invention and is not intended to limit the broad aspects of the invention to the embodiment illustrated.Other aspects, advantages, and salient features of the invention will become apparent to those skilled in the art from the following detailed description, which, taken in conjunction with the annexed drawings, discloses exemplary embodiments of the invention.

[0022] The terms and words used in the following description and claims are not limited to the bibliographical meanings, but, are merely used by the inventor to enable a clear and consistent understanding of the invention. Accordingly, it should be apparent to those skilled in the art that the following description of exemplary embodiments of the present invention are provided for illustration purpose only and not for the purpose of limiting the invention as defined by the appended claims and their equivalents. The skilled person will be able to devise various arrangements that, although not explicitly described herein, embody the principles of the present invention. All the terms and expressions in the description are only for the purpose of the understanding and nowhere limit the invention. Accordingly, those of ordinary skill in the art will recognize that various changes and modifications of the embodiments described herein may be made without departing from the scope of the invention. In addition, descriptions of well-known functions and constructions are omitted for clarity and conciseness. Moreover, all statements herein reciting principles, aspects, and embodiments of the invention, as well as specific examples thereof, are intended to encompass equivalents thereof. [0023] References in the present disclosure to “embodiment” or

“implementation” mean that a particular feature, structure, characteristic, or function described in connection with the embodiment or the implementation is included in at least one embodiment or implementation of the invention. The appearances of the phrase “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment.

[0024] According to an aspect of the present invention, the medical device includes a tubular support structure which is formed of a plurality of ringlets which are arranged sequentially along a common longitudinal axis thereof. In simpler language, the ringlets have coaxial central longitudinal axes. Each ringlet is formed of plurality of crowns connected along a circumferential direction and, in turn, each crown is formed by two straight struts disposed in a V-shaped configuration, each said struct is of a separate length. [0025] In an embodiment of the present invention, the length of the consecutive struts in a crown may be equal or unequal and a particular ringlet may be formed of crowns having equal length struts, crown having unequal length struts or a combination of them. At least one crown of the at least one helical ringlet has equal or unequal length struts towards the at least one cylindrical ringlet. In scope of the present invention, if the difference between the length of the two struts of a particular crown is less than 5% then the struts are considered equal in length. Based on these variations, a variety of ringlet designs may be created which exhibit different type of mechanical properties. In addition, different type of ringlets may be arranged sequentially along a common longitudinal axis and over a length of the medical device.

[0026] In the embodiment of the present invention, a plurality type of cylindrical ringlets may be formed of a plurality of crowns connected along a circumferential direction by keeping the length of the struts of the crowns equal in a ringlet. In the cylindrical ringlet, the peaks of the crowns have a common cross-sectional plane perpendicular to the longitudinal axis of the tubular support structure.

[0027] In the embodiment of the present invention, a plurality of helical ringlets may be formed of a plurality of crowns connected along a circumferential direction to have a helical structure by keeping the length of the struts of the crowns un-equal in a ringlet and following the same pattern in adjacent ringlet. The plurality of crowns are made of struts of different lengths. In the helical ringlets, by virtue of the helical design, the peaks of the crowns do not have a common cross-sectional plane perpendicular to the longitudinal axis of the tubular support structure, Further, based on difference in lengths of the adjacent struts in a crown, the angle of helix may be changed.

[0028] In the embodiment of the present invention, the tubular support structure has a plurality of transition region where two different type of ringlets converges while maintaining the diameter of the tubular support structure constant. For converging the two type of ringlets, strut lengths in crowns of a ringlets are changed such that the peaks of the adjacent ringlets touch a common cross-sectional plane perpendicular to the common longitudinal axis of the tubular support structure. The transition region is located between the cylindrical ringlet and the helical ringlet. [0029] According to the embodiment of the present invention, the medical device further includes a plurality of long connectors to connect the plurality of ringlets arranged adjacent to each other, and at least one long connector connects adjacent ringlets. The long connector is Z-shaped and consecutive long connectors which connect adjacent ringlets form a mirror-reflection of each other about a radial plane of reflection. The radial plane of reflection may be a plane perpendicular to the common longitudinal axis of the ringlets of the medical device. The long connector in consecutive ringlets may be of same length or their length may vary as per the design requirements. Such a design provides a set of mechanical properties which allow easy insertion and maneuvering of the medical device into lumens of small diameter having tortuous anatomy.

