EP2957337A1 - Vacuum mixing system and method for mixing of polymethylmethacrylate bone cement - Google Patents

Abstract

The invention relates to a vacuum mixing system for mixing polymethyl methacrylate bone cement comprising at least one cartridge (4) with an evacuatable interior for mixing the bone cement, a pump (18) for generating a negative pressure and a connecting line (12), the interior of the at least one cartridge (4) to the pump (18) for generating a negative pressure, wherein the vacuum mixing system comprises an integrated energy storage (28) for driving the pump (18) connected to the pump (18) or connectable and in the energy for at least a pumping operation of the pump (18) is stored, wherein in the pumping process by a consumption of energy from the integrated energy store (28) with the pump (18), a negative pressure can be generated, so that with the negative pressure through the connecting line (12) gas the interior of the at least one cartridge (4) can be evacuated. The invention also relates to a method for mixing polymethyl methacrylate bone cement in an interior of a cartridge (4) of a vacuum mixing system, wherein energy stored in a power storage device (28) integrated in the vacuum mixing system is used to drive a pump (18) of the vacuum mixing system. wherein with the thus driven pump (18) of the interior of the cartridge (4) is evacuated and in the interior of the cartridge (4) a bone cement is mixed.

Description

The invention relates to a vacuum mixing system for mixing polymethyl methacrylate bone cement (PMMA bone cement) from two starting components, in particular for mixing a medical bone cement, and for storing the starting components.

The invention further relates to a method for mixing polymethyl methacrylate bone cement.

The invention thus provides a vacuum mixing system for the storage, mixing and optionally also the discharge of polymethyl methacrylate bone cement. Furthermore, the invention relates to a method for transfer of monomer liquid into the vacuum mixing system and a method for mixing the components of polymethylmethacrylate bone cement.

Polymethylmethacrylate (PMMA) bone cements go back to the fundamental work of Sir Charnley. PMMA bone cements consist of a liquid monomer component and a powder component. The monomer component generally contains the monomer methyl methacrylate and an activator (N, N-dimethyl-p-toluidine) dissolved therein. The powder component, also referred to as bone cement powder, has one or more polymers, an X-ray opaque and the initiator dibenzoyl peroxide. The polymers of the powder component are prepared based on methyl methacrylate and comonomers such as styrene, methyl acrylate or similar monomers by polymerization, preferably suspension polymerization. When the powder component is mixed with the monomer component, swelling of the polymers of the powder component in methyl methacrylate produces a plastically deformable dough, the actual bone cement. Upon mixing the powder component with the monomer component, the activator reacts N, N-dimethyl-p-toluidine with dibenzoyl peroxide to form radicals. The radicals formed initiate the radical polymerization of the methyl methacrylate. As the polymerization of methyl methacrylate progresses, the viscosity of the cement dough increases until it solidifies.

The monomer most commonly used in polymethyl methacrylate bone cements is methyl methacrylate. Redox initiator systems usually consist of peroxides, accelerators and optionally suitable reducing agents. A radical formation takes place only when all components of the redox initiator systems interact. Therefore, the components of the redox initiator system are placed in the separate starting components so that they can not initiate radical polymerization. The starting components are storage stable with a suitable composition. It is only when the two starting components are mixed to form a cement dough that the components of the redox initiator system previously stored separately in the two pastes, liquids or powders react, forming radicals which trigger the radical polymerization of the at least one monomer. The radical polymerization then leads to the formation of polymers with consumption of the monomer, wherein the cement paste hardens.

PMMA bone cements can be mixed in suitable mixing beakers by means of spatulas by mixing the cement powder with the monomer liquid. A disadvantage of this approach that air pockets may be present in the formed cement dough, which may later cause a destabilization of the bone cement. For this reason, the mixing of bone cement powder with the monomer liquid in vacuum mixing systems is preferred because air entrainment from the cement dough is largely removed by mixing in a vacuum and thus optimum cement quality is achieved. Vacuum mixed bone cements have significantly reduced porosity and therefore exhibit improved mechanical properties. A variety of vacuum cementing systems have been disclosed, of which the following are by way of example: US 6,033,105 A . US 5,624,184 A . US 4,671,263 A . US 4,973,168 A . US 5,100,241 A . WO 99/67015 A1 . EP 1 020 167 A2 . US 5,586,821 A . EP 1 016 452 A2 . DE 36 40 279 A1 . WO 94/26403 A1 . EP 1 005 901 A2 . US 5,344,232 A , In the described vacuum cementing, it is necessary to connect an external vacuum pump to generate the negative pressure. These are generally operated with compressed air using the venturi principle. The compressed air required for the operation of the vacuum pumps is either from stationary compressed air systems or from electrically operated compressors based. In addition, it is also possible to use electrically operated vacuum pumps for vacuum generation.

A further development in cementing technology is cementing systems in which both the cement powder and the monomer liquid are already packed in separate compartments of the mixing systems and which are mixed together in the cementing system just prior to the cement application. Such full-prepacked mixing systems have been combined with the EP 0 692 229 A1 , of the DE 10 2009 031 178 B3 , of the US 5,997,544 A , of the US Pat. No. 6,709,149 B1 , of the DE 698 12 726 T2 and the US 5,588,745 A proposed. Even with these mixing systems, an external vacuum source is necessary. The patent DE 10 2009 031 178 B3 discloses a generic vacuum mixing device with a two-part discharge piston, which can also be used for a vacuum mixing device according to the invention.

When using vacuum mixing systems for cementing, external vacuum pumps must be provided. These vacuum pumps are expensive and must be cleaned after use. Furthermore, vacuum hoses are necessary for connecting the vacuum pumps with the vacuum mixing systems. These vacuum hoses must be enclosed with the vacuum mixing systems. Therefore, before mixing with a vacuum mixing system, the vacuum pump must first be set up in the operating room (operating room) and connected to an energy source such as compressed air or electricity. Thereafter, the vacuum pump is connected to the vacuum mixing system with a vacuum hose. These assembly steps cost valuable operating time and are potentially flawed. The vacuum pump and the connection lines to the vacuum mixing system and to external power sources and supply lines require space and represent potential tripping hazards and obstacles that can interfere with the occasionally hectic flow during an operation.

