US20210290397A1

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

Info

Publication number: US20210290397A1
Application number: US17/205,354
Authority: US
Inventors: Sebastian Vogt; Thomas Kluge
Original assignee: Heraeus Medical GmbH
Current assignee: Heraeus Medical GmbH
Priority date: 2020-03-20
Filing date: 2021-03-18
Publication date: 2021-09-23
Also published as: CA3107869A1; CN113491601A; CA3107860A1; AU2021200566A1; JP7048781B2; CA3107860C; AU2021200926B2; AU2021200566B2; US20210290396A1; CA3107869C; CN113491603A; JP2021146200A; US11998451B2; AU2021200926A1; JP2021146204A; JP7090186B2; CN113491603B

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 in patents DE 10 2015 104 704 B4 or EP 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 in EP 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 of 3 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 of claims 9 to 12 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 to FIG. 1;

FIG. 3 shows a schematic perspective cross-sectional view of the first device according to the invention according to FIGS. 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 to FIGS. 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 to FIG. 11;

FIG. 13 shows a schematic perspective cross-sectional view of the second device according to the invention according to FIGS. 11 and 12 with an extended adapter element;

FIG. 14 shows a schematic perspective view of the second device according to the invention according to FIG. 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 to FIGS. 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 to FIGS. 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 to FIGS. 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 to FIGS. 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 to FIG. 22 in the open state;

FIG. 24 shows a schematic perspective cross-sectional view through the valve according to FIGS. 22 and 23 in the open state;

FIG. 25 shows a schematic perspective view of the valve according to FIGS. 22 to 24 in the closed state;

FIG. 26 shows a schematic perspective partial cross-sectional view of the valve according to FIGS. 22 to 25 in the closed state;

FIG. 27 shows a schematic perspective cross-sectional view of the valve according to FIGS. 22 to 26 in the closed state; and

