US20210290397A1 - Device and method for producing spacers with a variable head - Google Patents

Abstract

The invention relates to a device for producing a spacer having a casting mold, wherein the casting mold has a stem mold and a mold cavity with a spherical surface-shaped inner surface, wherein the stem mold and the mold cavity delimit a common interior, at least one filling opening and at least one vent element, wherein the stem mold is dimensionally stable on injection of bone cement paste into the casting mold, while, on injection of bone cement paste into the casting mold, the mold cavity is expandable at least in the region of the spherical surface-shaped inner surface by pressure imparted by the injected bone cement paste. The invention also relates to a method for producing spacers using such a device.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application claims priority to European Patent Application No. 20171303.9 filed on Apr. 24, 2020, and European Patent Application No. 20164534.8 filed on Mar. 20, 2020, the entire disclosures of which are incorporated by reference herein.
BACKGROUND
• The invention relates to a device for producing a spacer by curing bone cement paste. The spacer is provided as a temporary placeholder in medical applications for temporarily replacing a joint or part of a joint comprising an articulating surface of a joint head. The spacer is preferably suitable and provided for temporarily replacing a hip joint or a shoulder joint. Accordingly, the device is preferably provided for producing a hip joint spacer or a shoulder joint spacer. The invention also relates to a method for producing such a spacer using such a device.
• The subject matter of the present invention thus in particular provides a casting mold for producing one-part hip and shoulder spacers, wherein, according to the invention, the diameter of the spacer head of the hip and shoulder spacers to be cast is continuously adjustable in accordance with the particular patient's anatomical circumstances. Hip and shoulder spacers are intended as temporary placeholders (spacers) for the interim phase in the context of two-stage revisions of infected hip and shoulder total articular endoprostheses. The casting mold is suitable for producing hip and shoulder spacers with low-viscosity and high-viscosity polymethyl methacrylate bone cement paste. The invention further provides methods for producing hip and shoulder spacers with a continuously adjustable diameter of the spacer head.
• Joint endoprostheses, such as hip joint endoprostheses and shoulder joint endoprostheses, are widely implanted worldwide. Unfortunately, in a small percentage of cases, joint endoprostheses are colonized by microbial microorganisms, in particular Gram-positive bacteria as well as Gram-negative bacteria, and to a very small extent by yeasts and fungi. These microbial microorganisms, mainly typical skin microbes such as Staphylococcus aureus and Staphylococcus epidermidis, may enter a patient's body during a surgical operation (OP). It is also possible for microbial microorganisms to enter joint endoprostheses hematogenically. When joint endoprostheses are colonized by microbial microorganisms, the surrounding bone and soft tissue also become infected and damaged by the microbial microorganisms.
• The prior art primarily encompasses two treatment methods for infected joint endoprostheses, one-stage septic revision and two-stage septic revision. In the case of one-stage revision, the infected joint endoprosthesis is removed first, next radical debridement is performed and then a revision joint endoprosthesis is implanted within one OP.
• In two-stage septic revisions, in a first OP the infected joint endoprosthesis is initially removed, then debridement is performed and thereafter a spacer is implanted. A hip joint spacer consists of a stem, a collar, a neck and a ball head and replicates hip joint endoprostheses in shape and size. Similarly, a shoulder joint spacer replicates a shoulder joint endoprosthesis in shape and size. The spacer is anchored with bone cement to the respective bone, i.e., for example in the case of hip joint spacers to the proximal femur or in the femoral canal. The spacer remains for up to several weeks in the patient until the inflammation has subsided and clinical inflammation markers have receded. The spacer is then removed in a second OP and a revision joint endoprosthesis implanted after fresh debridement.
• Spacers are of major significance as temporary placeholders in the interim phase in the context of two-stage septic replacement operations for hip and shoulder total articular endoprostheses. During intraoperative production of these spacers, medical staff may, depending on the available antibiogram of the microbial microorganisms responsible for the infection, add to the polymethyl methacrylate bone cement one or more antibiotic(s) specifically tailored to the microorganisms.
• In the case of spacers, antibiotics are added to the cement powder before actual spacer production. Using this antibiotically modified bone cement powder, a bone cement paste is then produced by admixing monomer liquid and spacers are cast from this bone cement paste which then cure by polymerization with the assistance of the monomer liquid added to the cement powder. The bone cement paste thus substantially incorporates the antibiotics. The antibiotic particles situated in areas close to the surface are released under the action of bodily fluids, such as wound secretions. Active ingredient release is greatest at the start and then diminishes over the course of several days.
• US 2010/0042213 A1 discloses a hip joint prosthesis with a reservoir for liquid inside the implant. WO 2017/178951 A1 discloses a hip spacer with indentations, wherein a substance for treating the bone may be introduced into the indentations. U.S. Pat. No. 6,245,111 B1 proposes a hip joint prosthesis, the surfaces of which are coated with an antibiotic. U.S. Pat. No. 5,681,289 discloses a device for distributing a liquid active ingredient with the assistance of a bladder inside the device. None of the stated prostheses is suitable for producing an irrigation circuit. EP 1 991 170 B1 and US 2011/0015754 A1 describe a hip joint spacer containing active ingredients. US 2019/0290833 A1 discloses an irrigatable hip joint spacer, with which a liquid circuit can be created. WO 2016/205077 A1 and U.S. Pat. No. 8,900,322 B2 describe further spacers with an irrigation function.
• It is known to use spacers provided with antibiotics. Spacers may on the one hand be produced by the OP personnel during the OP itself from PMMA bone cement powder, antibiotics and monomer liquid, for example with a spacer mold, as described for example inpatents DE 10 2015 104 704 B4 orEP 2 617 393 B1; on the other hand, it is also conventional to use hip joint spacers prefabricated industrially from bone cement.
• Resin casting molds are conventional for the intraoperative production of spacers with polymethyl methacrylate bone cement. Resin casting molds for intraoperative production of one-part hip spacers are described in U.S. Pat. No. 6,361,731 B1. These casting molds are transparent and have two separate filling openings. As a result, even high-viscosity bone cement paste can be introduced into the casting mold with little pressure, because the flow paths for the bone cement paste are relatively short. When using non-high-viscosity bone cement paste, the risk arises, once filling of the casting mold is complete, of bone cement paste flowing back out of the filling openings before curing begins. These casting molds are offered for sale with different spacer head diameters. The diameter of the spacer head is not variably adjustable. The medical user can only select between predetermined spacer head sizes. It would be desirable for the medical user as far as possible with one casting mold for the stem to be able to choose between different spacer head sizes.
• In a further development, patent specifications U.S. Pat. No. 7,789,646 B2, U.S. Pat. No. 8,480,389 B2 and U.S. Pat. No. 8,801,983 B2 propose multipart casting molds for the production of modular hip spacers. These modular hip spacers consist of a spacer head and a separate stem. Casting molds for the spacer head with different spacer head diameters are available for this purpose. This means that the casting mold for the stem is connected to the casting mold for the spacer head which has the selected diameter. The casting mold assembled in this manner is then in one piece and has a thread at the filling opening for connecting the casting mold to a cement cartridge. Another variant according to U.S. Pat. No. 7,637,729 B2 uses a casting mold for producing the stem and a separate casting mold for the spacer head. After completion of curing and demolding, the two spacer components are assembled. U.S. Pat. No. 7,789,646 B2 describes a modular casting mold in which the filling opening of the casting mold can be closed using a plug once the cement paste has been introduced into the casting mold. Before that, however, the casting mold has to be unscrewed from the cement cartridge. When using low-viscosity cement paste, it is therefore possible, if the casting mold is held in an unfavorable way, for cement paste to run out during separation of the casting mold from the cement cartridge before the plug has been screwed in. When using non-high-viscosity bone cement paste, it is therefore possible, if the casting mold is held in an unfavorable way, for bone cement paste to run out during separation of the casting mold from the bone cement cartridge before the plug has been screwed or put in. In either case, unwanted entrapped air may occur in the spacer mold by the bone cement paste coming away from the inner wall of the casting mold.
• US 2007/0222114 A1 describes a hip spacer mold. This spacer mold consists of a plurality of mold segments which are connected together. Thanks to the plurality of segments, the spacer mold may be adapted very precisely to the patient's anatomical circumstances. The spacer mold segments are joined together by means of worm drive hose clips. A PMMA bone cement paste (polymethyl methacrylate bone cement paste) is introduced through channels in the spacer mold. The complex structure of the casting mold makes it very complicated to join the spacer mold segments together and to remove the hip spacer once curing of the PMMA bone cement paste is complete.
• WO 2009/073 781 A2 proposes a spacer mold for a hip spacer consisting of two parts which may be displaced relative to one another in order to enable adaptation of the length of the stem. A further casting mold is disclosed inEP 2 522 310 A1. This device consists of at least two parts, wherein an insertion portion is arranged in a first part and an insertion receptacle is arranged in the second part. The two parts are able to be put into one another and form a casting mold for producing the stem of the hip spacer.EP 2 787 928 A1 describes a complex casting mold. This enables the production of hip spacers with different ball heads. The elements of the casting mold are fixed in place using connecting elements.
• The object of the present invention thus consists in overcoming the disadvantages of the prior art. In particular, the object of the invention consists in the development of an inexpensive device for producing a one-part spacer with a variable spacer head by curing bone cement paste and in the development of a method which can be carried out simply and inexpensively for producing a one-part spacer with a variable spacer head by curing bone cement paste, with which one-part spacers, in particular hip and shoulder spacers, can be produced by medical personnel in the operating room using bone cement paste, in particular polymethyl methacrylate bone cement. Hip and shoulder spacers are of similar construction. They consist of a stem and a spacer head as well as a neck which connects the stem and the spacer head.
• The intention is therefore to develop a device, in particular a casting mold, which is in principle suitable for producing hip and shoulder spacers with variable spacer head diameters. A metal core may be or have been arranged inside the hip and shoulder spacer for the purpose of mechanical stabilization. It should be possible to produce spacers using not only low or non-high-viscosity but also high-viscosity (polymethyl methacrylate) bone cement paste A high injection pressure is needed for completely filling a casting mold with a high-viscosity bone cement paste. The casting mold of the device is intended to be usable with this high injection pressure. The casting mold should therefore, if possible, on the hand withstand a pressure of 10 N/cm²and on the other hand be operable with such a pressure.
• It is intended that the device and in particular the casting mold of the device be such that bone cement paste or fluid bone cement paste can be injected into a casting mold from a bone cement cartridge. When using a non-high-viscosity bone cement paste, it is intended for the bone cement paste not to flow out of the casting mold once it has been filled. To this end, it is necessary to configure the casting mold so as reliably to prevent non-high-viscosity bone cement paste from flowing out of the casting mold during separation of the casting mold from the cement cartridge. Such closure should be possible without the need for openings for valves of complex construction in the wall of the casting mold. Openings in the wall of the casting mold may lead to leaks in the casting mold if the bone cement paste is injected into the casting mold under high pressure. Furthermore, the sprue region of the casting mold should be configured such that, on the one hand, easy filling of the casting mold with bone cement paste is possible and, on the other hand, any sprue residues can be easily removed once curing of the bone cement paste is complete.
SUMMARY
• The objects of the invention are achieved by a device for producing a spacer by curing bone cement paste, wherein the spacer is provided in the medical field for temporarily replacing a joint or part of a joint comprising an articulating surface of a head of the joint, in particular for temporarily replacing a hip joint or a shoulder joint, the device having
• a casting mold for molding the spacer from bone cement paste, wherein the casting mold has a stem mold for molding a stem and a neck and the casting mold has a mold cavity with a spherical surface-shaped inner surface for molding a sliding surface of a head of the spacer, wherein the stem mold and the mold cavity delimit a common interior, such that the head of a spacer molded with the casting mold is connected as one part via the neck to the stem,
• at least one filling opening for injecting a bone cement paste into the casting mold,
• at least one vent element which connects the common interior of the casting mold in gas-permeable manner to the surroundings of the casting mold,
• wherein the stem mold is dimensionally stable on injection of bone cement paste into the casting mold, while, on injection of bone cement paste into the casting mold, the mold cavity is expandable, at least in the region of the spherical surface-shaped inner surface, by pressure imparted by the injected bone cement paste.
• The spherical surface-shaped inner surface preferably has a radial deviation from a perfect surface of a sphere of at most 10% and particularly preferably of at most 1%. The spherical surface-shaped inner surface may further comprise a spherical surface segment which comprise an angular sector of at least 45°, preferably of at least 90° and particularly preferably comprises at least a hemisphere. A hemisphere has an angular sector of 180°.
• Provision may be made for the spherical surface-shaped inner surface to be a hemispherical surface-shaped inner surface.
• The diameter of the unexpanded spherical surface-shaped inner surface of the mold cavity may be between 10 mm and 60 mm and preferably between 30 mm and 50 mm.
• The head of the joint which is to be replaced least in part and in particular completely by the spacer, is preferably a femoral head or humeral head.
• The stem mold may be constructed in two parts, wherein the two parts of the stem mold are connected or connectable to one another, wherein the two parts of the stem mold are preferably connected or connectable to one another in fluid-tight manner. This applies optionally apart from the at least one filling opening which may be delimited by the two parts of the stem mold.
• Alternatively, the stem mold may also be in one part.
• A bone cement paste or a fluid bone cement paste is understood to mean a mixed (i.e. ready-to-use) bone cement paste which has a viscid consistency. The viscosity of a bone cement preferably corresponds to that of honey or even has more viscid consistency, i.e. a still higher viscosity. The terms fluid bone cement and bone cement paste are used synonymously.
• The casting mold is preferably internally hollow.