An interesting concept will be with the EP 1 886 647 A1 proposed. The cement powder is stored in an evacuated cartridge and the monomer liquid is in a separate container. When opening the under negative pressure cartridge, the monomer liquid is sucked into the cartridge without air flowing in. The result is a free of air bubbles bone cement dough. This concept requires that the cartridge during the Storage remains vacuum sealed before use and no non-sterile air can enter. The cartridge must be stably sealed hermetically. The disadvantage of this is that the structure is complicated and that the contents of the cartridge can not be mixed by an external mixing system to be used after sucking in the monomer liquid, since a passage for a mixing rod or a mixing tube is not readily permanently vacuum-tight.

The object of the invention is therefore to overcome the disadvantages of the prior art. In particular, the disadvantages of the known vacuum mixing systems with external vacuum source are to be overcome. The invention has the particular task of developing a vacuum mixing system in which a negative pressure is generated only immediately before the mixing of the cement components. The device should be maximally simplified and allow at least one time to generate a negative pressure in a cement cartridge with respect to the surrounding atmosphere. Furthermore, it may be advantageous if the vacuum mixing system is capable of allowing a transfer of monomer liquid from a monomer container into a cartridge filled with cement powder. A method is then also to be provided which allows for monomer transfer and vacuum mixing in full-prepacked mixing systems. Furthermore, the vacuum mixing system to be developed, mainly from inexpensive plastic can be manufactured.

Furthermore, a cost-effective and reliably functioning device for mixing a medical cement and optionally for storage of the starting components and a method for mixing the bone cement is to be found, in which the simplest possible manual operation for mixing the starting components can be used, if possible without an external or additional energy source must be used and without air pockets in the mix can arise.

The main component of the polymethyl methacrylate bone cement as a mix should be a powder and the second component should be in the form of a liquid. The two starting components of the bone cement are preferably to be stored separately in the vacuum mixing system and can be safely combined by using the device.

The objects of the invention are achieved by a vacuum mixing system for mixing polymethyl methacrylate bone cement comprising at least one cartridge with an evacuable interior for mixing the bone cement, a pump for generating a negative pressure and a connecting line, which generates the interior of the at least one cartridge with the pump a vacuum connects, wherein the vacuum mixing system has an integrated energy storage for driving the pump, which is connected to the pump or connectable and stored in the energy for at least one pumping operation of the pump, wherein in the pumping operation by a consumption of energy from the integrated energy storage With the pump, a negative pressure can be generated, so that with the negative pressure through the connecting line gas from the interior of the at least one cartridge is evacuated.

The term negative pressure in the present case always refers to a relative to the surrounding atmosphere related pressure, which is smaller than the surrounding atmospheric pressure.

It can preferably be provided that the pump is integrated in the vacuum mixing system.

The polymethyl methacrylate bone cement is preferably mixed from at least two components or can be produced from at least two components. Particularly preferably, one component is liquid and another component is powdery.

It may preferably be provided that the pressure in the interior of the at least one cartridge can be reduced by at least 50% by the pumping process, preferably by at least 90%.

The starting components for the mix, in particular for the PMMA bone cement, according to the invention already contained in the cartridges.

The device according to the invention is preferably also suitable for storing the starting components, in particular when the containers are inserted into the device or the containers are a fixed part of the device.

The mixture is particularly preferably a bone cement, in particular a PMMA bone cement.

With a development of the invention can also be provided that with the negative pressure through the connecting line gas from the interior of the at least one cartridge is evacuated and gas from a line between the interior and a liquid container can be evacuated and the negative pressure with a first component of the PMMA bone cement in the cartridge is to draw mixing liquid from the liquid container into the interior of the cartridge.

With a further development of the vacuum mixing system, it is proposed that the pump has a gas-tight pumping space and in the pump a movable piston or a movable wall is provided as a boundary of the pumping space, wherein the piston or the wall with the energy of the integrated energy storage in one direction, preferred unidirectional, can be driven, so that is increased by the movement of the piston or the wall of the pump chamber and with the resulting negative pressure in the pump chamber, the interior of the at least one cartridge can be evacuated through the connecting line.

Alternatively, it can also be provided that the pump has a rotating wheel, a periodically operating piston or a periodically operating diaphragm. However, the embodiment with a movable piston or a movable wall is preferred according to the invention, since the structure is much simpler, fehlerunanfälliger (rotating parts could block) and thus cheaper, but at the same time for the short-term generation of a negative pressure in the interior of the cartridge is already sufficient. Due to the special requirements, such as the low volume of the interior of the cartridge, more complex pump systems are not necessary.

In this embodiment can also be provided that the increase in volume of the pump chamber is at least as large as the free volume of the interior of the cartridge, preferably the increase in volume of the pump chamber is at least as large as the sum of the volume of the interior of the cartridge in which a first powdered Component of the PMMA bone cement is contained, and the volume of the connecting line and the volume of a conduit between the interior and a liquid container and the volume of a to be mixed with the first component of the PMMA bone cement in the cartridge Liquid in the liquid container, wherein the liquid is a second component of the PMMA bone cement.

This ensures that the pump can evacuate the interior of the cartridge. The volume of the pump space before the pumping process is ideally as small as possible. It may therefore be preferred that the volume of the pump chamber after pumping is at least 5 times greater than the volume of the pump chamber before the pumping process, more preferably at least 10 times greater than the volume of the pump chamber before the pumping process.

According to one embodiment of the present invention can be provided that the vacuum mixing system comprises a mixing device for mixing the contents of the at least one cartridge, wherein preferably the mixing device is arranged in the interior of the cartridge and / or manually or by a motor can be driven.

