Device for mixing and applying bone cement, and bone cement system

p0001The invention relates to an apparatus for mixing and discharging bone cement according to the features of the preamble of claim 1, comprising a mixing cylinder in which a mixing piston is arranged, wherein the mixing piston is axially movable by means of a sealed to a first end of the cylinder extending out actuating rod. Furthermore, the invention relates to a bone cement system having the features of patent claim 11.

p0002Polymethyl methacrylate (PMMA) -Knochenzemente go to the seminal work of Sir Charnley back (<nplcit id="ncit0001" npl-type="s"><text>Charnley, J .: Anchorage of the femoral head prosthesis of the shaft of the femur. J. Bone Joint Surg. 42 (1960) 28-30</text></nplcit>.). PMMA bone cements consist of a liquid monomer component and a powder component. The monomer component contains in general the monomer is methyl methacrylate and a dissolved activator (N, N-dimethyl-p-toluidine). The powder component, also referred to as bone cement powder, comprises one or more polymers which are based on methyl methacrylate and comonomers such as styrene, methyl acrylate or similar monomers through polymerization, preferably suspension polymerization, to a X-ray opacifiers and the initiator dibenzoyl peroxide. When mixing the powder component with the monomer is caused by swelling of the polymers of the powder component in a plastically deformable dough methyl methacrylate, the actual bone cement. When mixing the powder component with the monomer of the activator N, N-dimethyl-p-toluidine reacts with dibenzoyl peroxide to form radicals. The radicals thus formed initiate the radical polymerization of methyl methacrylate. With advancing polymerization of the methylmethacrylate increases the viscosity of the cement until it solidifies. Polymethylmethacrylate Knochenzemente in suitable Mischbechern using spatulas by mixing the Zementpulvers with the monomer liquid are mixed. A disadvantage of this procedure is that air inclusions in the formed cement paste may be present, which can disrupt the bone cement later. For this reason, the mixing of bone cement powder with the monomer liquid is preferably performed in vacuum mixing systems because air pockets are largely removed from the cement paste by mixing under vacuum and thus an optimal cement quality is achieved (<nplcit id="ncit0002" npl-type="s"><text>Breusch SJ et al .: The state of cementing in Germany, Z. Orthop. 1999, 137, 101-07</text></nplcit>). In vacuum mixed Knochenzemente have a significantly reduced porosity and thus show improved mechanical properties. There a variety of vacuum Zementiersystemen were disclosed, of which an example the following name:<patcit id="pcit0001" dnum="US6033105A"><text>US 6,033,105 A</text></patcit>. <patcit id="pcit0002" dnum="US5624184A"><text>US 5,624,184 A</text></patcit>. <patcit id="pcit0003" dnum="US4671263A"><text>US 4,671,263 A</text></patcit>. <patcit id="pcit0004" dnum="US4973168A"><text>US 4,973,168 A</text></patcit>. <patcit id="pcit0005" dnum="US5100241A"><text>US 5,100,241 A</text></patcit>. <patcit id="pcit0006" dnum="WO9967015A1"><text>WO 99/67015 Al</text></patcit>. <patcit id="pcit0007" dnum="EP1020167A2"><text>EP 1020167 A2</text></patcit>. <patcit id="pcit0008" dnum="US5586821A"><text>US 5,586,821 A</text></patcit>. <patcit id="pcit0009" dnum="EP1016452A2"><text>EP 1016452 A2</text></patcit>. <patcit id="pcit0010" dnum="DE3640279A1"><text>DE 36 40 279 A1</text></patcit>. <patcit id="pcit0011" dnum="WO9426403A1"><text>WO 94/26403 A1</text></patcit>. <patcit id="pcit0012" dnum="EP0692229A1"><text>EP 0692229 A1</text></patcit>. <patcit id="pcit0013" dnum="EP1005901A2"><text>EP 1005901 A2</text></patcit>. <patcit id="pcit0014" dnum="US5344232A"><text>US 5,344,232 A</text></patcit>, Also describes the<patcit id="pcit0015" dnum="EP1920738A2"><text>EP 1920738 A2</text></patcit> a vacuum cementing system, can be created by means of which bone cements.

