Apparatus for pressing out bone cement, use and system

Abstract

To provide an apparatus for pressing out bone cement from a cartridge, a use of the apparatus, and a system for pressing out bone cement.SOLUTION: An apparatus (10) for pressing out bone cement from a cartridge comprises a threaded rod (20) with an external thread (22), a handle (24) for rotating the threaded rod (20), and an adapter unit for mechanically connecting to a cartridge for bone cement. The adapter unit (26) has a passage (27) with an internal thread (28) for the threaded rod (20). An outer surface of a thread turn of the external thread (22) is 370 mm2 or less. This particularly facilitates pressing out highly viscous bone cement.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a device for extruding bone cement from a cartridge, the use of said device, and a system for extruding bone cement. Summary of the Invention [Problem to be solved by the invention]

[0002] Bone cements are usually produced by mixing a powder with a liquid. For example, polymethyl methacrylate (PMMA) bone cements are known, which are composed of a liquid monomer component and a powder component. The monomer component generally contains the monomer methyl methacrylate and in particular an activator dissolved therein, for example N,N-dimethyl-p-toluidine. The powder component, also called bone cement powder, has one or more polymers produced by polymerization, preferably suspension polymerization, based on methyl methacrylate and comonomers such as styrene, methyl acrylate or similar monomers, and in particular a radiopaque agent and / or a dibenzoyl peroxide initiator. When the powder component is mixed with the monomer component, for example the polymers of the powder component expanding in the methyl methacrylate produce a plastically deformable paste, the actual bone cement (also called bone cement paste). When the powder component is mixed with the monomer component, an activator, for example N,N-dimethyl-p-toluidine, reacts with the dibenzoyl peroxide to form radicals. The radicals formed are capable of initiating the radical polymerization of methyl methacrylate. As the polymerization of the methyl methacrylate progresses, the viscosity of the cement may continue to increase until the cement hardens.

[0003] PMMA bone cement is mainly used to permanently fix articular endoprostheses to bone. Typically, cement amounts of 50g to 125g or more are used to fix articular endoprostheses. Bone cement is needed during the patient's surgery and should be provided quickly. This is the main application field of the present invention.

[0004] Polymethylmethacrylate bone cement can be mixed by mixing the cement powder with the monomer liquid using a spatula in a suitable mixing beaker. During the process, air bubbles can become entrapped in the bone cement, which can adversely affect the mechanical properties of the hardened bone cement. Other drawbacks are the need to manually measure quantities and proper mixing is not always guaranteed.

[0005] Vacuum cementing systems are known to prevent the incorporation of air into the bone cement, for example US6033105A, US5624184A, US4671263A, US4973168A, US5100241A, WO99 / 67015A1, EP1020167A2, US5586821A, EP1016452A2, DE3640279A1, WO94 / 26403A1, EP1005901A2, EP1886647A1, US5344232A. A further development in cementing technology is represented by cementing systems, in which both the cement powder and the monomer liquid are already packaged in separate compartments and are mixed together immediately before the application of the cement in the cementing system. Such closed complete prepackaged mixing systems or similar systems are described, inter alia, in the documents EP 0380867 B1, EP 0796653 B1, EP 0692229 A1, DE 102009031178 B3, US 5997544 A, US 6709149 B1, WO 00 / 35506 A1 and EP 0796653 A2.

[0006] Mixing devices in which an external device for extruding the bone cement is used are disclosed in WO9416951A1, EP1741413B1, EP3054880B1 and DE19718648A1. Mixing devices or similar systems in which a vacuum is applied to allow the transfer or mixing of the components or bone cement are known from US8662736B2 and EP3093067B1. EP2393456B1 describes a mixing device in which a liquid is forced into a powder by overpressure means.

[0007] Manually operated ejection devices are based, for example, on a hand-actuated lever system that drives a push rod or a toothed bar connected to the cement cartridge. By repeatedly tilting the lever, the push rod or toothed bar is moved towards the ejection piston of the cartridge, which in turn moves towards the cartridge head, thereby pushing the polymethylmethacrylate bone cement out of the cartridge through an ejection tube attached to its front face. Such or similar ejection devices are disclosed in US589344A, US5638997A and WO9416951A.

[0008] Screw systems are generally used to extract small amounts of bone cement, up to approximately 10 g, and are used to stabilize fractured vertebral bodies. These screw systems known to date have low mechanical load-bearing capacity and are not suitable for the evacuation of large amounts of PMMA bone cement, at least 50 g. Examples of such evacuation devices or similar devices are the publications US6676663B2, US2012224452A1, CN218220290U, and CN213190021U.