Preferably, the cartridge has a pressure-tight passage through which a rod or a mixing tube is carried out, with which the mixing device is to be operated from outside the cartridge. For this purpose, the rod or the mixing tube is preferably rotatable and slidably mounted in the implementation in the longitudinal direction. With the mixing device, the contents of the cartridge can be mixed well.

Furthermore, it can be provided according to the invention that the vacuum mixing system has less than 30 kg total weight, more preferably less than 10 kg total weight.

These low weights are possible with the inventive design of the mixing device with integrated energy storage and the pump. The low weight has the advantage that the mixing device can be taken and can be used without connection to supply lines and without much preparation.

A particularly easy to use vacuum mixing system can be produced in that the vacuum mixing system has a manually operable control by the operation of the energy from the energy storage is releasable, which is driven by the energy released, the pump and the driven pump evacuated the interior of the cartridge.

This simplifies the operation of the vacuum mixing system. Despite the compact design so easy operation can be ensured.

According to a preferred embodiment of the invention can be provided that the energy storage is a filled gas pressure cartridge, preferably a CO ₂ gas cartridge, or a tensioned return element, preferably a tensioned spring, particularly preferably a tensioned steel spring.

These energy stores keep the energy for longer periods. In addition, the small amount of stored energy is sufficient to ensure a sufficient negative pressure for evacuating the interior of the cartridge.

Other possible and usable according to the invention energy storage batteries, accumulators or capacitors with which, for example, via an electromagnetic interaction, a short-term pulse for driving the pump can be triggered. Similarly, a chemical propellant could serve as an energy storage to drive the pump. However, these energy stores are much more complicated and difficult to implement as gas pressure cartridges and in particular as restoring elements such as springs. Therefore, gas pressure cartridges and tensioned restoring elements such as spring are particularly preferred according to the invention.

It is further proposed that in the interior of the cartridge, a movable discharge piston for discharging the mixed bone cement is arranged from the cartridge, wherein the discharge piston is preferably releasably locked or locked to prevent movement of the discharge piston under the action of negative pressure.

The discharge piston simplifies the operation of the vacuum mixing system.

Furthermore, it can be provided according to the invention that the pump is driven by a tensioned restoring element, in particular a tensioned spring element, wherein preferably an expansion or contraction of the restoring element, in particular of the spring element generates a negative pressure in the interior of the cartridge relative to the surrounding atmosphere.

This structure is particularly simple and inexpensive to implement. At the same time, however, a reliably operating vacuum mixing system can be constructed with this structure, which is relatively insusceptible to malfunction.

According to a further development of the invention, it can be provided that the cartridge is a cement powder filled cement cartridge and the vacuum mixing system has a container separate from the cement cartridge, in which a monomer liquid is contained, wherein the container by an openable partition liquid-impermeable to the interior of the cement cartridge is connected and the interior of the cement cartridge with the pump is connected gas-permeable or connectable.

1. A) einem Hohlzylinder, wobei der Hohlzylinder mit dem Innenraum der Kartusche verbunden oder verbindbar ist,
2. B) einem gasdichten Verschluss an einem Hohlzylinderende,
3. C) einem Kolben, der im Hohlzylinder gasdicht, axial beweglich angeordnet ist,
4. D) mindestens einem Federelement als integriertem Energiespeicher, das zwischen dem Kolben und dem Verschluss angeordnet ist,
5. E) einem Verbindungselement, das mit dem Kolben lösbar verbunden ist, das den Kolben im Hohlzylinder positionsfest hält und das Federelement gespannt oder komprimiert hält, wobei das Verbindungselement durch eine gasdichte Durchführung aus dem Hohlzylinder herausgeführt ist und von Außen vom Kolben lösbar ist, wobei nach Lösung der Verbindung des Verbindungselements durch Expansion des Federelements der Kolben axial entgegengesetzt zum Verschluss bewegbar ist.

In a particularly preferred embodiment of the invention can be provided that the pump is constructed with:

1. A) a hollow cylinder, wherein the hollow cylinder is connected or connectable to the interior of the cartridge,
2. B) a gas-tight closure at a hollow cylinder end,
3. C) a piston which is arranged gas-tight in the hollow cylinder, axially movable,
4. D) at least one spring element as an integrated energy store, which is arranged between the piston and the closure,
5. E) a connecting element which is detachably connected to the piston, which holds the piston in the hollow cylinder positionally and keeps the spring element tensioned or compressed, wherein the connecting element is led out by a gas-tight passage from the hollow cylinder and is detachable from the outside of the piston, wherein Solution of the connection of the connecting element by expansion of the spring element of the piston axially opposite to the shutter is movable.

This structure is particularly simple and the parts for this can be made of plastic by injection molding.

In this embodiment it can be provided that in the storage state, the spring element is compressed and is held by the piston of the pump by the locked connection element in the compressed state.

Furthermore, it can be provided that, after the expansion of the spring element within the hollow cylinder, the piston is displaced so that the volume of the pump chamber formed by the hollow cylinder, the closure and the piston is at least equal to the volume of the interior of the cartridge to be evacuated.

By adjusting the volumes ensures that the pump is sufficiently dimensioned for the purpose mentioned.

Furthermore, it can be provided that at the end of the hollow cylinder, a limiting element is arranged, that limits the movement of the piston such that it can not escape from the hollow cylinder.

According to a further development it can be provided that the piston on the side facing away from the closure contains an optical marker which is visually recognizable on the outside of the vacuum mixing system when the maximum movement of the piston has occurred and thereby indicates the position of the piston after its maximum movement.

This allows the user to recognize the condition of the vacuum mixing system from the outside.

The objects on which the present invention is based are also achieved by a method for mixing polymethyl methacrylate bone cement in an interior of a cartridge of a vacuum mixing system, in particular a vacuum mixing system according to the invention, in which an energy stored in an energy storage unit integrated in the vacuum mixing system is used to drive a pump of the vacuum mixing system is, with the thus driven pump, the interior of the cartridge is evacuated and in the interior of the cartridge, a bone cement is mixed.