p0003A further development Zementiersysteme represent, in which both the Zementpulver and the monomer liquid already in separate compartments of packed Mischsysteme are and immediately before Zementapplikation in cementing mixed together are (<patcit id="pcit0016" dnum="EP0692229A1"><text>EP 0692229 A1</text></patcit>). A major problem of these systems is the sterilization of the entire system, including the cement powder and monomer liquid previously sterile-filtered. A particular problem is the implementation of commonly used in bone cements ethylene oxide sterilization. This sterilization method has the advantage that the polymers contained in the cement powder are not degraded and remain the cement properties unaffected by ethylene oxide sterilization over sterilization with gamma rays. A problem with the sterilization with ethylene oxide, since the gaseous agent must penetrate first into the cartridge or to the cement reservoir and thus in the cement powder and after sterilization has to diffuse out of the cartridge. Unrestricted possible gas exchange between the inside of the cartridge and the reservoir and the area is therefore imperative. Contrariwise, the ready-mixed system must be sealed, that a mixing of the cement can be carried out under vacuum.

p0004In mixing systems on the market, this contradiction is solved in that on the cement cartridge, a cover is screwed with a porous disk that needs to be removed immediately prior to cement application. Instead of this lid a vacuum-tight cartridge head is screwed, which includes a mixer, a vacuum port and a port for the later-set-up dispensing. Therefore, the medical operator must open the cementing immediately before Zementanmischung and then reseal. This allows access to the previously disinfected bone cement powder etc. germs.

p0005It is the object of the present invention to provide an apparatus for mixing and discharging bone cement, in which the disadvantages mentioned are avoided, in particular contamination of the disinfected bone cement powder is prevented.

p0006To achieve this object an apparatus for mixing and discharging of bone cement having the features of claim 1 is proposed. It is also proposed to achieve this object, a bone cement system having the features of claim 10. In the dependent claims in each case preferred developments are carried out. Features and details, which are disclosed in connection with the device, are a matter of course also for the bone cement system according to the invention and vice versa.

p0007For the inventive device is provided that is arranged in the region of the first cylinder end an axially movable two-part piston system, the piston system comprises a sterilization plunger and a sealing plunger, the sterilization plunger and the seal piston on the actuating rod are separated axially movable, the sterilization plunger the mixing cylinder closes gas-permeable and the sealing plunger the mixing cylinder closes gas-tight.

p0008The sterilization plunger is arranged between the mixing piston and the piston seal on the actuator rod. By this arrangement, the two parts of the piston system is ensured that a sterilizing agent can flow into the mixing cylinder, without being obstructed by the sealing pistons thereto. Only after the sealing piston is applied to the sterilization piston, thus combining the two-piece piston system.

p0009The core of the invention described herein is to close one end of the mixing cylinder with a two-part piston system. The two parts of the piston system can be moved independently on the actuating rod axially. The sterilization plunger seals the mixing cylinder gas permeable. Thus, a sterilizing agent is introduced into the mixing cylinder and sterilize the bone cement powder stored there. The sealing piston of the piston system then allows a gas-tight closure of the mixing cylinder in order to connect it to a vacuum and suck a binder for the bone cement powder into the mixing piston. Preferably, the two-piece piston system is characterized in that the sterilization piston the mixing cylinder gas permeable closes to allow a purging a bone cement powder with a sterilizing agent and the sealing plunger the mixing cylinder gas-tight manner, to allow flushing of the bone cement powder with a binder, in particular a monomer.

p0010The peculiarity is that on one hand the highest possible gas-permeable surface in cement mixing system is available so that ethylene oxide can flow for sterilization and after sterilization may leak again and that on the other hand, a vacuum-tight seal in place for a vacuum mixing of bone cement in the sealed cartridge is possible. The piston system can simultaneously be used as a piston for ejecting the mixed cement from the cartridge. The two-piece piston system thus fulfills three advantages: First, it is possible to disinfect through a seal of the mixing cylinder by the sterilization piston bone cement powder with a gaseous fluid. Following the sealing piston is used to seal the sterilization plunger. This mixing of the bone cement powder with a binder, in particular a monomer, un is ter vacuum possible. Subsequently, the piston system is formed from sealing piston and sterilization piston is used to be inserted into the mixing cylinder, and thereby squeeze out the bone cement therefrom.

