Method of producing a bone replacement material.

The present invention relates to a method for producing bone substitute material, of collagen and apatite, tricalcium phosphate (X and β) and / or hydroxyl apatite and / or calcium phosphate ceramics existing mineral component. An input method mentioned is described in EP-A-0030583 of the same applicant. Extensive clinical studies have been, BD Katthagen published in the Journal of Orthopaedics 121 (1983), page 115-123, entitled "Clinical experience with collagen-apatite implantation for local bone regeneration", H. means Meier, from which it appears that encouraging and satisfactory success has been achieved with it. These studies further revealed that the material is not yet clinically massive enough during insertion into the tissue, particularly impregnation with blood and tissue fluid still relatively deliquescent and bone formation in spite of heat treatment and HCl vapor deposition. Therefore, a stronger material would be desirable, which also still produces better stimulation of bone growth.

In PCT-A-W081 / 00963 a method for producing a collagen product is described, which served as a bone substitute material for the above experiments, after admixing of fine apatite powder.

How 00963 mentioned in the aforementioned PCT-A-W081 /, was a substantial increase in absorbency and mechanical strength than previously known collagen fabrics are achieved in that the collagen product to an additional heat treatment or treatment with gaseous hydrogen halide was subjected.

From the same publication page 10, line 23 to page 11, line 3, also shows that it was well known, the physicochemical properties of collagen or gelatine products by chemical means, for example by cross-linking with aldehydes, especially formaldehyde or glutaraldehyde , to improve. However, these treatments have the disadvantage that the products obtained in the medical implantation FROM body only very slowly or not at all absorbed and cause inflammation, immune reactions or the formation of foreign body giant cells, especially in the body. The cross-linking of collagen products with aldehydes was carried out here exhaustively so fully networked, plastic-like products resulted, which are recognized by the body as foreign and so cause the aforementioned harmful reactions. Residual amounts of bonded aldehyde in the implant are also damaging to tissue.

From the publication Jap. Traumat. Surg. (1982) 99, pp 265-269 by K. Hayashi et al. is a collagen-hydroxylapatite preparation is known which has been freeze-dried after crosslinking. On one hand, relatively fine-grained apatite was used and on the other hand been no indication that the addition of glutaraldehyde should be such that none of the reactions described above occur.

It is accordingly an object of the present invention to provide a method for producing bone substitute material, with which it is possible to produce a firmer, less zerreissliches bone material that more favors the arrival and ingrowth of the bone and does not cause any unwanted side effects. The object is achieved by a method described in the claims.

It has now been found, surprisingly, that a very considerable improvement in the physicochemical properties of collagen could be caused by only partial cross-linking the collagen with formaldehyde or glutaraldehyde, without on the other hand, the finished product negative foreign body reactions triggers after implantation in the body, as previously described, or damage caused by residual amounts of aldehyde.

In the preparation of bone substitute material, which was the above-mentioned experiments provide a very fine powder apatite or tricalcium phosphate having particles in the size of 3-5 pm was used. It has now been found that the osteogenic effect of the apatite is substantially increased, if this is in the form of powder aggregates or larger particles. This increase in particle size may preferably be achieved by commercially available, present in finely crystalline form apatite or tricalcium phosphate into grains of about 20-1000 pm, preferably 50-300 pm diameter, sintered.

Have now conducted experiments erge ben that a bone substitute material, which consists of partially crosslinked with formaldehyde collagen and apatite or Triclaciumphosphat in the form of sintered grains that are already attached to the collagen solution before lyophilization, significantly better results yields than the prior art bone substitute material, whereby such a new bone substitute material is suitable for large area of indications. It is particularly advantageous to choose the distribution of apatite grains in collagen analogous to the distribution of the crossing points of the mineral structures in the natural bone, so that at the beginning of the formation of new bone, the bone replacement material is present as a kind of matrix of the forming bone is similar.

The starting material required for carrying out the inventive method can be prepared in the manner described below:<ul><li>1 kg bovine tendon was frozen at -10 to -20 ° C and while very finely comminuted 10-20 min. With a Messerhomogenisator high revs. The temperature of the ground material was maintained by the addition of ice chips below + 40 ° C. The tough fibrous Gewebebrei obtained was suspended in 5 liters of 10% NaCl solution containing 2.5 g of sodium azide and 50 ml of a 10% aqueous solution of the non-ionic wetting agent containing NP 55/52 (Polyoxyäthylennonoylphenyläther), with vigorous stirring. The suspension was further stirred at room temperature for 2 hours, and then centrifuged. The gray to brownish cloudy supernatant containing fat and unwanted water-soluble dietary fiber, was discarded. The residual white Hautfaserbrei was extracted twice more in the same manner, wherein the extraction liquid per liter of 0.1 mol of disodium hydrogen phosphate was added.</li></ul>

The starting material can also be used pigskin instead of bovine tendon.