It can be provided that the volume of a pump chamber of the pump is increased by relaxing a return element as an integrated energy storage and is evacuated by the resulting negative pressure of the interior of the cartridge.

It may be provided with a development that a cement powder is contained in the interior of the cartridge and a gas is evacuated from the interior of the cartridge with the pump, a monomer liquid is introduced into the interior of the cartridge and the monomer liquid with the cement powder in the evacuated Interior is mixed.

It can be provided that a connecting element is released from a piston of the pump, then a compressed return element moves the piston axially in a hollow cylinder of the pump, whereby a negative pressure relative to the surrounding atmosphere is generated, thereby through a connecting line of gas from the interior of the cartridge is sucked into the hollow cylinder, then manually or motor driven with a mixing device, a cement powder with a Monomer liquid is mixed, then the cartridge with the mixed cement dough is removed and pressed by axial movement of a Austragskolbens the cement dough from the cartridge.

It can further be provided that the cement powder is arranged in the cartridge, the monomer liquid is arranged in a separate container from the cartridge, wherein the monomer liquid is separated via a separating element of the cement powder in the cartridge, the separating element is opened before the connecting element of the piston is released, so that a liquid-permeable connection between the interior of the cartridge and the container is formed, then the compressed spring element moves the piston axially in the hollow cylinder, whereby a negative pressure is generated with respect to the surrounding atmosphere, thereby through the connecting line gas from the interior the cartridge is sucked into the hollow cylinder and is sucked by the negative pressure formed in the interior of the cartridge monomer liquid into the cartridge.

The invention is based on the surprising finding that with the aid of a pump and an integrated energy store in which a sufficient amount of energy is stored to evacuate the interior of the cartridge with the pump, a vacuum mixing system independent of external energy sources and other supply lines is possible provide. The vacuum mixing system according to the invention can be constructed compact, lightweight and space-saving. The pump can be constructed with the simplest means, so that the entire vacuum mixing system can be used as a single-use system. The energy can also be used according to the invention and preferably also for converting a monomer liquid into the cement powder with the pump. The two components of the PMMA bone cement can then be mixed in a vacuum or in the negative pressure.

The vacuum mixing system according to the invention also has the advantage that the gases evacuated from the cartridge are not released to the environment, since these gases then do not have to be filtered in order to remove unwanted constituents (such as, for example, methyl methacrylate vapors). Instead, the gases simply remain in the pump or pump space.

In cementing systems according to the present invention, there is included a vacuum generating device for temporarily generating a negative pressure before and during mixing of a powdery component with a liquid monomer component of the polymethyl methacrylate bone cement.

The idea underlying the invention is based on the recognition that only a relatively small amount of energy is necessary to generate the vacuum or negative pressure in a cartridge, which is necessary to mix the starting components of a bone cement under the vacuum or the vacuum. The amount of energy to transfer the monomer liquid into the cement powder is also low. This small amount of energy can be stored in an internal energy store of the vacuum mixing system with which the pump is driven. Already the amount of energy that is stored in a tensioned steel spring or another restoring element is sufficient according to the invention to provide the energy for driving a vacuum mixing system according to the invention.

Figur 1:

eine schematische Querschnittansicht eines erfindungsgemäßen Vakuummischsystems im Sterilisierungszustand vordem Pumpvorgang;

Figur 2:

das Vakuummischsystem nach Figur 1 mit geschlossenem zweiteiligem Kolbensystem bereit zum Evakuieren der Kartusche;

Figur 3:

das Vakuummischsystem nach Figur 1 und 2 mit ausgelöster Pumpe und evakuierter Kartusche nach dem Pumpvorgang; und

Figur 4:

eine schematische Querschnittansicht eines weiteren alternativen erfindungsgemäßen Vakuummischsystems.

In the following, further embodiments of the invention will be explained with reference to four schematically illustrated figures, without, however, limiting the invention. Showing:

FIG. 1:

a schematic cross-sectional view of a vacuum mixing system according to the invention in the sterilization state before the pumping operation;

FIG. 2:

the vacuum mixing system after FIG. 1 with closed two-piece piston system ready to evacuate the cartridge;

FIG. 3:

the vacuum mixing system after FIG. 1 and 2 with triggered pump and evacuated cartridge after pumping; and

FIG. 4:

a schematic cross-sectional view of another alternative vacuum mixing system according to the invention.

The FIGS. 1 to 3 show a schematic cross-sectional view of a vacuum mixing system according to the invention prior to the pumping operation. The vacuum mixing system consists essentially of three parts, a cartridge system 1, a liquid container 2 and a foot part 3. In this case, the cartridge system 1 is connected to the liquid container 2 via the foot part 3. The Foot part 3 forms, among other things, the base of the compact vacuum mixing system.

The cartridge system 1 has a cylindrical cartridge 4 with a circular base, which is fixed vertically to the foot part 3. For this purpose, an opening with an internal thread is provided at the front of the cartridge 4, which is screwed onto a socket on the foot part 3 with an external thread. Inside the cartridge 4, a cement powder (not shown) is contained. In addition, a mixing device 6 with two or more mixing blades 6, which are fastened to a mixing tube 8, is arranged inside the cartridge 4. The mixing tube 8 is rotatable and guided in the longitudinal direction displaceable by a sterilization piston 9. The implementation is pressure-tight and gas-tight. The sterilization flask 9 has a membrane (not shown) that is permeable to a sterilizing gas but is not permeable to the cement powder. The sterilization piston 9 is inserted after the filling of the cement powder in the cartridge 4 and closes the interior of the cartridge 4 to the outside. Subsequently, the contents of the cartridge 4 can be sterilized through the permeable membrane with ethylene dioxide.

A sealing piston 10 can be pressed into the sterilization piston 9 and connected to this gas and pressure-tight. The mutually attached pistons 9, 10 then together form a discharge piston 9, 10, with which the contents of the cartridge 4 can be pressed out through the bottom-side opening. First, the sterilization piston 9 but on the opposite side (in FIGS. 1 to 3 locked above), wherein the lock is releasable.

