DEVICE AND METHOD FOR PRODUCING SPACERS

Abstract

The invention relates to a device for producing a spacer having a casting mold lower part (1) with a cavity (2), a casting mold wall (3) which extends peripherally away from an edge of the cavity (2) and which is open on the opposite side, a casting mold upper part (5) with a shaping surface (6), wherein the casting mold upper part (5) can be inserted into an interior (4) of the casting mold lower part (1) and is displaceable in the direction of the cavity (2), such that a hollow space is formed which is delimited by the cavity (2), the shaping surface (6) and the casting mold wall (3) and in which the spacer is moldable, at least one container (7) for receiving excess bone cement paste, and at least one opening (8) in the shaping surface (6) and/or in the cavity (2), which opens into the at least one container (7) for receiving excess bone cement paste.

The invention also relates to a method for producing spacers using such a device.

Claims

1. A device for producing a spacer (42, 92, 142, 192) by curing bone cement paste (36) in a casting mold, wherein the spacer (42, 92, 142, 192) is provided to temporarily replace a joint or a part of a joint comprising an articulating surface of the joint in the medical field, in particular to temporarily replace a hip joint, a knee joint or a shoulder joint, the device having a casting mold lower part (1, 51, 101, 151), wherein the casting mold lower part (1, 51, 101, 151) has a cavity (2, 52, 102, 152) for receiving a bone cement paste (36) and for molding a first surface region of the spacer (42, 92, 142, 192) from the bone cement paste (36); a casting mold wall (3, 53, 103, 153) which extends peripherally from a peripheral edge of the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151) away from the cavity (2, 52, 102, 152) and which is open on the side opposite from the cavity (2, 52, 102, 152), such that the cavity (2, 52, 102, 152) is accessible through an interior (4, 54, 104, 154) delimited by the casting mold wall (3, 53, 103, 153); a casting mold upper part (5, 55, 105, 155), wherein the casting mold upper part (5, 55, 105, 155) has a shaping surface (6, 56, 106, 156) for molding a second surface region of the spacer (42, 92, 142, 192) from the bone cement paste (36), wherein the casting mold upper part (5, 55, 105, 155) is insertable through the open side of the casting mold wall (3, 53, 103, 153) opposite from the cavity (2, 52, 102, 152) into the interior (4, 54, 104, 154) and is displaceable in the direction of the cavity (2, 52, 102, 152), such that a hollow space is formed which is delimited by the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) and the casting mold wall (3, 53, 103, 153) and in which the spacer (42, 92, 142, 192) is moldable; at least one container (7, 57, 107, 157) for receiving excess bone cement paste (38); and at least one opening (8, 58, 108, 158) in the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) and/or in the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), wherein the at least one opening (8, 58, 108, 158) opens into the at least one container (7, 57, 107, 157) for receiving excess bone cement paste (38), wherein the device has one or two lid(s) (9, 59, 109, 159), with which the casting mold upper part (5, 55, 105, 155) is closed or closable to the outside on the side opposite from the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155), such that an upper container closed to the outside is formed as one of the at least one containers (7, 57, 107, 157) for receiving bone cement paste (36) between the casting mold upper part (5, 55, 105, 155) and the lid (9, 59, 109, 159), and/or with which the casting mold lower part (1, 51, 101, 151) is closed or closable to the outside on the side opposite from the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), such that a lower container closed to the outside is formed as one of the at least one containers (7, 57, 107, 157) for receiving bone cement paste (36) between the casting mold lower part (1, 51, 101, 151) and the lid (9, 59, 109, 159), wherein the or one of the lid(s) (9, 59, 109, 159) is placed or placeable into or onto the casting mold upper part (5, 55, 105, 155) or into or onto an internal wall (11, 61, 111, 161) of the casting mold upper part (5, 55, 105, 155) in order to close the side opposite from the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) to the outside and there form a closed container (7, 57, 107, 157) for receiving excess bone cement paste (38), and/or the or one of the lid(s) (9, 59, 109, 159) is placed or placeable into or onto the casting mold lower part (1, 51, 101, 151) in order to close the side opposite from the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151) to the outside and there forms a closed container (7, 57, 107, 157) for receiving excess bone cement paste (38).