[0009] The object of the present invention is to enable a particularly easy manual ejection of large amounts of bone cement, in particular to create a particularly simple and cost-effective device which overcomes at least some of the drawbacks of the prior art.

[0010] This object is achieved by an apparatus for mixing bone cement according to claim 1 and by the uses and systems according to the independent claims. Advantageous embodiments are defined in the dependent claims.

[0011] This object is achieved by a device for extruding bone cement, comprising a threaded rod with an external thread, a handle for rotating the threaded rod and an adapter unit for mechanically connecting to a cartridge for bone cement. The adapter unit has a passage with an internal thread for the threaded rod. In one embodiment, the outer surface of the thread of the external thread is at most 370 mm. 2 It is.

[0012] It has been found that the external surface has a strong influence on the friction losses when the threaded rod is rotated in the adapter unit and therefore on the force required to eject the bone cement. The external surface is a measure of the surface area of ​​the male thread that is in contact with the female thread. The resulting friction is therefore proportional to the external surface. Tests have shown that it is irrelevant whether the reduction of the external surface is achieved by reducing the thread depth, increasing the flank angle, reducing the diameter of the threaded rod, reducing the pitch or other measures, or by a combination of different measures. Only the absolute value of the external surface is important.

[0013] Bone cement is usually highly viscous. For this reason, particularly large forces are often required to extrude the bone cement. For example, a driving force of up to 2 kN may be required to extrude 130 g of highly viscous PMMA bone cement from a cement cartridge, which corresponds to a weight of almost 200 kg. It is therefore necessary to reduce friction so that the bone cement can be extruded with less manual force. In this way, even people with weak strength can easily operate the device. This is particularly important since the mixed bone cement continues to solidify over time and therefore the force required to extrude increases over time. Tests have shown that the above-mentioned maximum outer surface of the thread of the male screw thread allows any user to easily eject the bone cement by manually rotating the handle. If the outer surface were larger, the ejection would be very difficult due to static and sliding friction, making it difficult to handle.

[0014] The device can be made from plastic or metal filled plastic materials. Does not require complex mechanisms such as those found in cement guns. No levers, bolts, pins, clamps, locking elements, toothed bars and / or gears are required. The force required to extrude the bone cement is less than that required with conventional devices such as cement guns.

[0015] The device according to the invention is easy to handle since it does not require complicated manipulation of the gun: dispensing is effected simply by rotating the handle.

[0016] By thread turn is meant the helical line of the thread over a distance corresponding to a complete relative rotation of 360°. That is to say, one revolution is taken into account. The outer surface is the area of ​​the male thread that can come into contact with the corresponding female thread. The outer surface of a thread turn is composed, for example, of a surface of a first (e.g. ascending) thread flank, a surface of a second (e.g. descending) thread flank, a surface in the region of the peak of the thread, which may run parallel to the longitudinal axis and / or be located between the thread flanks, and a further surface in the region of the valley or trough of the thread, which may be located between the two thread flanks. These four surfaces are added up over one revolution. In other words, the surface area between two adjacent peaks or troughs of the thread is taken into account. The radius or transition between the individual surfaces is also part of the outer surface. The respective characteristic values ​​for the male thread of the threaded rod can be applied correspondingly to the female thread of the adapter unit.

[0017] For example, in the case of a trapezoidal thread, the outer surface corresponds to the surfaces of the two thread flanks, the outwardly facing surface therebetween in the region of the thread peak, which defines the major diameter of the male thread, and the outwardly facing surface in the region of the thread root, which defines the minor diameter of the male thread.

[0018] In the case of multiple start threads, the surface areas of all thread turns are added together over one revolution.

[0019] The threaded rod is designed to be rotated by manual rotation of the handle. In particular, for this purpose, the handle is connected to the threaded rod for coupled rotation. The female thread interacts with the male thread of the threaded rod so that the threaded rod can rotate relative to the female thread. The female thread and the male thread correspond. Due to the interaction of the threaded rod with the adapter unit, the rotation of the threaded rod causes an axial translational relative movement between the threaded rod and the adapter unit. The extension direction of the threaded rod defines the axial direction of the device. The threaded rod is preferably guided through a passage so that the female thread engages with the male thread. However, the threaded rod and the adapter unit may also be available separately, so that the user must first screw the threaded rod into the adapter unit before using it as intended.

