SE424401B - BLODKERLSPROTES - Google Patents

Description

However, previous attempts to achieve an inner endothelial lining on synthetic vascular prostheses in various ways have been unsuccessful. This problem has now been solved by the present invention.

Namely, it has been found that such a desired endothelial lining is obtained by implanting a vascular prosthesis of body-friendly, non-resorbable synthetic material, the inside of which is covered with resorbable material. In order to obtain the desired endothelial layer, the resorbable material layer must for the most part be arranged at some distance from the unresorbable material and have such a structure that erythrocytes and platelets can pass through it to the formed spaces, which serve as growth zones for the new tissue. This allows the construction of a relatively thick fibrin layer which will form the backbone of an eventually formed endothelial lined muscle cell layer.

The resorbable layer or cladding can be designed and applied in different ways. Thus, for example, the resorbable material may consist of an inner tubular element which is inserted and fixed in the outer tubular prosthetic element of non-absorbable material. The inner tube can in this case be formed by a coarse to fine-mesh net, consist of a tube with perforated or pore-provided walls, etc.

The fixing of the resorbable layer to the non-absorbable casing can of course also take place before the prosthesis material is tubular. Coating of the non-absorbable surface with the resorbable material by any method that provides the required gaps or growth zones as well as the necessary blood cell permeable structure of the resorbable material may also be considered. To increase the thickness of the fibrin layer which in the initial stage after implantation is to be retained by the resorbable material, two or possibly more according to the above at least partially separated layers of resorbable material can be applied or alternatively a relatively thick layer with sufficient porosity or perforation is used. The fixation of the resorbable mesh or tube in the non-absorbable prosthesis sleeve can take place in different ways, Lex. with resorbable sutures or glue. At least the inside of the outer non-resorbable element should be microporous, porous or halved to promote the growth of the newly formed vesicles. In this case, tubular prosthetic elements of everything from coarse-mesh nets to tubes with fine pores can be used. A suitable and well-functioning vascular prosthesis according to the invention can thus consist of a per se conventional vascular prosthesis, on the inside of which one or more nets of resorbable material have been applied.

The above-mentioned gaps between non-absorbable and resorbable material in the vascular prosthesis may each have a greater or lesser extent, but the total area for these gaps should preferably be so large that it approaches the size of the inner surface of the outer non-absorbable material layer. , i.e. the portions or points where the resorbable material for fixing to the non-absorbable material abuts it should be as small as possible. The distance between the relevant material surfaces in these spaces or growth zones should be at least about 10 p to allow penetration of erythrocytes and platelets, but should suitably not exceed about 5 mm. Preferably, the distance is about 0.5 -3 mm, whereby the blood vessel to be replaced must also be taken into account.

The resorbable material should be a tissue-friendly, non-toxic material, which is resorbed at such a rate that satisfactory tissue regeneration is allowed and which does not give rise to scar tissue. A number of such materials are known in the art and are described in the literature. Examples which may be mentioned are polyglycolic acid (PGA), copolymers of glycolic acid and lactic acid, and various lactide polymers. Polyglycolic acid can essentially be considered as a product of polymerization of glycolic acid, i.e. hydroxy-acetic acid, which is shown in simplified form by the reaction: c fl zc-of-x ___; H o-ci-Izc oH l n -Hzo u OH O O n n Preferably, n is such that the molecular weight is between about 10,000 and about 500,000. Such polyhydroxyacetic acid esters are described in e.g. U.S. Pat. No. 3,463,158. Copolymers between glycolic acid and lactic acid are described, for example, in U.S. Pat. Homo- and copolymers of lactic acid are described, for example, in U.S. Pat. No. 3,636,956. These polylactide compositions contain up to about 15% by weight of repeating units of the formula: R 'O ll -uom-p-c-o- RI! where R is lower alkylene, preferably methylene or ethylene, m is 0 or 1, R 'is hydrogen or lower alkyl, R "is hydrogen or alkyl of up to 22 carbon atoms when m is 0, and hydrogen or lower alkyl when m is 1 , wherein R 'and R "may be the same or different.