p0011In the invention, the sealing piston to complete the mixing cylinder gas-tight. This should be made clear that the sealing plunger seals the mixing cylinder against the pressures occurring during mixing and known to the expert. The water introduced into the mixing cylinder by a vacuum pump vacuum should not be weakened significantly by any leakage of the sealing piston relative to the mixing cylinder. In the present invention, the term "gas-permeable" clarify that a gaseous sterilization fluid can flow through the sterilization plunger into the mixing cylinder. Preferably, the sterilization piston has a gas-permeable grid, the particles which are smaller than 5 microns to pass through. Larger particles should not be left out of the gas-permeable sterilization plunger into the interior of the mixing cylinder.

p0012An advantageous embodiment of the device according to the invention is characterized in that the two-piece piston system encloses the operating rod. It has proven to be particularly advantageous if the piston system and / or the sterilization plunger and / or the sealing plunger are configured cylindrically. Due to the arrangement of the piston system to the operating rod a simple and reversible displacement of the sealing piston on the piston to sterilization and by this way is possible. In a sterilization position of the sterilization piston is located in the mixing cylinder during the sealing piston is arranged, for example, outside of the mixing cylinder, but on the operating rod. This ensures that a sterilizing agent can flow unhindered into the interior of the mixing cylinder. In a mixed situation of the sealing piston is then applied to the sterilization piston so that the piston system is arranged together. Through the sealing piston is prevented that the pressure prevailing in the interior of the mixing cylinder vacuum can be weakened.

p0013In order to produce a frictional and / or positive connection between the sealing piston and the piston sterilization, it has been found to be preferable if the seal piston is attachable to the sterilization piston. Both pistons of the piston system can grout over corresponding clip connections, so that the sterilization plunger is pushed onto the piston seal. This clip connection can be reversibly detachably configured to enable a multiple of application of the sterilization piston.

p0014A special feature of the device according to the invention is that in a sealing piston and a sterilization plunger not only the bone cement powder can be disinfected easily and without the risk of contamination due to the division of the piston system, but also discharging the finished bone cement with the two-part piston system is possible. Thus, it has proved to be advantageous when the plunger system in the mixing cylinder is axially depressible to select one of the bone cement powder and the binder, in particular the monomer mixed bone cement to discharge through a discharge. The discharge is situated on a second cylinder end of the mixing cylinder. The second cylinder end opposite the first end of the cylinder. When discharging the piston system is pushed out toward the first cylinder end toward the second end of the cylinder and pressed while the ready mixed bone cement out through the discharge port. In an advantageous embodiment, the discharge opening, a connection means, in particular a connecting thread, on. This connecting thread can be used, urn screw the mixing cylinder in the yet to be described bone cement system and / or to join the mixing cylinder to a tubing system through which the finished bone cement can be introduced into the bone. For this activity, a caulking gun can be used, in which the mixing cylinder is clamped. For ease of use of the injection gun, the operating rod may have a predetermined breaking point, so that a breaking of the actuator rod is possible at a defined location. For dispensing of ready-mixed bone cement, the operating rod is pulled in the direction of the piston system until the mixing plunger abuts the piston system. By then takes place separating the operating rod the piston system can be pressed with the front adjacent mixing plunger into the mixing cylinder.

p0015In order to fill the bone cement powder in the interior of the mixing cylinder, it has proven to be advantageous if the sterilization piston has a closable, in particular reversibly closable opening. By means of this filling opening is a light introduction of the bone cement powder in the mixing cylinder are possible without that the plunger system must be removed from the mixing cylinder. Thereby, a reduction of the complexity is achieved for filling the apparatus of the invention.