[0030] According to the embodiment of the present invention, the long connector is of Z-shaped configuration and connects the valleys of adjacent ringlets, i.e., one end of the long connector is connected to a valley-type formation formed in one ringlet and the other end of the long connector is connected to a similar valley-type formation in the adjacent ringlet. The valley type configuration may be formed between two struts connected in V-shape in the crown. In an example, two adjacent ringlets are connected through long connectors. Optionally, the long connectors may be arranged with an offset among them as well. In an example, each of the plurality of long connecting elements connects adjacent ringlets at an offset therebetween. In an example, the plurality of long connecting elements connect adjacent ringlets at no offset therebetween., i.e., connect in line with the adjacent ringlets [0031] According to the embodiment of the present invention, the long connector may be formed of two long sections and a short section to form a Z-shaped configuration. In addition, the short section connects the ends of the two parallel long sections in such a way to form an obtuse angle between the short section and the long section, thereby forming the Z-shape of the long connector. As a design element of the medical device, the angle between the short section and the long section of the long connecting member is decided at the time of fabrication. In an example, the angle may be between 91° and 160°, and the angles between one long section and the short section and the other long section and the short section may be substantially same. The ringlets and the Z-shaped long connector may be designed in such a way so that the angle in the long connector may vary or may not vary during crimping and expansion. In most of the scenarios, the axial length of the tubular support structure may not change or change less than 5% of its original length after the deployment (after expansion). In addition, at the time of fabrication, different expansion and flexural properties may be obtained by designing the angle between the short and long sections of the long connector. Therefore, a properly selected and designed angle in the long connector improves safety and performance of the medical device. Angle present in the long connector provides improved trackability while the tubular support structure is being maneuvered through the lumen to reach the target site and provides stability and radial stiffness too. Additionally, the angle present in the long connector provides flexibility to the tubular support structure.

[0032] According to the embodiment of the present invention, two consecutive Z- shaped long connectors are opposite or mirror-reflection to each other about a radial plane of reflection. In other words, the direction of the Z-shape of any two consecutive long connector, i.e., between any two consecutive ringlets is a mirror- reflection about the plane passing perpendicular to the longitudinal axis of the tubular support structure of the medical device. In addition, the long connector in consecutive ringlets may be of same length or their length may vary as per the design requirements. Such a design of the medical device provides stability, safety, trackability, fracture resistance, flexibility in crimped state. [0033] According to the embodiment of the present invention, the medical device further includes a plurality of short connectors to supplement the long connectors in connecting the ringlets in specific section of the medical device. The short connectors connect the ringlets at both end sections at specific points in peak-to- peak manner. The short connectors between one pair of ringlets, with respect to the short connectors in another pair of ringlets, may be in same direction, opposite direction or at a specific angle. The short connector restricts flexibility but bring higher bending stiffness to the tubular support structure of the medical device. In this case, the short connectors control the flaring tendency of the ends of the stent after deployment.

[0034] In an exemplary embodiment of the present invention, the plurality of short connectors to connect the plurality of ringlets arranged adjacent to each other. Each of plurality of short connectors connect peaks of two adjacent ringlets, i.e., one end of the short connector is connected to a peak formed in a ringlet and other end is connected to a similar peak formed in the adjacent ringlet. In an example, the short connectors connect to ringlets in such a way that there is no offset between the connected peaks, i.e., the short connector connect in-line peaks. Accordingly, the short connector is substantially parallel to the common longitudinal axis and may be at a right angle with the radial plane. [0035] In an exemplary embodiment of the present invention, each of plurality of short connectors connects peaks of adjacent ringlets where the peaks are at an offset. The short connectors connect to ringlets in such a way that there is offset between the connected peaks, i.e., the short connector connect the peaks at an angle with the common longitudinal axis but may be at a right angle with the radial plane.

[0036] In an exemplary embodiment, each of plurality of short connectors has a width at the peak and a width at the mid-point along the length of the short connector, wherein, the width at the mid -point is smaller than the width at the peak. [0037] According to the embodiment of the present invention, the medical device also includes a plurality of hybrid connectors. A plurality of hybrid connectors to connect the at least one cylindrical ringlet adjacent to the at least one of the plurality of the helical ringlets. The hybrid connector is basically one strut of a crown that terminates on peak of another crown in adjacent ringlet and thus creates a connection. According to an exemplary embodiment of the present invention, two adjacent ringlets are connected through hybrid connectors. Optionally, the hybrid connectors may be arranged with no offset among them.

