Device for inserting an implant

Translation of description of equivalent WO 2011147567 A1

DEVICE FOR INTRODUCING AN IMPLANT

p0002The invention relates to a device comprising an endovascular implant, which is provided for insertion into blood vessels or body cavities of the human or animal body, and an insertion aid, wherein the implant and the insertion aid are interconnected by means of a release element which is electrolytically formed corrodible, so that after insertion of the implant in the body by applying a voltage occurs an at least partial dissolution of the release element and a detachment of the implant from the inserter.

p0003The use of endovascular techniques for the occlusion of body lumens or vessels such as arteries, veins, fallopian tubes or vascular malformation (z. B. vascular aneurysms) is known in the art. Here z. B. called occlusion helixes are using a serving as an insertion endovascular guide wire inserted through a catheter into the cavity to be occluded and deposited there. Also known is the incorporation of other implants, such as stents. For the separation of the implant from the insertion device, various methods are known from the prior art. In addition to mechanical methods, especially the electrolytic severance of stainless steel wire tips has proved, as. For the first time in the electrocoagulation by Thompson et al and McAlister et al. was described in 1979 (Radiology 133: 335-340, November 1979, AJR 132: 998-1000 June 1979). Building on this also describes the EP 0484468 B1 an apparatus for implanting occlusion helixes based on an electrolytic detachment.

p0004Regardless of the type of concrete to be introduced implant it is for the doctor always important to keep the release times as short as possible, so that, for example, be no displacement of the implant or other unpredictable things during the detachment. For this reason, different materials were used in the past for the arranged between implant and insertion detachment element that allow for application of a voltage rapid dissolution. In WO 03/017852 A1, for example, a stainless steel is used, which was subjected to a Vorkorrosionsprozess via a heat treatment.

p0005It therefore has the object, starting from a device of the type described at the outset to make funds available that reduce the release time of the implant from the insertion on. This object is achieved by a device comprising an endovascular implant, which is intended for insertion into blood vessels or body cavities of the human or animal body, and an insertion, the implant and the insertion aid are interconnected via a release element formed electrolytically corrodible is such that, after insertion of the implant in the body by applying a voltage, an at least partial dissolution of the release element and a detachment of the implant from the insertion aid, whereby the release element of a cobalt-chromium alloy containing at least 20 wt .-% cobalt is and 10 to 40 wt .-% of chromium, manufactured. Surprisingly it has been found that release elements that are based on cobalt chromium alloys enable extremely short removal times when a voltage. These are generally less than 30 s (2 V, 2 mA). Also removal times of only 5 s are possible, the release times of course also depend on the thickness of the release element. Compared to the prior art, the z. B. in WO 2005/070308 A2 of 20 to 40 s speaking all things being equal, this represents a significant improvement.

p0006As cobalt-chromium alloys such can be used as it as Steinte^® be sold by the company. Deloro. can have This is to cobalt-chromium alloys, the proportions of tungsten, nickel, molybdenum, iron and other elements. Steinte^® are highly resistant to wear, which is why they are used in particular for components that are exposed to high loads. More surprising was the finding that from Steinten^® especially quickly let severance elements produced electrolytically dissolve.

p0007The content of cobalt is preferably max. 70 wt .-%, in particular a content of between 30 and 60 wt .-% is advantageous. The chromium content can in particular 15 to 30 wt .-% amount.

p0008Other elements may improve the properties of the release element. Thus, an alloy with 4 to 12 wt .-% of molybdenum and / or 5 to 20 wt.% Of tungsten is advantageous.

p0009The content of nickel, manganese or iron can be significantly higher if necessary, and to be in the case of manganese and iron to 30 wt .-%. The nickel content may be between 8 and 40 wt .-%. Examples of useful Co-Cr-alloys are those as described under the names Elgiloy^® or phynox^® to be expelled. The German material number is 2,471. 1 The alloy contains 40 wt .-% of cobalt, 20 wt .-% of chromium, 16 wt .-% iron, 15 wt .-% nickel and 7 wt .-% of molybdenum and possibly small amounts of manganese, carbon, silicon, phosphorus , sulfur, and beryllium.