[0020] The adapter unit is designed to be mechanically attached to a cartridge containing bone cement. In particular, a connection for coupled rotation is provided at least in the direction of rotation of the threaded rod, so that rotation of the threaded rod does not damage or loosen the attachment of the adapter unit to the cartridge. Typically, the adapter unit includes one or more first fastening means and the cartridge comprises one or more second fastening means, the two fastening means being adapted to interact and thus establish a mechanical fastening. For example, the cartridge may have an external thread and the adapter unit may have a corresponding internal thread. The passage of the adapter unit is in particular centrally located.

[0021] When the adapter unit is attached to the cartridge, axial movement of the threaded rod relative to the adapter unit, and thus relative to the cartridge, causes the end of the threaded rod remote from the handle to penetrate into the cartridge, thereby forcing the bone cement out of the cartridge, such that the bone cement can be forced out of the end of the cartridge opposite the adapter unit.

[0022] In particular, the device comprises, at the end of the threaded rod remote from the handle, a pressure element for applying pressure to the bone cement in the cartridge. This pressure can be applied directly or indirectly. For example, the pressure element can press directly against the bone cement or it can press against another element, such as a piston of the cartridge, which in turn presses against the bone cement.

[0023] In one embodiment, the outer surface of the thread turn of the male thread is at least 230 mm 2 It is.

[0024] The lower limit of the outer surface ensures that the mechanical stability of the threaded rod is maintained: for example, if the outer surface is too small, the thread depth or the diameter of the threaded rod may be too small, which may result in shearing of the male thread and / or twisting or buckling of the threaded rod.

[0025] The pitch of the male thread also influences the force required for ejection. The pitch of the male thread is the distance, measured axially, covered in one revolution. In general, if the pitch is too short, the rotation ratio will be too high, and therefore the effort during use will increase, since more revolutions must be made to eject the bone cement. This may result in too much time being required, which is undesirable, especially during surgery and / or when the bone cement is gradually hardening. In general, if the pitch is too long, the rotation ratio will be low, and therefore the force to eject the bone cement will be too high. In addition, if the pitch is too steep, the self-locking function may be reduced or eliminated, which in turn unnecessarily complicates the operation. The specific values ​​of these effects depend on different conditions, such as the materials used and the properties of the respective surfaces.

[0026] In one embodiment, the pitch of the male thread is at least 1 mm and / or at most 7 mm. This has proven to be particularly effective in tests. In particular, the pitch is at least 2 mm, preferably at least 3 mm, particularly preferably at least 4 mm and / or at most 5 mm, preferably at most 5 mm. In one embodiment, the pitch is approximately or exactly 4.5 mm.

[0027] In one embodiment, the external diameter of the male thread of the threaded rod is at least 12 mm and / or at most 17 mm. By external diameter is meant the maximum diameter measured between the two highest peaks of the thread, i.e. the diameter of an imaginary circular cylinder surrounding the male thread.

[0028] In particular, the outer diameter is at least 13.5 mm and / or at most 15 mm. In one embodiment, the outer diameter is approximately or exactly 14 mm. An outer diameter less than 12 mm is not suitable to withstand the forces or moments that occur. If the outer diameter is too large, the friction increases and therefore the force required for ejection increases.

[0029] In one embodiment, the female thread of the adapter unit comprises at least 2 and / or at most 7 thread turns. This means that the above mentioned number of turns are required to fully screw the threaded rod into the female thread. In general, too few threads in the adapter unit results in less retention, less strength and / or more load on each individual thread turn. In general, too many thread turns results in increased friction and therefore more force required to eject the bone cement. The mentioned figures have proven to be particularly useful.

[0030] In particular, the female thread comprises at least 3 thread turns, preferably at least or exactly 4 thread turns and / or at most 6 thread turns, preferably at most 5 thread turns, which has proven to be an optimum condition for the abovementioned effects.

[0031] In one embodiment, the thread of the threaded rod is a trapezoidal thread, which has proven to be particularly suitable.

[0032] In one embodiment, the external thread of the threaded rod has a thread depth of at least 1 mm and / or at most 4 mm. In principle, a thread depth that is too shallow reduces the strength of the thread and / or increases the mechanical stress. In general, a thread depth that is too deep increases friction and therefore the force required to eject the bone cement. The mentioned numerical values ​​have proven to be particularly useful.