[0038] In another exemplary embodiment of the present invention, one or more long connector from among the plurality of long connectors and one or more hybrid connector from among the plurality of hybrid connectors are connected to a common crown. In said example, a single hybrid connector and a single long connector may be connected at the same point where one side of the crown forms a valley for the long connector and the opposite side of the same crown forms a peak for the short connector on the opposite side.

[0039] In the exemplary embodiment of the present invention, one or more short connector from among the plurality of short connectors and one or more hybrid connector from among the plurality of hybrid connectors are connected to a common crown. In said example, a single hybrid connector and a single short connector may be connected at the same point where strut of the crown terminates on peak of another crown present in an adjacent ringlet and the peak of the crown of the hybrid connector connects to the short connector. The short connector and the hybrid connector are connected in continuity in a longitudinal direction.

[0040] In the exemplary embodiment of the present invention, each of the plurality of the hybrid connectors is formed by connecting a strut of the shorter length of the at least one helical ringlet to the peak of a crown situated just below an end of the struct of the shorter length. [0041] In the exemplary embodiment of the present invention, one or more short connector from among the plurality of short connectors, one or more hybrid connector from among the plurality of hybrid connectors and one or more long connector from among the plurality of long connectors are connected in series. [0042] According to the exemplary embodiment of the present invention, the tubular support structure is a combination of the cylindrical ringlets, the helical ringlets and the transition region which are arranged in a logical manner along the longitudinal axis of the tubular support structure and the ringlets are connected using the long connector, short connector, and the hybrid connector. In the transition region, the at least one cylindrical ringlet and the at least one helical ringlet are connected through a combination of the short connectors, and the hybrid connectors, the long connector or a combination thereof.

[0043] According to the exemplary embodiment of the present invention, a thickness of each of the straight struts, each of the long connectors, each of the short connectors, and each of the hybrid connector measured in a radial direction of a tubular support frame is constant along a length thereof.

[0044] According to the present invention, during fabrication, flexural and strength related properties of the medical device may be customized by defining number of ringlets of specific type and by defining number of connectors of specific types and their arrangement along the length of the tubular support structure. The short connectors and the hybrid connectors bring bending stiffness in the tubular support structure. The long connectors bring flexibility while controlling the twisting tendency in the tubular support structure. The cylindrical ringlets provide radial support while the helical ringlets provide conformance and scaffolding. The properties of the stent, such as radial strength, fracture resistance, flexibility, bending strength, and stability, may be achieved by selecting combinations of connectors and ringlets in the medical device and by customizing the density of connectors and ringlets along the length of the medical device. [0045] The tubular support structure, in the present invention, may be easily crimped while having high flexibility. In the crimped state, the medical device may be mounted on a catheter and guided through the vessel or organ to the targeted vessel part for deployment. After reaching the deployment state, the tubular support structure is self-expanded or balloon-expanded to its final state. [0046] Further, according to an example of the present invention, in the helical ringlet, two adjacent ringlets may be connected only by the long connectors. In addition, the long connector may be of same length or its length may vary in consecutive ringlet pairs. [0047] According to the present invention, the long connectors, short connectors, and the hybrid connectors aid in minimizing the stress generation or stress concentration at potential locations due to different mechanical forces applied on the medical device at the time of deploying it or after its deployment. The mechanical forces may be, for example, elongation, compression, torsional movement, bending movement and other physiological conditions, for instance, blood flow (after the deployment).

[0048] According to the present invention, width of the straight struts forming the crowns and the connectors measured in the circumferential direction of the tubular support structure remain constant along a length of the tubular support structure. Also, the thickness of the straight struts and the connectors measured in the radial direction of the tubular support structure also remains constant along the length. [0049] Referring Figures 1-5, disclose medical device (100) having a tubular support structure (100), a cylindrical ringlet (102), a helical ringlet (104), a transition region (106), a strut (108), a peak (110), a long connector (112), a short connector (114), and a hybrid connector (116).