On the mixing tube 8, a handle 11 is attached outside the cartridge 4, with which the mixing blades 6 in the interior of the cartridge 4, ie in the interior of the cartridge 4 are manually rotatable and displaceable in the longitudinal direction of the cartridge 4.

In the sealing piston 10, a passage is provided, which is connected to a connecting line 12 in the form of a flexible vacuum line 12. The sealing piston 10 is otherwise tight. The front of the cartridge 4 (in the FIGS. 1 to 3 below) is connected by the foot part 3 via a fluid line 14 pressure-tight manner with the liquid container 2. In the liquid line 14, a siphon 16 is provided, with which it is prevented that a monomer (not shown) contained in the liquid container 2 can unintentionally penetrate into the cartridge 4. The vacuum line 12 is also in the foot part 3rd guided and guided there in the foot part 3 to a pump 18, so that the implementation in the sealing piston 10 via the vacuum line 12 pressure-tight with the pump 18 is more precisely connected to the interior of the pump 18.

The pump 18 has a stable hollow cylinder 20 which is pressure-tightly separated into two parts via a piston 22. In the back part (in the FIGS. 1 to 3 left) of the interior in the hollow cylinder 20, the mouth 24 and the terminal 24 is provided for the vacuum line 12. This part of the interior of the hollow cylinder 20 forms a pump chamber 26. A negative pressure in the pump chamber 26 can thus act through the vacuum line 12 into the interior of the cartridge 4, or a gas from the interior of the cartridge 4 are evacuated when the sealing piston 10, as in the Figures 2 and 3 shown connected to the sterilization piston 9.

The vacuum mixing system is characterized by a tensioned steel spring 28, which is arranged in the pumping space 26 about a screw 30 and about a cylindrical extension on the piston 22 around. The screw 30 is gas and pressure tight and rotatably guided through a passage in the pump chamber 26. The screw 30 forms for a closure of the pump chamber 26 and the interior of the hollow cylinder 20. As a result, the pump chamber 26 to the port 24 tight. The screw 30 is screwed with an external thread 32 in an internal thread 33 in the cylindrical extension of the piston 22 and thus holds the piston 22 in position. The steel spring 28 is between the piston 22 and the side (the base) of the hollow cylinder 20 with the passage for the screw 30 (this page is in the FIGS. 1 to 3 drawn on the left side of the hollow cylinder 20) compressed or tensioned. The steel spring 28 is thus used as a compression spring 28. In the voltage of the compression spring 28, an amount of energy is stored sufficient to evacuate with the pump 18, the interior of the cartridge 4, the vacuum line 12 and the liquid line 14 and the monomer liquid from the liquid container 2 through the liquid line 14 into the interior of the cartridge 4 to draw.

On the opposite side of the screw 28 of the piston 22, an extension 34 is arranged in the form of a pin 34, which emerge from the hollow cylinder 20 through an opening 36 in the base of the hollow cylinder 20, which faces the base with the passage for the screw 30 can. When the pin 34 off the opening 36 protrudes, can be immediately recognized from the outside that the pump has triggered 18 and the pumping operation is completed.

In the liquid container 2, a glass ampoule 40 is arranged with a breakable head 42. The glass ampoule 40 contains the monomer liquid. The head 42 of the glass ampule 40 can be broken off or sheared off by turning a rotary lever 44. The rotary lever 44 thus opens the connection and thus establishes a connection between the monomer liquid and the liquid line 14. In addition, at the entrance of the liquid container 2 in the liquid line 14 also a valve element (not shown) may be provided, which can be opened with the rotary lever 44. The liquid container 2 is closed gas-tight and pressure-tight with a lid 46 after the glass ampoule 40 has been inserted into the liquid container 2. After breaking the glass ampule 40, the monomer liquid is available in the liquid container 2 and can be passed through the liquid line 14 into the interior of the ampoule 4, in which a negative pressure in the interior of the ampoule 4 is used to remove the monomer liquid from the liquid container 2 to suck the interior of the ampoule 4. In the interior of the ampoule 4, the monomer liquid can then be mixed with the cement powder with the mixing device 6 under vacuum or under reduced pressure to produce the bone cement or a bone cement paste.

The vacuum mixing system according to the invention is characterized by the following method. The pump 18 is triggered by the screw 30 is screwed out with the external thread 28 from the internal thread 33 of the piston 22. This is done when the cartridge 4 is ready for use by inserting the seal piston 10, as in FIG FIG. 2 shown. After loosening the screw 30, the energy of the compressed steel spring 28 is released and the piston 22 is accelerated in the direction of the opening 36. By this movement, the pump chamber 26 is increased. As a result, the pressure in the pump chamber 26 is reduced. Gas flows from the vacuum line 12, the interior of the cartridge 4 and the liquid line 14 into the pump chamber. The interior of the cartridge 4 is evacuated.

The piston 22 is up to the end of the hollow cylinder 20 (in the FIGS. 1 to 3 right) accelerates until the pin 34 protrudes from the opening 36. This arrangement is in FIG. 3 shown. The increase in volume of the pump chamber 26 must be sufficient to the Gas from the vacuum line 12 to evacuate the interior of the cartridge 4 and the liquid line 14 and to draw the monomer liquid from the liquid container 2 into the interior of the cartridge 4. Preferably, the expanded pumping space 26 is as in FIG. 3 shown, to greater than the volumes of the lines 12, 14, the interior of the cartridge 4 and the liquid volume of the monomer liquid. It should be remembered that the FIGS. 1 to 3 with respect to the size ratios of the pump chamber 26 and the other volumes are shown only schematically.