[0033] In particular, the depth of the thread is less than or equal to 2 mm and / or approximately or exactly 1.5 mm, which has proven to be optimal with regard to the effects mentioned.

[0034] In one embodiment, to apply pressure to the bone cement in the cartridge, the device has a pressure element at the end of the threaded rod remote from the handle, in particular the pressure element has a flat surface.

[0035] The pressure element can be designed to apply pressure directly or indirectly, as described above. For example, the pressure element can be designed as a plate. In one embodiment, the pressure element is connected to the threaded rod for coupled rotation. For example, the pressure element can be screwed onto the threaded rod, welded to it, or connected to the threaded rod by a bayonet connection.

[0036] The pressure element may be made entirely or partly of metal or plastic material, for example of fibreglass reinforced plastic material and / or polyamide.

[0037] In one embodiment, the pressure element is composed of two parts: a first part of the pressure element is connected to the threaded rod for coupled rotation, and a second part of the pressure element is connected to the first part for rotation about the longitudinal axis of the threaded rod.

[0038] The second part is used to apply pressure to the bone cement or part of the cartridge. The first part serves to connect the second part to the threaded rod and / or to transmit the compressive force of the threaded rod to the second part. To ensure a particularly smooth relative rotation between the first and second parts, a lubricant such as silicone may be provided between the first part of the pressure element. In one embodiment, the second part at least partially or circumferentially surrounds the first part. In other words, the second part engages behind the first part. This ensures that the first and second parts do not separate from each other. This prevents axial movement of the second part away from the first part and thus loss of the second part.

[0039] In particular, the surface of the second part facing the first part and / or the surface of the first part facing the second part are flat and / or smooth. This allows a particularly smooth relative rotation. In particular, the surface of the second part facing the first part and / or the surface facing the second part are made of metal.

[0040] In one embodiment, the adapter unit has a recess. In particular, the recess is arranged axially between a connection element or connection area of ​​the adapter unit for mechanically connecting to the cartridge of the adapter unit and / or an internal thread or passage. The recess is designed to at least substantially accommodate the pressure element.

[0041] In particular, the recess is circular in shape and / or is centrally located when viewed along the longitudinal axis of the threaded rod. In particular, the recess is circular-cylindrical in shape. The recess serves to accommodate the pressure element. This means that the pressure element does not protrude beyond the recess or not significantly in the direction of the connection element. This ensures that, for example, the connection area of ​​the cartridge remains free, in which the adapter unit can be plugged into the cartridge. The recess can have, for example, an axial extension of at least 3 mm, preferably 4 mm, and / or at most 10 mm, in particular at most 7 mm, preferably at most 5 mm. The axial extension of the recess may approximately or exactly correspond to the axial extension of the pressure element. The pressure element can be completely accommodated in the recess.

[0042] In one embodiment, the threaded rod comprises an inner rod, for example a metallic rod, and / or a casing, for example a plastic casing.

[0043] The inner rod results in a mechanically stable threaded rod. In particular, the rod is not rotationally symmetric. This ensures a reliable connection between the material of the rod, e.g. metal, and the material of the casing, e.g. plastic material. For example, the rod can be hexagonal or square. In particular, a metal rod is used that has or is made of stainless steel, such as 316L.

[0044] In particular, the rod is completely coated with plastic material. In particular, the thread is made of plastic material. This provides a particularly smooth thread. The rod is protected from external influences.

[0045] In one embodiment, the metallic rod has a diameter of at least 7 mm and / or at most 10 mm, preferably about or exactly 8 mm. Too small a diameter can lead to twisting and / or buckling of the threaded rod under full load. Too large a diameter increases the diameter of the threaded rod and therefore increases friction.

[0046] In one embodiment, the adapter unit is designed to be connected to the cartridge by a bayonet connection, in particular the direction of rotation of the adapter unit for connecting it to the cartridge corresponds to the direction of rotation for screwing the threaded rod into the adapter unit.

[0047] The adapter unit is therefore provided with a connection element for forming a bayonet connection with the cartridge, which in turn is provided with a corresponding connection element, which allows for a simple and secure connection, which also allows for interaction with existing cartridges.

[0048] The direction of rotation to screw the threaded rod into the adapter unit is the direction in which the handle, and therefore the threaded rod, is rotated to force the bone cement out of the cartridge. During this rotation, the connection is pushed towards the connected position. This prevents the connection from loosening or becoming loose due to rotation.