FIG. 28 shows a schematic cross-sectional view of the valve according to FIGS. 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 casting mold 1. The casting mold 1 may be constructed in multiple parts, in particular in three parts. FIGS. 1 and 3 to 11 show the casting mold 1 open or sectioned, such that the interior structure of the device is visible. The casting mold 1 may have a proximal mold cavity 32 for molding a head of the spacer and a distal stem mold 34 for molding a stem of the spacer. The shaping parts of the mold cavity 32 may be in one part and the shaping parts of the stem mold 34 may be in two parts (see FIG. 2). FIG. 2 shows all the parts of the casting mold 1. The mold cavity 32 may have a spherical surface-shaped inner surface in the form of a hemisphere. The spherical surface-shaped inner surface of the mold cavity 32 serves as a negative mold for forming a sliding surface of the head of the spacer. According to the invention, the mold cavity 32 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 the mold cavity 32.
A filling opening 2 for the introduction of bone cement paste 50 may be formed on one side of the casting mold 1, which filling opening may be defined in each case in both parts of the stem mold 34 by a semicircular cylindrical opening. This filling opening 2 may form a valve seat 3 which may be embodied as part of the stem mold 34. The valve seat 3 may be firmly connected to the casting mold 1. The mold cavity 32 and thus the spherical surface-shaped inner surface of the mold cavity can be continuously expanded by injecting the bone cement paste 50 into the casting mold 1. The diameter of the head of a spacer fabricated with the device may consequently be variably adjusted.
The valve seat 3 may take the form of a hollow cylinder which, apart from two first feed-throughs 5, is closed on a head side 4 oriented in the direction of the filling opening 2. The two first feed-throughs 5 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 the valve seat 3. A valve body 6 may be arranged in the interior of the valve seat 3 so as to be axially rotatable relative to the valve seat 3. The valve body 6 may have a sealing face 7 or surface oriented in the direction of the head side 4 of the valve seat 3. The valve body 6 may be constructed as a stepped hollow cylinder, the front part of which can be screwed or put into the valve seat 3.
Two second feed-throughs 8 may be arranged in the sealing face 7. The two second feed-throughs 8 may, similarly to the first feed-throughs 5, be quadrant-shaped and may preferably be arranged rotated relative to one another by 180° with regard to the cylinder axis of the valve body 6. The valve seat 3 and valve body 6 together form a valve of the device. An adapter element 9 for liquid-tight connection of a bone cement cartridge 10 may be or have been screwed into the valve body 6 (see FIGS. 1 and 3 to 8). The bone cement cartridge 10 and the adapter element 9 may be part of the device according to the invention. The valve body 6 may on its open side, which is remote from the sealing face 7, be formed as a port 11 for connecting the adapter element 9.
The bone cement cartridge 10 may have on its front side a delivery tube 37 with a delivery opening 12 for delivering the bone cement paste 50 from the bone cement cartridge 10. The delivery opening 12 may be arranged together with the delivery tube 37 in the adapter element 9 and be delimited by the delivery tube 37. The adapter element 9 may close the bone cement cartridge 10 on its front side apart from the delivery opening 12 and optionally apart from a vacuum port 44. Sealing may be provided by arranging in the adapter element 9 a seal 13 in the form of an O-ring of rubber, which seals against the delivery tube 37. A mixer 36 with a plurality of mixing blades, with which the bone cement paste 50 can be mixed in the interior of the bone cement cartridge 10, may be fastened at the end of the delivery tube 37 pointing into the interior of the bone cement cartridge 10 before the bone cement cartridge 10 is connected to the valve. The delivery tube 37 may to this end be mounted in axially linearly and rotatably mobile manner in the adapter element 9.
The mold cavity 32 may consist of a rubber-elastic plastics material. As a result, the mold cavity 32 can be expanded with the assistance of the bone cement paste 50, as is visible in FIGS. 9 and 10. FIG. 9 here shows an unexpanded mold cavity 32 and FIG. 10 an expanded mold cavity 32. The wall thickness of the mold cavity 32 is uniform, such that the mold cavity 32 expands uniformly when a pressure is exerted in the interior of the mold cavity 32 via the bone cement paste 50.
The stem mold 34 may be inexpensively fabricated from plastics film and is dimensionally stable, such that, in contrast to the mold cavity 32, it cannot or cannot substantially be expanded by a pressure exerted by the bone cement paste 50 in the interior of the casting mold 1. The plastics film may have a plurality of layers. The two parts of the stem mold 34 may be fastened flush together via flanges 14. The mold cavity 32 and the stem mold 34 may likewise be connected flush together via a flange 35 of the stem mold 34 and an annular disk 23 of the mold cavity 32. By connecting the parts of the casting mold 1 via the flanges 14, 35 and the annular disk 23, the casting mold 1 may be closed to the outside. The annular disk 23 may be screwed via a segmented annular mount 21 to the flange 35. Screws 25 may to this end be screwed into fittings 27 having inner threads which match the screws 25. The two parts of the stem mold 34 may likewise be fastened together with screws 31 which are screwed into fittings 33 having inner threads which match the screws 31. In order to simplify positioning of the two parts of the stem mold 34 relative to one another and of the mold cavity 32 on the stem mold 34, pins 29 may be provided which can be put into recesses 39 on the opposing flange 14 or flange 35. The annular disk 23 seals the connection of the mold cavity 32 to the stem mold 34 in the manner of a sealing ring.