[0050] Referring FIG. 1 illustrates a developed view of a medical device showing a section of a tubular support structure (100) in an initial, nominal diameter state according to an embodiment. In an example, the medical device (100) may be a stent. The medical device, according to the present invention, may be placed inside the lumen of human or animal, such as an artery, vein, bile duct, urinary tract, alimentary tract, tracheobronchial tree, cerebral aqueduct, or genitourinary system. Specifically, the medical device may be deployed in femoral artery, superficial femoral artery, popliteal artery, tibial artery, genicular artery, cerebral artery, carotid artery, vertebral artery, subclavian artery, radial artery, brachial artery, axillary artery, coronary artery, peripheral artery, iliac artery, or neuro-arteries. For example, the medical device may be used to remedy stenosis in superficial femoral artery.

[0051] According to the embodiment of the present invention, the tubular support structure (100), may be formed of close cell, open cell, or hybrid configuration. Further, the tubular support structure (100) is made of a material selected from a group of a metal, non-metal, alloy, polymer, biodegradable, bioresorbable material or a combination of two or more thereof. The tubular support structure comprises at least one radiopaque marker on its circumferential surface. For example, all deformable, medically possible metal, metal alloy may be used and include but are not limited to Stainless steel, Cobalt alloys, pure Iron, Nickel-titanium alloys, Tantalum, Niobium, Nickel alloys, Magnesium alloys, Zinc alloys, L605, MP25N, and Nitinol. For instance, the material used for the medical device deployable through balloon-expansion mechanism is selected from Cobalt Chromium, Stainless Steel, Magnesium, Platinum, bioresorbable polymer or a combination of two or more thereof. On the other hand, in said example, the material used for the tubular support structure (100) capable of self-expanding operation is mainly a shape-memory alloy e.g., Nitinol.

[0052] In addition, examples of polymers that may be used to fabricate the tubular support structure (100) in accordance with the present invention include but are not limited to polymers of L-lactide, Glycolide or combinations of thereof, poly(hydroxybutyrate), polyorthoesters, poly anhydrides, poly(glycolic acid), poly(glycolide), poly(L-lactic acid), poly(L-lactide), poly(D-lactic acid), poly(D- lactide), poly(caprolactone), poly(trimethylene carbonate), polyester amide, polyesters, polyolefins, polycarbonates, polyoxymethylenes, polyimides, polyethers, and copolymers and combinations thereof.

[0053] According to the embodiment of the present invention, the tubular support structure (100) carries a biocompatible material, which in one case, may be a layer of the biocompatible material coated on the tubular support structure (100) using any coating technique. The biocompatible material may be a drug -eluting biocompatible material.

[0054] According to the embodiment of the present invention, the tubular support structure 100 as illustrated in Fig. 1 and Fig. 3, shows an embodiment where the tubular support structure (100) may be formed of cylindrical ringlet (102), the helical ringlet (104) and the transition region (106) between the cylindrical ringlet and the helical ringlet where all three components are arranged along longitudinal axis and the ringlets are connected using the long connector (112), the short connector (114) and the hybrid connector (116). The ringlets are formed of a plurality of crowns (110) connected along a circumferential direction and, in turn, each crown (110) is formed by two straight struts (108) connected at their one end and form a V-shaped configuration.

[0055] According to the embodiment of the present invention, the tubular support structure (100) may be of different lengths and diameters. The length of the tubular support structure (100) depends on the number of ringlets (102, 104, 106) and the diameter of the tubular support structure (100) depend on the number of crowns (110) in each ringlet (102, 104, 106). Depending on the treatment required for a particular vessel or organ; the number of ringlets and number of crowns in each ringlet may be customized to prepare a suitable support structure for a specific vessel or organ treatment.

[0056] According to the embodiment of the present invention, the lengths of the struts (108) in a particular crown (110) may be equal or unequal and a particular ringlet may be formed of crowns having equal length struts, of crown having unequal length struts or a combination of them. Based on these variations, a variety of ringlet designs may be created which exhibit different type of mechanical properties. In addition, different type of ringlets may be arranged sequentially along a common longitudinal axis and over a length of the medical device.

[0057] According to the embodiment of the present invention, the cylindrical ringlets (102) are formed of the straight struts of equal or unequal lengths. In a cylindrical ringlet, the peaks of all the crowns touch a common cross-sectional plane that is perpendicular to the longitudinal axis of the tubular support structure (100).

[0058] According to the embodiment of the present invention, the helical ringlets (104) are formed by keeping the length of the struts (108) of the crowns (110) unequal and following the same pattern in adjacent crown. This inequality in lengths of the struts in a crown and repeating the pattern in all the connected crowns create the helical ringlet (104). In the helical ringlets (104), by virtue of the helical design, the peaks of the crowns (110) do not have a common cross-sectional plane perpendicular to the longitudinal axis of the tubular support structure (100), further, based on difference in lengths of the adjacent struts (108) in a crown (110), the angle of helix may be changed.