[0049] In one embodiment, the threaded rod has a length of at least 15 cm and / or at most 23 cm. In one embodiment, the adapter unit has a connection area for plugging into the cartridge. In one embodiment, the connection area has an inner diameter of at least 3.3 cm and / or at most 4.0 cm.

[0050] The length of the threaded rod is in particular at least 15 cm, preferably at least 17 cm, particularly preferably at least 19 cm and / or at most 25 cm, preferably at most 23 cm, particularly preferably at most 21 cm or 20 cm, which length is particularly suitable for expelling the desired amount of bone cement, for example at least 50 g and / or at most 130 g, quickly and with reasonable effort.

[0051] The connection area can be plugged onto one end of the cartridge. In the case of a screw or bayonet connection, this can be achieved, for example, by screwing in or unscrewing. The connection area can have an inner diameter of at least 3 cm, preferably at least 3.3 cm, in particular at least 3.5 cm and / or at most 4.0 cm, in particular at most 3.8 cm. The inner diameter of the connection area substantially corresponds to the outer diameter of the cartridge. Such a diameter has been shown to be particularly suitable for expelling the desired amount of bone cement, for example at least 50 g and / or at most 130 g, quickly and with reasonable effort.

[0052] In one embodiment, at least a part of the adapter unit, the handle and / or the threaded rod is made of a plastic material. In particular, the plastic material is polyamide, polyketone, polysulfone and / or polyoxymethylene. The plastic material is preferably polyamide 6, polyamide 6,6 and / or polyamide 12. These plastic materials have proven to be optimal in terms of strength, durability and cost.

[0053] A further aspect is the use of a device according to any one of the preceding claims for expelling an amount of bone cement of at least 50 g and / or at most 130 g from a cartridge. All features, advantages and configurations of the device described above apply to the use and vice versa.

[0054] In particular, PMMA bone cement is extruded. In particular, this is done for fixing an articular endoprosthesis to human bone tissue. In particular, the cartridge is a cartridge of a cementing system for fixing an articular endoprosthesis to human bone tissue.

[0055] A further aspect of the invention is a system for extruding bone cement, comprising a cartridge for bone cement and a device according to the invention for extruding bone cement. In particular, the cartridge contains bone cement or at least ingredients for the production of bone cement. All the features, advantages and embodiments of the device and uses described above also apply to the system and vice versa.

[0056] In particular, the cartridge comprises a connection area which interacts with a connection area of ​​the device so that a mechanical connection can be established between the adapter unit and the cartridge.

[0057] The cartridge can be connected at its end facing away from the adapter unit to one or more suitable hoses and / or one or more suitable tubes for transporting the bone cement to the desired location. It is also possible to fill one or more spacer moulds with bone cement.

[0058] A further aspect of the invention is a method for expelling bone cement from a cartridge, comprising manually rotating a handle of a device according to the invention such that bone cement is expelled from the cartridge. All features, advantages and embodiments of the device, uses and systems described above also apply to the method and vice versa.

[0059] Exemplary embodiments of the invention are also described in more detail below with reference to the drawings. The features of the exemplary embodiments can be combined with the claimed subject matter individually or in several places, unless otherwise stated. The scope of the claimed protection is not limited to the exemplary embodiments. [Brief description of the drawings]

[0060] In the drawings: [Figure 1] FIG. 1 is a perspective view of an apparatus comprising an alternative embodiment of an adapter unit according to the present invention. [Diagram 2] FIG. 2 is a cross-sectional view of an apparatus according to the invention. [Diagram 3]FIG. 3 shows a further cross-sectional view of the device according to the invention. [Figure 4] FIG. 4 shows a further cross-sectional view of the device according to the invention. [Diagram 5] FIG. 5 is a cross-sectional view of the use of a device according to the invention. [Figure 6] FIG. 6 shows a further cross-sectional view of the use of a device according to the invention. [Figure 7] FIG. 7 is an enlarged detail of the threaded rod.

[0061] 1 is a device 10 for extruding bone cement from a cartridge according to the invention. The device 10 comprises an adapter unit 26 with a connection area 37 for mechanically connecting to the cartridge. In the embodiment shown here, the connection area 37 can be plugged or screwed into a corresponding area of ​​the cartridge, as shown in figures 5 and 6. In the embodiment shown here, the adapter unit 26 has a connection element 29 for forming a bayonet connection. The direction of rotation for tightening the bayonet connection corresponds to the direction of rotation for screwing into the threaded rod 20.