p0010Another useful alloy is Steinte 25. This alloy contains inter alia about 50 wt .-% of cobalt, 20 wt .-% chromium, 10 wt .-% nickel and 15 wt .-% tungsten. Another example Stellite^®21 represents approximately 63 wt .-% of cobalt, 28 wt .-% chromium and 6 wt .-% molybdenum.

p0011When insertion is preferably a conventional guidewire, as it has been proven to bring occlusion helixes or stent through a catheter to its destination. The introducer includes proximal to the implant, ie advances in the direction from which the physician the implant.

p0012The implant may be an occlusion or stent. In addition, the implant can also be a stent-like system for influencing the flow of blood, which is either designed braided by laser cutting of a metal or plastic foil or suitable plastic membranes. Basically, however, the invention is applicable to all types of endovascular implants to be placed with the aid of an insertion aid to its destination and there separated from the inserter. Among implants, such objects are understood, which are formed only selectively removable and remain, depending on the course of treatment in the body or be removed. An example of this are removable stent retriever systems for removing or displacing of thrombi.

p0013Advantageously, the separation element from one or more wires. About the wires pushing or pulling forces can be passed well, so that the treating physician both a simple feed, but also the withdrawal of the implant is possible. A simple positioning is important so that the doctor can bring the implant precisely to the desired destination. The wire or wires may be round, square, oval or tubular cross-section. Here, any combination is possible, for example, round and rectangular wires. The production of the wires is generally carried out by pulling down of the raw material to the corresponding end cross-section. The drawing process, the microstructure and thus the release properties of the release element can be controlled. By varying the cross section and the shape of the wires they can be optimally adapted to the intended use.

p0014To facilitate the detachment further, it is possible to perform the peeling elements comprises a surface treatment. A roughening of the surface, for example, causes a faster resolution, since the surface of the release element is increased. Also known are other possibilities, a release member to move through an add-on to a more rapid resolution, for example, from the aforementioned WO 03/017852 A1, to which reference is hereby made. For example, the separation element to a heat treatment in the sense of an elimination process may be subjected, through which the metal is changed in its structure so that it decomposes quickly especially in an electrolyte when an electric voltage. Such heat treatment is possible with the aid of a laser, in an oven or by means of an induction coil. The cooling is advantageously relatively quickly in the form of a deterrent. In this way, structural conditions are created that promote the electrolytic dissolution.

p0015Cobalt shows during heating and cooling a reversible allotropic phase transformation. At high temperature the face-centered cubic phase (α-cobalt) is stable, which merges into the hexagonal ε- Cobalt on cooling at about 420 ° C. While ε-cobalt is very hard to form, the metastable α-phase is more ductile. The transition temperature between the two phases can be varied by selecting different alloying additions. Basically stabilize additions of chromium, molybdenum or tungsten, the hexagonal phase, and reduce the energy stacking faults, while the elements iron, nickel and manganese favor the cubic phase and increase the energy stacking faults. After the solution treatment, the alloy is usually primarily of α-cobalt, followed by cold forming (z. B. wire drawing) and / or excretion processes the content of ε-cobalt is increased. By precipitation of intermetallic phases can be eliminated from the alloy, whereby the susceptibility to corrosion of the alloy is increased. Ultimately, should the alloy mainly present as metastable α-cobalt, however, also have a certain amount of ε-Cobalt.