A in the manner described above from 1 kg of beef tendon preserved defatted and extracted fibrous Gewebebrei was suspended 0.5M acetic acid in 5 times the volume. The suspension was added to a solution of 1 g technical pepsin in 100 ml of 0.01 N HCl. The pH of the Saspension was adjusted with HCl to 2.9. The suspension was digested with frequent stirring for 48 h. The viscous collagen solution was filtered through a suction filter G 1 to remove undigerierte residues. The collagen was precipitated by addition of 30% aqueous sodium hydroxide from the suspension and separated by centrifugation. The collagen was purified by dissolving it in 0.5 M acetic acid and precipitation by slow addition of 3% sodium chloride. The purified collagen was dissolved in 0.5M acetic acid and diluted with water. Still present in the collagen residual sodium chloride was removed by washing on an ultrafilter. The ultrafiltration was continued until the eluate with the addition of silver nitrate no more chloride ions were detected, and the collagen concentration was about 1%. The collagen solution was filtered with 0.2 wt.% Formaldehyde and 5 parts by weight of sintered apatite grains the size of 20-1000 microns, both based on the collagen content of the collagen solution was added, stirred 20 minutes, poured into suitable molds, for several hours left , lyophilized and then sterilized by γ-irradiation.

example 1

600 g of a prepared according to the method described above, ultra-filtered collagen solution was clarified by filtration% with a collagen content of 0.88 wt., And 10.6 ml of a 0.1 wt.% By weight aqueous formaldehyde solution and stirred. While stirring the mixture 26.4 g of sintered apatite grains having about 50-150 pm in diameter, were added and stirred for 22 minutes. The pH of the solution increased during the stirring of original pH 3.5 to 6.35. The mixture was poured in portions of 70 g in polystyrene trays of size 12x7,5 cm, allowed to stand overnight, lyophilized the next day, then packed and finally sterilized by r-irradiation at a dose of 2.5 Mrad.

example 2

800 g of a prepared according to the method described above, ultra-filtered collagen solution with a collagen content of 1.07 wt.% Collagen was 6.83 ml of a 0.25 wt.% Aqueous solution of glutaraldehyde and with 17.12 g = twice the amount , based on the collagen content, added to the sintered apatite grains or tricalcium phosphate with about 300-700 pm diameter, stirred for half an hour, allowed to stand for 10 hours, filled in portions of 18 g in cups the size 6,4x3,8 cm, lyophilized , packaged and sterilized by irradiation with 2.5 Mrad t-rays.

example 3

% Was 5.82 g = three times the amount, based on the collagen content, mixed on sintered apatite grains of about 100 microns in diameter, 200 g of a prepared according to the method described above, ultra-filtered collagen solution with a collagen content of 0.97 wt. A stirred for half an hour, filled in portions of 40 g in round dishes with a diameter of 8 cm and lyophilised. The resulting material was not resistant to aqueous solutions and was therefore partially crosslinked by a, with 35 closed chamber of formaldehyde vapor was suspended for 2 hours wt.% Formaldehyde solution charged. The formaldehyde solution was removed from the chamber and the chamber evacuated 6 times and aerated to remove the formaldehyde gas unbound from the collagen-apatite material. In the third aeration air was passed through an aqueous ammonium hydroxide solution, to bind final residual amounts of formaldehyde in the inflowing ammonia. The bone substitute material obtained was suitable after this treatment in aqueous solutions and stable after sterilization for implantation into bone defects.

From the above example shows that one can achieve good results with an amount of formaldehyde, the weight below 1.%, Based on the dry weight is the collagen, preferably in an amount of 0.05-0.5 wt.%. When using other aldehydes corresponding to de amount to be used.

In addition to the mentioned form and glutaraldehyde may also be used a saturated or unsaturated, mono- or polyfunctional aliphatic aldehyde, glyoxal, unsubstituted or substituted di- or Trichlortriazine, wherein as gaseous crosslinking agent ethylene oxide also comes into consideration.

It is appropriate to reinforce the mechanical strength of the bone substitute material even further by treating it with honeycomb, reticular layer-like or woven-fabric-like (woven, twisted, knitted) supporting elements of plastic, textile, metal, aluminum, ceramics, carbon fiber, carbon, bone cement, fiberglass or Bioglasfaser combined. The support elements may have the shape of the bone part to be replaced. It may also be practical, the new bone substitute material shall be included antibiotics.

Purpose compacted and solidified the bone replacement material can be optionally compressed in the dry or wet state by heating.