[0062] The device further comprises a threaded rod 20 having external threads 22. The threaded rod 20 is threaded through the passage 27 such that the external threads 22 engage with the internal threads located within the passage 27. A manual operating handle 24 for rotation is located at the end shown on the right of the threaded rod 20. Rotation of the threaded rod 20 causes it to move axially through the adapter unit 26 so that bone cement can be extruded.

[0063] At the end of the threaded rod 20 remote from the handle 24, the threaded rod 20 is designed to apply a pressure or force to the bone cement. For this purpose, a pressure element may be present, for example the pressure element 30 shown in FIG.

[0064] An alternative adapter unit 26 is shown in a dashed circle. It is basically designed similarly to the above-mentioned adapter unit 26 shown below, but additionally comprises a grip 50, which can have the form of a radially protruding spike. The grip 50 serves as a counter-bearing during manual rotation of the handle 24. The user can turn the handle 24 with one hand and at the same time hold the adapter unit 26 or a cartridge connected to the adapter unit 26 firmly at the grip 50 with the other hand. This allows for lower holding forces and therefore easier rotation. The ejection of the bone cement is further simplified.

[0065] Figure 2 is an embodiment of the device 10 similar to Figure 1, in a cross-sectional view along the central longitudinal axis of the threaded rod 20. To avoid repetition, only the differences from Figure 1 will be described.

[0066] It can be seen that a pressure element 30 is disposed at the end of the threaded rod 20 remote from the handle 24. The pressure element 30 serves to apply pressure directly or indirectly to the bone cement in order to force it out of the cartridge. For example, the pressure element 30 can move a piston of the cartridge, which in turn forces the bone cement out of the cartridge.

[0067] The pressure element 30 consists of two parts. The first part 31 is rigidly connected to the threaded rod 20 so that it rotates with it when the threaded rod 20 rotates. The second part 32 is rotatably connected to the first part 31 so that the second part 32 does not rotate when the threaded rod 20 is rotated. In this way, no rotational movement is applied to the bone cement 15 and / or the piston, but only axial pressure. The contact surfaces of the first part 31 and the second part 32 are preferably flat and smooth to allow smooth rotation.

[0068] It can also be seen that the threaded rod 20 has an inner core, which in the example shown here is a metallic rod 40, and a casing, which in the example shown here is a plastic casing 41. The metallic rod 40 runs through the centre of the threaded rod 20 and contributes significantly to the mechanical stability of the threaded rod 20. The plastic casing 41 forms the external thread 22 and protects the metallic rod 40 from external influences. The metallic rod 40 is preferably not rotationally symmetrical to ensure a connection to the handle 24 for coupled rotation.

[0069] 2 also shows the female thread 28 in the passage 27 of the adapter unit 26. The female thread includes four or five thread turns. Both the male thread 22 and the female thread 28 have a pitch of 3 mm to 6 mm.

[0070] Figures 3 and 4 show an embodiment of the device 10 similar to that of Figure 2, in cross-section along the central longitudinal axis. Again, to avoid repetition, only additional features are described. In Figure 3, similar to Figures 1 and 2, the threaded rod 20 is shown in a position fully unscrewed from the adapter unit 26. In contrast, Figure 4 shows a position in which the threaded rod 20 has already been partially rotated through the adapter unit 26, as would be seen when extruding bone cement.

[0071] The adapter unit 26 is shown to have a recess 35 which can fully accommodate the pressure element 30, as shown in Fig. 3. In this way, the connection area 37 of the adapter unit 26 shown on the left remains free of the pressure element 30. The connection area 37 can thus be slid or plugged or screwed onto the corresponding end of the cartridge without disturbing the pressure element 30.

[0072] Figure 3 also shows some of the dimensions of the device 10. The threaded rod 20 has a length L of 18 cm to 20 cm. The length L is measured between the outermost areas where the external threads 22 are present. The connection area 37 of the adapter unit 26 has a diameter D of 34 mm to 40 mm. The diameter of the connection area 37 corresponds approximately to the outer diameter of the corresponding connection area of ​​the cartridge to be connected.

[0073] It can be seen that the second part 32 of the pressure element 30 surrounds and / or forms an engagement 34 with the first part 31 of the pressure element 30. On the right side, in particular the circumferential outer rim of the second part 32 extends inwards and engages behind the radially outer edge of the first part 31.

[0074] The first part 31 and / or the second part 32 can be designed in the form of a plate. The second part 32 may have a diameter of at least 20 mm and / or at most 30 mm, for example approximately or exactly 25 mm.