p0016Also possible are other types of additional treatment as a pre-corrosion, for example via an etching. Furthermore, it is possible to speed up the replacement passively by construction-dependent formation of local corrosion cells. Such corrosion cells are formed at adjacent arrangement different noble metals, ie, the separation element is made of a less noble metal than the implant and / or the insertion aid. The resolution of the release element is done by applying an electrical voltage. It may be either AC or DC power to which a low current (<3mA) is sufficient. The release element in this case represents the anode where the oxidation and dissolution of the metal takes place. To improve the active suggestibility of resolution, it may be useful to the severance element constructively interpreted as meaning that the local corrosion elements described above are avoided. This can be done by insulating adhesive bonds between severance element and implant z. B. by isolating the release element with respect to adjacent areas of the device z. B..

p0017The electrolytic detachment is carried out by an electrical voltage is applied to the release element by means of a voltage source. The release element serves as an anode while the cathode is positioned on the body surface. Of course, the release element must accordingly electrically conductive, in particular the insertion, be connected to the power source. The introducer also needs to be itself designed to be electrically conductive in this case. Since the adjusting itself corrosion current is controlled by the area of ​​the cathode, the surface of the cathode should be chosen to be significantly larger than the area of ​​the anode. To some extent can the dissolution rate of the release element controlled by adjusting the cathode surface in relation to the anode surface. The invention relates to Correspondingly, a device which includes a voltage source, and optionally a placeable on the body surface electrode.

p0018Alternatively or additionally, further measures can be taken to support the up and detachment of the release element. In this context, the use of light waves, sound (ultrasound) or magnetic forces may be mentioned.

p0019Additionally, it is expedient when the implant extends through a securing means. Such securing means have the advantage that in the event of incorrect positioning of the implant the necessary retraction is much safer in the catheter. The retraction example an occlusion without securing means involves the risk that parts of the Wendel pulled apart by tensile or torsional stress and deform plastically so irreversibly. In extreme cases, the spiral can crack or break, resulting in a life-threatening embolism can lead to. have been described both securing means of flexible polymer threads and made of materials with shape memory properties.

p0020have also been described devices in which a plurality of release elements are provided, so that if necessary variably dimensioned lengths of the implant can be placed at the destination. This allows, for example, settle occlusion helixes in exactly the right length in the aneurysm. In this connection reference is made to WO 01/32085 A1.

p0021The use of such, in several places electrolytically corrodible implants based on the recognition that when applying current to such a device specifically the detachment point the distal end of the catheter closest to dissolve by electrolysis. This is due to the fact that on the one hand in the catheter located ends rupture sites are isolated through the catheter from the ionic medium and therefore no electrolysis may be subject to and on the other hand, the current density due to the increasing resistance to distal from proximal to distal decreases. The distally first subsequent to the distal end of the catheter electrolytically corrodible point is therefore subjected to the intensive electrolytic process and dissolves preferably.

p0022To form the implants, in particular the use of platinum or platinum alloys has proven. These have inter alia the advantage that they are radiopaque and thus the introduction of the implant can be easily visualized. The cobalt-chromium alloys used for the separation element are usually MR compatible and therefore also allow visualization.

p0023The inventive device can also directly present in combination with a microcatheter through which the implant is brought to its destination by means of insertion. The catheter used and the implant should in this case be matched in terms of their dimensions. If necessary, the catheter may also exert a constraint on the implant, which causes the implant occupies a him previously imprinted secondary structure after liberation from the compulsion. In addition, the catheter is also provided with radiopaque markers, which allows the positioning in the target area with the aid of known imaging methods.

p0024Typically, the separation element has a length of 0.05 to 0.5 mm, in particular about 0.2 mm, and a diameter from 0.04 to 0.5 mm, in particular about 0.1 mm.

p0025The invention is further illustrated by the attached Figure. 1 This shows the schematic structure of the device according to the invention.

p0026The device consists of an implant 1, an insertion aid 2 and a release member. 3 Here, the introducer 2 is located at the proximal, the implant 1 to the distal end, ie in the advancing direction of the apparatus. The implant 1 is brought to its destination by advancing the inserter 2 in a catheter not illustrated here.