Carotid artery micro-net woven stent

Abstract

The invention relates to the technical field of medical instruments, and discloses a carotid artery micro-net woven stent. The stent comprises a stent main body divided into a stent middle part and a stent end part, the stent main body comprises a first stent, a second stent and a plurality of connecting structures, and the first stent and the second stent are both in a hollow pipe shape and are connected with each other through the connecting structures; the first support and the second support are connected at multiple positions through a plurality of connecting structures, so that movement of the first support and the second support can be limited, and the connecting structures comprise the first connecting structure and the second connecting structure. The two different connecting structures are arranged on the stent body, so that the requirement for different slippage degrees of the ends and the middle is met, layers of the intravascular stent are attached during use, the structural integrity of the stent is kept, the stent is tightly attached to a blood vessel, and good supporting and effective covering are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of medical devices, and in particular to a carotid artery micro-mesh braided stent. Background Art

[0002] Stroke, also known as apoplexy, has the characteristics of high morbidity, high disability rate, and high mortality rate. It has become the leading cause of death in my country. Carotid atherosclerotic stenosis is one of the main causes of ischemic stroke. In recent years, stent implantation has gradually become an effective alternative to carotid endarterectomy for the treatment and improvement of carotid atherosclerotic stenosis due to its high efficiency and minimally invasive characteristics.

[0003] At present, there are many problems with the stents used in the prior art for treating carotid atherosclerosis: 1. The mesh of the open-loop stent is relatively large and cannot effectively cover the plaque. Its "fish fin effect" affects the internal permeability. When the stent is released at the stenosis of the carotid artery, the stent rod is easy to cut the plaque, causing the plaque to break and fall off. The broken plaque will enter the brain with the blood flow and block the cerebral blood vessels, causing stroke or even death. 2. The mixed braided stent adopts the technology of mixing thick and thin wires, but because of the large difference in the diameter of the thick and thin wires, the processing technology is limited and it is difficult to achieve automated production. The mixed braided stent produced by manual production is limited by its minimum porosity, and the capture effect of small-sized plaques or emboli is limited. In addition, when the mixed braided stent is compressed in the sheath, all the strands of the stent are in contact with the outer wall of the sheath. During the release and recovery process, the wire material and the sheath wall slip, which can easily cause the braided structure to be chaotic and deformed, affecting the adhesion with the blood vessel and the embolus capture performance after release.

[0004] Although the existing double-layer braided stent can avoid the problems of hybrid braided stents such as the inability to automate production and the large minimum porosity, the connection strength is weak due to the braided connection, which limits the radial connection constraints between layers. When subjected to local compression (such as local stenosis plaque compression after implantation), the internal micro-network will deform and move inward, and large gaps will appear between layers, affecting blood flow, causing stent adhesion and thrombus, resulting in restenosis; or after implantation, intimal hyperplasia pushes the inner layer to deform and move inward, forming intimal hyperplasia between the inner and outer layers, causing restenosis. Summary of the invention

[0005] In order to solve the above technical problems, the present invention provides a carotid artery micromesh braided stent, which solves the interlayer separation problem that is prone to occur in double-layer stents by giving different degrees of free slip between layers at different positions of the stent and limiting the radial slip in the middle of the stent, while maintaining the integrity of the micromesh structure to improve the safety and effectiveness of the use of the carotid artery stent.

[0006] The present invention is implemented by the following technical scheme: a stent body is divided into a stent middle part and a stent end part, the stent body includes a first stent, a second stent and a plurality of connection structures, the first stent and the second stent are both in the form of hollow tubes and are connected to each other by the connection structure, the first stent and the second stent are connected at a plurality of positions by the plurality of connection structures, so that the movement of the first stent and the second stent can be restricted, the connection structure includes a first connection structure and a second connection structure, the first connection structure is located in the middle area of ​​the first stent, the second connection structure is located in the area near the end of the first stent, the first stent has a first axial slippage and a first radial slippage relative to the second stent in the middle area, the first stent has a second axial slippage and a second radial slippage relative to the second stent in the area near the end, the first axial slippage is less than the second axial slippage, and the first radial slippage is less than the second radial slippage, so that two different connection structures are provided at the stent end part and the stent middle part, which can take into account the different slippage requirements of the stent end part and the stent middle part, and ensure that the fit and structural integrity between the layers of the vascular stent can be maintained during use.

[0007] As a further improvement of the above scheme, the first bracket is formed by interlacing first braided wires, the first bracket has a first porosity n1, and the first braided wire has a first braided wire cross-sectional area; the second bracket is formed by interlacing second braided wires, the second bracket has a second porosity n2 larger than the first porosity, and the second braided wire has a second braided wire cross-sectional area larger than the first braided wire cross-sectional area.

[0008] As a further improvement of the above scheme, the cross-sectional area of ​​the first braided wire is smaller than that of the second braided wire, and the first porosity n1 is smaller than the second porosity n2. Therefore, the first stent selects a micromesh stent with a fine wire diameter and a small porosity, and the second stent selects a stent with a thick wire diameter and a large porosity, which is beneficial to reducing the contact area between the stent and the pushing outer sheath and reducing the pushing force of the stent body.

[0009] As a further improvement of the above scheme, the cross-sectional area of ​​the connecting structure is less than or equal to the cross-sectional area of ​​the first braided wire, thereby reducing the protrusion of the connecting structure on the inner and outer surfaces of the stent body, improving the surface flatness of the stent body, and reducing the pushing resistance of the stent body.

[0010] As a further improvement of the above solution, the first bracket and the second bracket form a tight connection at the first connection structure and a relatively movable connection at the second connection structure, thereby avoiding interlayer separation between the first bracket and the second bracket.

[0011] As a further improvement of the above scheme, the first braided wire includes a first warp and a first weft, the first warp and the first weft are two spiral braided wires with opposite braiding directions, and the adjacent first warp and first weft are cross-woven to form a plurality of first intersections and first meshes, the second braided wire includes a second warp and a second weft, the second warp and the second weft are two spiral braided wires with opposite braiding directions, and the second warp and the second weft are cross-woven to form a plurality of second intersections and second meshes, and the first bracket and the second bracket have the same or similar braiding angles.