At least one vent element 15 having in each case at least one vent opening 19 may be arranged in the casting mold 1. At least one vent element 15 may be arranged at the mold cavity 32 so that it is possible to expel air from the interior of the casting mold 1. Air or gas can escape through the vent opening 19 from the interior of the closed casting mold 1 when a bone cement paste 50 is filled into the casting mold 1 through the filling opening 2. A porous filter 17 which is permeable to gases but impermeable to the bone cement paste 50 can be arranged in the vent element 15. In this way, the bone cement paste 50 is prevented from being able to escape through the vent opening 19 during filling of the casting mold 1 and consequently on the one hand impairing the shape of the head of the spacer and on the other hand allowing the pressure of the bone cement paste 50 in the mold cavity 32 to decline by outflow of bone cement paste 50 from the mold cavity 32. This ensures that the mold cavity 32 remains in the desired expanded state while the bone cement paste 50 begins to cure in the casting mold 1. It may be sufficient for the free cross-sectional area of the vent opening 19 to be so small that the bone cement paste 50 cannot escape through the vent opening 19 due to its viscid consistency.
A metal core 16 may be placed in the interior of the casting mold 1. The metal core 16 may consist of surgical steel or of titanium. Alternatively, it would theoretically also be possible to fabricate the metal core 16 from a plastics material such as PMMA. The metal core 16 may be connected to the stem mold 34 via retaining pins 18. The metal core 16 may be spaced from the internal wall of the casting mold 1 with the aid of the retaining pins 18, such that the bone cement paste 50 can flow right around the metal core 16. The metal core 16 brings about stabilization of the spacer. The retaining pins 18 may consist of PMMA. This can irreversibly bond to a bone cement paste 50 of PMMA.
The valve seat 3 may have an inner thread 20 on its inside. On the front half of the valve body 6 facing the sealing face 7, the valve body 6 may have on the outside thereof an outer thread 22 matching the inner thread 20 of the valve seat 3. The valve body 6 may be screwed with its outer thread 22 into the inner thread 20 of the valve seat 3.
The first feed-throughs 5 and the second feed-throughs 8 may be brought into overlap with one another by screwing the valve body 6 into the valve seat 3 until the limit stop is reached. The valve is then in the open state. In this open state, a bone cement paste 50 may flow through the first feed-throughs 5 and through the second feed-throughs 8 out of the bone cement cartridge 10 into the casting mold 1. By making a quarter rotation (by 90°) of the valve body 6 relative to the valve seat 3, i.e. by unscrewing the valve body 6 from the valve seat 3, the first feed-throughs 5 and the second feed-throughs 8 may be offset relative to one another, such that the sealing face 7 of the valve body 6 covers the first feed-throughs 5 of the valve seat 3 and the closed regions of the head side 4 of the valve seat 3 cover the second feed-throughs 8 of the valve body 6. The valve is then in the closed state. Due to the small stroke of the valve body 6 relative to the valve seat 3 in the event of a quarter rotation, the gap arising between the valve body 6 and the valve seat 3 is so narrow (less than 1 mm wide) that a bone cement paste 50 of a normal, let alone high, viscosity, is incapable of passing through the gap. This is particularly the case because the bone cement paste 50 is deflected from its actual direction of flow by 90° in the gap.
The reverse side of the valve body 6 may have an inner thread 24 arranged in the port 11. The adapter element 9 has on its front side an outer thread 26 which matches the inner thread 24. The adapter element 9 may accordingly be screwed into the port 11 of the valve body 6. In this way, a liquid-tight connection can be created between the bone cement cartridge 10 and the valve body 6 and thus into the casting mold 1. The inner thread 20 of the valve seat 3, the outer thread 22 of the valve body 6, the inner thread 24 of the valve body 6 and the outer thread 26 of the adapter element 9 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 the adapter element 9 into the port 11 and continuing to rotate the adapter element 9 in the same direction. At the same time, the valve body 6 also provides a seal relative to the valve seat 3.
The adapter element 9 may be or have been connected via a latching means 28 on the adapter element 9 to a mating latch 30 on a cylindrical wall of the bone cement cartridge 10. A circumferential seal 48 which seals the cylindrical wall of the bone cement cartridge 10 relative to the adapter element 9 may be provided for sealing.
The casting mold 1 may include the mold cavity 32 for forming the joint head (head) of the spacer and the stem mold 34 for forming the stem of a spacer. Moreover, an orifice for a lever 38 of the valve body 6 may be arranged in the casting mold 1 in the region of the filling opening 2. The lever 38 may be connected to the valve body 6. The valve body 6 can be rotated in the valve seat 3 with the lever 38. The orifice is preferably precisely large enough for the valve body 6 to be rotatable only by a maximum of a quarter rotation relative to the valve seat 3. As a result, with the assistance of the lever 38, 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 the flanges 14, shapes 40 may be arranged in the stem mold 34 for cavities, in which shapes the retaining pins 18 may be arranged.
A vacuum port 44 which is capable of evacuating an interior of the bone cement cartridge 10 in which the bone cement paste 50 is mixed may be arranged in the adapter element 9. As a result, the bone cement paste 50 can be mixed under a vacuum.
A piston 46 for discharging the bone cement paste 50 from the bone cement cartridge 10 through the valve into the casting mold 1 may be arranged in the cylindrical interior of the bone cement cartridge 10. The piston 46 may to this end be cylindrically shaped on the outside and be sealed relative to the cylindrical interior via two circumferential seals 47. By advancing the piston 46, the bone cement paste 50 can be pressed out of the delivery opening 12 of the bone cement cartridge 10 into or through the open valve.