• Provision may preferably also be made for the mold cavity to have an interior which replicates a negative shape of a joint head, in particular of a hip joint head or a shoulder joint head.
• Provision may further be made for the casting mold to be in two, three or four parts or in multiple parts, wherein the parts of the casting mold are preferably fastenable to one another in liquid-tight manner via flanges and/or a thread. The casting mold is particularly preferably in two parts (mold cavity and stem mold), three parts (mold cavity and two-part stem mold) or four parts (mold cavity, two-part stem mold and a hollow cylinder adjustable in the cylinder axis as an adapter element for molding a neck of the spacer).
• The casting mold is intended to withstand a pressure of 10 N/cm², in order also to enable the use of high-viscosity bone cement paste.
• The mold cavity should preferably be expandable with a hydrostatic pressure of at least 1 N/cm²and particularly preferably with a hydrostatic pressure of at least 5 N/cm².
• In the present patent application, the statements of direction (“proximal”, “distal” and “lateral”) and the statements relating to planes (“sagittal plane”, “front plane” and “transverse plane”) relating to the spacer or the casting mold are used in the same way as would be understood as a main anatomical direction or body plane when inserted into the patient. For instance, “proximal” means towards the center of the body and “distal” means remote from the center of the body.
• The stem is provided for connection to a bone (in the case of hip joint spacers to the femur and in the case of shoulder joint spacers to the humerus) and for this purpose may preferably be introduced into a proximal end of the prepared bone or into the bone canal.
• Provision may preferably be made for the device for producing a spacer, in particular a hip joint spacer or shoulder joint spacer, to be suitable for application of at least one antibiotic and/or antimycotic active ingredient.
• The spacer should preferably be fabricated in one part from a biocompatible bone cement paste, such as polymethyl methacrylate (PMMA), wherein the PMMA particularly preferably contains at least one antibiotic and/or antimycotic dissolvable from the PMMA.
• Thanks to the at least one vent opening, air or gas can escape from the interior of the casting mold when the bone cement paste is introduced. Entrapped air and thus unevenness on the surface of the spacer may thereby be avoided and at the same time a uniformly acting pressure of the bone cement paste may be ensured in the interior of the mold cavity.
• The device may be embodied by the casting mold itself.
• Provision may be made for the at least one vent element to be permeable to gases and impermeable to bone cement paste and in particular impermeable to polymethyl methacrylate bone cement paste (PMMA bone cement paste).
• Provision may also be made for the at least one vent element to be arranged in the mold cavity or for the at least one vent element to be a plurality of vent elements, wherein at least one of the plurality of vent elements is arranged in the mold cavity and at least one of the plurality of vent elements is arranged in the stem mold.
• This ensures that no entrapped air is formed in the mold cavity which may absorb some of the pressure of the bone cement paste and expand during curing, which would modify the desired size and shape of the sliding surface. The entrapped air also interrupts the sliding surface which has to be filled or repaired after curing.
• A further development may provide that the mold cavity is radially expandable, and preferably radially and uniformly expandable, at least in the region of the spherical surface-shaped inner surface, by the pressure imparted by the injected bone cement paste.
• Provision may further be made for the mold cavity to be elastically expandable, and preferably rubber-elastically expandable, at least in the region of the spherical surface-shaped inner surface, by the pressure imparted by the injected bone cement paste.
• In this way, the size of the sliding surface or the head of the spacer may be uniformly and continuously varied. The head of the spacer can thus be particularly straightforwardly adapted to the treatment situation appropriate for a patient.
• The term “rubber-elastic” is taken to mean that, by application of pressure to the interior surface by polymethyl methacrylate bone cement paste, the spherical surface-shaped inner surface of the mold cavity can be enlarged by a factor of3 without tearing the wall of the mold cavity by expansion of the wall of the mold cavity at least in the region of the spherical surface-shaped inner surface. The term “rubber-elastic” is preferably taken to mean that, by application of pressure to the interior surface by polymethyl methacrylate bone cement paste, the volume of the spherical surface-shaped inner surface of the mold cavity can be enlarged at least by a factor of 5.5 without tearing the wall of the mold cavity by expansion of the wall of the mold cavity in the region of the spherical surface-shaped inner surface.
• Provision may moreover be made for the stem mold and the mold cavity to be connected or connectable to one another in liquid-tight manner via a flange or an adapter element, wherein an expandable part of the mold cavity, which comprises the spherical surface-shaped inner surface, is preferably fastened or fastenable with an annular mount to a flange of the stem mold or the adapter element, such that a peripheral annular disk of the expandable part is arranged between the annular mount and the flange and seals the connection, wherein the annular mount is particularly preferably screwed or screwable to the flange of the stem mold.
• In this way, the stem mold and the mold cavity, which must have different mechanical properties, can be fastened to one another in liquid-tight manner, such that the bone cement paste cannot be escape between the stem mold and the mold cavity.
• Liquid-tight means that the non-cured, i.e. fluid, bone cement paste and preferably also a liquid monomer liquid as starting component of the bone cement cannot flow out or penetrate between the mold cavity and stem mold. In the present document, liquid-tight should be taken to mean that at least the bone cement paste cannot escape through a liquid-tight connection.
• Provision may be made for the adapter element to project at an angle between 80° and 100° relative to a stem axis of the stem of the stem mold and preferably at an angle of 90° relative to a stem axis of the stem of the stem mold.
• The mold cavity preferably has a peripheral edge which is arranged or is to be arranged between the adapter element and a fastening element.
• Provision may also be made for the device to have a fastening element for fastening the mold cavity to the stem mold, wherein the fastening element is preferably detachable and, particularly preferably, the fastening element is a plurality of screws or has a plurality of screws.
• In this way, the mold cavity and the stem mold can be fastened in order to provide the casting mold for the spacer. Different mold cavities, which differ in shape from one another, may accordingly also be fastened to the stem mold or conversely different stem molds may be fastened to a mold cavity. As a result, still greater variability of the device can be achieved. The mold cavities may for example differ from one another by having a shape which deviates to a greater or lesser degree from the ideal spherical shape. The stem molds may for example differ from one another by having different lengths and/or diameters of the stem.
• Provision may be made for the fastening element to be at least partially connected to the stem mold.
• Provision may moreover be made for the fastening element to have clamping plates, wherein the fastening element preferably additionally has screws, thumb screws, nuts and/or threaded rods.
• As a result, a leak-tight connection can be produced in a structurally simple manner between the stem mold and the mold cavity.
• Torx screws, which can be screwed with the drive devices conventional in operating rooms, are particularly preferred as the screws.
• Provision may further be made for the at least one filling opening to be connected on a side remote from the casting mold to a port for liquid-tight connection of a bone cement cartridge, wherein the port is preferably suitable for pressure-tight connection of a bone cement cartridge, wherein the port particularly preferably has a thread and very particularly preferably has a circumferential seal and/or a circumferential sealing face or a circumferential sealing edge.
• As a result, it is ensured that the bone cement paste can be injected from a bone cement cartridge into the casting mold and a pressure can be exerted on the mold cavity with the bone cement cartridge via the bone cement paste in order to expand the mold cavity.
• Provision may also be made, at least in the region of the spherical surface-shaped inner surface, for the mold cavity to expand by injection of further bone cement paste into the casting mold already completely filled with bone cement paste, while the stem mold receives no additional bone cement paste and remains dimensionally stable.
• As a result, it is ensured that only the head of the spacer is reshaped by the injection of bone cement paste.
• The stem mold not receiving any additional bone cement paste should not be taken to mean that it cannot deform elastically.
• According to the invention, preferably at least 95%, and particularly preferably at least 99%, of the increase in volume of the casting mold as a result of injecting bone cement paste should occur in the mold cavity.
• According to one particularly preferred further development of the present invention, provision may be made for the device further to have
• a valve seat which is connected to the casting mold in the region of the at least one filling opening, wherein the valve seat has an in places closed head side with at least one first feed-through, wherein the at least one first feed-through opens into the at least one filling opening,
• a valve body which is mounted so as to be rotatable relative to the valve seat and which has a sealing face, wherein the sealing face is oriented in the direction of the in places closed head side of the valve seat, wherein at least one second feed-through is arranged in the sealing face,
• wherein the valve seat and the valve body together form a valve, wherein the valve is reversibly transferable into an open position and a closed position by rotation of the valve body relative to the valve seat, wherein, in the open position of the valve, the at least one first feed-through of the valve seat and the at least one second feed-through of the valve body are located above one another at least in places and provide a connection through the valve into the casting mold which is permeable to bone cement paste, wherein, in the closed position of the valve, the at least one first feed-through of the valve seat is covered by the sealing face of the valve body, wherein, in the closed position of the valve, the at least one filling opening of the casting mold is covered for bone cement paste.
• The valve is a particularly structurally straightforward way of ensuring that the bone cement paste can be separated and the bone cement paste within the casting mold simultaneously held under pressure in order to keep the mold cavity in an expanded state. The valve thus makes it possible to separate the sprue while pressure can simultaneously maintain on the mold cavity via the bone cement paste in order to keep the mold cavity at the desired degree of expansion. Thanks to a valve body which is rotatable in a valve seat, it is surprisingly also possible to provide a device with a casting mold in which the sprue can be sheared off or largely sheared off with the valve body and simultaneously, in the event of ongoing pressure from a bone cement cartridge, to close the casting mold or at least constrict the remaining channels to such an extent that the bone cement paste can continue to be held under pressure in the casting mold so that it can be pressed against the inside of the casting mold and the mold cavity can be kept expanded, wherein the bone cement paste is simultaneously prevented from being expelled back out from the casting mold through the at least one filling opening. The device also makes it possible to fill the casting mold in succession with the contents of a plurality of bone cement cartridges without the bone cement paste being able to flow back out of the casting mold through the at least one filling opening. In this way, even with bone cement cartridges which provide only small volumes of bone cement, it is possible to produce spacers with a large volume.
• Covered for bone cement paste means that the bone cement paste in the valve is prevented from flowing to such a degree that it cannot flow through the valve prior to curing. For normal-viscosity bone cement pastes, it is sufficient to this end for the bone cement paste to be incapable of flowing in a straight line through the valve and for the free passage cross-sections to be smaller than 1 mm. Bone cement pastes are viscous or high-viscosity fluids, as indicated by the term “paste”. The viscosity of a bone cement paste amounts to at least 10 Pa·s, which corresponds to the viscosity of liquid honey. In addition, the bone cement paste cures within a few minutes, meaning that passage is then no longer possible. Provision may preferably be made for the bone cement paste to have a viscosity of at least 10 Pa·s.
• Provision may be made for the sealing face to be closed apart from the at least one second feed-through.
• Provision may also be made for the valve seat to be connected to a casting mold wall of the casting mold in liquid-impermeable manner.
• Provision may further be made for the valve seat to be configured at one end face of a cavity delimited by the casting mold as a disk, in particular as a planar disk.
• Provision may preferably also be made for the valve seat and the valve body to be hollow-cylindrical.
• The terms “open state” and “closed state” of the valve or of the valve body relative to the valve seat and the terms “open position” and “closed position” of the valve or of the valve body relative to the valve seat are used synonymously.
• Provision may preferably be made for the in places closed head side of the valve seat and the sealing face of the valve body to be disks or be disk-shaped.
• Provision may preferably be made for the valve seat to delimit the at least one filling opening of the casting mold.
• Provision may be made in devices according to the invention with a valve for the valve to be connected on the side remote from the casting mold to a port for liquid-tight connection of a bone cement cartridge or for the valve have such a port.
• As a result, the casting mold can be filled with a bone cement cartridge and the mold cavity expanded by a pressure imparted by means of the injected bone cement paste.
• Provision may be made for the valve seat to be connected to the casting mold so as not to be rotatable relative to the casting mold, preferably for the valve seat to be connected fixedly and/or rigidly to the casting mold.
• In this way, the valve of the device can conveniently be operated from outside, in order to change or detach a bone cement cartridge.
• Provision may also be made for the valve to be operable by rotation or tilting of a cement cartridge connected to the port, wherein to this end the port is preferably arranged on the valve body.
• Provision may further be made for the valve to be manually operable, preferably manually operable from outside the device, wherein the valve body is particularly preferably manually rotatable relative to the valve seat and the valve is transferable by rotation from the closed position into the open position and from the open position into the closed position.
• In this way, the device can conveniently be operated from outside. In addition, the bone cement cartridge can also be replaced.
• Provision may moreover be made for the valve seat to have an inner thread on the inside and for the valve body to have a matching outer thread on the outside, such that the valve body can be screwed into the valve seat.
• Due to this measure, a good sealing effect can be achieved at the connection between the valve body and the valve seat. In addition, the valve can be simply and inexpensively assembled in this way.
• Provision may further be made for the port to comprise, for liquid-tight connection of a bone cement cartridge, an inner thread in the valve body or an outer thread on the valve body, wherein an adapter element of the bone cement cartridge or on the bone cement cartridge preferably has a mating thread matching the inner thread or the outer thread.