[0059] According to an example, the peaks of the helical ringlets and the peaks of the cylindrical ringlet are in same line longitudinally i.e., there is no offset. However, in the transition region, the peaks of the ringlets may be at an offset. [0060] According to the embodiment of the present invention, the transition region (106) in the tubular support structure (100) is a zone where two different type of ringlets converges while maintaining the diameter of the tubular support structure (100). For converging the two type of ringlets, strut lengths in crowns of a ringlet are changed such that the peaks of the adjacent crowns touch a common cross-sectional plane perpendicular to the common longitudinal axis of the tubular support structure. In the tubular support structure (100) as illustrated in Fig. 1, the difference between the lengths of the struts (108) in a crown (110) start reducing gradually and the strut lengths become equal when the helical ringlet (104) comes closer to the cylindrical ringlet (102) and thus both the ringlets converge while not affecting the diameter of the tubular support structure (100). In this process, the peak of the last crown of the helical ringlet (104) comes parallel to the peak of the crown just before the last crown in the helical ringlet (104) and both the peaks touch the common cross sectional plane perpendicular to the longitudinal axis of the tubular support structure.

[0061] According to the embodiment of the present invention, in the transition region, the cylindrical ringlet (102) and the helical ringlets (104) are connected through a combination of the short connectors (114) and the hybrid connectors (116).

[0062] According to the embodiment of the present invention, connectors in the tubular support structure (100) are described with respect to Fig. 2. Fig. 2 shows a detailed and magnified view of the tubular support structure (100). According to an example, the ringlets and the transition region in the tubular support structure (100) are connected with each other through different type of connectors. The adjacent helical ringlets are connected through the plurality of long connectors for example, the adjacent helical ringlets are connected through the Z-shaped long connectors (112) in a valley-to-valley configuration. After a pair of ringlets connected through a long connector (112), between next pair of helical ringlets (104), the long connector (112) is a mirror-reflection of the long connector (112) in previous pair of the helical ringlets (104) about a radial plane of reflection. The radial plane of reflection may be a plane perpendicular to the common longitudinal axis of the ringlets of the tubular support structure. Further, the long connector (112) in consecutive pair of ringlets may be of same length or their length may vary in comparison to the long connector (112) present between adjacent previous pair of ringlets or following pair of ringlets, as per the design requirements. This arrangement reduces strain development in one direction and bring greater stability, safety, radial stiffness, flexibility, fracture resistance and trackability. If all the long connectors (112) are in one direction, it brings an inherent tendency in the tubular support structure to twist along the longitudinal axis in a particular direction that may cause rotational movement along longitudinal axis which is not a required property and poses risk to the patient.

[0063] According to an example, the adjacent cylindrical ringlets are connected through the plurality of short connectors (114). The short connector connects the ringlets in a peak-to-peak manner. The connecting peaks may be in-line or at an offset with each other.

[0064] According to an example, the hybrid connector ( 116) is the last strut of the last crown of a helical ringlet that terminates on the peak of a crown that is below the strut and the crown is part of the helical ringlet. [0065] Additionally, no two adjacent ringlets have both type of connecting elements. Also, the ringlets need to be mandatorily connected with adjacent ringlets through at least one connecting element where the connecting element may be the long connector (112), the short connector (114) and the hybrid connector (116). [0066] However, it is possible to use either the long connectors ( 112) or the short connectors (114) or the hybrid connectors (116) in continuous manner or in blocks in blocks manner, some ringlets are connected through one type of connecting elements and followed by this block, some others are connected through another type of connecting element.

[0067] The short connectors (114) provide low flexibility and high bending stiffness to the tubular support structure (100) and the short connectors also control flaring. During fabrication, flexural and strength related properties of a stent may be customized by defining specific number of short connectors (114) and long connectors (112) present in the stent between ringlets. Their specific combination gives specific set of properties.