[0012] As a further improvement of the above solution, the first warp and the second warp have the same direction, the first weft and the second weft have the same direction, and the second connecting structure connects the first warp and the second warp; And / or, the second connecting structure connects the first weft thread and the second weft thread.

[0013] As a further improvement of the above solution, the first connecting structure connects a first intersection point and a second intersection point that are radially adjacent; Alternatively, the first intersection is connected to a radially adjacent second warp or second weft through a first connecting structure; Alternatively, the first warp thread is connected to the second warp thread, and the first weft thread is connected to the second weft thread to form a first connection structure.

[0014] As a further improvement of the above solution, the radially adjacent first intersection point and the second intersection point are connected by a first connecting structure, and the first connecting structure limits the first warp, the first weft, the second warp, and the second weft together; Alternatively, the first connecting structure connects the first warp, the first weft and the second warp or the second weft, and the first connecting structure limits the first warp, the first weft and the second warp or the second weft together, thereby providing radial mutual constraints for the first bracket and the second bracket to avoid interlayer separation, and the braided wire has a small radial slippage, so that when the bracket is in different states such as expansion or contraction, the first braided wire structure can be adjusted with the axial change of the tube diameter, and the braided structure remains intact and effective.

[0015] As a further improvement of the above solution, the first longitude is parallel to the second longitude or is arranged at an angle within a range of 5°, and the first latitude is parallel to the second latitude or is arranged at an angle within a range of 5°.

[0016] As a further improvement of the above solution, the first connection structure is distributed in the middle of the bracket body, distributed along the second longitude or the second latitude, and on the bracket body, the distance RZ between any two adjacent first connection structures satisfies , where E is the Young's modulus of the first braided wire, d is the diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and the value of F is 0N<F≤1N. Therefore, it is possible to avoid the connection structure between the first stent and the second stent being too dense, and to avoid the shear force of the braided wire being significantly increased during use, which affects the fatigue durability of the implanted stent, and the introduction of too many connection points increases the push resistance of the stent.

[0017] As a further improvement of the above solution, on the bracket body, the distance RZ between any two adjacent first connection structures (301) satisfies , where E is the Young's modulus of the first braided wire, d is the wire diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and the value of F is 0N<F≤1N.

[0018] As a further improvement of the above solution, on the bracket body, the radius R of the circle defined by any three adjacent first connection structures satisfies , where E is the Young's modulus of the first braided wire, d is the wire diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and the value of F is 0N<F≤1N.

[0019] As a further improvement of the above solution, the second connection structure is at least separated from the end of the bracket by a first intersection, and the second connection structure is distributed at the end of the bracket and along the second longitude or the second latitude; Alternatively, the second connection structure distributed along the second longitude or the second latitude and farthest from the stent body has an axial distance X of no more than 2 mm from the end of the first stent, and a radial projection angle formed by two adjacent second connection structures and the center of the stent cross section is less than or equal to 120°.

[0020] As a further improvement of the above scheme, the first connecting structure is distributed in the middle part of the bracket, and the second connecting structure is distributed at the end of the bracket and along the second longitude or the second latitude. At least one second connecting structure is arranged near the first connecting structure away from the bracket body. Therefore, the connecting structure has a radial constraint range for the first bracket and the second bracket. Within this range, the bending moment of the braided wire is limited when it is subjected to force, which can effectively avoid interlayer separation in a local range.

[0021] As a further improvement of the above solution, the connection structure further includes a third connection structure, and the first bracket and the second bracket are tightly connected at the third connection structure; the third connection structure is located in the middle area of ​​the first bracket and is mixed with the first connection structure; Alternatively, the third connecting structure is located between the first connecting structure and the second connecting structure region.

[0022] As a further improvement of the above scheme, a buffer bucket with an overall funnel shape is arranged in the cavity of the first stent, and the buffer bucket is divided into three parts: an expansion end, a bucket body and a tightening end. The buffer bucket is formed by interweaving a plurality of third braided wires that are intertwined with each other. The expansion end of the buffer bucket is connected to the first braided wire on the first stent. The buffer bucket can buffer the blood flow to avoid excessive perfusion.

[0023] As a further improvement of the above solution, the tightening end of the buffer bucket is provided with a plurality of expansion seams distributed in a ring shape, so that after the patient adapts to the increase in blood flow, the buffer bucket will gradually reduce the obstruction to the blood flow, thereby ensuring blood supply.

[0024] Compared with the prior art, the present invention has the following beneficial effects: The first stent is a thin stent, and the second stent is a thick stent. The second stent provides the main support force for the stent body, so that the stent body can fit closely with the blood vessel to achieve effective support and good coverage; the first stent, due to its micro-mesh structure, can better cover the plaque after being released into the blood vessel, prevent the plaque from prolapse or rupture and fall off, and avoid it from entering the downstream of the blood vessel and causing stroke, etc.; The tight constraint provided by the first connection structure is a strong connection, which can effectively ensure the fit of the working area of ​​the stent body, avoid delamination before and after use, especially when it is locally squeezed, improve the effectiveness of the stent body adhering to the wall, reduce the risk of thrombosis and hyperplasia in the stent, and improve the safety of the stent; The gap constraint provided by the second connection structure can give the stent body a greater axial and radial sliding degree near the end area relative to the middle area, thereby avoiding deformation or damage of the stent caused by the inevitable relative movement of the stent body, and ensuring good support and effective coverage of the stent on the plaque; By adopting the first connection structure in the middle of the stent and the second connection structure near the end area, the stent body can adjust the braided structure to a certain extent through the slippage of the wires in the state of blood vessels with different diameters, so that the stent can better cover the plaque, prevent the prolapse or rupture of the plaque, and avoid it from entering the downstream of the blood vessel to cause stroke. At the same time, the problem of interlayer separation during the use of the stent is avoided, and the smoothness and integrity of the micro-mesh stent structure are maintained during the compression and expansion process, reducing the risk of restenosis in the stent and improving the safety of the stent body. After the carotid artery stent surgery, the blood flow of the originally diseased blood vessels will suddenly increase after being supported by the stent, which may lead to overperfusion and cause symptoms such as headache and dizziness. By providing a buffer bucket inside the stent, the buffer bucket can play a certain buffering role on the blood flow, thereby lowering blood pressure. In addition, since the tightening end of the buffer bucket is provided with an expansion seam, the blood blocking effect of the buffer bucket will gradually decrease, thereby giving the buffer an adaptation period, thereby solving the problem of overperfusion that may occur after the stent surgery. In addition, the structure of the buffer bucket is similar to that of the first stent and the second stent, and it is also expandable, so that it can also assist the first stent and the second stent in supporting the blood vessel to avoid restenosis. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a first schematic diagram of the carotid artery micro-mesh braided stent of the present invention; Figure 2 A second schematic diagram of the carotid artery micro-mesh braided stent of the present invention; Figure 3 It is a compression braiding angle variable diagram of the carotid micro-mesh braided stent of the present invention; Figure 4 A second connection structure display diagram and a connection mode cross-sectional diagram; Figure 5 A first embodiment of a first connection structure is shown in a diagram and two cross-sectional views of its two connection modes; Figure 6 A second embodiment of the first connection structure is shown, and a connection method thereof is a cross-sectional view in which a first intersection point is connected to a second radially adjacent latitude line through the first connection structure; Figure 7 A third embodiment of the first connection structure is shown in FIG. 1 and a cross-sectional view of the connection between the first weft thread and the second weft thread in the connection method thereof; Figure 8 is a point layout diagram of a first connection structure; Fig. 9 This is an expanded view of the carotid artery micro-mesh braided stent of the present invention; Fig.10 is a point layout diagram of a second connection structure; Fig.11 is a layout diagram of the first connection structure and the second connection structure; Fig.12 This is a plan view of the carotid artery micro-mesh braided stent and buffer bucket; Fig.13 A three-dimensional cross-sectional view of the carotid artery micro-mesh braided stent and buffer bucket; Fig.14 This is a plan view of the buffer bucket.