• In this way, a stable and liquid-tight connection to the port may on the one hand be produced and on the other hand use may be made of the rotation during the screwing movement at the start or after the end of the screwing movement to rotate the valve body relative to the valve seat and so transfer the valve from the open to the closed state or transfer the valve from the closed to the open state.
• By using a suitable thread, an additional safety function of the device may in particular be achieved by its only being possible to detach the bone cement cartridge with the valve closed and its only being possible to open the valve with the bone cement cartridge connected.
• Provision may be made in devices according to the invention with a valve element for the inner thread in the valve body or the outer thread on the valve body to be a right-hand thread and for the valve to be transferable from the closed to the open position by equidirectional rightward rotation of the valve body and for the valve to be transferable from the open to the closed position by contradirectional leftward rotation of the valve body or
• for the inner thread in the valve body or the outer thread on the valve body to be a left-hand thread and for the valve to be transferable from the closed to the open position by equidirectional leftward rotation of the valve body and for the valve to be transferable from the open to the closed position by contradirectional rightward rotation of the valve body or
• for the inner thread of the valve seat and the inner thread and the outer thread of the valve body all to be left-hand threads or all to be right-hand threads, wherein an outer thread of an adapter element for liquid-tight connection of a bone cement cartridge to the port preferably also has the same direction of rotation.
• The purpose of these measures is also to ensure that the valve closes automatically when the bone cement cartridge is unscrewed and the valve opens automatically when the bone cement cartridge is screwed in.
• Provision may be made in devices with the valve for the at least one first feed-through of the valve seat to be covered, in the closed position of the valve, with the sealing face of the valve body, wherein the in places closed head side of the valve seat and the sealing face of the valve body are preferably spaced apart from one another by a maximum of 2 mm, particularly preferably by a maximum of 1 mm and very particularly preferably by a maximum of 0.5 mm.
• In this way, it may be ensured that the bone cement paste filled into the casting mold (the fluid bone cement) cannot be expelled back out of the casting mold through the valve when the valve is closed. If the bone cement paste cures with these thicknesses or cross-sections in the region of the sprue, it may be readily manually broken off or cut through once the spacer has cured and need not be separated with a saw. Sprues of such thicknesses are therefore harmless since they do not appreciably delay OP procedures during an OP.
• Provision may further be made in devices with the valve for the valve body to be mounted so as to be rotatable about an axis of rotation relative to the valve seat, wherein the axis of rotation extends perpendicular to the sealing face of the valve body or wherein the axis of rotation extends along an axis of rotational symmetry of the sealing face of the valve body.
• As a result, the bone cement paste flowing through the valve can be cut or twisted off the valve body by rotation. This enables a smooth cut surface and little application of force during shearing off. Rotation of the bone cement cartridge may further also be used for shearing off the bone cement paste. It is preferred for the axis of rotation to extend along the axis of rotational symmetry of the sealing face of the valve body. If the axis of rotation extends perpendicular to the sealing face of the valve body, the valve may be constructed in the manner of a tap (for example for beer).
• Provision may also be made for the valve body to be mounted so as to be rotatable about an axis of rotation relative to the valve seat, wherein the axis of rotation is oriented in the direction of the filling opening.
• Provision may further be made for the valve body to be rotatable by an angle of a maximum of 280° relative to the valve seat, preferably of a maximum of 180°, particularly preferably of a maximum of 100° relative to the valve seat and very particularly preferably of up to 90° relative to the valve seat.
• Two feed-throughs may preferably be arranged in each of the valve seat and the valve body, wherein two feed-throughs are preferably arranged offset by 180° about the center point of disks of the valve seat and of the valve body, wherein the disks form the in places closed head side of the valve seat and the sealing face of the valve body.
• Provision may moreover be made in devices with the valve for the valve body to have a port for liquid-tight connection of a bone cement cartridge or to be firmly connected to such a port.
• In this way, the valve body can be operated by means of a connected bone cement cartridge.
• Provision may also be made in devices with the valve for the sum of all openings of the at least one first feed-through in the closed head side to be at most as large as the closed surface of the head side and for the sum of all openings of the at least one second feed-through in the sealing face to be at most as large as the closed surface of the sealing face.
• This ensures that the valve can be closed stably and impermeably to the bone cement paste by rotation of the valve body relative to the valve seat.
• Provision may preferably be made in devices with the valve for the at least one first feed-through in the in places closed head side to have the same size and shape as the at least one second feed-through in the sealing face.
• Provision may preferably likewise be made for the at least one first feed-through in the in places closed head side to be two first feed-throughs and the at least one second feed-through in the sealing face to be two second feed-throughs, wherein the two first feed-throughs are preferably arranged in the valve seat in quadrants arranged opposingly with regard to the axis of rotation of the valve body and the two second feed-throughs are arranged in the sealing face in quadrants arranged opposingly with regard to the axis of rotation of the valve body.
• Due to these two measures, a sufficient flow area can be provided for the viscid bone cement paste and unilateral loading of the valve, which might otherwise lead to valve leaks, can be avoided.
• Provision may further be made in devices with the valve for a collar to be arranged on the sealing face of the valve body, which collar rests on an edge of the valve seat or a collar is arranged on the in places closed head side of the valve seat, which collar rests on an edge of the valve body.
• In this way, stable guidance of the valve body on the valve seat can be achieved. In the event of a given thread length of the valve body, the position of the at least one second feed-through may further be precisely defined with regard to the at least one first feed-through.
• Provision may in this case be made for a radially oriented lever to be arranged on the circumferential surface of the valve body next to the collar.
• Provision may also be made in devices with the valve for a lever to be arranged on the valve body, which lever has a radial extent with regard to the axis of rotation of the valve body, wherein the lever preferably projects through an orifice in the casting mold or in the valve seat, wherein the orifice in the casting mold is optionally arranged in the region of the connection to the valve seat, wherein the orifice is dimensioned such that the valve may be transferred from the open position into the closed position and vice versa by rotation of the valve body in the valve seat by means of the lever, wherein the orifice is particularly preferably dimensioned such that the valve body may be rotated by a maximum of 90° relative to the valve seat.
• As a result, the valve is conveniently manually operable from outside. Using this lever, the valve body can be rotated from the open position into the closed position of the valve.
• Provision may further be made in devices with the valve for the valve body and the valve seat to be fabricated of a plastics material, in particular of a thermoplastic, wherein the valve seat is preferably adhesively bonded or welded to a wall of the casting mold.
• In this way, the valve and thus the device can be fabricated inexpensively and as a hygienic disposable product.
• Provision may preferably be made for the valve seat to have ribs on its outside, which enter into or may enter into form-fitting connection with the casting mold.
• Provision may also be made for the device to have an adapter element which is connected or connectable to a bone cement cartridge, wherein the adapter element is detachably and interlockingly connected or connectable to the port, such that an interior of the bone cement cartridge is connected or connectable permeably for bone cement paste via the adapter element to the filling opening. If the device has the valve, provision may be made for the interior of the bone cement cartridge to be connected or connectable, via the adapter element for bone cement paste and permeably to bone cement paste, to the at least one second feed-through in the valve body of the valve.
• Provision may be made for the device to have a bone cement cartridge for mixing bone cement starting components and for delivering mixed bone cement paste from the bone cement cartridge and preferably to have a bone cement cartridge for mixing polymethyl methacrylate bone cement starting components and for delivering mixed polymethyl methacrylate bone cement paste from the bone cement cartridge, wherein the bone cement cartridge particularly preferably contains the bone cement starting components for producing the bone cement in mutually separate regions.
• In this way, the device is further completed since the device may then also provide the bone cement paste which is filled into the casting mold for forming the spacer and with which the mold cavity of the casting mold is expanded by the bone cement cartridge exerting the pressure required for this purpose on the bone cement paste.
• Provision may moreover be made for the casting mold to have at least three or four cavities, starting from an inner chamber of the casting mold, for receiving retaining pins, wherein the cavities are preferably arranged in the stem mold and the stem mold is particularly preferably in two parts or three parts and the cavities are arranged in edges or in longitudinal flanges of at least one part of the two-part stem mold.
• Using these cavities, a metal core may be arranged and precisely positioned in the casting mold and thus in the spacer as reinforcement.
• Provision may also be made for the device to have a metal core which is to be arranged in the casting mold, wherein the metal core preferably has bores for receiving retaining pins, wherein those bores which are to be arranged in the stem mold are particularly preferably arranged within the part of the metal core.
• The metal core preferably consists of a biocompatible metal or of a biocompatible metal alloy, particularly preferably of surgical steel.
• Provision may also be made for the device to have at least three or four retaining pins for retaining the metal core in the casting mold.
• The metal core serves to stabilize the spacer and so ensure better durability of the treated joint.
• The metal core is held by the retaining pins in a defined position within the casting mold. In this way, the thickness of the bone cement jacket around the metal core is defined. The retaining pins are preferably fabricated from a biocompatible plastics material. Polymethyl methacrylate is particularly suitable for this. Retaining pins of polymethyl methacrylate bond irreversibly to the bone cement paste. After curing of the bone cement paste, the retaining pins projecting out of the spacer are simply cut off. The residues of the retaining pins located inside the spacer remain therein.
• Provision may preferably also be made for the spherical surface-shaped inner surface of the mold cavity to have, in the unexpanded state, a diameter of at least 35 mm or of at least 40 mm and preferably of between 40 mm and 50 mm.
• It can also be provided that the spherical surface-shaped inner surface of the mold cavity to have, in the maximally expanded state, a diameter of at most 70 mm and preferably of between 60 mm and 70 mm.
• Furthermore it can be provided that in the unexpanded state, the diameter of the spherical surface-shaped inner surface of the mold cavity is smaller than the diameter of the spherical surface-shaped inner surface of the mold cavity in the expanded state.
• The maximally expanded state is the state which is achievable when the pressure on the bone cement paste is produced with the assistance of a conventional bone cement cartridge. A conventional bone cement cartridge is for example a Palacos® bone cement cartridge, as is obtainable from Heraeus Medical GmbH.
• In this way, it is possible to produce spacers with heads as are conventional in the field of hip spacers. It is here preferred that, even in the case of the smallest size, an expanded state of the mold cavity is necessary such that, even in the case of the smallest size, the mold cavity also exerts pressure on the bone cement paste in the casting mold with which the desired shape is achieved and with which entrapped air from the bone cement paste can be expelled from the casting mold through the at least one vent element. It is further possible in this manner to produce, using the device, hip spacers with conventional spacer head diameters in the range from 46 mm to 65 mm. Shoulder spacers with spacer head diameters of 40 mm to 50 mm can likewise be produced.
• Provision may moreover be made for the mold cavity to consist, at least in the region of the spherical surface-shaped inner surface, of a rubber-elastic material, preferably of rubber, silicone rubber, a synthetic rubber or an ethylene-propylene-diene rubber (EPDM).
• Ethylene-propylene-diene rubbers (EPDM) are terpolymers of ethylene, propylene and a diene which is not specified in greater detail.
• The materials are particularly well suited for the mold cavity or the region of the spherical surface-shaped inner surface of the mold cavity in order to enable elastic deformation. Any other rubber-elastic, biocompatible plastics material may additionally be considered as a material for forming the mold cavity.
• Provision may also be made for the at least one filling opening to contain a shut-off element which, in a closed state, prevents the bone cement paste from flowing out of the casting mold through the at least one filling opening.
• In this way, the pressure of the bone cement paste in the casting mold can be maintained during curing and the mold cavity can thus be kept in the expanded state, wherein the at least one filling opening is simultaneously closed with the shut-off element. The formation of a solid sprue can be prevented as a result.
• Provision may further be made for the stem mold to comprise a length-variable adapter element with which the length of the neck of the spacer which connects the stem to the head of the spacer connector is able to be varied, wherein the adapter element is preferably able to be varied in length by a screw connection.
• As a result, the length of the neck of the spacer can be varied and adjusted and thus adapted to the individual treatment situation.
• Provision may also be made for the device to have a plurality of dimensionally stable mating molds which are suitable for receiving the mold cavity, wherein the dimensionally stable mating molds enable a different degree of expansion of the mold cavity, such that, at least in the region of the spherical surface-shaped inner surface, expansion of the mold cavity is limited by the dimensionally stable mating molds to different diameters when the mold cavity is inserted into the respective dimensionally stable mating mold, wherein the dimensionally stable mating molds are preferably embodied by at least one blister pack or a plastics shell with one or a plurality of indentations as the dimensionally stable mating molds.
• Provision may moreover be made for the device to have a check gage or a vernier caliper for measuring the current diameter of the spherical surface-shaped inner surface of the mold cavity, wherein the check gage or vernier caliper may be placed or is arranged on the outside of the mold cavity and wherein the diameter of the spherical surface-shaped inner surface of the mold cavity is preferably directly readable.
• These measures simplify use of the device. The user can in this way determine or adjust the desired diameter of the head of the spacer. Thanks to the dimensionally stable mating molds, the user can produce a spacer with a head having the desired diameter or desired shape without in this connection having to pay particularly precise attention to the pressure exerted on the bone cement paste.