A porous disk 52 may be arranged in the adapter element 9. The porous disk 52 is impermeable to the bone cement paste 50 and its starting components. The vacuum port 44 can be covered by the porous disk 52. This prevents any bone cement powder as a starting component of the bone cement paste 50 from being able to penetrate into the vacuum port 44.
The course of a method according to the invention is shown in FIGS. 4 to 10 with reference to the first device according to the invention. First of all, the metal core 16 may be positioned with the retaining pins 18 in the stem mold 34. To this end, the retaining pins 18 may be arranged and retained at one end between the two parts of the stem mold 34 in the cavities formed by the shapes 40 and arranged with the other end in matching bores in the metal core 16. In order to fasten the two parts of the stem mold 34 together, the flanges 14 of the two parts of the stem mold 34 can firstly be positioned via the pins 29 in the recesses 39 and then the two parts of the stem mold 34 can be screwed together with the assistance of the screws 31. The casting mold 1 may then be closed by fastening the mold cavity 32 to the stem mold 34. The annular disk 23 may to this end be laid on the flange 35. The two half rings of the mount 21 can then be laid on the annular disk 23 and positioned via the pins 29 and the recesses 39. The mold cavity 32 can then be fastened to the stem mold 34 by tightening the screws 25, wherein the annular disk 23 seals the connection. The casting mold 1 is then closed with the metal core 16 therein and can be provided to mold a spacer.
A bone cement paste 50 can be mixed under a vacuum in the bone cement cartridge 10. The bone cement cartridge 10 can then be screwed with the adapter element 9 into the port 11 of the valve body 6. On screwing in the adapter element 9, the valve can be transferred into the open position by screwing the valve body 6 into the valve seat 3 until the limit stop is reached. FIGS. 1 and 5 show this situation.
The bone cement paste 50 is then pressed out of the bone cement cartridge 10 through the valve and through the overlapping first feed-throughs 5 and second feed-throughs 8 into the casting mold 1 by advancing the piston 46. FIG. 6 shows this situation. By closing the valve by manually operating the lever 38 and so rotating the valve body 6 by a quarter rotation relative to the valve seat 3, a new bone cement cartridge 10 can be attached at intervals if the volume of the bone cement paste 50 from a single bone cement cartridge 10 is not enough to fill the casting mold 1 completely. The bone cement paste 50 contained in the casting mold 1 cannot flow back out again since the first passages 5 and the second passages 8 are covered in the closed position of the valve and the gap therebetween is insufficient for the viscous bone cement paste 50 to be able flow through. Simultaneously, pressure from the bone cement paste 50 is maintained in the interior of the mold cavity 32 by the closed valve.
At some point, the casting mold 1 is filled with the bone cement paste 50. FIG. 7 shows this situation. Air or gas can escape from the casting mold 1 through the vent element 15 or through the vent openings 19 in the mold cavity 32. The mold cavity 32 can be expanded to the desired size by further injection of bone cement paste 50 (see FIG. 10 in comparison with FIG. 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 the mold cavity 32. Since the wall thickness of the mold cavity 32 is known, the current diameter of the spherical surface-shaped inner surface of the mold cavity 32 is also determinable. Alternatively or additionally, a dimensionally stable mating mold (not shown) with a known and defined diameter may be provided into which the mold cavity 32 can be laid, such that the mold cavity 32 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 the mold cavity 32 has been reached, the valve can be closed.
By closing the valve with the lever 38, the bone cement paste 50 is sheared or cut off This situation is shown in FIGS. 4 and 8 show this situation. The bone cement cartridge 10 can be unscrewed and removed. Any remaining thin connections simply tear or break away. This situation is shown in FIGS. 9 and 10.
In this state, the bone cement paste 50 can be cured in the casting mold 1. The size or diameter of the head of the spacer here matches the diameter of the spherical surface-shaped inner surface of the expanded mold cavity 32. 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, the mold cavity 32 is already slightly expanded such that the bone cement paste 50 is under pressure in the casting mold 1 while it cures.
Then, the spacer formed in this way is removed from the casting mold 1. The projecting retaining pins 18 may be cut off. Any sprue caused by the valve seat 3 and the first passages 5 can likewise be cut off and removed. Points or unevenness caused by the vent opening 19 may also be removed. The surface of the spacer can be polished and/or coated, for example with antibiotics.
Instead of a casting mold 1 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 in FIGS. 14 to 21.
The second device according to the invention is suitable and provided for producing a spacer 120, 130 (see FIGS. 20 and 21) for a shoulder joint. The device comprises a casting mold 61. The casting mold 61 may be constructed in multiple parts, in particular in four parts. FIGS. 12 to 14 and 16 to 19 show the casting mold 61 open or sectioned, such that the interior structure of the device is visible. The casting mold 61 may have a proximal mold cavity 92 for molding a head of the spacer and a distal stem mold 94 for molding a stem of the spacer. The shaping parts of the mold cavity 92 may be in one part and the shaping parts of the stem mold 94 may be in two parts (see FIG. 15). FIG. 15 shows all the parts of the casting mold 61. The mold cavity 92 may have a spherical surface-shaped inner surface in the form of a hemisphere. The spherical surface-shaped inner surface of the mold cavity 92 serves as a negative mold for forming a sliding surface of the head of the spacer. According to the invention, the mold cavity 92 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 the mold cavity 92.
