BONE CEMENT FOR THE ANCHORAGE OF IMPLANTS AND JOINT ENDOPROSTHESES

The invention concerns a bone cement for the anchorage of implants and joint endoprostheses, which at least powdered Polymethyhnethacrylat contains monomeres Methyhnethacrylat and a tertiary amine if necessary as filler and as liquid component as Besehleuniger as well as the further powdered and/or liquid catalysts and Roentgen contrast means. AIs accelerators can e.g. serve in well-known way Dimethylsuiliu or Dimethyl p Toluidin, while as Roentgen contrast means for example barium sulfate or zircon oxide use can find. For the anchorage of implants and joint prostheses one uses for a long time polymerizationable plastics of the composition mentioned, which are called in the implant surgery generally 'bone cement ". With the 1Viischung of the powdered and the liquid component of such material combinations that begins liquid to polymerize and to-harden monomers Methyhnethacrylatunter effect of the liquid and powdered catalysts. The reactions running off thereby are exothermic; the freed warmth fiihrt to unwanted temperature paste run gene in the environment of the bone cement, whereby with exceeding of a certain Temperaturgrenze damages of the bone fabric can be caused. From different block letters polymerizationable masses are, those as Gebißund Z 1 nüillungen to serve can well-known. Thus for example the liquid mixtures contain 1937 871 and No. 966,278 as well as in accordance with the German disclosure writing 1,933,917 and the USA Patentschrfft No. 3.468.977 free acids in accordance with the German patent specifications No., predominantly Methacrylsäuren; because of their Wechselwirkangen with IVBrperflüssigkeiten however acids for mixtures, which are to serve as bone cements, are absolutely unsuitable. While during the mixtures after the German Patentsehrift No. 927,890 as liquid component pure Methylmethacrylat is used, the liquid component contains,617,582 biflmk onelle Methacrylate in accordance with the German laying out writing 1, i.e. TriäthylenglykDl di methacrylat. Such MehrfachMethacrylate causes with the polymerization however non like desired according to invention - a degradation, but on the contrary an increase of the ReakGonstemperatur. Beside free acids the liquid component contains 3.468.977 Methacrylate with a free hydroxyl group of the USA Patentschrfft in accordance with No., thus alcohol remainders of multi-valued alcohols. Apart from the higher costs, which cause these acrylates of multi-valued alcohols, they are not fiir bone cements likewise suitably, because the Wirlamgen of the hydroxyl groups in connection with isolation liquids does not admit and are investigated, thus over its compatibility a statement to be made can. How lets itself see, thus the requirements at Kaochenzement, which is eingefiillt into living fabric of the human body, of those are those outer self-quenching masses for Gebißund fillings confess become completely different. The invention is the basis from there primarily the task to decrease the rises in temperature arising during the bone cement to hardening without worsening mechanical or other characteristics inadmissibly. The subject of the invention is a bone cement for the anchorage of implants and joint endoprostheses, which m contains udestens powdered Polymethyimethacrylat as filler and as liquid component of monomeres Methylmethacrylat and a tertiary amine as accelerator as well as if necessary further powdered and/or liquid catalysts and l%. .öntgenkontrastmittel, which is characterized by that the liquid component beside iudestens 50% of its weight at monomerem Methylmethacrylat and up to 5 of their weight at tertiary amine, in a quantity from 10 to 45 Gew. - % into actually well-known way at least a univalent, monofunktionellenù Methacrylsäureester from the group with satisfied, aliphatic alcohol component with 2 to 6 C-atoms in the alcohol remainder contains. The Zusarnrnensetzung according to invention has the advantage over the avoidance of strong rises in temperature outside that with the degradation of the arising maximum temperature the effective working time extends at the same time fär the bone cement, whereby the work of the operating surgeons is facilitated. Furthermore the bone cement according to invention has opposite well-known bone cements - turned out as in the meantime in practice - a further substantial advantage. It showed up that the physical properties affecting Porösitätsgrad of the hardened bone cement is very many smaller with erfindnngsgemäf the EN mixture, as with used mixtures. This favorable characteristic of the cement according to invention is on it z rücl ufiihren that the new mixture remains longer liquid (about 4 ùiu from the time of the 1Viischens of the liquid with the powdered component with ambient temperatures from 15 to 25°C) as the well-known mixtures. Thus 5S has air stirred with mixing the components longer time to escape. Further the lower, arising polymerization temperature causes that develop for fewer steam bubbles of the evaporating Nfonomeren. This additional, for which use of the mixture according to invention is not as bone cement very substantial advantage anywhere described. As favourable a content from 20 to 40% of the weight of the liquid component at