[0026] Description of main symbols: 1. First bracket; 2. Second bracket; 3. Connection structure; 301. First connection structure; 302. Second connection structure; 4. First braiding wire; 401. First warp; 402. First weft; 5. Second braiding wire; 501. Second warp; 502. Second weft; 6. Expanding line; 7. Buffer bucket; 8. Expansion seam. DETAILED DESCRIPTION

[0027] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0028] In the present application, the terms "proximal" and "distal" refer to the relative orientation, relative position, and direction of components or actions relative to each other from the perspective of an operator using the medical device. Although "proximal" and "distal" are not restrictive, the "proximal" usually refers to the end of the medical device that is close to the operator during normal operation, and the "distal" usually refers to the end that first enters the patient's body.

[0029] It should be understood by those skilled in the art that the discussion of any of the above embodiments is merely illustrative and is not intended to imply that the scope of the present invention (including the claims) is limited to these examples. Under the concept of the present invention, the technical features in the above embodiments or different embodiments may also be combined, the steps may be implemented in any order, and there are many other variations of the different aspects of the present invention as described above, which are not provided in detail for the sake of simplicity.

[0030] The present invention is further described below in conjunction with the accompanying drawings and specific implementation methods.

[0031] Please combine Figures 1 to 14 The carotid micro-mesh braided stent comprises: a stent body divided into a stent middle portion and a stent end portion, the stent body comprising a first stent 1, a second stent 2 and a plurality of connection structures 3; The first stent 1 is formed by interlacing and weaving the first braided wires 4 to form a generally hollow tube, the first stent 1 has a first porosity, the first braided wires 4 have a first braided wire 4 cross-sectional area, the proximal outer diameter of the first stent 1 is greater than or equal to the distal outer diameter, and the proximal outer diameter of the second stent 2 is greater than or equal to the distal outer diameter, that is, the stent body can be cylindrical or conical; The second stent 2 is formed by interlacing the second braided wires 5 to form a generally hollow tube, the second stent 2 has a second porosity different from the first porosity, the second braided wires 5 have a second braided wire 5 cross-sectional area different from the cross-sectional area of ​​the first braided wires 4, and the second stent 2 is connected to the two ends with a flared portion, the flared portion is provided with a flared wire 6, and the flared wires 6 are connected in pairs to form a closed end. The flared wires can also be set to be open, or multiple strands are connected to form a closed loop.

[0032] The first braided wire 4 includes a first warp thread 401 and a first weft thread 402, the first warp thread 401 and the first weft thread 402 are two spiral braided threads with opposite braiding directions (i.e., the braiding direction is clockwise or counterclockwise), and the adjacent first warp threads 401 and the first weft threads 402 are cross-woven to form a plurality of first intersections and first meshes, and the second braided wire 5 includes a second warp thread 501 and a second weft thread 502, the second warp thread 501 and the second weft thread 502 are two spiral braided threads with opposite braiding directions (i.e., the braiding direction is clockwise or counterclockwise), and the second warp thread 501 and the second weft thread 502 are cross-woven to form a plurality of second intersections and second meshes.

[0033] When the flared portion of the second bracket 2 is a closed loop, the second warp lines 501 and the second weft lines 502 at the ends of the second bracket 2 are connected in pairs to form a closed end.

[0034] The first stent 1 and the second stent 2 have the same or similar braiding angles. The materials of the first stent 1 and the second stent 2 are medical metal wire materials. The medical metal materials include medical stainless steel, nickel-titanium memory alloy, cobalt-based alloy, titanium alloy, magnesium alloy, etc., preferably nickel-titanium memory alloy. At least one braided wire of the first stent 1 or the second stent 2 has developing properties; Among them, the first bracket 1 and the second bracket 2 are connected at multiple positions through the connecting structure 3, so as to limit the relative movement of the first bracket 1 and the second bracket 2; the connecting structure 3 includes a first connecting structure 301 and a second connecting structure 302, the first connecting structure 301 is located in the middle area of ​​the first bracket 1, the middle area of ​​the first bracket 1 is located in the middle of the bracket, the second connecting structure 302 is located in the area near the end of the first bracket 1, the area near the end of the first bracket 1 is located at the end of the bracket, the first bracket 1 has a first axial slip and a first radial slip in the middle area relative to the second bracket 2, the first bracket 1 has a second axial slip and a second radial slip in the area near the end relative to the second bracket 2, the first axial slip is less than the second axial slip, and the first radial slip is less than the second radial slip, so that two different connecting structures 3 are provided at the end of the bracket and the middle of the bracket, which can take into account the different slip requirements of the end of the bracket and the middle of the bracket, and ensure that the layers of the vascular bracket can maintain the fit and structural integrity when in use, so as to achieve good support and effective coverage of the carotid micro-mesh braided bracket.