In contrast with the first device according to the invention, the casting mold 61 additionally has an adapter element 102 with an inner thread 103. The adapter element 102 can be screwed with its inner thread 103 onto a hollow cylinder 105 with a matching outer thread 107. The fitting 105 can be molded by the two parts of the stem mold 94. The adapter element 102 allows the mold cavity 92 to be variably spaced from the stem mold 94. The adapter element 102 and the interior shape of the hollow cylinder 105 shape the neck of a spacer 120, 130 produced with the second device according to the invention. The length of the neck of the spacer can be modified by screwing the adapter element 102 relative to the hollow cylinder 105 (see FIGS. 20 and 21). Such an adapter element 102 with a hollow cylinder 105 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 filling opening 62 for the introduction of bone cement paste 50 may be formed on one side of the casting mold 61, which filling opening may be defined in each case in both parts of the stem mold 94 by a semicircular cylindrical opening. This filling opening 62 may form a valve seat 63 which may be embodied as part of the stem mold 94. The valve seat 63 may be firmly connected to the casting mold 61. The mold cavity 92 and thus the spherical surface-shaped inner surface of the mold cavity can be continuously expanded by injecting the bone cement paste 50 into the casting mold 61. The diameter of the head of a spacer fabricated with the device may consequently be variably adjusted.
The valve seat 63 may take the form of a hollow cylinder which, apart from two first feed-throughs 65, is closed on a head side 64 oriented in the direction of the filling opening 62. The two first feed-throughs 65 may be quadrant-shaped and may preferably be arranged rotated relative to one another by 180° with regard to the cylinder axis of the valve seat 63. A valve body 66 may be arranged in the interior of the valve seat 63 so as to be axially rotatable relative to the valve seat 63. The valve body 66 may have a sealing face 67 or surface oriented in the direction of the head side 64 of the valve seat 63. The valve body 66 may be constructed as a stepped hollow cylinder, the front part of which can be screwed or put into the valve seat 63.
Two second feed-throughs 68 may be arranged in the sealing face 67. The two second feed-throughs 68 may, similarly to the first feed-throughs 65, be quadrant-shaped and may preferably be arranged rotated or offset relative to one another by 180° with regard to the cylinder axis of the valve body 66. The valve seat 63 and valve body 66 together form a valve of the device. An adapter element 69 for liquid-tight connection of a bone cement cartridge 10 may be screwed into the valve body 66 (see FIG. 16). The bone cement cartridge 10 and the adapter element 69 may be part of the device according to the invention. The valve body 66 may on its open side, which is remote from the sealing face 67, be formed as a port 71 for connecting the adapter element 69. The same bone cement cartridge 10 as described in the first exemplary embodiment described may be used to fill the casting mold 61 with bone cement paste 50. The same reference signs are therefore used for both embodiments.
The bone cement cartridge 10 may have on its front side a delivery tube 37 with a delivery opening 12 for delivering the bone cement paste 50 from the bone cement cartridge 10. The delivery opening 12 may be arranged together with the delivery tube 37 in the adapter element 9 and be delimited by the delivery tube 37. The adapter element 9 may close the bone cement cartridge 10 on its front side apart from the delivery opening 12 and optionally apart from a vacuum port 104. Sealing may be provided by arranging in the adapter element 9 a seal 73 in the form of an O-ring of rubber, which seals against the delivery tube 37. A mixer 36 with a plurality of mixing blades, with which the bone cement paste 50 can be mixed in the interior of the bone cement cartridge 10, may be fastened at the end of the delivery tube 37 pointing into the interior of the bone cement cartridge 10 before the bone cement cartridge 10 is connected to the valve. The delivery tube 37 may to this end be mounted in axially linearly and rotatably mobile manner in the adapter element 9.
The mold cavity 92 may consist of a rubber-elastic plastics material. As a result, the mold cavity 92 can be expanded with the assistance of the bone cement paste 50, as is visible in FIGS. 17, 18 and 19. FIG. 17 here shows an unexpanded mold cavity 92, FIG. 18 dimensions for additional possible expanded mold cavities 92 as dashed lines and FIG. 19 an expanded mold cavity 92. The wall thickness of the mold cavity 92 is uniform, such that the mold cavity 92 expands uniformly when a pressure is exerted in the interior of the mold cavity 92 via the bone cement paste 50.
The stem mold 94 and the adapter element 102 may be inexpensively fabricated from plastics film and are dimensionally stable, such that, in contrast to the mold cavity 92, they cannot or cannot substantially be expanded by a pressure exerted by the bone cement paste 50 in the interior of the casting mold 61. The plastics film may have a plurality of layers. The two parts of the stem mold 94 may be fastened flush together via flanges 74. The mold cavity 92 and the adapter element 102 may likewise be connected flush together via a flange 95 of the adapter element 102 and an annular disk 83 of the mold cavity 92. By connecting the parts of the casting mold 61 via the flanges 74, 95 and the annular disk 83 and via the inner thread 103 and outer thread 107, the casting mold 61 may be closed to the outside. The annular disk 83 may be screwed via a segmented annular mount 81 to the flange 95. Screws 85 may to this end be screwed into fittings 87 having inner threads which match the screws 85. The two parts of the stem mold 94 may likewise be fastened together with screws 91 which are screwed into fittings 93 having inner threads which match the screws 91. In order to simplify positioning of the two parts of the stem mold 94 relative to one another and of the mold cavity 92 on the flange 95 of the adapter element 102, pins 89 may be provided which can be put into recesses 99 on the opposing flange 74 or flange 95. The annular disk 83 seals the connection of the mold cavity 92 to the adapter element 102 in the manner of a sealing ring.