[0075] Furthermore, the outer diameter D of the threaded rod 20, measured radially between the peaks of the male threads 22 A In the example shown here, the outer diameter D A is 13.5mm~15mm.

[0076] Figures 5 and 6 show the use of the device 10 according to the invention with different cartridges 12. The connection area 37 of the adapter unit 26 is slid onto one end of the cartridge 12 and mechanically clamped there, as explained. The cartridge 12 has an outlet opening at the opposite end to which a tube 51 is connected for example for discharging the bone cement 15. Inside the cartridge there is the bone cement 15. Typically the cartridge 12 also comprises a piston 13 which is at least substantially sealed against the inner wall of the cartridge 12. The pressure element 30 of the device 10 is designed to apply an axial pressure to this piston 13, for example to push the bone cement 15 out of the cartridge. Figure 5 shows a first pressing process, in which the pressure element 30 and the piston 13 are pressed to the left until the bone cement 15 is flat against the piston 13. Figure 6 shows a more advanced pressing process, in which the bone cement 15 is transported out through the tube 51 by continued rotation of the handle 24.

[0077] 7 is an enlarged cross-sectional view of the threaded rod 20. It includes an inner metal rod 40 and a plastic casing 41 that completely encases the metal rod 40. The outer diameter D of the threaded rod 20, which corresponds to the maximum diameter between the peaks on either side of the male thread 22, is A In addition, the inner diameter D of the threaded rod 20, which corresponds to the minimum diameter between the recesses or valleys on either side of the male thread 22, is shown. I The thread has a thread depth of 1 mm to 2 mm. Therefore, the inner diameter D I and outer diameter D A The difference between them is 2mm to 4mm.

[0078] The thread turn 66 is delimited by a dashed line as an example. A thread turn corresponds to one complete revolution of the male thread 22 relative to the corresponding female thread. The threaded rod 20 is designed so that the outer surface of the thread turn 66 of the male thread 22 is at most 370 mm. 2In the example of a trapezoidal thread shown here, the outer surface of the thread is determined as the sum of an upper surface 61 corresponding to the surface in the region of the peak of the thread, a lower surface 62 corresponding to the surface in the region of the valley of the thread, a first (upward) flank surface 63, and a second (downward) flank surface 64.

[0079] In one embodiment, the outer surface of the thread turn of the male thread is at most 450 mm 2 , especially up to 430 mm 2 , preferably at most 400 mm 2 , particularly preferably at most 370 mm 2 In one embodiment, the outer surface of the thread turn of the male thread is at most 350 mm 2 , especially up to 330 mm 2 , preferably at most 300 mm 2 In one embodiment, the outer surface of the thread turn of the male thread is at least 100 mm 2 , typically at least 130 mm 2 , especially at least 160 mm 2 , preferably at least 180 mm 2 , particularly preferably at least 200 mm 2 , more preferably at least 215 mm 2 In one embodiment, the outer surface of the thread turn of the male thread is at least 250 mm 2 , typically at least 280 mm 2 , especially at least 320 mm 2 , preferably at least 350 mm 2 These values ​​may be particularly suitable depending on the design and materials.

[0080] Example 1: Thread pitch 4.5mm, outer diameter D of male thread AA device was created with a thread depth of 14 mm and 1.5 mm. This proved optimal for rapid extrusion of up to 130 g of highly viscous bone cement from the cement cartridge with little effort. Complete ejection of 130 g of bone cement from the applicant's commercial PALAMIX® cement cartridge could be achieved within 1.5 minutes. Similar results were achieved with the applicant's closed cementing system PALACOS PRO® (2021 version).

[0081] Example 2: The adapter unit 26, threaded rods 20 with diameters of 30 mm, 25 mm, 20 mm and 14 mm and pitches of 4.5 mm and 7.0 mm, and matching handles were manufactured from polyamide 12 using selective laser sintering (SLS). In particular, some or all components are then chemically smoothed. The threaded rods 20 contain a standard stainless steel hex rod inside. In particular, this was manufactured and then pressed into the plastic part.

[0082] The push-out test used the commercially available mixed system PALAMIX and polymethylmethacrylate bone cement PALACOSR+G from the applicant, as well as the commercially available vancomycin hydrochloride.

