Typical applications include the vascular system, gastrointestinal system and urethral system. Stents are usually brought in compressed form through a catheter through the body to be treated to the desired treatment site and released there. The unfolding of the catheterised stent is done by its own spring-like reinforcement or support of the hollow body in humans or animals. It is necessary that the stent is statically and dynamically variable over a long period of time without significant loss of shape, with its original location and flexibility being ideally suited to the implanted body.
A number of stents have been developed, made of metallic materials, synthetic materials, material that can be absorbed or not absorbed into the body, and a combination of materials, for example in the form of a coating.
The US patents 4,655,771; 4,768,507 and 4,907,336 describe self-expanding, non-absorbable stents. US patent 4,990,155 reveals a thermoreversible, non-absorbable stent. In EP 0335341 and US patent 4,799,479 balloon-dilated, non-absorbable stents are described. US patents 4,950,258 and 5,670,161 and EP 0809981 concern thermoreversible, absorbable stents. In US patents 5,980,564; 5,968,092; 5,500,013; 5,762,625; 6,080,177; 5,306,286; 4,057,537 and Canadian patents 2,025,625x in EP 0,797,63 are described as self-absorbable stents, as well as the most commonly used stents.
The stents currently on the market have a recurrent adverse clinical profile and undesirable clinical outcomes, such as material fatigue, stent dislocation, inflammation, thrombosis or restenosis, which affect the success and sustainability of treatment to the detriment of the patient.
The challenge is therefore to provide an improved stent that overcomes the shortcomings of state-of-the-art stents, is easy to use and safe.
This is achieved by means of a tubular implant, in particular a stent, in the form of a circular mesh of cross-linked threads of biocompatible material running in opposite turns, characterised by the fact that the ends of the tubes are free of threaded ends and that the threads present there are returned to the braided structure. Unlike known stents, which are cut from long tubes or tubes and therefore have interfering threads on the tubes, such threads are not present on the ends of the tubes of the stent of the invention. It is therefore not necessary to cover such threads or to insert them into another braided material.
This eliminates the disadvantages of conventional braided stents, which are made up of a variety of monofilament or multifilament threads or wires, and which, after the manufacturing process, have numerous blunt or sharp interfaces and open end-interfaces that require post-treatment by coating, soldering, welding or covering to prevent their traumatic effects.
According to the invention, the tubular implant can be characterized by having a tubular, radially compressible and expandable, axially flexible structure. In the unloaded state, i.e. without the action of external radial forces, the stent has a radially uniform, tube-like shape. Preferably, the implant can be flexible in the radial and axial direction.
The advantage of the implant according to the invention is that it can be made of threads which are monofilamentary wires. Monofilamentary wires (monofilament) can have a diameter of 30 μm to 2 mm, especially 70 μm to 500 μm. In further training, parallel wires can be slightly twisted together.
In a particular embodiment of the invention, the braid of the implant is formed from a single thread, i.e. a so-called endless thread.
In another particular embodiment of the invention, the braid of the implant may be formed from two parallel preferably opposite monofilaments (double strand), preferably also when the braid is formed from a single endless strand.
The angle α (see Figure 1) at which the threads cross in the intertwining between intersecting monofilaments may be greater than 45°, in particular 70 to 150°, and preferably 90 to 120°. According to the invention, the filaments on the implanted end may be curved, in particular curved or serpentine. It is preferable that the threads, especially the two ends of the single thread, lie in the mantle plane or mantle surface of the rounded web. Furthermore, the threads, in particular all the threads, may lie close together in the respective twist and preferably point in opposite directions.
The invention may be used to the advantage of threaded areas wrapped around at least one pipe end and retracted in a rotational manner in the plane of the braid; in a particular embodiment threaded areas may be looped around at least one pipe end, in particular a pipe end, in a reverse rotation and retracted in the same loop; in an embodiment threaded areas may be retracted at at at least one pipe end, in particular a pipe end, at an angle of 60 to 120°, in particular about 90° and in an opposite rotation; preferably threaded areas may be retracted at at at least one pipe end, in particular at a pipe end, in a cross-sectional loop of 150 to 300°, in particular about 270° and in a counter-rotating loop.
The invention prefers that at least one tube, in particular one tube, alternately has a thread area of 60 to 120° and a thread area of the same winding of 150 to 300° as a crossing loop, and that the thread wrapped is traced in the immediately adjacent reverse winding and the thread wrapped only angularly in the subsequent parallel reverse winding.
The tubular implant of the invention may also be characterized by its grid-like shape and, in the relaxed state, by a grid width of 0,5 to 8 mm, in particular 2 to 5 mm, the cross-sectional angles of which may be greater than 45°, in particular 70 to 150°, preferably 90 to 120°.