At least one vent element 75 having in each case at least one vent opening 79 may be arranged in the casting mold 61. At least one vent element 75 may be arranged in the mold cavity 92 so that it is possible to expel air from the interior of the casting mold 61. Air or gas can escape through the vent opening 79 from the interior of the closed casting mold 61 when a bone cement paste 50 is filled into the casting mold 61 through the filling opening 62. A porous filter 77 which is permeable to gases but impermeable to the bone cement paste 50 can be arranged in the vent element 75. In this way, the bone cement paste 50 is prevented from being able to escape through the vent opening 79 during filling of the casting mold 61 and consequently on the one hand impairing the shape of the head of the spacer and on the other hand allowing the pressure of the bone cement paste 50 in the mold cavity 92 to decline by outflow of bone cement paste 50 from the mold cavity 92. This ensures that the mold cavity 92 remains in the desired expanded state while the bone cement paste 50 begins to cure in the casting mold 61. It may be sufficient for the free cross-sectional area of the vent opening 79 to be so small that the bone cement paste 50 cannot escape through the vent opening 79 due to its viscid consistency.
A metal core 76 may be placed in the interior of the casting mold 61. The metal core 76 may consist of surgical steel or of titanium. Alternatively, it would theoretically also be possible to fabricate the metal core 76 from a plastics material such as PMMA. The metal core 76 may be connected to the stem mold 94 via retaining pins 78. The metal core 76 may be spaced from the internal wall of the casting mold 61 with the aid of the retaining pins 78, such that the bone cement paste 50 can flow right around the metal core 76. The metal core 76 brings about stabilization of the spacer 120, 130. The retaining pins 78 may consist of PMMA. This can irreversibly bond to a bone cement paste 50 of PMMA.
The valve seat 63 may have an inner thread 80 on its inside. On the front half of the valve body 66 facing the sealing face 67, the valve body 66 may have on the outside thereof an outer thread 82 matching the inner thread 80 of the valve seat 63. The valve body 66 may be screwed with its outer thread 82 into the inner thread 80 of the valve seat 63.
The first feed-throughs 65 and the second feed-throughs 68 may be brought into overlap with one another by screwing the valve body 66 into the valve seat 63 until the limit stop is reached. The valve is then in the open state. In this open state, a bone cement paste 50 may flow through the first feed-throughs 65 and through the second feed-throughs 68 out of the bone cement cartridge 10 into the casting mold 61. By making a quarter rotation (by 90°) of the valve body 66 relative to the valve seat 63, i.e. by unscrewing the valve body 66 from the valve seat 63, the first feed-throughs 65 and the second feed-throughs 68 may be offset relative to one another, such that the sealing face 67 of the valve body 66 covers the first feed-throughs 65 of the valve seat 63 and the closed regions of the head side 64 of the valve seat 63 cover the second feed-throughs 68 of the valve body 66. The valve is then in the closed state. Due to the small stroke of the valve body 66 relative to the valve seat 63 in the event of a quarter rotation, the gap arising between the valve body 66 and the valve seat 63 is so narrow (less than 1 mm wide) that a bone cement paste 50 of a normal, let alone high, viscosity, is incapable of passing through the gap. This is particularly the case because the bone cement paste 50 is deflected from its actual direction of flow by 90° in the gap.
The reverse side of the valve body 66 may have an inner thread 84 arranged in the port 71. The adapter element 69 has on its front side an outer thread 86 which matches the inner thread 84. The adapter element 69 may accordingly be screwed into the port 71 of the valve body 66. In this way, a liquid-tight connection can be created between the bone cement cartridge 10 and the valve body 66 and thus into the casting mold 61. The inner thread 80 of the valve seat 63, the outer thread 82 of the valve body 66, the inner thread 84 of the valve body 66 and the outer thread 86 of the adapter element 69 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 the adapter element 69 into the port 71 and continuing to rotate the adapter element 69 in the same direction. At the same time, the valve body 66 also provides a seal relative to the valve seat 63.
The adapter element 69 may be or have been connected via a latching means 88 on the adapter element 69 to a mating latch 30 on a cylindrical wall of the bone cement cartridge 10. A circumferential seal 48 which seals the cylindrical wall of the bone cement cartridge 10 relative to the adapter element 69 may be provided for sealing.
The casting mold 61 may include the mold cavity 92 for forming the joint head (head) of the spacer and the stem mold 94 for forming the stem of a spacer. The adapter element 102 may be considered to be part of the stem mold 94. The stem mold is then in three parts. Moreover, an orifice for a lever of the valve body 66 may be arranged in the casting mold 91 in the region of the filling opening 92. The lever may be connected to the valve body 66. The valve body 66 can be rotated in the valve seat 63 with the lever. The orifice is preferably precisely large enough for the valve body 66 to be rotatable only by a maximum of a quarter rotation relative to the valve seat 63. 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 the flanges 74, shapes 100 may be arranged in the stem mold 94 for cavities, in which shapes the retaining pins 78 may be arranged.
