Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Patent
1988-06-23
1991-09-24
Bleutge, John C.
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
525265, 604416, 2223865, 222 80, C08F26506, A61M 532, A61B 1900
Patent
active
050514822
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
This invention relates to a method of preparing a self-curing two-component powder liquid bone cement comprising a powder component consisting of particles containing a polymerization catalyst, and a liquid component containing a polymerizable monomer, prepolymer or mixtures thereof.
Various proposals have been made for mixing bone cement under vacuum, but mostly for avoiding inhalation of the toxic monomer vapours developing during preparation of bone cement. No utilizable cement mixture is obtained with all these known methods unless the powder and liquid components are not mechanically stirred and homogenized.
It is known, however, that such mechanical stirring, even under vacuum, produces air inclusions which weaken the finally hardened cement mass. Furthermore the accuracy of the powder liquid ratio cannot be guaranteed with the known methods of bone cement mixing since errors of the operator are always possible.
In the pending but not prepublished International Patent Application No. PCT/EP 85/00227 a method for mixing bone cement under vacuum according to the preamble of claim 1 of the present invention is described which uses normal polymethylmethacrylate (PMMA) beads coated with benzoyl peroxide (BPO) as a polymerization catalyst. Whereas this method overcomes the most essential drawbacks of commercially available bone cements, namely poor mixing, high exotherm and creation of porosities, its disadvantage lies in the fact that the BPO deposited on the surface of the PMMA-beads is quickly washed away when the evacuated powder component is flooded with the liquid component (methylmethacrylate) producing an inhomogeneous gradiant in the BPO concentration and thereby an irregular polymerization process.
SUMMARY OF THE INVENTION
The invention as claimed is intended to remedy these drawbacks. It solves the problem of how to design a method for preparing a bone cement without manual or mechanical mixing exhibiting a regular course of polymerization and a homogeneous structure of the hardened cement with practically no porosities.
The advantages offered by the invention are mainly the ease of handling, the quick and reliable mixing, the prevention of high exotherm and of porosities and the significantly improved physical values of the bone cement obtained by the method according to the invention.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For the better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which are illustrated and described preferred embodiments of the invention.
BRIEF DESCRIPTION OF THE DRAWINGS
In the drawings:
FIG. 1 is a perspective view of a powder particle used in the method according to the invention;
FIG. 2 is a perspective view of a specially manufactured powder particle used in the method according to the invention;
FIG. 3 is a sectional view of the empty syringe used for carrying out the method according to the invention;
FIG. 4 is a sectional view of the filled syringe used for carrying out the method according to the invention;
FIG. 5 is a sectional view of the syringe according to FIG. 4 with the inserted adapter according to FIG. 7;
FIG. 6 is a sectional view of the syringe according to FIGS. 4 and 5 with the piston being advanced for extrusion of the cement mixture; and
FIG. 7 is a sectional view of the ampoule and the adapter used for introducing the liquid component.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The basic method according to this invention consist of flooding polymethylmethacrylate (PMMA) beads confined in an inflexible, at least partially evacuated tubular chamber 4 of a syringe 11 with liquid methylmethacrylate, thereby obtaining a self-curing cement mixture without the need of manual or mechanical mixing.
The chemical composition of the main components and of the usual additives
REFERENCES:
patent: 3739947 (1973-06-01), Baumann et al.
patent: 4463875 (1984-08-01), Tepic
patent: 4490497 (1984-12-01), Evrard et al.
patent: 4808184 (1989-02-01), Tepic
Bleutge John C.
Farley Walter C.
Jagannathan Vasu S.
Laboratorium fur experimentelle Chirurgie
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