[0035] Through the above technical solution, the middle part of the stent is the main working area of ​​the stent body. The first stent 1 mainly provides effective coverage for the diseased plaque to prevent the plaque from moving, prolapsing or falling off. The second stent 2 provides sufficient support force, and the two stents work together. Combined with the treatment mechanism of stenosis of vascular stents, the stenotic lesions are mechanically propped open, and the blood vessels are reconstructed through subsequent regrowth of endothelial coverage. Small relative movement or no relative movement between stents is conducive to the stent's wall adhesion effect, which is conducive to the completion of endothelial growth and blood vessel reconstruction.

[0036] Furthermore, in this embodiment, the first bracket 1 is located in the cavity of the second bracket 2, the cross-sectional area or wire diameter of the first braided wire 4 is different from the cross-sectional area or wire diameter of the second braided wire 5, the first bracket 1 on the bracket body is located in the inner cavity of the second bracket 2, the outer diameters of the two brackets are different, and the outer diameter of the first bracket 1 is larger than the inner diameter of the second bracket 2.

[0037] Although the braiding angles of the first stent 1 and the second stent 2 are consistent or similar in the expanded form, during the compression process, the changes in the braiding angles of the two stents are different, resulting in the braiding angle of the first stent and the braiding angle of the second stent being unable to remain the same or similar during the compression process, which is manifested as the first stent 1 and the second stent having a relatively large relative movement in the axial direction. Considering the limitations of the stent processing technology and the precision limits, the above process causes the first stent 1 and the second stent 2 to have axial relative movement during the expansion or contraction process. If the two stents are forcibly constrained so that they cannot move relative to each other in the axial direction, the integrity of the stent body will be affected, or the stent body will be deformed or damaged, affecting the safety and effectiveness of the use of the stent body; if certain constraints are not given to allow it to have a large relative movement in the radial direction, the stent body will be displaced and separated, affecting the support and covering performance of the stent body. The present application provides a first connection structure 301 and a second connection structure 302 with different axial sliding degrees at the middle and ends of the stent, respectively, to reduce the possibility of unavoidable relative movement, deformation or displacement separation of the stent body caused by the geometric structure and processing of the stent body, thereby improving the wall adhesion effect of the stent body, reducing the probability of restenosis of the stent, and allowing blood vessel reconstruction; at the same time, the first connection structure 301 allows small or no relative movement in the radial direction between the first stent 1 and the second stent 2, which is beneficial to the wall adhesion effect of the stent body, conducive to the completion of endothelial growth, and reduces restenosis in the stent body, allowing blood vessel reconstruction;

[0038] At the ends of the stents, in addition to a certain relative movement in the axial direction, the first stent 1 and the second stent 2 have different expansion forces at the ends during the expansion or contraction process (including when locally squeezed) due to the differences in materials, braided wire cross-sectional areas and braided structures between the first stent 1 and the second stent 2. This is manifested as relative movement of the ends of the first stent 1 and the second stent 2 in the radial and axial directions, and the greater the difference in braided wire cross-sectional areas or wire diameters between the first stent 1 and the second stent 2, the greater the difference in braided porosity, and the more obvious the relative movement.

[0039] During the expansion or contraction of the stent body, a single braided wire is only constrained at the proximal end, and there is no external force constraint at the distal end of the stent body, so it can be regarded as a "cantilever beam unit". At this time, the internal force at the distal end of the "cantilever beam" is mainly the anti-deformation force stored in the braided wire itself, which is related to the cross-sectional area, material, and geometric structure of the braided wire. Under the influence of the interlacing of adjacent braided wires, the adjacent braided wires constrain the expansion of the "cantilever beam" and provide it with an inward compression force. The anti-deformation force of the braided wire and the compression force of the adjacent braided wires jointly determine the final shape of the braided wire. The denser the number of braided wires, the more obvious the influence of the compression force, the more inward the braided wires shrink, and the smaller the degree of expansion at the end of the stent.

[0040] When the stent is being deployed or contracted, the slippage of the stent braided wires (the first braided wire 4 and the second braided wire 5) accumulates from the middle to both ends when there are no other constraints. If the stent is in the sheath, due to the constraint at the proximal end, the slippage of the stent braided wires starts to accumulate from the proximal end and reaches a maximum at the distal end. Taking into account the limitations of the stent processing technology and the precision limit, the above process makes it necessary for the first stent 1 and the second stent 2 to have axial relative movement during the deployment / contraction process of the stent. If the two stents are forcibly constrained to have no relative movement, it will inevitably affect the integrity of the stent, or cause the stent to deform or damage, affecting the safety and effectiveness of the stent.

[0041] Taking the above reasons into consideration, different axial slippage degrees are given between layers at different positions of the stent, while limiting the radial slippage degree in the middle part of the stent, in order to solve the interlayer separation problem of the double-layer stent proposed in the above background technology, and avoid deformation and damage of the stent structure, so as to further improve the safety and effectiveness of the use of carotid stents.

[0042] In this embodiment, the first braided wires 4 of the first bracket 1 and the second braided wires 5 of the second bracket 2 are not interwoven together and are not mixed; in other embodiments, the first bracket 1 may also be configured such that part or all of the first braided wires 4 and the second braided wires 5 of the second bracket 2 are interwoven together.

[0043] Please combine Figures 4 to 7The first connecting structure 301 includes a first ring for connecting the first stent 1 and the second stent 2, and the first ring is perpendicular to the axis of the stent body (carotid micromesh braided stent). The second connecting structure 302 includes a second ring for connecting the first stent 1 and the second stent 2, and the second ring is perpendicular to the extension direction of the braided wire connected by the second connecting structure 302.

[0044] The first loop is perpendicular to the axis of the stent body (carotid micro-mesh braided stent), that is, the winding direction of the first loop is along the radial direction of the stent. The second loop is perpendicular to the extension direction of the braided wire connected to the second connecting structure 302, that is, the winding direction of the second loop is along the radial direction of the braided wire.