If the starting components were mixed in the interior of the cartridge 4, the mixing tube 8 is pulled out as far as from the interior of the cartridge 4 upwards and can then be stopped at a predetermined breaking point. The sealing piston 10 is rotated against the sterilization piston 9 and thus the gas passage closed by the sealing piston 10. The vacuum line 12 is withdrawn from the sealing piston 10. The cartridge 4 is unscrewed from the foot part 3 and screwed into the internal thread a dispensing tube (not shown), through which the mixed bone cement can be applied. The delivery piston or discharge piston assembled from the sterilization piston 9 and the sealing piston 10 is unlocked and can be driven into the interior of the cartridge 4 with an application device (not shown). As a result, the contents of the cartridge 4, that is, the mixed under negative pressure bone cement from the opposite opening and pressed by the screwed discharge pipe.

The components of the vacuum mixing system can be made of a plastic except for the glass ampoule 40 and the steel spring 28 and the output components of the bone cement by injection molding. The lines 12, 14 may be made of a different plastic. The vacuum line 12 must be flexible in order to be able to arrange the sealing piston 10 movably on the mixing tube 8.

The lines 12, 14 and the pump 18 are arranged up to the head of the screw 30 in a plastic housing, which has a flat bottom, so that the vacuum mixing system can be placed on a flat surface.

With the described vacuum mixing system, the two starting components of the bone cement can be stored and mixed at any later time under vacuum. It has to do that Vacuum mixing system to be connected to any external supply (electricity, water or compressed gas). The energy required to generate the negative pressure is stored in the tensioned steel spring 28 as energy storage. Alternatively to the compression spring 28 and a tensioned tension spring could be used, which is stretched between the opening 36 and the piston 22 in the interior of the hollow cylinder 20 to train, or it could be a tensioned gas spring are used. However, the construction with a steel spring 28, in particular with a compression spring 28 is simpler and less expensive.

The FIG. 4 shows a schematic cross-sectional view of another vacuum mixing system according to the invention with a simplified structure. The vacuum mixing system comprises a cartridge system 51 which is screwed onto a base 53. The cartridge system 51 includes a cartridge 54 having a cylindrical interior. The interior of the cartridge 54 is at the front (in FIG. 4 below), wherein the front discharge opening has an internal thread and the cartridge 54 is screwed with the internal thread on an external thread on the base 53.

In the interior, mixing vanes 56 of a mixing device 56 are arranged on a mixing tube 58 which is movable in the interior of the cartridge 54 in the longitudinal direction and can be rotated axially. The mixing tube 58 is guided by a two-part discharge piston 59, 60, which consists of a sterilization piston 59 and a sealing piston 60. The function of the two Austragskolbenteile 59, 60 corresponds to the function of Austragskolbenteile 9, 10 according to the first embodiment. The mixing tube 58 terminates at a handle 61 with which the mixing device 56 from outside the cartridge 54 is operable.

In contrast to the execution after the FIGS. 1 to 3 this version does not have a fluid line which is located in the connection area (in FIG. 4 below) would have to open into the cartridge 54. In the execution after FIG. 4 All components of the bone cement are simply attached to the back of the cartridge 54 (in FIG. 4 top) filled in the interior of the cartridge 54. For this purpose, the two piston parts 59, 60 are first released from the cartridge 54. After filling the starting components, the sterilizing piston 59 is first inserted, the contents briefly sterilized (for this purpose, the sterilizing piston 59 is permeable to ethylene dioxide) and then the sealing piston 60 with a flexible connecting line 62 connected thereto or vacuum line 62 inserted into the sterilization piston 59 and connected thereto via a detent. By inserting the sealing piston 60, the interior of the cartridge 54 is sealed to the outside gas-tight and pressure-tight up to the connection for the vacuum line 62 to the outside.

The vacuum line 62 is connected to a pump 68 which is open on one side at the base surfaces in some areas (in FIG. 4 Open below) hollow cylinder 70 is constructed, which is perpendicular to the base 53. The pump 68 also has a piston 72, which in an unlocked state (in FIG. 4 not shown) in the hollow cylinder 70 is axially movable and divides the interior of the hollow cylinder 70 in two gas-tight and pressure-tight parts. Via a connection 74, the vacuum line 62 opens into a pump chamber 76, which is closed to the outside gas and pressure-tight. Between the piston 72 and the upper deck base of the hollow cylinder 70 (in FIG. 4 Above) a tensioned compression spring 78 is arranged in the pump chamber 76, which presses the piston 72 in the direction of the base 53 facing the base surface of the hollow cylinder 70. The reason why the piston 72 does not move in the locked state due to the compression spring 78 is because the piston 72 is secured with a screw 80 manually operable from the outside. The screw 80 has for this purpose an external thread 82, which engages in an internal thread 83 in an axial tube piece of the piston 72 and thereby holds this in position. The screw 80 is gas- and pressure-tight and rotatably guided by the upper top surface of the hollow cylinder 70. By turning the screw 80 it can be released from the piston 72 and the pump 68 is triggered. The screw 80 thus serves as a manual control element for retrieving the energy from the compression spring 78, which serves as an energy store.

The pressure spring 78 accelerates the unlocked or released piston 72 in the direction of the pedestal 53. While the air escapes from the part of the interior of the hollow cylinder 70 facing the pedestal 53 through an opening 86, the pressure in the expanding pump chamber 76 decreases. As a result, gases are evacuated from the vacuum line 62 and through the vacuum line 62 from the interior of the cartridge 54. The piston 72 is pressed by the compression spring 78 as far as the stop on the base 53 facing the base surface of the hollow cylinder 70. In this case, an extension 84 is pressed on the base 53 facing the side of the piston 72 through the opening 86 and tilts there a rocker arm 87. By the movement and the position of the rocker arm 87 can be detected from the outside be that and whether the pump 68 has completed the pumping process. The increase in volume of the pumping space 76 by the pumping operation is sufficient to generate a sufficient vacuum in the interior of the cartridge 54. A vacuum may already be sufficient if the pressure in the interior of the cartridge 54 is reduced by at least 50%, but is preferably reduced by at least 90%.