A vacuum port 104 which is capable of evacuating an interior of the bone cement cartridge 10 in which the bone cement paste 50 is mixed may be arranged in the adapter element 69. As a result, the bone cement paste 50 can be mixed under a vacuum.
A piston 46 for discharging the bone cement paste 50 from the bone cement cartridge 10 through the valve into the casting mold 61 may be arranged in the cylindrical interior of the bone cement cartridge 10. The piston 46 may to this end be cylindrically shaped on the outside and be sealed relative to the cylindrical interior via two circumferential seals 47. By advancing the piston 46, the bone cement paste 50 can be pressed out of the delivery opening 12 of the bone cement cartridge 10 into or through the open valve.
A porous disk 52 may be arranged in the adapter element 69. The porous disk 52 is impermeable to the bone cement paste 50 and its starting components. The vacuum port 104 can be covered by the porous disk 52. This prevents any bone cement powder as a starting component of the bone cement paste 50 from being able to penetrate into the vacuum port 104.
The course of a method according to the invention is shown in FIGS. 12 to 21 with reference to the second device according to the invention. First of all, the metal core 76 may be positioned with the retaining pins 78 in the stem mold 94. To this end, the retaining pins 78 may be arranged and retained at one end between the two parts of the stem mold 94 in the cavities formed by the shapes 100 and arranged with the other end in matching bores in the metal core 76. In order to fasten the two parts of the stem mold 94 together, the flanges 74 of the two parts of the stem mold 94 can firstly be positioned via the pins 79 in the recesses 99 and then the two parts of the stem mold 94 to be joined together via the flange 74 can be screwed together with the assistance of the screws 91. The adapter element 102 may then be screwed onto the fitting 105. The adapter element 102 may here be screwed onto the fitting 105 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 the adapter element 102. The casting mold 61 may then be closed by fastening the mold cavity 92 to the adapter element 102. The annular disk 83 may to this end be laid on the flange 95. The two half rings of the mount 81 can then be laid on the annular disk 83 and positioned via the pins 89 and the recesses 99. The mold cavity 92 can then be fastened to the adapter element 102 by tightening the screws 85, wherein the annular disk 83 seals the connection. The casting mold 61 is then closed with the metal core 76 therein and can be provided to mold a spacer. This situation is shown in FIG. 15.
A bone cement paste 50 can be mixed under a vacuum in the bone cement cartridge 10. The bone cement cartridge 10 can then be screwed with the adapter element 69 into the port 71 of the valve body 66. On screwing in the adapter element 69, the valve can be transferred into the open position by screwing the valve body 66 into the valve seat 63 until the limit stop is reached.
The bone cement paste 50 is then pressed out of the bone cement cartridge 10 through the valve and through the overlapping first feed-throughs 65 and second feed-throughs 68 into the casting mold 61 by advancing the piston 46. This situation is shown in FIG. 16. By closing the valve by rotating the valve body 66 by a quarter rotation relative to the valve seat 63, a new bone cement cartridge 10 can be attached at intervals if the volume of the bone cement paste 50 from a single bone cement cartridge 10 is not enough to fill the casting mold 61 completely. The bone cement paste 50 contained in the casting mold 61 cannot flow back out again since the first passages 65 and the second passages 68 are covered in the closed position of the valve and the gap therebetween is insufficient for the viscous bone cement paste 50 to be able flow through. Simultaneously, pressure from the bone cement paste 50 is maintained in the interior of the mold cavity 92 by the closed valve.
At some point, the casting mold 61 is filled with the bone cement paste 50. Air or gas has escaped from the casting mold 1 through vent openings in the casting mold 61. This situation is shown in FIG. 16. Air or gas can escape from the casting mold 61 through the vent element 75 or through the vent openings 79 in the mold cavity 92. The mold cavity 92 can be expanded to the desired size by further injection of bone cement paste 50 (see FIGS. 18 and 19 in comparison with FIG. 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 the mold cavity 92. Since the wall thickness of the mold cavity 92 is known, the current diameter of the spherical surface-shaped inner surface of the mold cavity 92 is also determinable. Alternatively or additionally, a dimensionally stable mating mold (not shown) with a known and defined diameter may be provided into which the mold cavity 92 can be laid, such that the mold cavity 92 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 the mold cavity 92 has been reached, the valve can be closed.
By closing the valve, the bone cement paste 50 is sheared or cut off The bone cement cartridge 10 can be unscrewed and removed. Any remaining thin connections simply tear or break away. This situation is shown in FIGS. 17 and 19.
In this state, the bone cement paste 50 can be cured in the casting mold 61. This situation is shown in FIG. 19. The size or diameter of the head of the spacer here matches the diameter of the spherical surface-shaped inner surface of the expanded mold cavity 92. 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, the mold cavity 92 is already slightly expanded such that the bone cement paste 50 is under pressure in the casting mold 61 while it cures.
Then, the spacer 120, 130 (see FIGS. 20 and 21) formed in this way is removed from the casting mold 1. The projecting retaining pins 78 may be cut off. Any sprue caused by the valve seat 63 and the first passages 65 can likewise be cut off and removed. Points caused by the vent openings may also be removed. This situation is shown in FIGS. 20 and 21.