[0068] In addition, the present invention also envisages a method for fabricating the tubular support structure (100) as explained above. According to an embodiment, the medical device is manufactured by: setting-up a design of the medical device to be fabricated in a designing instrument; carving the design on a medically cleaned and approved work piece to fabricate the medical device; finishing the medical device by removing material from a surface of the medical device and polishing the medical device and coating the finished medical device. For the manufacturing of the tubular support structure (100), the method involves, firstly, loading a medically clean and approved workpiece in a designing instrument. According to one example of the present invention, the workpiece or the specimen may be in shape of a hollow circular tube, a film, or a sheet. Then the required design of the tubular support structure 100 is set-up or uploaded in the designing instrument, such as a computer-numerical controlled (CNC) machine for manufacturing. Subsequently, the required design is carved out of the workpiece to fabricate the tubular support structure (100), such as a stent. In one example, the fabrication technique i.e., carving used in the designing instrument is selected from laser fabrication, chemical-etching, photochemical-etching or electro-discharge machining. For instance, the tubular support structure (100) is fabricated by slitting a metallic hollow circular tube with a laser beam, the laser beam following a predefined cutting contour to produce the design of the tubular support structure (100), as has been explained in the foregoing description of the present invention. Once the tubular support structure (100) has been manufactured, the undesired material is removed from the surface of the tubular support structure (100) for finishing. The cleaned and finished tubular support structure (100) is then polished or coated with an appropriate coating. For example, it may be coated with an anti- reactive agent which prevents it from reacting with the atmosphere where either the tubular support structure (100) is stored or deployed. Additionally, or alternatively, the tubular support structure (100) may be covered with a medicinal substance, depending on the purpose, mode, and location of deployment of the tubular support structure (100). Further, the tubular support structure (100) may be manufactured using 3D printing technique or additive manufacturing. 3D printing technique may be selected from Stereolithography (SLA), Digital light processing (DLP), Fused deposition modelling (FDM), Selective laser sintering (SLS), Selective laser melting (SLM), Electronic beam melting (EBM), Laminated object manufacturing (LOM), Polyjet technology or a combination of thereof. [0069] Overall, the tubular support structure (100) has high radial stiffness, enhanced flexibility, and better bending stiffness. This ensures excellent and uniform bracing of the tubular support structure (100) with the wall of the lumen, thereby providing effective support. The tubular support structure (100), according to the present invention, therefore, be easily crimped and expanded through balloon-expandable delivery mechanism or self-expanded delivery mechanism. For example, the design supports easy crimping of the tubular support structure (100) during the deployment process. However, the inherent flexibility and stability due to the design helps in easy movement of the tubular support structure (100) along the tortuous paths of a vessels during the implantation, with a higher safety level for both the patient and the physician.

[0070] Although design and application of the tubular support structure (100) are described, it is to be understood that the present invention is not limited to the specific features or methods described. Rather, the specific features and methods are disclosed as implementations of the tubular support structure (100).

[0071] There has been disclosed a tubular support structure formed of cylindrical ringlets, helical ringlets, short connectors, long connectors, and hybrid connectors. Cylindrical ringlets are formed by keeping the length of the struts of the crowns equal in a ringlet. While in helical ringlet, crowns are made of struts of different lengths. Both type of ringlets converges in a transition region where the helical ringlet converges with the cylindrical ringlet by gradually changing its strut lengths. The long connectors mainly join helical ringlets whereas the short connectors bridge the cylindrical ringlets and the helical ringlets. The hybrid connectors are mainly strut of the helical ringlet which terminates on peak of another crown present in another adjacent helical ringlet. The tubular support structure described here offers high degree of flexibility, controlled flair at the ends after deployment, good radial strength, and stability due to balanced torsional forces.

[0072] It will be also apparent to a skilled person that the embodiments described above are specific examples of a single broader invention, which may have greater scope than any of the singular descriptions taught. There may be many alterations made in the description without departing from the scope of the invention. The present invention is simple in construction and design, integrated, cost effective and easy to manufacture. While particular embodiments of the invention have been described, it is not intended that the invention be limited said configuration disclosed thereto, as it is intended that the invention be as broad in scope as the art will allow and that the specification be read likewise. Thus, while particular structure specific type of arrangement of elements, type of configurations, numbers, have been disclosed, it will be appreciated that the embodiments may be manufactured with other design parameters and configurations as well and are not limited thereto and may be as per operational requirements and nowhere limits the scope of the invention. Further, the methods and configuration of the device, are provided only for reference and for understating purpose of the invention. The scope of the invention should, therefore, be determined with reference to the appended claims, along with the full scope of equivalents to which such claims are entitled. In the appended claims, the terms “including” is used as the plain-English equivalent of the respective term “comprising” respectively.