[0045] The connection structure 3 is set as a wire coil structure, and the connection interface formed by the coil of the connection structure 3 is placed between the braided grids of the stent to avoid causing abnormal protrusions on the outer surface of the stent and increasing the pushing resistance of the stent; Specifically, one or more wires are wound around a fixed point for a certain number of times (the wound wire loops are arranged in parallel), and the interface is fixed by knotting, hot melting or bonding (knotting fixation, such as square knots, surgical knots, etc., the wire end is enlarged or fixed after knotting to avoid the knot from slipping and loosening, and improve the effectiveness of holding the knot); the interface maintains its firmness under micro-vibration; The material of the connecting structure 3 is a metal material or a polymer material, preferably a polymer material. The polymer material connecting structure 3 is preferably a flexible wire made of a polymer material with good biocompatibility such as polytetrafluoroethylene (PTFE), polyethylene terephthalate (PET), polypropylene (PP), polylactic acid (PLA), polydioxanone (PDO), etc.; the connecting silk thread can be a single strand or multiple strands. Preferably, a single strand is smoother and less likely to hide a source of infection.

[0046] Specifically, the cross-sectional area or wire diameter of the first braided wire 4 is smaller than the cross-sectional area or wire diameter of the second braided wire 5, and the first porosity n1 is smaller than the second porosity n2. In this way, the first stent 1 arranged in the inner layer is a micro-mesh stent with a fine wire diameter and a small porosity, and the second stent 2 arranged in the outer layer is a stent with a thick wire diameter and a large porosity, which is beneficial to reduce the contact area between the stent and the push sheath, and reduce the push resistance of the stent. In addition, the micro-mesh of the first stent 1 is in the inner layer, which can avoid direct contact with the plaque and continuous cutting into small-sized plaques, and when the plaque prolapses through the outer mesh, there is still the inner micro-mesh to provide protection.

[0047] Furthermore, n2=c*n1, and the range of c is 1<c≤20. For round wires, the wire diameter difference is recommended to be controlled within 0.02-0.3; for non-round wires, the cross-sectional area ratio is 2-100. In this way, the metal coverage and support performance of the entire stent are guaranteed to be within the appropriate range.

[0048] The cross-sectional area of ​​the connecting structure 3 is smaller than or equal to the cross-sectional area of ​​the first braided wire 4. Selecting a small cross-sectional area of ​​the connecting structure 3 is conducive to reducing the protrusion of the connecting structure 3 on the inner and outer surfaces of the stent body, improving the surface flatness of the stent body, and reducing the pushing resistance of the stent body.

[0049] At the first connection structure 301 , the first bracket 1 and the second bracket 2 are tightly connected via the first connection structure 301 ; At the second connection structure 302 , a gap exists between a portion of the second connection structure 302 and the first bracket 1 and the second bracket 2 , that is, the first bracket 1 and the second bracket 2 are connected to each other in a relatively movable manner through the second connection structure 302 .

[0050] The middle part of the stent is the main working area of ​​the stent body, so the smaller the relative movement between the first stent 1 and the second stent 2 in the radial direction in this area, the better; at the same time, due to the different outer diameters of the two stents in the middle area of ​​the stent body, although the braiding angles of the two stents are consistent in the unfolded state, the changes in the braiding angles of the two stents during the compression process are different, which is manifested as a certain relative movement of the first stent 1 and the second stent 2 in the axial direction. In addition, considering the limitations of the stent processing technology and the precision limit, the first stent 1 and the second stent 2 must have axial relative movement during the expansion / contraction process of the double-layer stent. If the two stents are forced to have no relative movement, it will inevitably affect the integrity of the stent, or cause the stent to deform or damage, affecting the safety and effectiveness of the stent. The middle part of the stent of the present application is tightly connected by the first connecting structure 301, which avoids the interlayer separation of the first stent 1 and the second stent 2 in this area, is beneficial to the wall adhesion effect of the stent, and is conducive to the completion of endothelial growth and vascular reconstruction; at the same time, the first stent 1 and the second stent 2 are given a smaller possibility of axial movement, avoiding deformation and damage of the stent.

[0051] At the ends of the stents, the first stent 1 and the second stent 2 have a certain relative movement in the axial direction. Due to the differences in the materials, cross-sectional areas of the braided wires, and braided structures of the two stents, the expansion forces of the two stents at the ends are different during the opening or compression process (including when they are partially squeezed), which is manifested as relative movement of the ends of the two stents in the radial and axial directions. And this relative movement becomes more obvious as the difference in the cross-sectional areas of the braided wires and the difference in the braided porosity become greater. The second connecting structure 302 is used to relatively movably connect the stents near the end areas, giving the first stent 1 and the second stent 2 greater axial and radial movement possibilities relative to the middle area, avoiding deformation or damage of the stents caused by the inevitable relative movement of the stents.

[0052] Taking the above reasons into consideration, by giving different degrees of slip between layers at different positions of the stent, providing a small axial displacement and strong radial constraint in the middle, and leaving larger axial displacement at both ends and relatively smaller radial constraint than in the middle, the interlayer separation problem of the double-layer stent proposed in the above background technology can be solved, while avoiding deformation and damage of the stent structure, so as to further improve the safety and effectiveness of the use of carotid stents.

[0053] Please combine Figure 3 The first bracket 1 and the second bracket 2 have the same or similar braiding angles, the first warp 401 and the second warp 501 are parallel or set at an angle within a range of 5°, and the first weft 402 and the second weft 502 are parallel or set at an angle within a range of 5°. In this way, a close expansion and contraction rate is ensured between the two, and the relative movement between each other during contraction and expansion of the vascular stent is reduced, so that the fitting between the layers is achieved during use; in this way, the first bracket 1 and the second bracket 2 have basically similar geometric structures (which can be similar as a whole or similar at the same relative position of the two brackets), and the first bracket 1 and the second bracket 2 are connected at the proximal end and the distal end.