Preferred are units derived from (K-hydroxycarboxylic acids and especially comonomer units derived from glycolide or DL-lactide. Examples of suitable comonomers are glycolide, β-propiolactone, tetramethylglycolide, β-butyrolactone, β-butyrolactone, β-butyrolactone, and intermolecular cyclic esters of ol-hydroxybutyric acid, ol-hydroxyisobutyric acid, oL-hydroxyvaleric acid, oL-hydroxyisovaleric acid, α-hydroxycaproic acid, oL-hydroxy-α-ethylbutyric acid, oL-hydroxyisocaproic acid, oL-hydroxy-β-methylvaleric acid , M-hydroxyoctanoic acid, β-hydroxydecanoic acid, α-hydroxymyristic acid, α-hydroxystearic acid and ol-hydroxylignoceric acid In the particular case of glycolide as comonomer, the polylactide composition may contain about 35 mole percent derived therefrom.

Production of various surgical products, such as suture thread, suture mesh, etc. based on the above materials is also described in the literature.

Examples of commercially available suture materials are e.g. polyglactin 910 (VICRYL, Ethicon, Sommerville, New Jersey, USA), which is a copolymer containing 90% glycolic acid and 1096 lactic acid and DEXON® (Davis 6: Geck) which is polyglycolic acid. Of course, other materials can also be used provided that they have the desired properties as above.

As material for the non-resorbable prosthesis part, in principle any conventional body-friendly, non-resorbable material commonly used for similar purposes can be used. Examples of such materials are polyethylene terephthalates, such as DACROJ® and TERYLEBQ (eg microporous expanded) polytetrafluoroethylene (TEFLOBQ, linear polyethylene, isotactic polypropylene, nylon (polyamide), etc. This non-resorbable prosthetic part may be present as a net with the specified materials in different weave forms (knitted, woven, possibly provided with outer or inner velor surfaces) or also as a more or less porous tube.Possibly the non-resorbable material can be combined with resorbable material, e.g. made of threads or fibers of non-resorbable material coated with resorbable material, be woven with elements of threads of resorbable material, etc. Of course, other materials having such properties that they allow implantation can also be used.

The lining of the prosthesis of resorbable material should be such that its absorption into the organism takes at least 20 days, and preferably 40-150 days.

An example of a vascular prosthesis according to the invention is shown in the accompanying drawing, which is a perspective view of a vascular prosthesis according to the invention.

The vascular prosthesis illustrated in the figure comprises an outer tube 1 of porous non-resorbable material, and an inner lining or tube 2 of resorbable material. The inner tube 2 is in the figure formed by a net, which is attached to the outer tube 1 by means of a number of sutures (not shown) of resorbable material. The cladding 2 in the figure abuts the outer tube 1 only at the attachment points, and the mesh portions between them hang down "hammock-like" from the inner surface 1a of the tube 1 and form the above-mentioned growth zones, to which the blood cells after implantation can pass via the meshes in the net 2. The mesh size of the net 2 is not in itself critical, but mesh sizes up to approx. 5 x 5 mm can be used.

As mentioned above, e.g. the net 2 is replaced by a tubular element of more or less (eg microporous) porous material. Of course, both the outer tube I and the coverings 2 can be made of net, whereby woven or knitted materials can also be used. Furthermore, the inner tube 2 can be a porous tube structure, while the outer tube 1 consists of a tubular net. The fixing of the inner tube or cladding 2 and the outer tube 1 can also take place in other ways than as shown above, e.g. by gluing with any suitable material. The distance between the pipe surface 1a and claddings 2 is suitably chosen so that it is about 0.5 - 3 mm.

The thickness of the muscle cell / endothelial layer to be formed can be varied e.g. by using several nets 2 separated at appropriate intervals as above.

In the case where the inner tube 2 consists of a porous tube, its thickness can be varied, however, the porosity as above should be sufficient for good penetration of the blood cells. Suitably, the thicknesses of the outer tube 1 and the lining layer 2 are selected so that the outer tube 1 corresponds to the outer connective tissue layer (adventitia) and the layer 2 muscle cell and endothelial layer of the blood vessel or blood vessel portion to be replaced by the vascular prosthesis. Optionally, in the same way as for the nets, several mutually separated layers of porous material can be used.