• The objects underlying the present invention are also achieved by a method for producing a spacer for temporarily replacing a joint or part of a joint, in particular a hip joint or a shoulder joint, comprising an articulating surface of the joint, wherein the method is carried out with an above-stated device, the method having the following chronological steps:
• A) injecting bone cement paste through the at least one filling opening into the casting mold and simultaneously displacing air from the casting mold through the at least one vent element by injection of the bone cement paste;
• B) further injecting bone cement paste though the at least one filling opening into the casting mold, wherein injection of the bone cement paste expands the mold cavity at least in the region of the spherical surface-shaped inner surface, while the stem mold remains dimensionally stable;
• C) curing the bone cement paste in the casting mold; and
• D) removing the resultant molded and cured spacer from the casting mold.
• Provision here may be made for the bone cement paste to expel the air from the casting mold through the at least one vent element until the bone cement paste impinges on a filter impermeable to bone cement paste, in particular a porous filter permeable to gas but impermeable to bone cement paste, in the at least one vent element.
• The method is not put to direct medical therapeutic use. Only the spacer produced by the method according to the invention may be used for therapeutic measures or for medical treatment. Production of the spacer does not involve intervention on the body.
• The spacer is intended for medical applications. The method according to the invention does not comprise implantation in a patient but merely forming the spacer. After step D), the spacer can be trimmed of flash, smoothed, sanded, cleaned, polished and/or roughened in places.
• In order to remove the molded and cured spacer from the casting mold in step D), the casting mold can be opened after step C).
• Provision may be made for a bone cement cartridge to be connected in liquid-tight manner to a port of the device before step A), wherein the port is connected to the at least one filling opening in liquid-permeable manner and in step A) the bone cement paste is pressed out of the bone cement cartridge into the casting mold.
• In this way, the bone cement cartridge can be used for filling the casting mold and for building up the pressure on the bone cement paste in the casting mold in order to expand the cavity with the bone cement paste.
• Provision may here be made for a device according to any one ofclaims9 to12 to be used with a valve, wherein bone cement paste is injected in step A) through the valve in the open position into the casting mold, wherein a step B1) proceeds after step B) and before step C):
• B1) rotating the valve body relative to the valve seat and so transferring the valve into the closed position and shearing off the bone cement paste at the at least one first feed-through in the in places closed head side of the valve seat by rotation of the valve body relative to the valve seat, wherein a bone cement cartridge is then preferably detached from a port which is connected to the at least one filling opening in liquid-permeable manner.
• As a result, the pressure which is exerted by the bone cement paste on the mold cavity can also be maintained when the valve is closed and a bone cement cartridge is no longer connected. As a result, on the one hand a thin, easily severable sprue is produced and on the other hand bone cement paste is prevented from flowing back out of the casting mold and so resulting in a head of the spacer which has an excessively small diameter.
• Provision may further be made for the following intermediate steps to proceed after step B1) and before step C):
• B2) connecting a new bone cement cartridge to the port of the device in liquid-tight manner, wherein bone cement paste or starting components for producing the bone cement paste is or are present in the new bone cement cartridge;
• B3) rotating the valve body relative to the valve seat and so transferring the valve into the open position;
• B4) injecting bone cement paste from the new bone cement cartridge through the valve in the open position into the casting mold;
• B5) rotating the valve body relative to the valve seat and so transferring the valve into the closed position and shearing off the bone cement paste at the at least one first feed-through in the in places closed head side of the valve seat by rotation of the valve body relative to the valve seat; and
• B6) detaching the new bone cement cartridge from the port;
• wherein steps B2) to B6) are preferably repeated once or multiple times with in each case new bone cement cartridges which contain bone cement paste or the starting components thereof until the casting mold is completely filled with bone cement paste and furthermore until, with the assistance of the bone cement paste, the mold cavity is expanded to the desired size at least in the region of the spherical surface-shaped inner surface.
• In this way, a casting mold with a large volume may be filled with a plurality of bone cement cartridges containing small volumes of the bone cement paste. This is advantageous, for example, for the production of large-volume hip joint spacers.
• Provision may be made for the bone cement paste to be mixed before step A), and preferably before connection of the bone cement cartridge, in the bone cement cartridge from a monomer liquid and a cement powder, wherein, optionally before step B3) and preferably before step B2), the bone cement paste is preferably mixed in the new bone cement cartridge from a monomer liquid and a cement powder.
• In this way, a freshly mixed bone cement paste can be used for producing the spacer. PMMA bone cement pastes in particular can be stored for periods of more than a few minutes only with difficulty if at all in the mixed state. In addition, suitable therapeutic pharmaceutical active substances, such as antibiotics and antimycotics, may accordingly be mixed into the bone cement paste only shortly before production of the spacer.
• Provision may also be made for the bone cement cartridge and/or the new bone cement cartridge to be rotated or screwed into the port for liquid-tight connection of the bone cement cartridge and/or the new bone cement cartridge to the port and, for detaching the bone cement cartridge and/or the new bone cement cartridge from the port, the bone cement cartridge or the new bone cement cartridge is rotated out of or unscrewed from the port.
• In addition to being screw-fastened, the bone cement cartridge may for example be connected to the port with a bayonet closure.
• By rotating or screwing the bone cement cartridge into the port, it is possible to provide a liquid-tight connection between the port and the bone cement cartridge. In addition the rotation may also rotate or cause the valve body to rotate relative to the valve seat.
• Provision may further be made for rotation of the valve body relative to the valve seat to proceed by screwing the valve body in the valve seat or by manually rotating the valve body relative to the valve seat, wherein manual rotation preferably proceeds by operation of a lever extending radially away from the valve body and extending through an orifice in the casting mold or in the valve seat.
• As a result, the valve is simply operable by the user.
• Provision may moreover be made for injection of the bone cement paste from the bone cement cartridge or the new bone cement cartridge to proceed by pushing a piston into an interior of the bone cement cartridge.
• In this way, the bone cement paste can straightforwardly be injected from the bone cement cartridge through the open valve into the casting mold.
• Provision may also be made for a metal core to be arranged within the casting mold before step A) and preferably before connecting the bone cement cartridge, wherein the metal core is preferably spaced from an internal wall of the stem mold via a plurality of retaining pins, wherein the plurality of retaining pins are particularly preferably fastened in bores in the metal core and in cavities for receiving retaining pins in the internal wall of the stem mold.
• In this way, with the assistance of the device, the spacer may be constructed with an internal reinforcement. The bone cement paste in this case flows around the metal core arranged in the casting mold.
• Provision may preferably further be made for the mold cavity of the casting mold to be used in one of a plurality of dimensionally stable mating molds, wherein the dimensionally stable mating molds enable a different degree of expansion of the mold cavity, such that, at least in the region of the spherical surface-shaped inner surface, expansion of the mold cavity is limited by the dimensionally stable mating mold used to a specific diameter while the bone cement paste is pressed into the casting mold in order to expand the mold cavity.
• Provision may moreover be made for a check gage or a vernier caliper for measuring the current diameter of the spherical surface-shaped inner surface of the mold cavity to be used to read off the current diameter of the spherical surface-shaped inner surface of the mold cavity, wherein injection of the bone cement paste into the casting mold is preferably stopped once a desired diameter is reached.
• These measures simplify the application of the method. The user can in this way determine or adjust the desired diameter of the head of the spacer. Thanks to the dimensionally stable mating molds, the user can produce a spacer with a head having the desired diameter or desired shape without in this connection having to pay particularly precise attention to the pressure exerted on the bone cement paste.
• The invention is based on the surprising recognition that, thanks to the expandable mold cavity, it is possible to provide a casting mold with a variable head size for producing a spacer, such that spacers with different heads, in particular with heads with different diameters, can be produced with the casting mold. The diameter may here be adjusted continuously. The diameter of the head of the spacer can be adjusted by a pressure imparted (in particular manually) by means of the injected bone cement paste. The device is consequently particularly simple and intuitive to use.
• One particular advantage of the present invention consists in its being possible by expanding the casting mold in the head region to produce spacers with different head diameters with a hip or shoulder spacer casting mold, without separate head casting molds being required for each desired head diameter which have to be connected in troublesome manner to the stem mold for the spacer stem. The head diameter of the spacers can be continuously adjusted by the user by injecting polymethyl methacrylate bone cement. This means that hip and shoulder spacers with all anatomically possible head diameters can be produced with a single casting mold. There are normally at least four different head sizes in conventional spacer casting molds. These can be replaced by a single casting mold. Costs for manufacturing and also logistics are considerably reduced as a consequence.
• Additional advantages are obtained for devices with a valve. Bone cement paste, in particular non-high-viscosity bone cement paste, cannot flow out of the casting mold through the closure or closed valve. Contraction of the mold cavity and consequently a reduction in the diameter of the spacer head is prevented as a consequence. Any formation of defects in the spacer as a result of bone cement flowing out is likewise prevented. Furthermore, the measures according to the invention ensure that the residue of bone cement paste left behind in the bone cement cartridge is separated from the bone cement paste in the casting mold. Once curing of the bone cement paste is complete, it is therefore no longer necessary to separate the sprue mechanically, for example by sawing. Any remaining thin connections can easily be broken or cut off This saves time and effort for the OP personnel.
• The sprue of the spacer is formed by the at least one filling opening with the valve seat and the valve body. Rotating the valve body relative to the valve seat from the open position into the closed position of the valve closes the casting mold impermeably to bone cement paste. This means that the sprue formed by the valve seat and the valve body, or the sprue-shaping parts simultaneously function as a valve. There is no need for complex additional valves.
• The valve body may be manually rotated relative to the valve seat by a lever on the outside of the valve body. Rotation may advantageously also proceed by the valve body being co-rotated by the bone cement cartridge when the bone cement cartridge is unscrewed. It is, however, necessary here for a limit stop to limit the rotational movement of the valve body relative to the valve seat so that closure can be reliable and so that the valve body cannot be completely unscrewed from the valve seat.
• A spacer produced with the device may advantageously be used in the context of two-stage septic revisions, in which an infection with two or more microbial microorganisms and in particular with problematic microorganisms is present.
• An exemplary device according to the invention may be composed of
• a) a dimensionally stable hollow stem mold which reproduces the stem and the neck of the spacer,
• b) a port (as the at least one filling opening) for injecting polymethyl methacrylate bone cement paste,
• c) a rubber-elastic, at least hemispherical mold cavity which is connected or connectable to the dimensionally stable hollow stem mold of the casting mold,
• d) at least one vent element which connects the interior of the dimensionally stable hollow stem mold and the rubber-elastic, at least hemispherical mold cavity to the surrounding atmosphere, wherein the at least one vent element is permeable to gases and impermeable to pasty polymethyl methacrylate bone cement, and
• e) wherein the diameter of the rubber-elastic, at least hemispherical mold cavity, is continuously enlarged or enlargeable by the volume of polymethyl methacrylate bone cement paste injected into the casting mold with expansion of the rubber-elastic, at least hemispherical mold cavity.
• The device according to the invention or the exemplary casting mold of the device may also have hollow cylinders movable relative to one another for molding a neck of the spacer, wherein the neck connects the head and the stem of the spacer together and the length of the neck and thus the distance between the head and the stem of the spacer can be adjusted by relatively positioning the two hollow cylinders movable relative to one another.
• Such a device may for example have:
• a) a dimensionally stable hollow stem mold which reproduces the stem and the neck of the spacer, wherein the neck is moldable by a first hollow cylinder of the stem mold, wherein the first hollow cylinder has an inner thread,
• b) a port (as the at least one filling opening) for injecting polymethyl methacrylate bone cement paste on the dimensionally stable hollow stem mold,
• c) a rubber-elastic, at least hemispherical mold cavity which is connected to a dimensionally stable annular support, wherein a second hollow cylinder is arranged on the opposing underside, which hollow cylinder is liquid-permeably connected to the rubber-elastic, at least hemispherical mold cavity and wherein the second hollow cylinder has an outer thread, wherein
• d) the second hollow cylinder is screwed or screwable into the first hollow cylinder, whereby the distance of the hollow rubber-elastic, at least hemispherical mold cavity from the longitudinal axis of the stem mold can be varied, and wherein
• e) the diameter of the rubber-elastic, at least hemispherical mold cavity can be continuously enlarged by the volume of the polymethyl methacrylate bone cement paste injected into the casting mold with expansion.
• An exemplary method according to the invention for producing spacers with the device according to the invention may comprise the following successive steps:
• a) providing the casting mold,
• b) mixing a bone cement powder with a monomer liquid in a bone cement cartridge until a bone cement paste has formed,
• c) connecting the bone cement cartridge to the port,
• d) injecting the polymethyl methacrylate bone cement paste while simultaneously displacing the air from the casting mold into the surrounding atmosphere,
• e) further injecting polymethyl methacrylate bone cement paste with expansion of the rubber-elastic, at least hemispherical mold cavity until the desired diameter is reached,
• f) curing the polymethyl methacrylate bone cement paste, and
• g) removing the spacer from the casting mold.
• An alternative exemplary method according to the invention for producing spacers with the device according to the invention may comprise the following successive steps:
• a) mixing the bone cement powder with the monomer liquid in a bone cement cartridge until a bone cement paste has formed,
• b) connecting the bone cement cartridge to the port,
• c) screwing a second hollow cylinder of the casting mold into a first hollow cylinder of the casting mold until the desired distance between the rubber-elastic, at least hemispherical mold cavity and the longitudinal axis of the stem mold is established,
• d) injecting the polymethyl methacrylate bone cement paste while simultaneously displacing the air from the casting mold into the surrounding atmosphere,
• e) further injecting polymethyl methacrylate bone cement paste with expansion of the rubber-elastic, at least hemispherical mold cavity until the desired diameter is reached,
• f) curing the polymethyl methacrylate bone cement paste, and
• g) removing the spacer from the casting mold.
BRIEF DESCRIPTION OF THE DRAWINGS
• Further exemplary embodiments of the invention are explained below with reference to twenty-eight schematic figures but without thereby limiting the invention. Therein:
• FIG. 1 shows a schematic perspective cross-sectional view of a first exemplary device according to the invention for producing a hip joint spacer;
• FIG. 2 shows a schematic perspective external view of the first device according to the invention according toFIG. 1;
• FIG. 3 shows a schematic perspective cross-sectional view of the first device according to the invention according toFIGS. 1 and 2 with the valve open;
• FIG. 4 shows a schematic perspective cross-sectional view of the first device according to the invention according toFIGS. 1 to 3 with the valve closed;
• FIG. 5 shows a schematic cross-sectional view of the first device according to the invention with the valve open prior to the filling of bone cement paste into a casting mold of the device;
• FIG. 6 shows a schematic cross-sectional view of the first device according to the invention during the filling of bone cement paste into the casting mold;
• FIG. 7 shows a schematic cross-sectional view of the first device according to the invention with a casting mold filled with bone cement paste;
• FIG. 8 shows a schematic cross-sectional view of the first device according to the invention with a casting mold filled with bone cement paste with the valve closed;
• FIG. 9 shows a schematic cross-sectional view of the first device according to the invention with the valve closed with an unexpanded mold cavity after removal of a bone cement cartridge and an adapter element from the casting mold;
• FIG. 10 shows a schematic cross-sectional view of the first device according to the invention with the valve closed and a bone cement cartridge detached from the mold cavity;
• FIG. 11 shows a schematic perspective view of a second exemplary device according to the invention for producing a shoulder joint spacer with an open two-part stem mold;
• FIG. 12 shows a schematic perspective view of the second device according to the invention according toFIG. 11;
• FIG. 13 shows a schematic perspective cross-sectional view of the second device according to the invention according toFIGS. 11 and 12 with an extended adapter element;
• FIG. 14 shows a schematic perspective view of the second device according to the invention according toFIG. 13 with an open two-part stem mold and an extended adapter element;
• FIG. 15 shows a schematic perspective external view of the closed second device according to the invention according toFIGS. 11 to 14;
• FIG. 16 shows a schematic cross-sectional view of the second device according to the invention filled with bone cement paste from the bone cement cartridge;
• FIG. 17 shows a schematic cross-sectional view of the second device according to the invention with the valve closed after removal of a bone cement cartridge and an adapter element from the casting mold;
• FIG. 18 shows a schematic perspective external view of the closed second device according to the invention according toFIGS. 11 to 17 with an extended adapter element and expanded mold cavity dimensions indicated by dashed lines;
• FIG. 19 shows a schematic perspective cross-sectional view of the second device according to the invention with an expanded mold cavity and with an extended adapter element;
• FIG. 20 shows a perspective view of a spacer which has been produced using a second device according to the invention according toFIGS. 11 to 19;
• FIG. 21 shows a perspective view of a spacer with an extended neck which has been produced using a second device according to the invention according toFIGS. 11 to 19;
• FIG. 22 shows a schematic perspective view of a valve for a device according to the invention in the open state;
• FIG. 23 shows a schematic perspective partial cross-sectional view of the valve according toFIG. 22 in the open state;
• FIG. 24 shows a schematic perspective cross-sectional view through the valve according toFIGS. 22 and 23 in the open state;
• FIG. 25 shows a schematic perspective view of the valve according toFIGS. 22 to 24 in the closed state;
• FIG. 26 shows a schematic perspective partial cross-sectional view of the valve according toFIGS. 22 to 25 in the closed state;
• FIG. 27 shows a schematic perspective cross-sectional view of the valve according toFIGS. 22 to 26 in the closed state; and
• FIG. 28 shows a schematic cross-sectional view of the valve according toFIGS. 22 to 27 in the closed state.
DETAILED DESCRIPTION
• FIGS. 1 to 11 are drawings showing various views of a first exemplary embodiment of a device according to the invention for producing a hip joint spacer and parts thereof.
• The first device according to the invention is suitable and provided for producing a spacer for a hip joint. The device comprises a castingmold1. The castingmold1 may be constructed in multiple parts, in particular in three parts.FIGS. 1 and 3 to 11 show the castingmold1 open or sectioned, such that the interior structure of the device is visible. The castingmold1 may have aproximal mold cavity32 for molding a head of the spacer and adistal stem mold34 for molding a stem of the spacer. The shaping parts of themold cavity32 may be in one part and the shaping parts of thestem mold34 may be in two parts (seeFIG. 2).FIG. 2 shows all the parts of the castingmold1. Themold cavity32 may have a spherical surface-shaped inner surface in the form of a hemisphere. The spherical surface-shaped inner surface of themold cavity32 serves as a negative mold for forming a sliding surface of the head of the spacer. According to the invention, themold cavity32 is expandable in order to enable production of sliding surfaces with different radii or spacer joint heads (heads of spacers) with different diameters which are molded by the spherical surface-shaped inner surface of themold cavity32.
• A fillingopening2 for the introduction ofbone cement paste50 may be formed on one side of the castingmold1, which filling opening may be defined in each case in both parts of thestem mold34 by a semicircular cylindrical opening. This fillingopening2 may form avalve seat3 which may be embodied as part of thestem mold34. Thevalve seat3 may be firmly connected to the castingmold1. Themold cavity32 and thus the spherical surface-shaped inner surface of the mold cavity can be continuously expanded by injecting thebone cement paste50 into the castingmold1. The diameter of the head of a spacer fabricated with the device may consequently be variably adjusted.
• Thevalve seat3 may take the form of a hollow cylinder which, apart from two first feed-throughs5, is closed on ahead side4 oriented in the direction of the fillingopening2. The two first feed-throughs5 may be quadrant-shaped and may preferably be arranged rotated or offset relative to one another by 180° with regard to the cylinder axis of thevalve seat3. Avalve body6 may be arranged in the interior of thevalve seat3 so as to be axially rotatable relative to thevalve seat3. Thevalve body6 may have a sealingface7 or surface oriented in the direction of thehead side4 of thevalve seat3. Thevalve body6 may be constructed as a stepped hollow cylinder, the front part of which can be screwed or put into thevalve seat3.
• Two second feed-throughs8 may be arranged in the sealingface7. The two second feed-throughs8 may, similarly to the first feed-throughs5, be quadrant-shaped and may preferably be arranged rotated relative to one another by 180° with regard to the cylinder axis of thevalve body6. Thevalve seat3 andvalve body6 together form a valve of the device. Anadapter element9 for liquid-tight connection of abone cement cartridge10 may be or have been screwed into the valve body6 (seeFIGS. 1 and 3 to 8). Thebone cement cartridge10 and theadapter element9 may be part of the device according to the invention. Thevalve body6 may on its open side, which is remote from the sealingface7, be formed as aport11 for connecting theadapter element9.
• Thebone cement cartridge10 may have on its front side adelivery tube37 with adelivery opening12 for delivering thebone cement paste50 from thebone cement cartridge10. Thedelivery opening12 may be arranged together with thedelivery tube37 in theadapter element9 and be delimited by thedelivery tube37. Theadapter element9 may close thebone cement cartridge10 on its front side apart from thedelivery opening12 and optionally apart from avacuum port44. Sealing may be provided by arranging in the adapter element9 aseal13 in the form of an O-ring of rubber, which seals against thedelivery tube37. Amixer36 with a plurality of mixing blades, with which thebone cement paste50 can be mixed in the interior of thebone cement cartridge10, may be fastened at the end of thedelivery tube37 pointing into the interior of thebone cement cartridge10 before thebone cement cartridge10 is connected to the valve. Thedelivery tube37 may to this end be mounted in axially linearly and rotatably mobile manner in theadapter element9.
• Themold cavity32 may consist of a rubber-elastic plastics material. As a result, themold cavity32 can be expanded with the assistance of thebone cement paste50, as is visible inFIGS. 9 and 10.FIG. 9 here shows anunexpanded mold cavity32 andFIG. 10 an expandedmold cavity32. The wall thickness of themold cavity32 is uniform, such that themold cavity32 expands uniformly when a pressure is exerted in the interior of themold cavity32 via thebone cement paste50.
• Thestem mold34 may be inexpensively fabricated from plastics film and is dimensionally stable, such that, in contrast to themold cavity32, it cannot or cannot substantially be expanded by a pressure exerted by thebone cement paste50 in the interior of the castingmold1. The plastics film may have a plurality of layers. The two parts of thestem mold34 may be fastened flush together viaflanges14. Themold cavity32 and thestem mold34 may likewise be connected flush together via aflange35 of thestem mold34 and anannular disk23 of themold cavity32. By connecting the parts of the castingmold1 via theflanges14,35 and theannular disk23, the castingmold1 may be closed to the outside. Theannular disk23 may be screwed via a segmentedannular mount21 to theflange35.Screws25 may to this end be screwed intofittings27 having inner threads which match thescrews25. The two parts of thestem mold34 may likewise be fastened together withscrews31 which are screwed intofittings33 having inner threads which match thescrews31. In order to simplify positioning of the two parts of thestem mold34 relative to one another and of themold cavity32 on thestem mold34, pins29 may be provided which can be put intorecesses39 on the opposingflange14 orflange35. Theannular disk23 seals the connection of themold cavity32 to thestem mold34 in the manner of a sealing ring.
• At least onevent element15 having in each case at least onevent opening19 may be arranged in the castingmold1. At least onevent element15 may be arranged at themold cavity32 so that it is possible to expel air from the interior of the castingmold1. Air or gas can escape through the vent opening19 from the interior of theclosed casting mold1 when abone cement paste50 is filled into the castingmold1 through the fillingopening2. Aporous filter17 which is permeable to gases but impermeable to thebone cement paste50 can be arranged in thevent element15. In this way, thebone cement paste50 is prevented from being able to escape through the vent opening19 during filling of the castingmold1 and consequently on the one hand impairing the shape of the head of the spacer and on the other hand allowing the pressure of thebone cement paste50 in themold cavity32 to decline by outflow ofbone cement paste50 from themold cavity32. This ensures that themold cavity32 remains in the desired expanded state while thebone cement paste50 begins to cure in the castingmold1. It may be sufficient for the free cross-sectional area of the vent opening19 to be so small that thebone cement paste50 cannot escape through the vent opening19 due to its viscid consistency.
• Ametal core16 may be placed in the interior of the castingmold1. Themetal core16 may consist of surgical steel or of titanium. Alternatively, it would theoretically also be possible to fabricate themetal core16 from a plastics material such as PMMA. Themetal core16 may be connected to thestem mold34 via retaining pins18. Themetal core16 may be spaced from the internal wall of the castingmold1 with the aid of the retaining pins18, such that thebone cement paste50 can flow right around themetal core16. Themetal core16 brings about stabilization of the spacer. The retaining pins18 may consist of PMMA. This can irreversibly bond to abone cement paste50 of PMMA.
• Thevalve seat3 may have aninner thread20 on its inside. On the front half of thevalve body6 facing the sealingface7, thevalve body6 may have on the outside thereof anouter thread22 matching theinner thread20 of thevalve seat3. Thevalve body6 may be screwed with itsouter thread22 into theinner thread20 of thevalve seat3.
• The first feed-throughs5 and the second feed-throughs8 may be brought into overlap with one another by screwing thevalve body6 into thevalve seat3 until the limit stop is reached. The valve is then in the open state. In this open state, abone cement paste50 may flow through the first feed-throughs5 and through the second feed-throughs8 out of thebone cement cartridge10 into the castingmold1. By making a quarter rotation (by 90°) of thevalve body6 relative to thevalve seat3, i.e. by unscrewing thevalve body6 from thevalve seat3, the first feed-throughs5 and the second feed-throughs8 may be offset relative to one another, such that the sealingface7 of thevalve body6 covers the first feed-throughs5 of thevalve seat3 and the closed regions of thehead side4 of thevalve seat3 cover the second feed-throughs8 of thevalve body6. The valve is then in the closed state. Due to the small stroke of thevalve body6 relative to thevalve seat3 in the event of a quarter rotation, the gap arising between thevalve body6 and thevalve seat3 is so narrow (less than 1 mm wide) that abone cement paste50 of a normal, let alone high, viscosity, is incapable of passing through the gap. This is particularly the case because thebone cement paste50 is deflected from its actual direction of flow by 90° in the gap.
• The reverse side of thevalve body6 may have aninner thread24 arranged in theport11. Theadapter element9 has on its front side anouter thread26 which matches theinner thread24. Theadapter element9 may accordingly be screwed into theport11 of thevalve body6. In this way, a liquid-tight connection can be created between thebone cement cartridge10 and thevalve body6 and thus into the castingmold1. Theinner thread20 of thevalve seat3, theouter thread22 of thevalve body6, theinner thread24 of thevalve body6 and theouter thread26 of theadapter element9 may all have the same direction of rotation, i.e. all these threads are right-hand threads or left-hand threads. As a result, the valve can be opened by screwing theadapter element9 into theport11 and continuing to rotate theadapter element9 in the same direction. At the same time, thevalve body6 also provides a seal relative to thevalve seat3.
• Theadapter element9 may be or have been connected via a latching means28 on theadapter element9 to amating latch30 on a cylindrical wall of thebone cement cartridge10. Acircumferential seal48 which seals the cylindrical wall of thebone cement cartridge10 relative to theadapter element9 may be provided for sealing.
• The castingmold1 may include themold cavity32 for forming the joint head (head) of the spacer and thestem mold34 for forming the stem of a spacer. Moreover, an orifice for alever38 of thevalve body6 may be arranged in the castingmold1 in the region of the fillingopening2. Thelever38 may be connected to thevalve body6. Thevalve body6 can be rotated in thevalve seat3 with thelever38. The orifice is preferably precisely large enough for thevalve body6 to be rotatable only by a maximum of a quarter rotation relative to thevalve seat3. As a result, with the assistance of thelever38, the valve can be transferred manually from outside from the open state into the closed state or from the closed state into the open state.