FIG. 20 shows the removed spacer 120. The spacer 120 has a head 122 which has been shaped by the mold cavity 92. The spacer 120 was shaped by curing the bone cement paste 50 in the casting mold 61, as shown in FIG. 17. The head 122 is connected via a neck 126 to a stem 124 of the spacer 120.
FIG. 21 shows an alternative spacer 130 with a longer neck 136 which has been molded by extension with the adapter element 102 (see FIGS. 18 and 19). The spacer 130 has a head 132 which has been shaped by the mold cavity 92. The spacer 130 was shaped by curing the bone cement paste 50 in the casting mold 61, as shown in FIG. 18. The head 132 is connected via the neck 136 to a stem 134 of the spacer 130. In its proximal region, the neck 134 has the shape of a thread since it is a negative shape of the inner thread 103 of the adapter element 102. If required, the surface in this region can be smoothed.
The surface of the spacer 120, 130 can be polished and/or coated, for example with antibiotics.
Instead of a casting mold 61 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 to FIGS. 1 to 11 and of the second device according to the invention according to FIGS. 12 to 19, but may also be used with other casting molds to produce other spacers.
The valve has a valve seat 163, which may be arranged in a filling opening of a casting mold (not shown). The valve seat 163 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 the valve seat 163 to a casting mold, the valve seat 163 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 the valve seat 163.
The valve seat 163 may take the form of a hollow cylinder which, apart from two first feed-throughs 165, is closed on a head side 164. The two first feed-throughs 165 may be quadrant-shaped and may preferably be arranged rotated relative to one another by 180° with regard to the cylinder axis of the valve seat 163. A valve body 166 may be arranged in the interior of the valve seat 163 so as to be axially rotatable relative to the valve seat 163. The valve body 166 may have a sealing face 167 or surface oriented in the direction of the head side 164 of the valve seat 163. The valve body 166 may be constructed as a stepped hollow cylinder, the front part of which can be screwed or put into the valve seat 163.
Two second feed-throughs 168 may be arranged in the sealing face 167. The two second feed-throughs 168 may, similarly to the first feed-throughs 165, be quadrant-shaped and may preferably be arranged rotated or offset relative to one another by 180° with regard to the cylinder axis of the valve body 166. The valve seat 163 and valve body 166 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 the valve body 166. The valve body 166 may on its open side, which is remote from the sealing face 167, be formed as a port 171 for connecting an adapter element.
The valve seat 163 may have an inner thread 180 on its inside. On the front half of the valve body 166 facing the sealing face 167, the valve body 166 may have on the outside thereof an outer thread 182 matching the inner thread 180 of the valve seat 163. The valve body 166 may be screwed with its outer thread 182 into the inner thread 180 of the valve seat 163.
The first feed-throughs 165 and the second feed-throughs 168 may be brought into overlap with one another by screwing the valve body 166 into the valve seat 163 until the limit stop is reached. The valve is then in the open state. In this open state (see FIGS. 22 to 24), a bone cement paste may flow through the first feed-throughs 165 and through the second feed-throughs 168. By making a quarter rotation (by 90°) of the valve body 166 relative to the valve seat 163, i.e. by unscrewing the valve body 166 from the valve seat 163, the first feed-throughs 165 and the second feed-throughs 168 may be offset relative to one another, such that the sealing face 167 of the valve body 166 covers the first feed-throughs 165 of the valve seat 163 and the closed regions of the head side 164 of the valve seat 163 cover the second feed-throughs 168 of the valve body 166. The valve is then in the closed state (see FIGS. 25 to 28). Due to the small stroke of the valve body 166 relative to the valve seat 163 in the event of a quarter rotation, the gap 220 arising between the valve body 166 and the valve seat 163 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 gap 220 (see FIG. 28). This is particularly the case because the bone cement paste is deflected from its actual direction of flow by 90° in the gap 220. A projection 216 may be provided in order to ensure more stable, non-rotatable connection of the valve seat 163 to the casting mold.
The reverse side of the valve body 166 may have an inner thread 184 arranged in the port 171. An adapter element (not shown) may accordingly be screwed into the port 171 of the valve body 166. The inner thread 180 of the valve seat 163, the outer thread 182 of the valve body 166 and the inner thread 184 of the valve body 166 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 the port 171 and continuing to rotate the adapter element in the same direction. At the same time, the valve body 166 also provides a seal relative to the valve seat 163.
Furthermore, a lever 198 may be arranged on the valve body 166. The valve body 166 can be rotated in the valve seat 163 with the lever 198. As a result, with the assistance of the lever 198, 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

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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 5, characterized in that the fastening element has clamping plates.

7. The device according to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 1, characterized in that

the spherical surface-shaped inner surface of the mold cavity has, 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, 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 22, characterized in that

a device according to claim 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 to claim 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 to claim 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 to claim 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 to claim 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 to claim 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.