With the new vascular prosthesis according to the invention, it has been shown in animal experiments that both an endothelial layer and an underlying cell layer of smooth muscle tissue are formed on the inside of the synthetic non-resorbable vascular prosthesis material. The newly formed layer on the inside of the synthetic material is developed in a short time by regeneration of normal constituents in the vessel wall from the edges of the animal's own vessel, at the same time as the resorbable material disappears. The newly formed endothelium exhibits all the characteristics of a normal enciotel. After the healing process is completed, the transplanted vessel thus consists of an outer part of synthetic material, which gives sufficient strength to the vessel, and of an inner part of body tissue with structure as a normal vessel. The vascular prosthesis according to the invention thus functions mainly as a normal blood vessel.

The invention is further illustrated by the following examples of animal experiments with a vascular prosthesis according to the invention, but is in no way limited to the particular prosthesis design used herein. Example 1 A vascular prosthesis was prepared by applying to the inside of a 10 cm long tube of expanded polytetrafluoroethylene (Impra Inc., Phoenix, Arizona, USA) having a net diameter of 13 mm polyglactin 910 (VicrylQ Ethicon, Sommerville, New). Jersey, USA). The net had a wire thickness of 140 in 20 p and a pore size of 400 x 400; and attached to the PTFE tube with polyglactin sutures. The tube thus constructed was then inserted into the thoracic aorta of the pig as a replacement for a removed section.

The implanted tube worked completely satisfactorily, and six weeks after the operation, the animal was slaughtered and the implanted batch was taken for microscopic examination. This showed that the polyglactin network had been almost completely resorbed. At the site of the network, a considerable layer of smooth muscle cells had grown in, and the inside of this layer was lined with endothelial cells.

Example 2 A vascular prosthesis was prepared as above, using as an outer tube a double velor knitted Dacron tube, (Dacron is a polyethylene terephthalate fiber), Meadox Medicals, Oakland, New Jersey, USA, of the same length as above and with 10 mm inner diameter and as inner tube a polyglactin mesh of the same type as in Example 1. The mesh is attached with polyglactin sutures to the outer tube. With this constructed tube, the same experiments were then performed on pigs as in Example 1. The result after six weeks of implantation was completely consistent with the result in Example 1.

Example 3 A tube structure similar to that in Example 1 was prepared, using as an outer tube a tube of Dacron fabric (Dacron is a polyethylene terephthalate fiber) with a thread thickness of about 20 μ and a mesh size of about 600 x 600 μ, and the inner tube was of pclyglactin nets of the same type as in Example 1. With this constructed tube, the same experiments were then performed on pigs as in Example i. The result after six weeks of implantation was completely consistent with the result in Example 1.

The invention is of course not limited to the embodiment specifically described and shown above, but many modifications and variations are possible within the scope of the appended claims. This applies not least to the resorbable and non-absorbable materials, the design of cladding and outer pipes, the dimensioning of the various components, etc.

Claims (7)

A blood vessel prosthesis, comprising a tubular element (1) of a Tissue-friendly, inert, completely or partially non-absorbable material, and an inner structure (2) of a tissue-friendly, resorbable material, characterized in that said resorbable material is for the most part arranged at intervals, preferably 10 u - 5 mm, to the inner surface (1a) of the tubular element (1) and has such a structure that passage of blood cells to the spaces between the inner tubular surface (1a) and the structure ( 2) admitted. Blood vessel prosthesis according to claim I, characterized in that said structure (2) comprises at least two layers of porous resorbable material, which are at least partially separated. Blood vessel prosthesis according to claim 1 or 2, characterized in that said structure (2) comprises nets of resorbable material. ll. Blood vessel prosthesis according to one of Claims 1 to 3, characterized in that the tubular element (1) is microporous or porous. Blood vessel prosthesis according to any one of claims 1 to 1, characterized in that the resorbable material comprises polyglycolic acid, copolymers between glycolic acid and lactic acid or lactide polymers or copolymers. Blood vessel prosthesis according to any one of claims 1-5, characterized in that the material for the tubular element (i) is selected from polyethylene terephthalates, polytetrafluoroethylene, polyethylene and polypropylene. Blood vessel prosthesis according to one of Claims 4 to 6, characterized in that the tubular element (1) is woven or knitted.