• In the region of theflanges14, shapes40 may be arranged in thestem mold34 for cavities, in which shapes the retaining pins18 may be arranged.
• Avacuum port44 which is capable of evacuating an interior of thebone cement cartridge10 in which thebone cement paste50 is mixed may be arranged in theadapter element9. As a result, thebone cement paste50 can be mixed under a vacuum.
• Apiston46 for discharging thebone cement paste50 from thebone cement cartridge10 through the valve into the castingmold1 may be arranged in the cylindrical interior of thebone cement cartridge10. Thepiston46 may to this end be cylindrically shaped on the outside and be sealed relative to the cylindrical interior via twocircumferential seals47. By advancing thepiston46, thebone cement paste50 can be pressed out of thedelivery opening12 of thebone cement cartridge10 into or through the open valve.
• Aporous disk52 may be arranged in theadapter element9. Theporous disk52 is impermeable to thebone cement paste50 and its starting components. Thevacuum port44 can be covered by theporous disk52. This prevents any bone cement powder as a starting component of thebone cement paste50 from being able to penetrate into thevacuum port44.
• The course of a method according to the invention is shown inFIGS. 4 to 10 with reference to the first device according to the invention. First of all, themetal core16 may be positioned with the retaining pins18 in thestem mold34. To this end, the retaining pins18 may be arranged and retained at one end between the two parts of thestem mold34 in the cavities formed by theshapes40 and arranged with the other end in matching bores in themetal core16. In order to fasten the two parts of thestem mold34 together, theflanges14 of the two parts of thestem mold34 can firstly be positioned via thepins29 in therecesses39 and then the two parts of thestem mold34 can be screwed together with the assistance of thescrews31. The castingmold1 may then be closed by fastening themold cavity32 to thestem mold34. Theannular disk23 may to this end be laid on theflange35. The two half rings of themount21 can then be laid on theannular disk23 and positioned via thepins29 and therecesses39. Themold cavity32 can then be fastened to thestem mold34 by tightening thescrews25, wherein theannular disk23 seals the connection. The castingmold1 is then closed with themetal core16 therein and can be provided to mold a spacer.
• Abone cement paste50 can be mixed under a vacuum in thebone cement cartridge10. Thebone cement cartridge10 can then be screwed with theadapter element9 into theport11 of thevalve body6. On screwing in theadapter element9, the valve can be transferred into the open position by screwing thevalve body6 into thevalve seat3 until the limit stop is reached.FIGS. 1 and 5 show this situation.
• Thebone cement paste50 is then pressed out of thebone cement cartridge10 through the valve and through the overlapping first feed-throughs5 and second feed-throughs8 into the castingmold1 by advancing thepiston46.FIG. 6 shows this situation. By closing the valve by manually operating thelever38 and so rotating thevalve body6 by a quarter rotation relative to thevalve seat3, a newbone cement cartridge10 can be attached at intervals if the volume of thebone cement paste50 from a singlebone cement cartridge10 is not enough to fill the castingmold1 completely. Thebone cement paste50 contained in the castingmold1 cannot flow back out again since thefirst passages5 and thesecond passages8 are covered in the closed position of the valve and the gap therebetween is insufficient for the viscousbone cement paste50 to be able flow through. Simultaneously, pressure from thebone cement paste50 is maintained in the interior of themold cavity32 by the closed valve.
• At some point, the castingmold1 is filled with thebone cement paste50.FIG. 7 shows this situation. Air or gas can escape from the castingmold1 through thevent element15 or through thevent openings19 in themold cavity32. Themold cavity32 can be expanded to the desired size by further injection of bone cement paste50 (seeFIG. 10 in comparison withFIG. 9). Radial expansion can be determined with the assistance of a check gage or a vernier caliper (not shown) for measuring the current diameter of themold cavity32. Since the wall thickness of themold cavity32 is known, the current diameter of the spherical surface-shaped inner surface of themold cavity32 is also determinable. Alternatively or additionally, a dimensionally stable mating mold (not shown) with a known and defined diameter may be provided into which themold cavity32 can be laid, such that themold cavity32 can only expand until it rests against the mating mold. In this way, the desired diameter of the head of the spacer produced with the device can be straightforwardly established. Once the desired radial expansion of the spherical surface-shaped inner surface of themold cavity32 has been reached, the valve can be closed.
• By closing the valve with thelever38, thebone cement paste50 is sheared or cut off This situation is shown inFIGS. 4 and 8 show this situation. Thebone cement cartridge10 can be unscrewed and removed. Any remaining thin connections simply tear or break away. This situation is shown inFIGS. 9 and 10.
• In this state, thebone cement paste50 can be cured in the castingmold1. The size or diameter of the head of the spacer here matches the diameter of the spherical surface-shaped inner surface of the expandedmold cavity32. In order to avoid unevenness of the sliding surface of the spacer, it is preferred according to the invention that, even when producing spacers with heads having the smallest diameter, themold cavity32 is already slightly expanded such that thebone cement paste50 is under pressure in the castingmold1 while it cures.
• Then, the spacer formed in this way is removed from the castingmold1. The projecting retaining pins18 may be cut off. Any sprue caused by thevalve seat3 and thefirst passages5 can likewise be cut off and removed. Points or unevenness caused by thevent opening19 may also be removed. The surface of the spacer can be polished and/or coated, for example with antibiotics.
• Instead of a castingmold1 for molding a hip joint spacer, it is also straightforwardly possible to use a casting mold for molding a different spacer.
• FIGS. 12 to 19 are drawings showing various views of a second exemplary embodiment of a device according to the invention for producing a spacer for a shoulder joint and parts thereof.FIGS. 20 and 21 show a shoulder joint spacer which has been produced using such a second device according to the invention as the result of a method according to the invention, the method steps of which are shown chronologically inFIGS. 14 to 21.
• The second device according to the invention is suitable and provided for producing aspacer120,130 (seeFIGS. 20 and 21) for a shoulder joint. The device comprises a castingmold61. The castingmold61 may be constructed in multiple parts, in particular in four parts.FIGS. 12 to 14 and 16 to 19 show the castingmold61 open or sectioned, such that the interior structure of the device is visible. The castingmold61 may have aproximal mold cavity92 for molding a head of the spacer and adistal stem mold94 for molding a stem of the spacer. The shaping parts of themold cavity92 may be in one part and the shaping parts of thestem mold94 may be in two parts (seeFIG. 15).FIG. 15 shows all the parts of the castingmold61. Themold cavity92 may have a spherical surface-shaped inner surface in the form of a hemisphere. The spherical surface-shaped inner surface of themold cavity92 serves as a negative mold for forming a sliding surface of the head of the spacer. According to the invention, themold cavity92 is expandable in order to enable production of sliding surfaces with different radii or spacer joint heads (heads of spacers) with different diameters which are molded by the spherical surface-shaped inner surface of themold cavity92.
• In contrast with the first device according to the invention, the castingmold61 additionally has anadapter element102 with aninner thread103. Theadapter element102 can be screwed with itsinner thread103 onto ahollow cylinder105 with a matchingouter thread107. The fitting105 can be molded by the two parts of thestem mold94. Theadapter element102 allows themold cavity92 to be variably spaced from thestem mold94. Theadapter element102 and the interior shape of thehollow cylinder105 shape the neck of aspacer120,130 produced with the second device according to the invention. The length of the neck of the spacer can be modified by screwing theadapter element102 relative to the hollow cylinder105 (seeFIGS. 20 and 21). Such anadapter element102 with ahollow cylinder105 for adjusting the length of the neck of the spacer may in principle also be used in the first device according to the invention.
• A fillingopening62 for the introduction ofbone cement paste50 may be formed on one side of the castingmold61, which filling opening may be defined in each case in both parts of thestem mold94 by a semicircular cylindrical opening. This fillingopening62 may form avalve seat63 which may be embodied as part of thestem mold94. Thevalve seat63 may be firmly connected to the castingmold61. Themold cavity92 and thus the spherical surface-shaped inner surface of the mold cavity can be continuously expanded by injecting thebone cement paste50 into the castingmold61. The diameter of the head of a spacer fabricated with the device may consequently be variably adjusted.
• Thevalve seat63 may take the form of a hollow cylinder which, apart from two first feed-throughs65, is closed on ahead side64 oriented in the direction of the fillingopening62. The two first feed-throughs65 may be quadrant-shaped and may preferably be arranged rotated relative to one another by 180° with regard to the cylinder axis of thevalve seat63. Avalve body66 may be arranged in the interior of thevalve seat63 so as to be axially rotatable relative to thevalve seat63. Thevalve body66 may have a sealingface67 or surface oriented in the direction of thehead side64 of thevalve seat63. Thevalve body66 may be constructed as a stepped hollow cylinder, the front part of which can be screwed or put into thevalve seat63.
• Two second feed-throughs68 may be arranged in the sealingface67. The two second feed-throughs68 may, similarly to the first feed-throughs65, be quadrant-shaped and may preferably be arranged rotated or offset relative to one another by 180° with regard to the cylinder axis of thevalve body66. Thevalve seat63 andvalve body66 together form a valve of the device. Anadapter element69 for liquid-tight connection of abone cement cartridge10 may be screwed into the valve body66 (seeFIG. 16). Thebone cement cartridge10 and theadapter element69 may be part of the device according to the invention. Thevalve body66 may on its open side, which is remote from the sealingface67, be formed as aport71 for connecting theadapter element69. The samebone cement cartridge10 as described in the first exemplary embodiment described may be used to fill the castingmold61 withbone cement paste50. The same reference signs are therefore used for both embodiments.
• Thebone cement cartridge10 may have on its front side adelivery tube37 with adelivery opening12 for delivering thebone cement paste50 from thebone cement cartridge10. Thedelivery opening12 may be arranged together with thedelivery tube37 in theadapter element9 and be delimited by thedelivery tube37. Theadapter element9 may close thebone cement cartridge10 on its front side apart from thedelivery opening12 and optionally apart from avacuum port104. Sealing may be provided by arranging in the adapter element9 aseal73 in the form of an O-ring of rubber, which seals against thedelivery tube37. Amixer36 with a plurality of mixing blades, with which thebone cement paste50 can be mixed in the interior of thebone cement cartridge10, may be fastened at the end of thedelivery tube37 pointing into the interior of thebone cement cartridge10 before thebone cement cartridge10 is connected to the valve. Thedelivery tube37 may to this end be mounted in axially linearly and rotatably mobile manner in theadapter element9.
• Themold cavity92 may consist of a rubber-elastic plastics material. As a result, themold cavity92 can be expanded with the assistance of thebone cement paste50, as is visible inFIGS. 17, 18 and 19.FIG. 17 here shows anunexpanded mold cavity92,FIG. 18 dimensions for additional possible expandedmold cavities92 as dashed lines andFIG. 19 an expandedmold cavity92. The wall thickness of themold cavity92 is uniform, such that themold cavity92 expands uniformly when a pressure is exerted in the interior of themold cavity92 via thebone cement paste50.
• Thestem mold94 and theadapter element102 may be inexpensively fabricated from plastics film and are dimensionally stable, such that, in contrast to themold cavity92, they cannot or cannot substantially be expanded by a pressure exerted by thebone cement paste50 in the interior of the castingmold61. The plastics film may have a plurality of layers. The two parts of thestem mold94 may be fastened flush together viaflanges74. Themold cavity92 and theadapter element102 may likewise be connected flush together via aflange95 of theadapter element102 and anannular disk83 of themold cavity92. By connecting the parts of the castingmold61 via theflanges74,95 and theannular disk83 and via theinner thread103 andouter thread107, the castingmold61 may be closed to the outside. Theannular disk83 may be screwed via a segmentedannular mount81 to theflange95.Screws85 may to this end be screwed intofittings87 having inner threads which match thescrews85. The two parts of thestem mold94 may likewise be fastened together withscrews91 which are screwed intofittings93 having inner threads which match thescrews91. In order to simplify positioning of the two parts of thestem mold94 relative to one another and of themold cavity92 on theflange95 of theadapter element102, pins89 may be provided which can be put intorecesses99 on the opposingflange74 orflange95. Theannular disk83 seals the connection of themold cavity92 to theadapter element102 in the manner of a sealing ring.
• At least onevent element75 having in each case at least onevent opening79 may be arranged in the castingmold61. At least onevent element75 may be arranged in themold cavity92 so that it is possible to expel air from the interior of the castingmold61. Air or gas can escape through the vent opening79 from the interior of theclosed casting mold61 when abone cement paste50 is filled into the castingmold61 through the fillingopening62. Aporous filter77 which is permeable to gases but impermeable to thebone cement paste50 can be arranged in thevent element75. In this way, thebone cement paste50 is prevented from being able to escape through the vent opening79 during filling of the castingmold61 and consequently on the one hand impairing the shape of the head of the spacer and on the other hand allowing the pressure of thebone cement paste50 in themold cavity92 to decline by outflow ofbone cement paste50 from themold cavity92. This ensures that themold cavity92 remains in the desired expanded state while thebone cement paste50 begins to cure in the castingmold61. It may be sufficient for the free cross-sectional area of the vent opening79 to be so small that thebone cement paste50 cannot escape through the vent opening79 due to its viscid consistency.
• Ametal core76 may be placed in the interior of the castingmold61. Themetal core76 may consist of surgical steel or of titanium. Alternatively, it would theoretically also be possible to fabricate themetal core76 from a plastics material such as PMMA. Themetal core76 may be connected to thestem mold94 via retaining pins78. Themetal core76 may be spaced from the internal wall of the castingmold61 with the aid of the retaining pins78, such that thebone cement paste50 can flow right around themetal core76. Themetal core76 brings about stabilization of thespacer120,130. The retaining pins78 may consist of PMMA. This can irreversibly bond to abone cement paste50 of PMMA.
• Thevalve seat63 may have aninner thread80 on its inside. On the front half of thevalve body66 facing the sealingface67, thevalve body66 may have on the outside thereof anouter thread82 matching theinner thread80 of thevalve seat63. Thevalve body66 may be screwed with itsouter thread82 into theinner thread80 of thevalve seat63.