p0016Furthermore, it has been found to be advantageous if the sterilization piston and / or the sealing piston has at least one guide means which serves to support opposite the actuating rod. Through the guide means prevents one of said pistons of the piston system is tilted in the mixing cylinder. This canting could occur in particular when the sealing piston is moved along the actuating rod to be applied to the sterilization plunger. It is furthermore advantageous when the piston system and / or sterilization of the piston and / or the piston seal have at least one sealing means in order to achieve a sealing with respect to the mixing cylinder. The sealing piston is to achieve a gas tight seal of the mixing cylinder. In addition, it is envisaged that the sterilization piston can flow only particles less than 5 microns in the mixing cylinder. To meet this requirement, it has proved to be advantageous if sealing means comprises an outer surface that is in contact with the mixing cylinder via a sealing agent. This sealing means can be for example a rubber seal, which prevents ambient air flows into the interior of the mixing cylinder provided with a vacuum.

p0017A further advantageous embodiment of the device according to the invention is characterized in that the piston system and / or the sterilization plunger and / or the sealing piston has at least one vacuum port. Via this vacuum connection the device can be connected to a vacuum pump. The vacuum pump generates those negative pressure that shall prevail in the mixing cylinder. As will be described in detail, the vacuum for an influx of the binder, in particular the monomer, into the bone cement powder makes. The arrangement of the vacuum port in the piston system has been found to be particularly advantageous due to the easy accessibility.

p0018The above object is also solved by a bone cement system having a device for mixing and discharging bone cement, a storage element for a binder, in particular a monomer and a base member wherein the base member apparatus and the storage element superimposed on, the device comprising a mixing cylinder, in which a mixing piston is arranged, wherein the mixing piston is by means of a sealed to a first end of the cylinder extending out actuating rod movable axially, an axially movable two-piece piston system is arranged in the region of the first cylinder end, the piston system including a sterilization piston and a sealing piston, a sterilization piston and the sealing piston separated axially on the actuating rod can be moved, the sterilization plunger the mixing cylinder gas permeable closes and the sealing plunger seals the mixing cylinder gas-tight. Features and details that have been here described in connection with the device, also apply in connection with the bone cement system and vice versa, because the bone cement system includes the device according to the invention in two parts designed piston system. In this case, the piston system is characterized such that the sterilization piston the mixing cylinder gas permeable closes to allow a purging a bone cement powder with a sterilizing agent and the sealing piston the mixing cylinder gas-tight manner to enable a flushing of the bone cement powder with a binder, in particular a monomer.

p0019An advantageous embodiment of the bone cement system of the invention is characterized in that the base member comprises a coupling means for a non-positive and / or positive connection with the device, in particular a discharge opening of the apparatus. The base member serves as a bearing for both the inventive apparatus, as well as the storage element for the binder. As a kind of foundation of the bone cement system, the inventive device and the storage element can at and / or on the base member be arranged. Since the device according to the invention will also be used for discharging the bone cement, it is advantageous when the device is reversibly separable from the base member. This can be achieved by the coupling element according to the invention. Advantageously, it is at the coupling element is a thread onto which the discharge opening of the device can be screwed. Thus, a secure connection between the base member and the apparatus is ensured.

p0020Furthermore, it is advantageous if the storage element has a storage container for the binder, in particular the monomer superimposed. For the preparation of the bone cement must the binder, particularly of the monomer can be introduced into the bone cement powder. After a certain period of time, the bone cement hardens then. Obviously, the bone cement can not therefore be austragsfertig delivered in the device. It is thus necessary that the bone cement powder and the binder, in particular the monomer to shall be stored separately shortly before the discharge of the bone cement. Thus, it makes sense, if the storage element a reservoir for the binder, in particular the monomer having. disinfected as easily especially glass containers have been found to be, used as a storage container for the binder, in particular the monomer. To control a flow of the monomer, the storage element may comprise a valve means. This valve means controls and / or triggers the flow of the monomer out of the reservoir in the inventive device from.

p0021Thus, the binder, in particular monomer, may flow from the storage element in the device, the base member to a conduit means. In this line means it can be in particular a capillary. The binder, in particular the monomer flows from the reservoir through the valve means and the conduit means in the device, in particular in the mixing cylinder. There is a mixing of the binder, particularly of the monomer, the bone cement powder instead to form the bone cement.

