Biologically absorbable implant material, and method for its preparation

(42) Date of commencement of the patent: 15. 4.1994 (45) Date of issue: 25.11.1994

<td>(56) Documents:</td><td>(73) Patent owner:</td>

<td>DE-A-361 7898 DE-A-3617896 DE-C-2917135 DE-B-2854490</td><td>IMMING AKTIENGESELLSCHAFT</td>

<td>EP-A-171176 EP-A-174737 WO-A-86/526 US-A-4394370 US ~ A-4i7212o</td><td>A-1221 VIENNA (AT). (72) Inventor: REDL HEINZ Oi. VIENNA (AT). Beat GÜNTHER DR. VIENNA (AT). PRIDUN NESTOR DR. VIENNA (AT).</td>

(54) BIOLOGICAL RESORBABLE IMPLANT MATERIAL AND METHOD 20R MANUFACTURE THEREOF (57) There is described a bioabsorbable lapidation material and a method of making the same, which is for filling or closing soft tissue cavities and for replacement of soft tissue.

The implant material consists of cancellous bone tissue of human or animal origin, has a pore volume of 55 to 95%, is decalcified and the original protein content of the bone hard substance is left; By crosslinking these native proteins with a protein crosslinking agent, one achieves elasticity, good resistance and a pronounced Memcry effect.

The process for its preparation comprises the degreasing, decalcification and crosslinking of the original Prcteine, whereupon the material dried. and sterilize.

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AT 398 373 rsassraees

AT 398 373 B

The invention relates to a bioabsorbable implantation material for filling or closing of soft tissue cavities and for the replacement of soft tissues and a method for the production. -desselben.

In the field of orthopedics implant materials for filling of bone cavities are known which are produced by partial deoxygenation and denaturation of the residual protein from cancellous bone tissue (DE-C 961 654). This material, known as Kieler spongiosa, has essentially the same calcium content as native cancellous bone. It is therefore hard and completely inelastic and unsuitable for application in soft tissues.

In bone surgery, further, a material made of corticalis bone, ie, tubular bones, by descaling is known (Journal of Surgical Research 37, 487-496 (1984), which has an osteoinductive effect attributed to its content of Bone Morphogenetic Protein. Because of this osteoinductive property, use outside of a bone is contraindicated.

EP-A-0 171 176 describes a composition for the treatment of bone defects which is prepared from bone collagen by descaling and lyophilising and which forms a gel after reconstitution. Because of the desired osteoinductive effect of this material, care is taken that no crosslinking of the collagen takes place during preparation.

Furthermore, from DE-B-28 54 490 a bone substitute material based on collagen is known which consists of bone by removing the blood pigment and other water-soluble proteins, degreasing and dissolving out the mineral components by complexing agent or ion exchanger and final

Freeze-drying is made. The material is insufficiently elastic after reconstitution and not suitable for application in soft tissues.

For application to or in soft tissue only Kollagenviiese have been known as cover and implant materials. However, these nonwovens have no dimensional stability and no elasticity when wet; they are for a firm anchorage in a moving tissue, e.g. B. in the lungs, only conditionally suitable. Synthetic materials, such as acrylates, which have also been proposed, have again other disadvantages, of which are massive foreign body irritation, Abkapse ment, lack of healing and possible release of toxic degradation and by-products in the foreground.

Also known in the art are prosthetic implantation materials made from body tissues by treatment with protein crosslinking agents. Such materials are used to improve the stability of certain organs, e.g. B, of heart valves or vascular prostheses. Such implants are z. In EP-B-0 174 737 and in US-A-4 120 649.

The invention has as its object to provide a well-tolerated implant material that can be used on the one hand to close tissue cavities, on the other hand, but also for the replacement of certain Gewebetei35 sources and does not have the adverse or the therapeutic use limiting properties of the known products.