• The first feed-throughs65 and the second feed-throughs68 may be brought into overlap with one another by screwing thevalve body66 into thevalve seat63 until the limit stop is reached. The valve is then in the open state. In this open state, abone cement paste50 may flow through the first feed-throughs65 and through the second feed-throughs68 out of thebone cement cartridge10 into the castingmold61. By making a quarter rotation (by 90°) of thevalve body66 relative to thevalve seat63, i.e. by unscrewing thevalve body66 from thevalve seat63, the first feed-throughs65 and the second feed-throughs68 may be offset relative to one another, such that the sealingface67 of thevalve body66 covers the first feed-throughs65 of thevalve seat63 and the closed regions of thehead side64 of thevalve seat63 cover the second feed-throughs68 of thevalve body66. The valve is then in the closed state. Due to the small stroke of thevalve body66 relative to thevalve seat63 in the event of a quarter rotation, the gap arising between thevalve body66 and thevalve seat63 is so narrow (less than1 mm wide) that abone cement paste50 of a normal, let alone high, viscosity, is incapable of passing through the gap. This is particularly the case because thebone cement paste50 is deflected from its actual direction of flow by 90° in the gap.
• The reverse side of thevalve body66 may have aninner thread84 arranged in theport71. Theadapter element69 has on its front side anouter thread86 which matches theinner thread84. Theadapter element69 may accordingly be screwed into theport71 of thevalve body66. In this way, a liquid-tight connection can be created between thebone cement cartridge10 and thevalve body66 and thus into the castingmold61. Theinner thread80 of thevalve seat63, theouter thread82 of thevalve body66, theinner thread84 of thevalve body66 and theouter thread86 of theadapter element69 may all have the same direction of rotation, i.e. all these threads are right-hand threads or left-hand threads. As a result, the valve can be opened by screwing theadapter element69 into theport71 and continuing to rotate theadapter element69 in the same direction. At the same time, thevalve body66 also provides a seal relative to thevalve seat63.
• Theadapter element69 may be or have been connected via a latching means88 on theadapter element69 to amating latch30 on a cylindrical wall of thebone cement cartridge10. Acircumferential seal48 which seals the cylindrical wall of thebone cement cartridge10 relative to theadapter element69 may be provided for sealing.
• The castingmold61 may include themold cavity92 for forming the joint head (head) of the spacer and thestem mold94 for forming the stem of a spacer. Theadapter element102 may be considered to be part of thestem mold94. The stem mold is then in three parts. Moreover, an orifice for a lever of thevalve body66 may be arranged in the castingmold91 in the region of the fillingopening92. The lever may be connected to thevalve body66. Thevalve body66 can be rotated in thevalve seat63 with the lever. The orifice is preferably precisely large enough for thevalve body66 to be rotatable only by a maximum of a quarter rotation relative to thevalve seat63. As a result, with the assistance of the lever, the valve can be transferred manually from outside from the open state into the closed state or from the closed state into the open state.
• In the region of theflanges74, shapes100 may be arranged in thestem mold94 for cavities, in which shapes the retaining pins78 may be arranged.
• Avacuum port104 which is capable of evacuating an interior of thebone cement cartridge10 in which thebone cement paste50 is mixed may be arranged in theadapter element69. As a result, thebone cement paste50 can be mixed under a vacuum.
• Apiston46 for discharging thebone cement paste50 from thebone cement cartridge10 through the valve into the castingmold61 may be arranged in the cylindrical interior of thebone cement cartridge10. Thepiston46 may to this end be cylindrically shaped on the outside and be sealed relative to the cylindrical interior via twocircumferential seals47. By advancing thepiston46, thebone cement paste50 can be pressed out of thedelivery opening12 of thebone cement cartridge10 into or through the open valve.
• Aporous disk52 may be arranged in theadapter element69. Theporous disk52 is impermeable to thebone cement paste50 and its starting components. Thevacuum port104 can be covered by theporous disk52. This prevents any bone cement powder as a starting component of thebone cement paste50 from being able to penetrate into thevacuum port104.
• The course of a method according to the invention is shown inFIGS. 12 to 21 with reference to the second device according to the invention. First of all, themetal core76 may be positioned with the retaining pins78 in thestem mold94. To this end, the retaining pins78 may be arranged and retained at one end between the two parts of thestem mold94 in the cavities formed by theshapes100 and arranged with the other end in matching bores in themetal core76. In order to fasten the two parts of thestem mold94 together, theflanges74 of the two parts of thestem mold94 can firstly be positioned via thepins79 in therecesses99 and then the two parts of thestem mold94 to be joined together via theflange74 can be screwed together with the assistance of thescrews91. Theadapter element102 may then be screwed onto the fitting105. Theadapter element102 may here be screwed onto the fitting105 to such an extent that the desired length of the neck is obtained. Markings (not shown), from which the length of the neck of the spacer to be produced with the device can be read off, may to this end be arranged on the outside of theadapter element102. The castingmold61 may then be closed by fastening themold cavity92 to theadapter element102. Theannular disk83 may to this end be laid on theflange95. The two half rings of themount81 can then be laid on theannular disk83 and positioned via thepins89 and therecesses99. Themold cavity92 can then be fastened to theadapter element102 by tightening thescrews85, wherein theannular disk83 seals the connection. The castingmold61 is then closed with themetal core76 therein and can be provided to mold a spacer. This situation is shown inFIG. 15.
• Abone cement paste50 can be mixed under a vacuum in thebone cement cartridge10. Thebone cement cartridge10 can then be screwed with theadapter element69 into theport71 of thevalve body66. On screwing in theadapter element69, the valve can be transferred into the open position by screwing thevalve body66 into thevalve seat63 until the limit stop is reached.
• Thebone cement paste50 is then pressed out of thebone cement cartridge10 through the valve and through the overlapping first feed-throughs65 and second feed-throughs68 into the castingmold61 by advancing thepiston46. This situation is shown inFIG. 16. By closing the valve by rotating thevalve body66 by a quarter rotation relative to thevalve seat63, a newbone cement cartridge10 can be attached at intervals if the volume of thebone cement paste50 from a singlebone cement cartridge10 is not enough to fill the castingmold61 completely. Thebone cement paste50 contained in the castingmold61 cannot flow back out again since thefirst passages65 and thesecond passages68 are covered in the closed position of the valve and the gap therebetween is insufficient for the viscousbone cement paste50 to be able flow through. Simultaneously, pressure from thebone cement paste50 is maintained in the interior of themold cavity92 by the closed valve.
• At some point, the castingmold61 is filled with thebone cement paste50. Air or gas has escaped from the castingmold1 through vent openings in the castingmold61. This situation is shown inFIG. 16. Air or gas can escape from the castingmold61 through thevent element75 or through thevent openings79 in themold cavity92. Themold cavity92 can be expanded to the desired size by further injection of bone cement paste50 (seeFIGS. 18 and 19 in comparison withFIG. 17). Radial expansion can be determined with the assistance of a check gage or a vernier caliper (not shown) for measuring the current diameter of themold cavity92. Since the wall thickness of themold cavity92 is known, the current diameter of the spherical surface-shaped inner surface of themold cavity92 is also determinable. Alternatively or additionally, a dimensionally stable mating mold (not shown) with a known and defined diameter may be provided into which themold cavity92 can be laid, such that themold cavity92 can only expand until it rests against the mating mold. In this way, the desired diameter of the head of the spacer produced with the device can be straightforwardly established. Once the desired radial expansion of the spherical surface-shaped inner surface of themold cavity92 has been reached, the valve can be closed.
• By closing the valve, thebone cement paste50 is sheared or cut off Thebone cement cartridge10 can be unscrewed and removed. Any remaining thin connections simply tear or break away. This situation is shown inFIGS. 17 and 19.
• In this state, thebone cement paste50 can be cured in the castingmold61. This situation is shown inFIG. 19. The size or diameter of the head of the spacer here matches the diameter of the spherical surface-shaped inner surface of the expandedmold cavity92. In order to avoid unevenness of the sliding surface of the spacer, it is preferred according to the invention that, even when producing spacers with heads having the smallest diameter, themold cavity92 is already slightly expanded such that thebone cement paste50 is under pressure in the castingmold61 while it cures.
• Then, thespacer120,130 (seeFIGS. 20 and 21) formed in this way is removed from the castingmold1. The projecting retaining pins78 may be cut off. Any sprue caused by thevalve seat63 and thefirst passages65 can likewise be cut off and removed. Points caused by the vent openings may also be removed. This situation is shown inFIGS. 20 and 21.
• FIG. 20 shows the removedspacer120. Thespacer120 has ahead122 which has been shaped by themold cavity92. Thespacer120 was shaped by curing thebone cement paste50 in the castingmold61, as shown inFIG. 17. Thehead122 is connected via aneck126 to astem124 of thespacer120.
• FIG. 21 shows analternative spacer130 with alonger neck136 which has been molded by extension with the adapter element102 (seeFIGS. 18 and 19). Thespacer130 has ahead132 which has been shaped by themold cavity92. Thespacer130 was shaped by curing thebone cement paste50 in the castingmold61, as shown inFIG. 18. Thehead132 is connected via theneck136 to astem134 of thespacer130. In its proximal region, theneck134 has the shape of a thread since it is a negative shape of theinner thread103 of theadapter element102. If required, the surface in this region can be smoothed.
• The surface of thespacer120,130 can be polished and/or coated, for example with antibiotics.
• Instead of a castingmold61 for molding a shoulder joint spacer, it is also straightforwardly possible to use a casting mold for molding a different spacer.
• FIGS. 22 to 28 show a valve for a device according to the invention for producing a spacer in the open position (FIGS. 22 to 24) and in the closed position (FIGS. 25 to 28). The valve corresponds to the valves of the first device according to the invention according toFIGS. 1 to 11 and of the second device according to the invention according toFIGS. 12 to 19, but may also be used with other casting molds to produce other spacers.
• The valve has avalve seat163, which may be arranged in a filling opening of a casting mold (not shown). Thevalve seat163 may be firmly connected to a part of the casting mold or have been made in one piece with the casting mold. For better and tighter connectability of thevalve seat163 to a casting mold, thevalve seat163 may have patterning on its external surface, for example longitudinal grooves, which are arranged parallel to the cylinder axis of a cylindrical outer wall of thevalve seat163.
• Thevalve seat163 may take the form of a hollow cylinder which, apart from two first feed-throughs165, is closed on ahead side164. The two first feed-throughs165 may be quadrant-shaped and may preferably be arranged rotated relative to one another by 180° with regard to the cylinder axis of thevalve seat163. Avalve body166 may be arranged in the interior of thevalve seat163 so as to be axially rotatable relative to thevalve seat163. Thevalve body166 may have a sealingface167 or surface oriented in the direction of thehead side164 of thevalve seat163. Thevalve body166 may be constructed as a stepped hollow cylinder, the front part of which can be screwed or put into thevalve seat163.
• Two second feed-throughs168 may be arranged in the sealingface167. The two second feed-throughs168 may, similarly to the first feed-throughs165, be quadrant-shaped and may preferably be arranged rotated or offset relative to one another by 180° with regard to the cylinder axis of thevalve body166. Thevalve seat163 andvalve body166 together form the valve of a device according to the invention. An adapter element (not shown) for liquid-tight connection of a bone cement cartridge (not shown) may be screwed into thevalve body166. Thevalve body166 may on its open side, which is remote from the sealingface167, be formed as aport171 for connecting an adapter element.
• Thevalve seat163 may have aninner thread180 on its inside. On the front half of thevalve body166 facing the sealingface167, thevalve body166 may have on the outside thereof anouter thread182 matching theinner thread180 of thevalve seat163. Thevalve body166 may be screwed with itsouter thread182 into theinner thread180 of thevalve seat163.
• The first feed-throughs165 and the second feed-throughs168 may be brought into overlap with one another by screwing thevalve body166 into thevalve seat163 until the limit stop is reached. The valve is then in the open state. In this open state (seeFIGS. 22 to 24), a bone cement paste may flow through the first feed-throughs165 and through the second feed-throughs168. By making a quarter rotation (by 90°) of thevalve body166 relative to thevalve seat163, i.e. by unscrewing thevalve body166 from thevalve seat163, the first feed-throughs165 and the second feed-throughs168 may be offset relative to one another, such that the sealingface167 of thevalve body166 covers the first feed-throughs165 of thevalve seat163 and the closed regions of thehead side164 of thevalve seat163 cover the second feed-throughs168 of thevalve body166. The valve is then in the closed state (seeFIGS. 25 to 28). Due to the small stroke of thevalve body166 relative to thevalve seat163 in the event of a quarter rotation, thegap220 arising between thevalve body166 and thevalve seat163 is so narrow (less than 1 mm wide) that a bone cement paste of a normal, let alone high, viscosity, is incapable of passing through the gap220 (seeFIG. 28). This is particularly the case because the bone cement paste is deflected from its actual direction of flow by 90° in thegap220. Aprojection216 may be provided in order to ensure more stable, non-rotatable connection of thevalve seat163 to the casting mold.
• The reverse side of thevalve body166 may have aninner thread184 arranged in theport171. An adapter element (not shown) may accordingly be screwed into theport171 of thevalve body166. Theinner thread180 of thevalve seat163, theouter thread182 of thevalve body166 and theinner thread184 of thevalve body166 may all have the same direction of rotation, i.e. all these threads are right-hand threads or left-hand threads. As a result, the valve can be opened by screwing an adapter element into theport171 and continuing to rotate the adapter element in the same direction. At the same time, thevalve body166 also provides a seal relative to thevalve seat163.
• Furthermore, alever198 may be arranged on thevalve body166. Thevalve body166 can be rotated in thevalve seat163 with thelever198. As a result, with the assistance of thelever198, the valve can be transferred manually from outside from the open state into the closed state or from the closed state into the open state.
• The features of the invention disclosed in the preceding description, as well as in the claims, figures and exemplary embodiments, may be essential both individually and in any combination for realizing the invention in its various embodiments.
LIST OF REFERENCE NUMERALS
• 1,61 Casting mold
• 2,62 Filling opening
• 3,63,163 Valve seat
• 4,64,164 Head side
• 5,65,165 Feed-through
• 6,66,166 Valve body
• 7,67,167 Sealing face
• 8,68,168 Feed-through
• 9,69 Adapter element
• 10 Bone cement cartridge
• 11,71,171 Port
• 12 Delivery opening
• 13,73 Seal
• 14,74 Flange
• 15,75 Vent element
• 16,76 Metal core
• 17,77 Porous filter
• 18,78 Retaining pin
• 19,79 Vent opening
• 20,80,180 Inner thread
• 21,81 Mount
• 22,82,182 Outer thread
• 23,83 Annular disk
• 24,84,184 Inner thread
• 25,85 Screw
• 26,86 Outer thread
• 27,87 Fitting
• 28,88 Latching means
• 29,89 Pin
• 30 Mating latch
• 31,91 Screw
• 32,92 Mold cavity
• 33,93 Fitting
• 34,94 Stem mold
• 35,95 Flange
• 36 Mixer
• 37 Delivery tube
• 38 Lever
• 39,99′ Recess
• 40,100 Shape for cavities
• 44,104 Vacuum port
• 46 Piston
• 47 Seal
• 48 Seal
• 50 Bone cement paste
• 52 Porous disk
• 102 Adapter element
• 103 Internal thread
• 105 Hollow cylinder
• 107 Outer thread
• 120,130 Spacer
• 122,132 Head
• 124,134 Stem
• 126,136 Neck
• 216 Projection
• 220 Gap