After the interior of the cartridge 54 has been evacuated, the starting components filled therein can be mixed with the mixing device 56 by moving the mixing tube 58 with the handle 61. Subsequently, the sealing piston 60 is rotated against the sterilizing piston 59 and thus the gas passage closed by the sealing piston 60. The vacuum line 62 is withdrawn or removed from the sealing piston 60. The cartridge 54 is unscrewed from the base 53 and screwed into the internal thread, a dispensing tube (not shown), through which the mixed bone cement from the cartridge 54 can be applied. The dispensing piston 59, 60 assembled from the sterilizing piston 59 and the sealing piston 60 is unlatched and can be driven into the interior of the cartridge 54 with an application device, that is, with a conventional dispensing device (not shown). As a result, the contents of the cartridge 54, ie the bone cement mixed under reduced pressure, are squeezed out of the opposite opening and through the screwed-on dispensing tube.

The components of the vacuum mixing system can be manufactured by injection molding of a plastic except for the starting components of the bone cement. Preferably, however, there is also the compression spring 78 made of steel. The vacuum line 62 may be made of a different plastic. The vacuum line 62 must be flexible in order to be able to arrange the sealing piston 60 movably on the mixing tube 58.

The vacuum mixing system does not need to be connected to any external supply (electricity, water or compressed gas) to be fully functional. As a result, the vacuum mixing system interferes less than conventional vacuum mixing systems and can also be used mobile at any time. The energy required to generate the negative pressure or vacuum is stored in the tensioned compression spring 78 as energy storage, which can easily be triggered by operating the screw 80. As an alternative to the compression spring 78 could also be a tensioned tension spring or a tensioned Gas spring can be used. The structure with a compression spring 78 made of steel is simpler and less expensive and therefore preferred.

The features of the invention disclosed in the foregoing description, as well as the claims, figures and embodiments may be essential both individually and in any combination for the realization of the invention in its various embodiments.

LIST OF REFERENCE NUMBERS

1, 51

cartridge system

2

liquid container

3

footboard

4, 54

cartridge

6, 56

mixing blades

8, 58

mixing tube

9, 59

sterilization piston

10, 60

seal piston

11, 61

grip

12, 62

Connecting line / vacuum line

14

liquid line

16

siphon

18, 68

pump

20, 70

hollow cylinder

22, 72

piston

24, 74

Mouth / connection

26, 76

pump chamber

28, 78

feather

30, 80

Connecting element / screw

32, 82

external thread

33, 83

inner thread

34, 84

Extension / pin

36, 86

opening

40

glass ampoule

42

Head of glass ampoule

44

lever

46

cover

53

stand

87

rocker arm

90

threaded attachment

Claims (20)