In a preferred embodiment, each loop in the braid of the implant according to the invention is formed by at least two parallel strands, in particular two parallel strands. In particular, at a stent end, two parallel strands may run in opposite directions at a straight number of strands of a loop.
According to the invention, in one embodiment the braided structure may have a thread course 1 over 1, 1 under 1; in another embodiment the braided structure may have a thread course 2 over 2, 2 under 2.
According to the invention, the tubular implant may be formed with a radially uniform diameter. In a particular embodiment of the invention, the tubular implant may be permanently rejuvenated, i.e. have a smaller diameter at the end. Such rejuvenation of the stent may be appropriate for filtering purposes, e.g. in the bloodstream. In another preferred embodiment of the invention, the tubular implant may be permanently exposed in the relaxed state, i.e. at least at one, preferably both ends, have a larger diameter than at the intermediate end. Such a radial extension may be appropriate to prevent dislocations of the stent after insertion.
In the case of the tubular implant of the invention, at least one of the implantants may be radially divergently formed. In other words, in one embodiment of the invention, one end of the tubular implant may be enlarged. In another embodiment of the invention, both ends of the tubular implant may be enlarged. The transition from the linear part of the implant to the divergent end may be stepless. Such a diameter extension may be funnel-shaped or tulip-shaped.
In the case of the implant according to the invention, the biocompatible material may be metallic material. Typical examples are metal filaments made of titanium, titanium alloys, stainless steel for medical purposes, such as Cr-Ni steels, W1.4310, Elgiloy®, Phynox®, iridium or metal oxide alloys.
In another embodiment of the invention, the biocompatible material may be a synthetic polymer material. Typical examples are filaments made of synthetic polymers such as polyethylene terephthalate (PET), polyurethane (PUR), polypropylene (PP), high-density polyethylene (HDPE), polyamide, copolymers, blends or mixtures of such polymers. For absorbable implants or absorbable parts of implants, polymers based on α-polyhydroxycarbon acids, β-polyhydroxycarbon powders or polyanhydrides in the form of their homopolymers, copolymers, teres, block polymers or mixtures thereof may be used preferably.
In a particular embodiment of the invention, the biocompatible material may be a composition of different materials, in particular a composite material. Typical examples are blended polymers, bicomponent monofiles such as monofiles with core-mantle structure, metal-polymer composites, in particular with metal matrix, as well as polymer coated metals. The thread material of the stents may have a metal surface coating, in particular if the thread material is a polymer.
A number of modifications of filaments can be used as appropriate for the desired application, such as structured monofiles, hollow capillary monofiles, coated monofiles with single or multilayer coating, and monofilament wires may have a structured cross-section, e.g. a star-shaped cross-section or a cross-section with core-mantle structure.
The filament material used in accordance with the invention can be found in a wide range of fibre strengths and fibre thicknesses (filament diameters), with diameters of 10 to 800 μm, especially 30 to 300 μm, being preferred for metal wires and diameters of 30 to 1000 μm, especially 50 to 500 μm, for polymer filaments.
In one embodiment of the invention, the biocompatible material may not be bioresorbable; in another embodiment of the invention, the biocompatible material may be at least partially bioresorbable; and in another embodiment of the invention, the biocompatible material may be fully bioresorbable.
The monofilament used to form the braided structure of the tubular implant can have a high tensile strength in the range of 100 N/mm2 and/or a high modulus of elasticity in the range of 500 N/mm2.
The tubular implant of the invention may have the advantage of being elastic and/or plastic, the elastic and/or plastic properties being based on the combination of monofilament and braided structure of the invention.
In the case of a tubular implant, the originally open-pore braided structure may be at least partially covered on the inside and/or outside by a coating; in another embodiment, the originally open-pore braided structure may be at least partially covered on the inside and/or outside by a coating; materials with elastic and/or plastic properties may be used as coating.
A coating may completely embed the implant of the invention. Alternatively, only certain parts of the implant may be coated, for example one or both ends. The coating may only cover the thread material, so that the rough openings of the braid are uncovered. The coating may also close the implant wall, especially in the case of elastic coating material. The coating may be in the form of a so-called covering, whereby the tubular implant is raised onto a preformed shell or film and coated inside and/or outside.
In one embodiment of the invention, the coating and/or coating may be bonded adhesively; in another embodiment of the invention, the coating and/or coating may be covalently bonded.
The advantage of the invention is that the implant may be equipped with at least one additive in the training. In particular, the additive may be a pharmacological active substance. Examples of such additives are agents to improve antithrombogenicity such as hirudin, prostacycline, heparin. When using the implant as a drug delivery carrier for drug release, additives such as anticancer agents such as Taxol®, thalodmide® may be added. In another embodiment, the additive may be an X-ray drug marker.In a special embodiment, the additive may be a living cell.