After lung resections or after other diseases of the lung bronchopleural fistulas can occur. These are septic openings or cavities between the bronchial tree and the pleura, which are filled with secretion or pus. You will be breathing and coughing continuously from air and

Secretions flow through, their size can be a few millimeters to several inches in diameter. It has been an unsolved problem in thoracic surgery to close and heal such bronchial fistulas, especially if the implant is to be introduced endoscopically, which would be the fastest and gentlest way. Special requirements are placed on an implantation material which is to be introduced and fixed endoscopically. On the one hand, it must enable a mechanical spreading, on the other hand, it must be able to be brought to the fistula through the bronchial tree.

The implant must be deformable and compressible. It must be able to return to its original shape in the presence of moisture, ie have a high memory effect. Furthermore, the material must have a considerable strength, but still remain absorbable, as adhering to non-absorbable so materials germs and can always lead to abscesses or new fistulas. In addition, according to a further aspect of the invention, it should be possible to achieve an immediate gas- and liquid-tight closure after introduction of the implant. Finally, it should be possible in

- To incorporate the material bactericidal or wound healing stimulating or other pharmaceutical substances.

The invention, with which these objects are achieved, is a biological, resorbable

Implantation material of human or animal origin for filling or closing of soft tissue cavities and for replacement of soft tissues, which implant material is compressible in the dry state, but in the presence of moisture, the original form resumes, ie

AT 398 373 Β has a pronounced memory effect, and which implantation material consists of molded into shaped bodies, a pore volume of 55 to 95% having cancellous bone tissue, which

- is decalcified,

- whose native proteins are cross-linked with a protein cross-linking agent to avoid an osteoinductive effect,

- The moldings have a high elasticity at low hysteresis between loaded and unloaded state.

According to the invention, therefore, the original protein content of the decalcified bone hard substance is left in place and the high elasticity and resistance is brought about by the crosslinking of the native proteins.

The decalcification is carried out so far that the residual calcium content max. 80 mmol / g wet weight.

According to a preferred embodiment, the implant material is impregnated with pharmaceutically active substances.

In a particularly preferred embodiment, the implant material may include a tissue adhesive based on fibrinogen or collagen.

The invention further includes a method of making the implant material, which is characterized that native proteinaceous cancellous bone material is decalcified with a descaling agent, washed free by the descaling agent, then treated with a protein crosslinking agent, repeatedly washed to remove the protein crosslinking agent, optionally with pharmaceutical solutions, like solutions of tissue adhesives, fibrinogen or collagen based, finally dried and sterilized.

As crosslinking agents aldehydes, in particular glutaric aldehyde, polyepoxide compounds, Isodicyanatderivate or carbodiimides can be used.

The bone material may conveniently be degreased before or after decalcification with an organic solvent such as chloroform-methanol.

Before or after protein crosslinking, it may also be envisaged to treat the bone material with agents which reduce any level of unwanted antigens, e.g. As detergents or enzymes.

The implant material according to the invention or the process for its preparation can be modified in various ways, whereby additional pharmaceutical effects or Properties can be achieved. Thus, by the mentioned concomitant use of a detergent, for. B. of the Octylphenoxypolyethoxyäthanol-Triton X-100 in one percent concentration, in the washing solutions not only the content of unwanted antigens are reduced, but it can the risk of a subsequent calcification of the implant can be reduced. Furthermore, it is possible to provide a low level (about 0.5 M) of sodium ethylenediamine tetrasaurate in the wash solutions, thereby improving descaling.

It may also be an intermediate treatment of the implantation material with a buffer solution containing enzymatically active substances, for example, Ficin and / or Neuraiminidase, are provided, which also reduces the antigen content in the finished product.

To ensure that the finished product contains no traces of glutaraldehyde, the material can be rinsed with a glycine or lysine solution (content about 5 mg / ml) after the cross-linking treatment!

If the implant material according to the invention has been produced from cancellous bone, it is expedient to compress it to the final container before filling, approximately to half the volume.