Isobutylmethacrylat proved. The invention is more near described in the following on the basis a remark example. B e i s p i e 1: The Kuoehenzement according to invention is manufactured as mixture of commercial products, whereby first a liquid component is zusammengemiseht, which consists in per cent of its Gewiehtes of the following organic substances: 2.5% 57.5% monomers Isobutyhnethacrylat Dimethyl pToluidin contain monomeres Methylmeihacrylat the monomers the Methacrylate in well-known way in small quantities Hydrochinon (for example 25 to 100 TpM of their weight) as stabilizers. The powdered component consists of polymethyl metacrylate, only about 3% of its weight at Benzoylperoxyd are admitted to which as catalyst for after the mixture of the hardening reactions running off both components. In addition can the Palverkomponente of managing composition inert Roentgen contrast means on inorganic basis - as for example barium sulfate or zircon oxide erwähut - in quantities from 5 to 15 Gew. - % of the powder added its. Both components prove as over a longer time storably. Separated from the two so far components held are mixed intimately with one another now two parts of powders and a part of liquid, so that itself a paste-like mass also, which inspection results in after, as homogeneous a distribution of all components as possible. With merging the hardening by precipitation of the cement begins; their duration and the maximum Spitzentemperaün reached thereby: compared with a bone cement present at the market are determined, which does not exhibit Methacrylat with more than one C-atom in the alcohol remainder contrary to the mixture according to invention, but consists, apart from Beschlenrägern and/or catalysts, in its liquid component only of Methylmethacrylat. For the registration of the Härümgsverlaufes as Teraperatur/time curve about in each case 12 g (gram) mixed with one another of the components become into a Alumininmbeeher of 30 mm in diameter and about 15 mm of Füllhöhe eingefü after the mixture! lt, which is embedded for thermal insulation into an asbestos case, with the help of a thermocouple the temperature gradient is drawn directly on a writer in function of the time on. Fig. 1 shows an example of this temperature/time Härtungsknrve, whereby on the abscissa the time in minutes and on the ordinate the temperature in °C are laid on. The curves 0 are valid for the mentioned, well-known bone cement and the curve 1 for the mixture in accordance with the example of the invention. With the attempts it showed up that the measurements certain Strenungen are subjected; these are affected partially by the quality of the mixing and the even distribution of the liquid and the powdered component. From several, that in Fig. 1 for in each case a sample hardening curves shown are from there for the hardening time, i.e. for the time, in which during the described experimental assembly the temperature maximum is reached, and for this maximum following average values to be determined. Number of the mixture 0 1 time min. Temperature degrees of 115 - 125 91 - 95 working time min < 3 the attempts shows that with the new Kuochenzement the unwanted temperature point can be substantially lowered, without - as Biegeversuehe resulted in 77,103 with probes of 60 x 10 x 4 mm after VSM in the case of a span of 50 mm - important falling losses of the mechanical characteristics in purchase be taken must. Special advantages arise for the operating surgeon with the invention as a result of aul the erordenüiche extension of the Verarbeiümgszeit, i.e. the time, in which the Kaochenzement can be deformed before the Aushärümg. By the extension of this time by a repeated the operating surgeon is no longer compelling to work from the time of mixing the components on under extreme time pressure. Here it is mentioned that the descriptive attempts in their absolute Zeitund temperature levels do not permit any Rüelasehlüsse on appropriate values with use the cement in the bone, but only already admitted a relative comparison between that product and that according to invention mixtures permit. When measure for the brittleness are further stress-strain curves provided, in which the stretch “(in %) against the tension “(in kp/mm2), determined from the mentioned deflection attempts, was laid on, whereby the curves shown represent average values from a set of measurements. The values for the elongation at rupture (WHETHER), which in following table likewise as average values as well as the associated Bruohspannungen (it B) to be again pointed out, represent a good measure for the brittleness, whereby higher C-values refer to a smaller brittleness, i.e. better plastic ductility. The likewise indicated values for the modulus of elasticity E show that the flexible characteristics, in particular the flexible maximum stress, which new Kuochenzementmisehung is changed not substantially opposite those of the well-known bone cement. Mechanical values (r E B /m 2 B kp of 2 E bone cement 0 6, 27,2.6,271 1 6, 02,2.8,237 Fig. 2 and the managing table, in which for the designation of the mixtures the same numbers 0 and 1 as for the Härtungskarven in the example 1 were selected, shows clearly that by erflndungsgemäl the e composition also the meehanischen characteristics are improved.