The advantage of coating technologies is that additives can be added to the implant according to the invention, and that, depending on the choice of active substances and coating process, it is possible to surface-dop and/or deposit the additives into the polymer matrix, thus controlling the release of one or more of the added active substances by the degradation and/or absorption behaviour of the polymer material used.
The invention also relates to a method for the production of a tubular implant from a biocompatible material in monofilament form by textile braiding to form a flexible tubular braid with a completely closed structure. To form the tubular implant according to the invention, braiding can be done with the advantage of a thorn. In preferred training, braiding is done by machine, especially automatically. The raw braid can be re-formed, thermal aftertreatment (tamping), coating, covering, coating or any combination of such treatments. Preferably, the raw braid for the tubular implant can be thermal aftertreatment.
The advantage of the manufacturing process according to the invention is that a distal and proximal closed atraumatic plexus structure is formed, thus avoiding the need for stent-end masking and similar post-processing steps.
An advantage is that a tubular implant according to the invention is suitable for use in the treatment of pathologically altered defects in the hollow organs in human and veterinary medicine. Examples are: malignant and benign obstructions, stenosis, aneurysms and lesions of hollow organs. Typical applications for stents according to the invention are blood vessels, oesophagus, trachea, duodenum, colon and other parts of the digestive system, as well as the urinary and urinary tract.
The tube-shaped implant of the invention is capable of supporting and/or keeping open a human or animal cavity organ for a specified period of time or for a specified duration, depending on the material chosen and precisely adjusted according to medical requirements.
For practical purposes, the tubular implant of the invention can be compressed with conventional catheters, brought to the treatment site and placed in situ with conventional release systems. The tubular implant of the invention is self-expanding by its structure and is pressed against the hollow organ to be treated with a correspondingly selected reserve force.
The present invention is explained below by means of a description of particular embodiments, using examples and referring to the accompanying drawings. In these embodiments, individual features of the invention may be realized alone or in combination with other features. A particular embodiment described is intended only to explain and improve the understanding of the invention and is not to be understood as a limitation in any way.
A brief description of the charactersFig. 1 shows a terminal section of an uncompressed tubular stent. The arrows indicate the possibilities of displacement of the monofilaments in the braided structure of the tubular implant of the invention. α denotes the angle of thread crossing in the braid. At the end of the stent, the monofilaments are wrapped around and returned in the same winding.
Figure 2 shows the stent and, as shown in Figure 1, radial compression and axial dilation.
Fig. 3 shows a fully developed tubular stent with divergent ends on both sides, i.e. with tulip-shaped extensions at the distal and proximal ends. This embodiment is described in example 1. The two tubes show different retraction of the threads in the mantle plane of the tubular plexus. The plexus consists of a single monofilic thread. The two invisible threaded ends, which may be connected to each other, lie in the mantle plane of the plexus.
Fig. 4 shows in one embodiment the filament course at the end of the braided stent, in particular at one (upper) end of the stent as shown in Fig. 3. The coils are clearly visible, so that no free ends of the threads stand out at the end.
Figure 5 shows in another embodiment the filament course at the end of the braided stent, in particular at another (lower) end of the stent as shown in Figure 3. Here again loop-shaped thread loops are shown, so that no free thread ends protrude at the end.
In all figures, two monofilaments are paired in the turns of the braid, which is preferable.
Example 1Stent for the esophagus/trachea areaThe yarn material used is a polyester monofilament of polyethylene terephthalate (PET) with a filament diameter of 0.3 mm. The braid was formed with a 110° thread cross angle over an 18 mm diameter spine. The stents are radially divergent on both sides. The diameter of the stent is 24 mm. See Figure 3 for this.
Example 2Stent for the biliary tractThe thread material used is a polylactide monofilament of P-L-LA with a filament diameter of 0.3 mm. The braid was formed with a thread cross angle of 100° over a spine of 8 mm diameter. The stent has a uniform lumen, i.e. the stent tips are not divergently formed and have a diameter of 8 mm.
Example 3Stent for the colon areaThe thread material used is a stainless steel wire of type W 1.4310 with a diameter of 0.15 mm. The braid was formed with a 90° thread cross angle over a 22 mm diameter spine. The stent is radially divergently formed on one side. The diameter at the end of the stent is 28 mm.
The invention is based on the invention of a device which is capable of producing the implant, in particular stents, by means of machine braiding. In a preferred embodiment, a single, in particular monofilar, thread is placed in parallel longitudinal loops in a tubular arrangement. These loops of two parallel adjacent threads are simultaneously beaten alternately to the right and left and interlaced, resulting in a tube or tube mesh of right and left turns, which is then fixed, in particular by heat.