[0054] like Figure 3 , take braided wire M and braided wire N as the first braided wire 4 of the first bracket 1, and braided wire P and braided wire Q as the second braided wire 5 of the second bracket 2 as an example, in the initial state, the braiding angles of the first bracket 1 and the second bracket 2 are the same or similar in the unfolded state, and the braided wire M is parallel to the braided wire P or within a certain range of angles, and the braided wire N is parallel to the braided wire Q or within a certain range of angles. At this time, the point m1 on the braided wire M, the point n1 on the braided wire N, the point p1 on the braided wire P, and the point q1 on the braided wire Q are in overlapping positions. In the process of compressing the bracket body into the conveying system, the braiding angle changes of the first bracket 1 and the second bracket 2 are different during the compression process. If the points m1, n1, p1, and q1 are not connected and constrained by the connection structure, the first bracket 1 and the second bracket 2 will have unlimited movement, displacement separation, and interlayer separation problems; if the points m1, n1, p1, and q1 are set with a fixed connection structure for fixed constraints, the first bracket 1 or the second bracket 2 will be deformed. Similarly, when the stent body is released from the delivery system and deployed to the deployment position, there is also the unavoidable relative movement between the first stent 1 and the second stent 2, which causes the stent to be displaced, separated or deformed. The stent of the present application is provided with a first connection structure 301 tightly connected to the first stent 1 and the second stent 2 in the middle part, which not only provides a certain degree of slippage between the first stent 1 and the second stent 2 in the axial direction, but also reduces the degree of slippage between the first stent 1 and the second stent 2 in the radial direction. By controlling the different degrees of slippage of the stent in the axial and radial directions, it takes into account the clinical needs of adaptive adjustment of the stent structure and prevention of interlayer separation, and effectively reduces the risk of plaque detachment and prolapse and restenosis in the stent.

[0055] Please combine Figure 8 and Fig. 9 The first connection structure 301 is distributed in the middle of the support body, along the second meridian 501 or the second latitude 502; on the side unfolding structure of the support body, the distance RZ between any two adjacent first connection structures 301 satisfies , where E is the Young's modulus of the first braided wire, d is the diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and F is 0N<F≤1N. That is, within the range of the distance RZ of any first connecting structure 301, there is at least one first connecting structure 301, where . In this way, the connection structure 3 is prevented from being too sparse, and the effectiveness of the inter-layer bonding between the first stent 1 and the second stent 2 is prevented from being limited. The reasonable distribution of the connection structure 3 has a significant impact on the safety and effectiveness of the first stent 1 and the second stent 2. The first connection structure 301 has a certain radial constraint range on the stent body. Within this range, the bending moment of the braided wire is limited when it is stressed, which can effectively avoid inter-layer separation in a local area. This radial constraint range is mainly affected by the wire diameter and material properties of the first braided wire 4.

[0056] Further, in the side unfolding structure of the bracket body, the distance between any two adjacent first connecting structures 301 satisfies , where E is the Young's modulus of the first braided wire, d is the diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and F is 0N<F≤1N. In this way, the connection structure between the first stent 1 and the second stent 2 is avoided to be too dense, and the shear force of the braided wire is avoided to be significantly increased during use, which affects the fatigue durability of the implanted stent, and too many connection points are introduced to increase the push resistance of the stent and increase the product cost.

[0057] Furthermore, on the bracket body, the radius R of the circle defined by any three adjacent first connection structures satisfies , where E is the Young's modulus of the first braided wire, d is the diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and F is 0N<F≤1N. In this way, the connection structure on the stent body is ensured to be evenly distributed, avoiding the limitation of the effectiveness of the lamination between the first stent 1 and the second stent 2.

[0058] Please combine Fig.10, the second connection structure 302 is at least one first intersection away from the end of the stent; the second connection structure 302 is distributed at the end of the stent, along the second warp 501 or the second latitude 502; or along the second warp 501 or the second latitude 502, the second connection structure 302 farthest from the stent body is not more than 2 mm from the axial distance X of the end of the first stent 1, and the radial projection angle formed by the two adjacent second connection structures 302 and the center of the cross section of the stent is not more than 120°; that is, any second connection structure 302 has at least one first connection structure 301 or second connection structure 302 within its distance RZ range; in this way, the second connection structure 302 has a certain radial constraint range on the stent, within which the bending moment of the braided wire is limited when it is stressed, and the interlayer separation in a local range (such as the fish mouth phenomenon) can be effectively avoided. This radial constraint range is mainly affected by the wire diameter and material properties of the first braided wire 4. The "fish mouth phenomenon" often occurs at positions with relatively large diameter spans, especially stents woven with wires with small cross-sectional areas, such as the blood flow guide device FD. The carotid stent is often used in the bifurcation of the common carotid artery and the starting section of the internal carotid artery. The stent often needs to cover the internal carotid artery and the common carotid artery, and the diameter difference is relatively large. However, due to the micro-mesh structure and the small cross-sectional area of ​​the braided wire of the first stent 1, when the blood vessel size and the stent size are not suitable, the above-mentioned "fish mouth phenomenon" will occur, which will affect the stent wall adhesion effect and hemodynamics, and increase the probability of restenosis. The connection structure 3 is set at the end to avoid the "fish mouth phenomenon". Because the two stent ends have different expansion forces, and the expansion force gradually increases in the direction away from the stent body, a movable transition area is reserved in the middle and end areas for fixing the two stents to the movable transition to avoid excessive constraints. In other words, because the two stent ends have different expansion forces, and the expansion force gradually increases in the direction away from the stent body, due to the need for axial displacement of the end wire and the requirement of a certain range around the second connection structure 302, it is necessary to ensure that the braided wire has axial freedom.

[0059] Please combine Fig.11 The first connecting structure 301 is distributed in the middle of the bracket, the second connecting structure 302 is distributed at the end of the bracket and along the second longitude 501 or the second latitude 502, and there is at least one second connecting structure 302 within the distance RZ of the first connecting structure 301 farthest from the bracket body; in this way, the connecting structure 3 has a certain radial constraint range for the first bracket 1 and the second bracket 2, within which the bending moment of the braided wire is limited when subjected to force, and local interlayer separation can be effectively avoided.

[0060] Please combine Figure 1 and Figure 4 , the weaving directions of the first warp thread 401 and the second warp thread 501 are the same, and the weaving directions of the first weft thread 402 and the second weft thread 502 are the same; see Figure 1In the connection structure of the middle D region, the second connection structure 302 connects the first warp 401 and the second warp 501; and / or, the second connection structure 302 connects the first weft 402 and the second weft 502. In this way, the second connection structure 302 selects two wires in the same direction for connection, only radially constrains one braided wire of each stent, and provides a larger moving space in the axial direction, which can ensure that the two stents are axially constrained and fit before and after use, and the braided wires have relative movement in the radial direction, avoiding connection failure or deformation and damage of the braided structure, so that the stent has better safety and effectiveness.