p0022Further details and advantages of the invention result from the claims, the following description and the drawings. In the drawings the invention is shown in one embodiment. Show it:<dl id="dl0001" compact="compact"><dt>Fig. 1</dt><dd>is a schematic sectional drawing of a bone cement system of the invention,</dd><dt>FIG. 2</dt><dd>an inventive piston system in a sterilizing position and</dd><dt>Fig. 3</dt><dd>the piston system of the invention in a mixing position.</dd></dl>

p0023In <figref idrefs="f0001">figure 1</figref> 100 is shown an inventive bone cement system. The bone cement system 100 comprises an apparatus for mixing and discharging of bone cement. This device 10 is mounted in the illustrated embodiment, on a base member 120. That basic element 120 also carries a storage element 110 for a binder, in particular a monomer. The bone cement system 100 is used for mixing the bone cement. For this purpose, bone cement powder is poured into a mixing cylinder 20 of the device 10th That bone cement powder may then be mixed with the binder, especially a monomer to form bone cement. Below reference will be made only to the use of monomer, but this should not be taken as a limitation. With known bone cement systems, it has proven to be disadvantageous that the disinfected bone cement systems occur shortly before the merging of the monomer and the bone cement powder again with the environment in contact and thereby impurities, in particular germs can enter the bone cement powder. This disadvantage is overcome by the device 10 and the presently disclosed bone cement system 100 according to the invention.

p0024The device 10 for mixing and dispensing bone cement includes a mixing cylinder 20th In the mixing cylinder 20 is an actuator rod 50 is arranged which can be moved by a handle 52 axially. As shown, the operating rod 50 at one end a mixing piston 21 which can be used for mixing the bone cement powder and monomer. At a first end of the cylinder 30 a piston system 40 is located. By the piston system 40, the operating rod 50 is led out sealed. The special feature of the device 10 according to the invention is that the piston system 40 is axially movable and is constructed in two parts. The piston system 40 includes a sterilization piston 41 and a piston seal 42nd

p0025The <figref idrefs="f0002">figures 2</figref> and <figref idrefs="f0003">3</figref> serve to illustrate the use of the two-part piston system 40th Before delivery of the bone cement system 100 of the mixing cylinder 20 of the device 10 is filled by the manufacturer with bone cement powder. Following the gas-permeable sterilization plunger is inserted 41 into the mixing cylinder 20th The thus resulting sterilization position 150 is in<figref idrefs="f0002">figure 2</figref> shown. The sealing piston 42 is not inserted in the sterilization position 150 in the mixing cylinder 20, but moved to the operating rod 50 in the direction of the handle 52nd In the sterilization position 150, the manufacturer is bone cement, the device 10 and the bone cement system 100 sterilize with a fluid. Preferably, ethylene oxide is used for the sterilization. The ethylene oxide can flow through the gas-permeable sterilization plunger into the mixing cylinder and the bone cement powder rinse. The sterilization piston 41 has a mesh-like structure 66th This mesh-like structure 66 permits inflow of sterilizing gas into the mixing cylinder 20. Advantageously, the mesh-like structure 66, only a flow of particles less than 5 microns. This prevents that impurities may flow into the bone cement powder. After sterilization of the bone cement system and / or the device, this is packaged in general, and sent to the medical user. In the context of an operation of the medical operator that the bone cement system 100 and / or the device may then remove 10 of the package. For mixing the bone cement powder with the monomer, the apparatus 10 is transferred from the sterilizing position 150 in a mixing position 155 in<figref idrefs="f0003">figure 3</figref> is shown. As part of the mixing position 155 is the second part of the piston system 40 - the sealing piston 42 - axially displaced in the direction of the mixing cylinder 40 on the actuating rod 50th The sealing piston 42 can be plugged onto the sterilization plunger. For this purpose, both pistons can have corresponding means 41,42 in order to achieve a non-positive and / or positive connection. Following the transfer of the piston system 40 in the mixing position 155 the device 10 is connected to a vacuum system. For this purpose, the piston system 40 includes a vacuum port 68. This vacuum port 68 is disposed in the sealing piston 42nd Since the sterilization piston 41 is gas-permeable, this requires no vacuum port. The vacuum connection 68 is used to achieve a vacuum in the interior of the mixing cylinder 20th