A particular field of application of the material according to the invention is the replacement of tubular tissue parts, such as trachea parts. As a starting material for such an implant femur bones are used, which are reduced by mechanical surface removal on the lathe tubular to about 2 mm wall thickness before they are subjected to the inventive combined treatment by descaling and protein crosslinking.

The final product according to the invention, when it is to be used for filling tissue cavities, is expediently made into a block form.

The material can be sterilized by gamma rays and placed in containers, the z. As a 70% ethanol solution are stored. The blocks are rinsed with Ringer's solution on the patient before application.

It is also possible to dry the blocks after sterilization with gamma rays

Store condition, wherein according to a particularly preferred embodiment of the invention, the blocks are impregnated with a fibrin glue solution under sterile conditions and then lyophilized in the final container.

AT 398 373 B

Of course, the product according to the invention, apart from the already described block or tubular shape, can also be provided in disc or sheet form.

In the following example, the method according to the invention or the product produced thereafter is explained in more detail.

kg of cancellous bone veal material was obtained by dicing a femoral head.

These spongiosa cubes were rinsed with hot water (50 ° C) and then decalcified at room temperature in 0.6 N hydrochloric acid (10 l) with constant movement and repeated changing, pressing and washing the cancellous bone (24 - 72 hours). Subsequently, the blocks were rinsed acid-free and incubated for one hour at room temperature with 1% glutaric aldehyde in 0.05 M phosphate buffer solution (1 L) at a pH of 7.4 for crosslinking.

By washing with a sterile washing solution at least five times and pressing out the cancellous bone, the remaining glutaric aldehyde was removed from the cancellous bone. The blocks were freeze-dried, filled in the final package and sterilized with 2.5 Mrad gamma rays.

An implantation material in the form of blocks, which had been prepared in this way, was used as a fistula closure by endoscopy in patients: the patient was intubated with the rigid bronchoscope and ventilated in an open system with the injection timer. After inspection of the fistula, a suitable cancellous bone was cut and compressed to allow it to be passed through the bronchoscope. With biopsy forceps, the implant was placed in the fistula, where it wetted by contact with the bronchial wall, expanded and spread very rapidly. With a three-lumen spray catheter, immediately after placing the implant, 1 to 2 ml of fibrin glue was dropped around the implant, causing it to continue to swell and stick to the bronchial wall. An immediate airtight closure of the fistula was achieved

The implantation material according to the invention has no osteoinductive effect, which can be determined by measuring alkaline phosphatase or by histological examination. Therefore, the material can safely be used for soft tissue applications.

The implant material produced according to the invention has excellent elasticity properties. For comparison with known preparations, spongiosa blocks 1.5 cm in edge length were prepared, on the one hand, without treatment with a protein crosslinking agent and, on the other hand, according to the invention by combined decalcification and protein crosslinking, as described in the preceding exemplary embodiment. The blocks were dried and then moistened with a 0.9% NaCl solution. All blocks were tested in a loading machine (transducer 0 - 1000 pond at a loading speed of 1 cm / min), whereby loading or Relief curves resulted, as illustrated in the drawing.

The load curve and the unloading curve (force-displacement) of the spongiosa blocks which have not undergone cross-linking treatment are designated 1 and 2; 1 'and 2' represent the corresponding curves of the preparations according to the invention. It can be seen that in the non-crosslinked preparations belonging to the prior art, a relatively low strength and a strong hysteresis occur, while the spongiosa blocks according to the invention show no hysteresis and have high strengths.

The tissue compatibility of spongiosa blocks according to the invention with a dimension of 0.5 × 0.5 × 1 cm, prepared according to the exemplary embodiment, was tested in rat experiments, the blocks being implanted subcutaneously on the back of the rat, removed at different times, fixed and worked up histologically.

It showed that uncrosslinked spongiosa blocks showed stronger inflammatory reactions, more foreign body giant cells, more fibrosis and already after 14 days absorption approaches and after 4 weeks clear signs of degradation occurred. In contrast, no such by-effects could be detected in samples treated according to the invention.