Claims (28)

We claim:

1. A device for producing a spacer by curing bone cement paste, wherein the spacer is provided in the medical field for temporarily replacing a joint or part of a joint comprising an articulating surface of a head of the joint, in particular for temporarily replacing a hip joint or a shoulder joint, the device comprising:

a casting mold for molding the spacer from bone cement paste, wherein the casting mold has a stem mold for molding a stem and a neck and the casting mold has a mold cavity with a spherical surface-shaped inner surface for molding a sliding surface of a head of the spacer, wherein the stem mold and the mold cavity delimit a common interior, such that the head of a spacer molded with the casting mold is connected as one part via the neck to the stem;

at least one filling opening for injecting a bone cement paste into the casting mold; and

at least one vent element which connects the common interior of the casting mold in a gas-permeable manner to the surroundings of the casting mold,

wherein the stem mold is dimensionally stable on injection of bone cement paste into the casting mold, and wherein, on injection of bone cement paste into the casting mold, the mold cavity is expandable, at least in the region of the spherical surface-shaped inner surface, by pressure imparted by the injected bone cement paste.

2. The device according toclaim 1, characterized in that

the at least one vent element is permeable to gases and is impermeable to bone cement paste, in particular to polymethyl methacrylate bone cement paste (PMMA bone cement paste), and/or

the at least one vent element is arranged in the mold cavity or the at least one vent element is a plurality of vent elements, wherein at least one of the plurality of vent elements is arranged in the mold cavity and at least one of the plurality of vent elements is arranged in the stem mold.

3. The device according toclaim 1, characterized in that

the mold cavity is radially expandable at least in the region of the spherical surface-shaped inner surface, by the pressure imparted by the injected bone cement paste, and/or

the mold cavity is elastically expandable, at least in the region of the spherical surface-shaped inner surface, by the pressure imparted by the injected bone cement paste.

4. The device according toclaim 1, characterized in that

the stem mold and the mold cavity are connected or connectable to one another in a liquid-tight manner via a flange or an adapter element, wherein an expandable part of the mold cavity, which comprises the spherical surface-shaped inner surface, is fastened or fastenable with an annular mount to a flange of the stem mold or the adapter element, such that a peripheral annular disk of the expandable part of the mold cavity is arranged between the annular mount and the flange and seals the connection, wherein the annular mount is particularly preferably screwed or screwable to the flange of the stem mold.

5. The device according toclaim 1, characterized in that

the device has a fastening element for fastening the mold cavity to the stem mold, wherein the fastening element is detachable and comprises a plurality of screws.

6. The device according toclaim 5, characterized in that the fastening element has clamping plates.

7. The device according toclaim 1, characterized in that

the at least one filling opening is connected on a side remote from the casting mold to a port for liquid-tight connection of a bone cement cartridge, wherein the port is suitable for pressure-tight connection of a bone cement cartridge, wherein the port has a thread and a circumferential seal and/or a circumferential sealing face or a circumferential sealing edge.

8. The device according toclaim 1, characterized in that,

at least in the region of the spherical surface-shaped inner surface, the mold cavity expands by injection of further bone cement paste into the casting mold already completely filled with bone cement paste, while the stem mold receives no additional bone cement paste and remains dimensionally stable.

9. The device according toclaim 1, characterized by

a valve seat, which is connected to the casting mold in the region of the at least one filling opening, wherein the valve seat has an in places closed head side with at least one first feed-through, wherein the at least one first feed-through opens into the at least one filling opening,

a valve body which is mounted so as to be rotatable relative to the valve seat and which has a sealing face, wherein the sealing face is oriented in the direction of the in places closed head side of the valve seat, wherein at least one second feed-through is arranged in the sealing face;

wherein the valve seat and the valve body together form a valve, wherein the valve is reversibly transferable into an open position and a closed position by rotation of the valve body relative to the valve seat, wherein, in the open position of the valve, the at least one first feed-through of the valve seat and the at least one second feed-through of the valve body are located above one another at least in places and provide a connection permeable to bone cement through the valve into the casting mold, wherein, in the closed position of the valve, the at least one first feed-through of the valve seat is covered by the sealing face of the valve body, wherein, in the closed position of the valve, the at least one filling opening of the casting mold is covered for bone cement paste.

10. The device according toclaim 9, characterized in that

the valve is connected on the side remote from the casting mold to a port for liquid-tight connection of a bone cement cartridge or the valve has such a port and/or the valve seat is connected to the casting mold so as not to be rotatable relative to the casting mold, preferably the valve seat is firmly and/or rigidly connected to the casting mold.

11. The device according toclaim 9, characterized in that

the valve is manually operable, preferably manually operable from outside the device, wherein the valve body is manually rotatable relative to the valve seat and the valve is transferable by rotation from the closed position into the open position and from the open position into the closed position.

12. The device according toclaim 9, characterized in that

the valve seat has an inner thread on the inside and the valve body has a matching outer thread on the outside, such that the valve body can be screwed into the valve seat and/or

the port comprises, for liquid-tight connection of a bone cement cartridge, an inner thread in the valve body or an outer thread on the valve body, wherein an adapter element of the bone cement cartridge or on the bone cement cartridge preferably has a mating thread matching the inner thread or the outer thread.

13. The device according toclaim 1, characterized in that

the device has a bone cement cartridge for mixing bone cement starting components and for delivering mixed bone cement paste from the bone cement cartridge and has a bone cement cartridge for mixing polymethyl methacrylate bone cement starting components and for delivering mixed polymethyl methacrylate bone cement paste from the bone cement cartridge, wherein the bone cement cartridge contains the bone cement starting components for producing the bone cement in mutually separate regions.

14. The device according toclaim 1, characterized in that

the casting mold has at least three or four cavities, starting from an inner chamber of the casting mold, for receiving retaining pins, wherein the cavities are arranged in the stem mold and the stem mold is in two parts or three parts and the cavities are arranged in edges or in longitudinal flanges of at least one part of the two-part stem mold.

15. The device according toclaim 1, characterized in that

the device has a metal core which is to be arranged in the casting mold, wherein the metal core has bores for receiving retaining pins, wherein those bores which are to be arranged in the stem mold are arranged within the part of the metal core.

16. The device according toclaim 1, characterized in that

the spherical surface-shaped inner surface of the mold cavity has, in the unexpanded state, a diameter of at least35 mm or of at least40 mm and preferably of between 40 mm and 50 mm, and/or, in the maximally expanded state, has a diameter of at most 70 mm, wherein, in the unexpanded state, the diameter of the spherical surface-shaped inner surface of the mold cavity is smaller than the diameter of the spherical surface-shaped inner surface of the mold cavity in the expanded state.

17. The device according toclaim 1, characterized in that

the mold cavity consists, at least in the region of the spherical surface-shaped inner surface, of a rubber-elastic material.

18. The device according toclaim 1, characterized in that

the at least one filling opening contains a shut-off element which, in a closed state, prevents bone cement paste from flowing out of the casting mold through the at least one filling opening.

19. The device according toclaim 1, characterized in that

the stem mold comprises a length-variable adapter element with which the length of the neck of the spacer is able to be varied, said neck connecting the stem to the head of the spacer, wherein the adapter element is able to be varied in length by a screw connection.

20. The device according toclaim 1, characterized in that

the device has a plurality of dimensionally stable mating molds which are suitable for receiving the mold cavity, wherein the dimensionally stable mating molds enable a different degree of expansion of the mold cavity, such that, at least in the region of the spherical surface-shaped inner surface, expansion of the mold cavity is limited by the dimensionally stable mating molds to different diameters when the mold cavity is inserted into the respective dimensionally stable mating mold, wherein the dimensionally stable mating molds are embodied by at least one blister pack or a plastics shell with one or a plurality of indentations as the dimensionally stable mating molds, and/or

the device has a check gage or a vernier caliper for measuring the current diameter of the spherical surface-shaped inner surface of the mold cavity, wherein the check gage or vernier caliper may be placed or is arranged on the outside of the mold cavity and wherein the diameter of the spherical surface-shaped inner surface of the mold cavity is preferably directly readable.

21. A method for producing a spacer for temporarily replacing a joint or part of a joint, in particular a hip joint or a shoulder joint, comprising an articulating surface of the joint, wherein the method is carried out with the device according toclaim 1, the method having the following chronological steps:

A) injecting bone cement paste through the at least one filling opening into the casting mold and simultaneously displacing air from the casting mold through the at least one vent element by injection of the bone cement paste;

B) further injecting bone cement paste though the at least one filling opening into the casting mold, wherein injection of the bone cement paste expands the mold cavity at least in the region of the spherical surface-shaped inner surface, while the stem mold remains dimensionally stable;

C) curing the bone cement paste in the casting mold; and

D) removing the resultant molded and cured spacer from the casting mold.

22. The method according toclaim 21, characterized in that,

prior to step A), a bone cement cartridge is connected in liquid-tight manner to a port of the device, wherein the port is connected to the at least one filling opening in a liquid-permeable manner and in step A) the bone cement paste is pressed out of the bone cement cartridge into the casting mold.

23. The method according toclaim 22, characterized in that

a device according toclaim 1 with a valve is used, wherein bone cement paste is injected in step A) through the valve in the open position into the casting mold, wherein a step B1) proceeds after step B) and before step C):

B1) rotating the valve body relative to the valve seat and so transferring the valve into the closed position and shearing off the bone cement paste at the at least one first feed-through in the in places closed head side of the valve seat by rotation of the valve body relative to the valve seat, wherein a bone cement cartridge is then detached from a port which is connected to the at least one filling opening in a liquid-permeable manner.

24. The method according toclaim 23, characterized in that

the following intermediate steps proceed after step B1) and before step C):

B2) connecting a new bone cement cartridge to the port of the device in a liquid-tight manner, wherein bone cement paste or starting components for producing the bone cement paste is or are present in the new bone cement cartridge;

B3) rotating the valve body relative to the valve seat and so transferring the valve into the open position;

B4) injecting the bone cement paste from the new bone cement cartridge through the valve in the open position into the casting mold;

B5) rotating the valve body relative to the valve seat and so transferring the valve into the closed position and shearing off the bone cement paste at the at least one first feed-through in the in places closed head side of the valve seat by rotation of the valve body relative to the valve seat; and

B6) detaching the new bone cement cartridge from the port;

wherein steps B2) to B6) are preferably repeated once or multiple times with in each case new bone cement cartridges which contain bone cement paste or the starting components thereof until the casting mold is completely filled with bone cement paste and furthermore until, with the assistance of the bone cement paste, the mold cavity is expanded to the desired size at least in the region of the spherical surface-shaped inner surface.

25. The method according toclaim 21, characterized in that the mold cavity of the casting mold is inserted into one of a plurality of dimensionally stable mating molds, wherein the dimensionally stable mating molds enable a different degree of expansion of the mold cavity, such that, at least in the region of the spherical surface-shaped inner surface, expansion of the mold cavity is limited by the dimensionally stable mating mold used to a specific diameter while the bone cement paste is pressed into the casting mold in order to expand the mold cavity.

26. The method according toclaim 21, characterized in that a check gage or a vernier caliper for measuring the current diameter of the spherical surface-shaped inner surface of the mold cavity is used to read off the current diameter of the spherical surface-shaped inner surface of the mold cavity, wherein injection of the bone cement paste into the casting mold is preferably stopped once a desired diameter is reached.

27. The method according toclaim 25, characterized in that the mold cavity of the casting mold is inserted into one of a plurality of dimensionally stable mating molds, wherein the dimensionally stable mating molds enable a different degree of expansion of the mold cavity, such that, at least in the region of the spherical surface-shaped inner surface, expansion of the mold cavity is limited by the dimensionally stable mating mold used to a specific diameter while the bone cement paste is pressed into the casting mold in order to expand the mold cavity.

28. The method according toclaim 25, characterized in that a check gage or a vernier caliper for measuring the current diameter of the spherical surface-shaped inner surface of the mold cavity is used to read off the current diameter of the spherical surface-shaped inner surface of the mold cavity, wherein injection of the bone cement paste into the casting mold is preferably stopped once a desired diameter is reached.

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