Vacuum mixing system for mixing polymethyl methacrylate bone cement
at least one cartridge (4, 54) with an evacuatable interior for mixing the bone cement,
a pump (18, 68) for generating a negative pressure and
a connection line (12, 62) connecting the interior of the at least one cartridge (4, 54) to the pump (18, 68) for generating a negative pressure,
characterized in that
the vacuum mixing system has an integrated energy store (28, 78) for driving the pump (18, 68) connected to or connectable to the pump (18, 68) and storing energy for at least one pumping operation of the pump (18, 68) is, wherein in the pumping operation by a consumption of energy from the integrated energy storage (28, 78) with the pump (18, 68), a negative pressure can be generated, so that with the negative pressure through the connecting line (12, 62) gas from the interior the at least one cartridge (4, 54) is evacuated. Vacuum mixing system according to claim 1, characterized in that the pump (18, 68) has a gas-tight pumping chamber (26, 76) and in the pump (18, 68) a movable piston (22, 72) or a movable wall as a boundary of the pumping space (26, 76) is provided, wherein the piston (22, 72) or the wall with the energy of the integrated energy store (28, 78) in one direction, preferably unidirectionally driven, so that by the movement of the piston (22, 72) or the wall of the pump chamber (26, 76) is increased and with the thereby resulting in the pump chamber (26, 76) negative pressure of the interior of the at least one cartridge (4, 54) through the connecting line (12, 62) is evacuated. Vacuum mixing system according to claim 2, characterized in that the volume increase of the pump chamber (26, 76) is at least as large as the free volume of the interior of the cartridge (4, 54), preferably the Volume increase of the pump chamber (26, 76) is at least as large as the sum of the volume of the interior of the cartridge (4, 54), in which a first powdered component of the PMMA bone cement is contained, and the volume of the connecting line (12, 62) and the volume of a conduit (14) between the interior space and a liquid container (2) and the volume of a liquid to be mixed with the first component of the PMMA bone cement in the cartridge (4, 54) in the liquid container (2), the liquid is a second component of the PMMA bone cement. Vacuum mixing system according to one of the preceding claims, characterized in that
the vacuum mixing system comprises a mixing device (6, 56) for mixing the contents of the at least one cartridge (4, 54), wherein preferably the mixing device (6, 56) is arranged in the interior of the cartridge (4, 54) and manually or by a motor is drivable. Vacuum mixing system according to one of the preceding claims, characterized in that
the vacuum mixing system has less than 30 kg total weight, more preferably less than 10 kg total weight. Vacuum mixing system according to one of the preceding claims, characterized in that
the vacuum mixing system has a manually operable operating element (30, 80), by the operation of which the energy can be released from the energy store (28, 78), the pump (18, 68) being driven by the energy released and the driven pump (18, 68) evacuates the interior of the cartridge (4, 54). Vacuum mixing system according to one of the preceding claims, characterized in that
the energy store (28, 78) is a filled gas pressure cartridge, preferably a CO ₂ gas cartridge, or a cocked return element (28, 78) is preferred a tensioned spring (28, 78), more preferably a tensioned steel spring (28). Vacuum mixing system according to any of the preceding claims, characterized, in that
in the interior of the cartridge (4, 54), a movable discharge piston (9, 10, 59, 60) for discharging the mixed bone cement from the cartridge (4, 54) is arranged, wherein the discharge piston (9, 10, 59, 60) is preferably releasably locked or locked to prevent movement of the discharge piston (9, 10, 59, 60) under the action of negative pressure. Vacuum mixing system according to one of the preceding claims, characterized in that
the pump (18, 68) is to be driven by a tensioned restoring element (28, 78), in particular a tensioned spring element (28, 78), wherein preferably an expansion or contraction of the restoring element (28, 78), in particular of the spring element (28, 78) creates a negative pressure in the interior of the cartridge (4, 54) relative to the surrounding atmosphere. Vacuum mixing system according to one of the preceding claims, characterized in that
the cartridge (4, 54) is a cement cartridge (4, 54) filled with cement powder, and the vacuum mixing system has a container (2) separate from the cement cartridge (4, 54), in which a monomer liquid is contained, the container (2) by an openable partition (44) liquid impermeable to the interior of the cement cartridge (4, 54) is connected and the interior of the cement cartridge (4, 54) with the pump (18, 68) is connected in a gas-permeable manner or is connectable. Vacuum mixing system according to one of the preceding claims, characterized in that
the pump (18, 68) is constructed with
a hollow cylinder (20, 70), wherein the hollow cylinder (20, 70) is connected or connectable to the interior of the cartridge (4, 54),
a gas-tight closure at a hollow cylinder end,
a piston (22, 72) which is arranged gas-tight, axially movable in the hollow cylinder (20, 70),
at least one spring element (28, 78) as an integrated energy store (28, 78), which is arranged between the piston (22, 72) and the closure, a connecting element (30, 80) with the piston (22, 72) releasably is connected, which holds the piston (22, 72) in the hollow cylinder (20, 70) fixed position and the spring element (28, 78) tensioned or compressed holds, wherein the connecting element (30, 80) by a gas-tight passage from the hollow cylinder (20 , 70) and is detachable from the outside of the piston (22, 72),
wherein after dissolution of the connection of the connecting element (30, 80) by expansion of the spring element (28, 78) of the piston (22, 72) axially opposite to the closure is movable. Vacuum mixing system according to claim 11, characterized in that
in the storage state, the spring element (28, 78) is compressed and with the piston (22, 72) of the pump (18, 68) by the locked connection element (30, 80) is kept in the compressed state. Vacuum mixing system according to claim 11 or 12, characterized in that
after the expansion of the spring element (28, 78) within the hollow cylinder (20, 70) of the piston (22, 72) is shifted so that the volume of the hollow cylinder (20, 70), the closure and the piston (22, 72 ) formed pumping space (26, 76) is at least equal to the volume of the interior of the cartridge to be evacuated (4, 54). Vacuum mixing system according to one of claims 11 to 13, characterized in that
at the end of the hollow cylinder (20, 70) a limiting element is arranged, that the movement of the piston (22, 72) limited such that it can not escape from the hollow cylinder (20, 70). Vacuum mixing system according to one of claims 11 to 14, characterized in that
the piston (22, 72) on the side facing away from the closure comprises an optical marker (34, 87) which is visually recognizable on the outside of the vacuum mixing system when the maximum movement of the piston (22, 72) has taken place and thereby the position of the piston (22, 72) indicates its maximum movement. A method for mixing polymethyl methacrylate bone cement in an interior of a cartridge (4, 54) of a vacuum mixing system, in particular a vacuum mixing system according to one of the preceding claims, characterized in that
an energy stored in an energy storage device (28, 78) integrated in the vacuum mixing system is used to drive a pump (18, 68) of the vacuum mixing system, wherein the interior of the cartridge (4, 54) evacuates with the thus driven pump (18, 68) and in the interior of the cartridge (4, 54) a bone cement is mixed. A method according to claim 16, characterized in that
the volume of a pump chamber (26, 76) of the pump (18, 68) is increased by relaxing a return element (28, 78) as an integrated energy store (28, 78) and by the resulting negative pressure of the interior of the cartridge (4, 54) is evacuated. A method according to claim 16 or 17, characterized in that
a cement powder is contained in the interior of the cartridge (4, 54) and a gas is evacuated from the interior of the cartridge (4, 54) with the pump (18, 68), a monomer liquid into the interior of the cartridge (4, 54) is introduced and the monomer liquid with the cement powder in the evacuated interior of the cartridge (4, 54) is mixed. Method according to one of claims 16 to 18, characterized in that a connecting element (30, 80) of a piston (22, 72) of the pump (18, 68) is released,
then a compressed return element (28, 78) moves the piston (22, 72) axially in a hollow cylinder (20, 70) of the pump (18, 68), thereby creating a negative pressure relative to the surrounding atmosphere,
while gas from the interior of the cartridge (4, 54) is sucked into the hollow cylinder (20, 70) through a connecting line (12, 62),
then manually or motor-driven with a mixing device (6, 56) a cement powder is mixed with a monomer liquid,
then the cartridge (4, 54) is removed with the mixed cement dough and
by axial movement of a Austragskolbens (9, 10, 59, 60) of the cement dough from the cartridge (4, 54) is pressed. Method according to one of claims 16 to 19, characterized in that the cement powder in the cartridge (4, 54) is arranged,
the monomer liquid is arranged in a separate container (2) from the cartridge (4, 54), the monomer liquid being separated from the cement powder in the cartridge (4, 54) via a separating element (44),
the separating element (44) is opened before the connecting element (30, 80) is released from the piston (22, 72), so that a liquid-permeable connection between the interior of the cartridge (4, 54) and the container (2) is formed .
Thereafter, the compressed spring element (28, 78) moves the piston (22, 72) axially in the hollow cylinder (20, 70), whereby a negative pressure relative to the surrounding atmosphere is generated,
In this case, gas is sucked out of the interior of the cartridge (4, 54) into the hollow cylinder (20, 70) through the connecting line (12, 62) and monomer liquid into the cartridge (in the interior of the cartridge (4, 54)). 4, 54) is sucked.

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