[0061] Please combine Figure 1 , Figures 5 to 7 In the first embodiment of the present invention, the first connecting structure 301 connects the first intersection point and the second intersection point which are radially adjacent to each other. Figure 1 The connection structure of the middle A region; Specifically, the radially adjacent first intersection point and the second intersection point are connected by a first connection structure 301, and the first connection structure 301 limits the first warp line 401, the first latitude line 402, the second warp line 501, and the second latitude line 502 together; Alternatively, the first connecting structure 301 connects the first warp 401, the first weft 402 and the second warp 501 or the second weft 502, and the first connecting structure 301 limits the first warp 401, the first weft 402 and the second warp 501 or the second weft 502 together, so that radial mutual constraints can be provided for the first bracket 1 and the second bracket 2 to avoid interlayer separation, and the braided wire has a small radial slippage, so that the bracket is in different states such as expansion or contraction, and the first braided wire 4 structure can be adjusted with the axial change of the tube diameter, and the braided structure remains intact and effective.

[0062] The first connection structure 301 is a radial tight constraint for the first bracket 1 and the second bracket 2. The two warps and two wefts at the intersection are closely attached to each other through the first connection structure 301, with substantially no gap therebetween. The first ring of the first connecting structure 301 is perpendicular to the axis of the support; the second connecting structure 302 connects a first warp 401 (or a first weft 402) of the first support 1 and a second warp 501 (or a second weft 502) of the second support 2; The second loop of the second connecting structure 302 is perpendicular to the connected stent warp (or weft), and there is a gap between the second connecting structure 302 and the first braided wire 4 or the second braided wire 5, thereby providing the connected warp (or weft) with a certain degree of slippage in its axial direction.

[0063] In the second embodiment of the present invention, the first intersection point is connected to the radially adjacent second warp line 501 or second weft line 502 via a first connecting structure 301. Figure 1 The connection structure of the middle B region.

[0064] In the third embodiment of the present invention, the first warp line 401 is connected to the second warp line 501, and the first weft line 402 is connected to the second weft line 502 to form a first connection structure 301, see Figure 1 The connection structure of the middle C region.

[0065] The connection schemes of the first connection structure 301 can provide strong radial connection, limit the radial relative displacement of the two brackets, and give the two brackets a certain degree of axial slippage; so that there is no gap between the two bracket layers and their structural integrity is maintained.

[0066] In the fourth embodiment of the present invention, the connection structure 3 also includes a third connection structure, which is located in the middle area of ​​the first stent 1 and mixed with the first connection structure 301, and the first stent 1 and the second stent 2 are tightly connected at the third connection structure; or it is arranged between the first connection structure 301 and the second connection structure 302 in the axial direction of the first stent 1. The third connection structure is arranged at a position where the first connection structure 301 cannot be arranged on the stent, providing further radial slippage restriction for the stent, thereby ensuring that the stent has a connection structure within any RZ range, so as to avoid interlayer separation of the stent and reduce the risk of restenosis in the stent.

[0067] Regarding the connection setting of the third connecting structure and the braided wires of the first bracket 1 and the second bracket 2, the third connecting structure connects the first intersection and the adjacent second warp 501 or the second weft 502; or, the third connecting structure connects the adjacent first warp 401, the first weft 402 and the second warp 501 or the second weft 502, and the third connecting structure limits the first warp 401, the first weft 402 and the second warp 501 or the second weft 502 together.

[0068] The positional arrangement relationship between the third connecting structure and the first connecting structure and the second connecting structure on the bracket is the same as the positional arrangement relationship between the first connecting structures and the positional arrangement relationship between the first connecting structure and the second connecting structure on the bracket, and will not be repeated here.

[0069] Please combine Figure 12 to Figure 14A funnel-shaped buffer bucket 7 is also provided in the cavity of the first stent 1. The buffer bucket 7 is divided into three parts: an expansion end, a bucket body and a tightening end. The buffer bucket 7 is woven by a plurality of interlaced third braided wires, and the density is higher than that of the first stent 1. The expansion end of the buffer bucket 7 is connected to the first braided wire 4 on the first stent 1. The buffer bucket 7 can buffer the blood flow to avoid excessive perfusion. The tightening end of the buffer bucket 7 is provided with a plurality of expansion seams 8 distributed in an annular shape, so that after the patient adapts to the increase in blood flow, the buffer bucket 7 will gradually reduce the obstruction to the blood flow, thereby ensuring blood supply.

[0070] After the carotid artery stent surgery, the blood flow of the originally diseased blood vessels will suddenly increase after being supported by the stent, which may lead to overperfusion, causing symptoms such as headaches and dizziness, and even cerebral hemorrhage. Therefore, the blood pressure can be restricted to a certain extent through the buffer bucket 7, and the buffer bucket 7 is provided with an expansion seam 8, so that the tightened end of the buffer bucket 7 will gradually expand with the continuous impact of the blood flow. During this period, it is the patient's adaptation period, so that the patient can gradually adapt to the increase in blood pressure, and after adaptation, the obstruction to blood flow can be minimized. ‌

[0071] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A carotid artery micro-mesh braided stent, characterized in that: include: A support body is divided into a support middle portion and a support end portion, the support body comprising a first support (1), a second support (2) and a plurality of connection structures (3), the first support (1) and the second support (2) are both in the form of hollow tubes and are connected to each other via the connection structures (3), and is characterized in that: The first bracket (1) and the second bracket (2) are connected at multiple positions via multiple connection structures (3), thereby limiting the movement of the first bracket (1) and the second bracket (2), the connection structures comprising a first connection structure (301) and a second connection structure (302), the first connection structure (301) being located in a middle region of the first bracket (1), the second connection structure (302) being located in a region close to an end of the first bracket (1), the first bracket (1) having a first axial slippage and a first radial slippage relative to the second bracket (2) in the middle region, the first bracket (1) having a second axial slippage and a second radial slippage relative to the second bracket (2) in a region close to an end, the first axial slippage being smaller than the second axial slippage, and the first radial slippage being smaller than the second radial slippage.