p0026As the <figref idrefs="f0001">figure 1</figref> illustrates part of the bone cement system and the storage element 110. The storage element 110 stores a reservoir 112 for the monomer. Via a valve means 115, a discharge of the monomer from the storage tank 112 is controlled and / or triggered. Advantageously, it is in the reservoir 112 to a glass container which is opened by the valve means 115 in the head region. The monomer then flows through a conduit means 122 from the reservoir 112 into the mixing cylinder 20. The overflow of the monomer is enhanced by that in the mixing cylinder 20 is under vacuum. By means of the actuation rod and the mixing plunger 21, a lightweight and simple mixing of the bone cement powder and monomer is then possible. After finished mixing the apparatus 10 can be unscrewed from the base element 120th For this purpose, the base member 120, a coupling means 121, which cooperates with a connecting means 22 of the mixing piston. After separation of the device 10 from the base member 120, the operating rod 50 is axially displaced such that the mixing piston 21 comes to lie on the piston system 40th Then allows the actuator rod bend at the predetermined breaking point 51st The device 10 can be now integrated into a cementing gun. Pressing the cementing gun a rack with plate in direction of the piston system 40 is moved. Advantageously, the piston system 40 is not only to be used for the sterilization and mixing of the bone cement, but can also be used for discharging the bone cement. For this purpose, the piston system 40 is arranged axially movable. For this, the piston system 40 is axially engageable into the mixing cylinder 20th Thus it is achieved that the mixed bone cement powder and the monomer bone cement can be discharged through a discharge 23rd

p0027Both the sterilization piston 41 and the seal piston 42 of the piston system 40 according to the invention comprise sealing means 65th These prevent environmental influences can flow into the interior of the mixing cylinder. Moreover, the two pistons 41,42 of the piston system 40 guide means 67 which serve to support opposite the actuating rod 50th Thus, tilting of the two pistons 41,42 is prevented. Thus 41 must not be removed from the mixing cylinder 20 when filling the device 10 with the bone cement powder sterilization flask sterilization piston 41 can have a filling 69th By this particular reversibly closable filling the bone cement powder may be filled into the interior of the mixing cylinder 20th

numeral

p0028<dl id="dl0002" compact="compact"><dt>10</dt><dd>device</dd></dl><dl id="dl0003" compact="compact"><dt>20</dt><dd>mixing cylinder</dd><dt>21</dt><dd>mixing piston</dd><dt>22</dt><dd>connection means</dd><dt>23</dt><dd>discharge</dd></dl><dl id="dl0004" compact="compact"><dt>30</dt><dd>first cylinder end</dd><dt>35</dt><dd>second cylinder end</dd></dl><dl id="dl0005" compact="compact"><dt>40</dt><dd>piston system</dd><dt>41</dt><dd>sterilization piston</dd><dt>42</dt><dd>seal piston</dd></dl><dl id="dl0006" compact="compact"><dt>50</dt><dd>actuating rod</dd><dt>51</dt><dd>Predetermined breaking point</dd><dt>52</dt><dd>handle</dd></dl><dl id="dl0007" compact="compact"><dt>62</dt><dd>guide means</dd><dt>65</dt><dd>sealant</dd><dt>66</dt><dd>mesh-like structure</dd><dt>67</dt><dd>guide means</dd><dt>68</dt><dd>vacuum connection</dd><dt>69</dt><dd>filling</dd></dl><dl id="dl0008" compact="compact"><dt>100</dt><dd>Bone cement system</dd></dl><dl id="dl0009" compact="compact"><dt>110</dt><dd>stock item</dd><dt>112</dt><dd>reservoir</dd><dt>115</dt><dd>valve means</dd></dl><dl id="dl0010" compact="compact"><dt>120</dt><dd>basic element</dd><dt>121</dt><dd>coupling means</dd><dt>122</dt><dd>conduit means</dd></dl><dl id="dl0011" compact="compact"><dt>150</dt><dd>sterilization position</dd><dt>155</dt><dd>mixing position</dd></dl>