[0083] Extrusion tests were performed using approximately 118g of bone cement obtained from two packs of PALACOSR+G (2 x 40.8g cement powder + 2 x 18.5g monomer liquid) mixed in a PALAMIX cartridge. The bone cement was then extruded using the fabricated devices to evaluate the ease of handling of each device. The results are shown in Table 5 below.

[0084] [Table 1]

[0085] In addition, similar experiments were carried out using two packs of PALACOSR+G and two monomer ampoules, each containing 18.5 g of monomer liquid, to which 4.0 g of vancomycin hydrochloride was added. The theoretical amount of cement was about 126 g of cement paste. Similar results were obtained as in the first series of experiments.

[0086] Reference List 10 equipment 12 Cartridge 13 Piston 15 Bone cement 20 Threaded Rod 22 Male thread 24 Handle 26 Adapter unit 27 Passage 28 Female thread 29 Connection Elements 30 Pressure Elements 31 First Part 32 Second Part 33 Surface 34 Engagement 35 Recess 37 Connection Area 40 Metal Rod 41 Plastic Casing 50 Grip 51 Tube 61 Top surface 62 Bottom surface 63 First flank surface 64 Second Flank Surface 66 Thread Turn D Inner diameter D I Inner diameter D A Outside diameter L Length

Claims

1. A device (10) for extruding bone cement (15) from a cartridge (12), comprising a threaded rod (20) having an external thread (22), a handle (24) for rotating said threaded rod (20), and an adapter unit (26) for mechanically connecting to a cartridge (12) for bone cement (15), said adapter unit (26) having a passage (27) with an internal thread (28) for said threaded rod (20), The outer surface of the thread turn (66) of the male thread (22) is at most 370 mm ２ An apparatus comprising:

2. The outer surface of the thread turn (66) of the male thread (22) is at least 230 mm ２ 2. The device (10) according to claim 1, characterized in that:

3. 2. The device (10) according to claim 1, characterized in that the pitch of the external thread (22) is at least 1 mm and / or at most 7 mm.

4. The outer diameter (D Ａ 2. The device (10) according to claim 1, characterized in that the distance between the first and second electrodes is at least 12 mm and / or at most 17 mm.

5. The device (10) of claim 1, characterized in that the internal thread (28) of the adapter unit (26) comprises at least two and / or at most seven thread turns.

6. 2. The device (10) according to claim 1, characterized in that the external thread (22) of the threaded rod (20) has a thread depth of at least 1 mm and / or at most 4 mm.

7. The device (10) according to claim 1, characterized in that the device (10) comprises, at the end of the threaded rod (20) remote from the handle (24), a pressure element (30) having a flat surface (33) for directly or indirectly applying pressure to the bone cement (15) located in the cartridge (12).

8. 8. The device (10) according to claim 7, characterized in that the pressure element (30) is made up of two parts, a first part (31) of the pressure element (30) being connected to the threaded rod (20) for coupled rotation and a second part (32) of the pressure element (30) being connected to the first part for rotation about the longitudinal axis of the threaded rod (20).

9. 8. The device (10) according to claim 7, characterized in that the adapter unit (26) has a recess (35), which is axially arranged between a connection area (37) or a connection element (29) of the adapter unit (26) for mechanically connecting to the cartridge (12) and the female thread (28), and the recess (35) is adapted to at least substantially accommodate the pressure element (30).

10. 2. The device (10) according to claim 1, characterized in that said threaded rod (20) comprises an inner metallic rod (40) and a plastic casing (41).

11. 2. The device (10) of claim 1, wherein the adapter unit (26) is designed to be connected to the cartridge (12) by a bayonet connection, and wherein a direction of rotation of the adapter unit (26) for connecting the adapter unit (26) to the cartridge (12) corresponds to a direction of rotation for screwing the threaded rod (20) into the adapter unit (26).

12. 2. The device (10) according to claim 1, characterized in that the threaded rod (20) has a length (L) between 15 cm and 23 cm and / or the adapter unit (26) has a connection area (37) for plugging into a cartridge (12), the connection area (37) having an inner diameter (D) between 3.3 cm and 4.0 cm.

13. 2. The device (10) according to claim 1, characterized in that at least a portion of the adapter unit (26), the handle (24) and / or the threaded rod (20) are made of polyamide, polyketone, polysulfone and / or polyoxymethylene.

14. Use of the device (10) according to claim 1 for expelling an amount of bone cement (15) between 50g and 130g from a cartridge (12).

15. A system for extruding bone cement (15), comprising a cartridge (12) for bone cement (15) and a device (10) according to claim 1.

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