2. The carotid artery micro-mesh braided stent according to claim 1, characterized in that: The first stent (1) is formed by interlacing first braided wires (4), the first stent (1) having a first porosity n1, the first braided wires (4) having a first braided wire (4) cross-sectional area, the second stent (2) is formed by interlacing second braided wires (5), the second stent (2) having a second porosity n2 greater than the first porosity, the second braided wires (5) having a second braided wire (5) cross-sectional area greater than the first braided wire (4) cross-sectional area.

3. The carotid artery micro-mesh braided stent according to claim 2, characterized in that: The cross-sectional area of ​​the connecting structure (3) is smaller than or equal to the cross-sectional area of ​​the first braided wire (4).

4. The carotid artery micro-mesh braided stent according to claim 2, characterized in that: The first bracket (1) and the second bracket (2) are tightly connected at the first connection structure (301), and are relatively movable connected at the second connection structure (302).

5. The carotid artery micro-mesh braided stent according to claim 4, characterized in that: The first braided wire (4) comprises a first warp (401) and a first weft (402), the first warp (401) and the first weft (402) being two types of spiral braided wires having opposite braiding directions, and the adjacent first warp (401) and first weft (402) are cross-woven to form a plurality of first intersections and first meshes, the second braided wire (5) comprises a second warp (501) and a second weft (502), the second warp (501) and the second weft (502) being two types of spiral braided wires having opposite braiding directions, and the second warp (501) and the second weft (502) are cross-woven to form a plurality of second intersections and second meshes, and the first bracket (1) and the second bracket (2) have the same or similar braiding angles.

6. The carotid artery micro-mesh braided stent according to claim 5, characterized in that: The first warp (401) and the second warp (501) are in the same direction, the first weft (402) and the second weft (502) are in the same direction, and the second connecting structure (302) connects the first warp (401) and the second warp (501); And / or, the second connecting structure (302) connects the first weft thread (402) and the second weft thread (502).

7. The carotid artery micro-mesh braided stent according to claim 5, characterized in that: The first connection structure (301) connects radially adjacent first intersection points and second intersection points; Alternatively, the first intersection is connected to a radially adjacent second warp line (501) or second weft line (502) via a first connection structure (301); Alternatively, the first warp thread (401) is connected to the second warp thread (501), and the first weft thread (402) is connected to the second weft thread (502) to form a first connection structure (301).

8. The carotid artery micro-mesh braided stent according to claim 7, characterized in that: The radially adjacent first intersection point and second intersection point are connected via a first connection structure (301), and the first connection structure (301) limits the first warp line (401), the first weft line (402), the second warp line (501), and the second weft line (502) together; Alternatively, the first connecting structure (301) connects the first warp (401), the first weft (402) and the second warp (501) or the second weft (502), and the first connecting structure (301) limits the first warp (401), the first weft (402) and the second warp (501) or the second weft (502) together.

9. The carotid artery micro-mesh braided stent according to claim 5, characterized in that: The first meridian (401) and the second meridian (501) are parallel or arranged at an angle within a range of 5°, and the first latitude (402) and the second latitude (502) are parallel or arranged at an angle within a range of 5°.

10. The carotid artery micro-mesh braided stent according to claim 5, characterized in that: The first connection structure (301) is distributed in the middle of the support body, along the second longitude (501) or the second latitude (502), and on the support body, the distance RZ between any two adjacent first connection structures (301) satisfies , where E is the Young's modulus of the first braided wire, d is the wire diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and the value of F is 0N<F≤1N.

11. The carotid artery micro-mesh braided stent according to claim 10, characterized in that: On the support body, the distance RZ between any two adjacent first connection structures (301) satisfies , where E is the Young's modulus of the first braided wire, d is the wire diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and the value of F is 0N<F≤1N.

12. The carotid artery micro-mesh braided stent according to claim 10, characterized in that: On the bracket body, the radius R of the circle defined by any three adjacent first connection structures satisfies , where E is the Young's modulus of the first braided wire, d is the wire diameter of the first braided wire, and F is the possible local extrusion force after the stent is implanted, and the value of F is 0N<F≤1N.

13. The carotid artery micro-mesh braided stent according to claim 5, characterized in that: The second connection structure (302) is spaced apart from the end of the bracket by at least one first intersection, and the second connection structure (302) is distributed at the end of the bracket, along the second longitude (501) or the second latitude (502); Alternatively, the second connection structure (302) which is farthest from the stent body and distributed along the second meridian (501) or the second latitude (502) has an axial distance X from the end of the first stent (1) of no more than 2 mm, and a radial projection angle formed between two adjacent second connection structures (302) and the center of the stent cross section is less than or equal to 120°.

14. The carotid artery micro-mesh braided stent according to claim 5, characterized in that: The first connection structure (301) is distributed in the middle of the bracket, and the second connection structure (302) is distributed at the end of the bracket and along the second longitude (501) or the second latitude (502). At least one second connection structure (302) is provided near the first connection structure (301) away from the bracket body.

15. The carotid artery micro-mesh braided stent according to claim 1, characterized in that: The connection structure (3) further comprises a third connection structure, and the first bracket (1) and the second bracket (2) are tightly connected at the third connection structure; the third connection structure is located in the middle area of ​​the first bracket (1) and is mixed with the first connection structure (301); Alternatively, the third connecting structure is located between the first connecting structure (301) and the second connecting structure (302) regions.

16. The carotid artery micro-mesh braided stent according to claim 2, characterized in that: A funnel-shaped buffer bucket (7) is arranged in the cavity of the first stent (1). The buffer bucket (7) is divided into three parts: an expansion end, a bucket body and a tightening end. The buffer bucket (7) is formed by interlacing a plurality of third braided wires that are interlaced with each other. The expansion end of the buffer bucket (7) is connected to the first braided wire (4) on the first stent (1). The buffer bucket (7) can buffer blood flow to avoid excessive perfusion.

17. The carotid artery micro-mesh braided stent according to claim 16, characterized in that: The tightening end of the buffer bucket (7) is provided with a plurality of expansion slits (8) distributed in an annular shape, so that after the patient adapts to the increase in blood flow, the buffer bucket (7) will gradually reduce the obstruction to the blood flow, thereby ensuring blood supply.

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