2. The device according to claim 1, characterized in that mutually opposing parts of the casting mold wall (3, 53, 103, 153) are oriented parallel to one another or the casting mold wall (3, 53, 103, 153) tapers slightly conically in the direction of the cavity (2, 52, 102, 152) or the casting mold wall (3, 53, 103, 153) has the shape of a right or skewed general cylinder, the base area of which is delimited by the peripheral edge of the cavity (2, 52, 102, 152).

3. The device according to claim 1, characterized in that the internal wall (11, 61, 111, 161) of the casting mold upper part (5, 55, 105, 155) extends peripherally from a peripheral edge of the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) away from the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), wherein the internal wall (11, 61, 111, 161) preferably at least in places delimits the at least one container (7, 57, 107, 157) and/or mutually opposing parts of the internal wall (11, 61, 111, 161) are oriented parallel to one another or the internal wall (11, 61, 111, 161) has the shape of a right or skewed general cylinder, the base area of which is delimited by the peripheral edge of the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155).

4. The device according to claim 3, characterized in that the internal wall (11, 61, 111, 161) and the casting mold wall (3, 53, 103, 153) rest flush against one another when the casting mold upper part (5, 55, 105, 155) is pushed into the casting mold wall (3, 53, 103, 153) and/or the internal wall (11, 61, 111, 161) forms a seal against the casting mold wall (3, 53, 103, 153) for the bone cement paste (36) when the casting mold upper part (5, 55, 105, 155) is pushed into the casting mold wall (3, 53, 103, 153).

5. The device according to claim 1, characterized in that the lid or lids (9, 59, 109, 159) has at least one vent opening and/or the lid or lids (9, 59, 109, 159) are gas-permeably closed or closable with the casting mold upper part (5, 55, 105, 155).

6. The device according to claim 1, characterized in that the volume of the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151) and the volume delimited by the casting mold wall (3, 53, 103, 153) together are larger than the volume of the spacer (42, 92, 142, 192) to be produced.

7. The device according to claim 1, characterized in that the casting mold wall (3, 53, 103, 153) and the casting mold lower part (1, 51, 101, 151) are formed as one part, wherein the casting mold wall (3, 53, 103, 153) is preferably part of the casting mold lower part (1, 51, 101, 151).

8. The device according to claim 1, characterized in that the device has a mixing system for mixing bone cement paste (36), a cement powder and a monomer liquid, wherein the cement powder and the monomer liquid are stored separately from one another, wherein the bone cement paste (36) is mixable from the cement powder and the monomer liquid with the assistance of the mixing system.

9. The device according to claim 8, characterized in that the mixing system includes a mixing cup (26) which preferably has a spout (28) for introducing the bone cement paste (36) from the mixing cup (26) into the cavity (2, 52, 102, 152) and the interior (4, 54, 104, 154) delimited by the casting mold wall (3, 53, 103, 153), or the mixing system is a bone cement cartridge for storing and mixing the cement powder and the monomer liquid and for delivering mixed bone cement paste (36) from the bone cement cartridge, wherein the bone cement cartridge preferably contains the cement powder and the monomer liquid in regions separated from one another in liquid-tight manner.

10. The device according to claim 1, characterized in that the casting mold lower part (1, 51, 101, 151) and the casting mold upper part (5, 55, 105, 155), and preferably also the casting mold wall (3, 53, 103, 153) and if present the lid or lids (9, 59, 109, 159) consist of a plastics film or substantially consist of a plastics film or the casting mold lower part (1, 51, 101, 151) and the casting mold upper part (5, 55, 105, 155), and preferably also the casting mold wall (3, 53, 103, 153) and if present the lid or lids (9, 59, 109, 159) are in each case composed of two or more plastics films which are connected together and particularly preferably welded or adhesively bonded together.

11. The device according to claim 1, characterized in that the casting mold lower part (1, 51, 101, 151), the casting mold upper part (5, 55, 105, 155) and the casting mold wall (3, 53, 103, 153) and if present the lid or lids (9, 59, 109, 159) substantially or entirely consist of a plastics material and are preferably fabricated from a polyolefin, polyethylene (PE) or polypropylene (PP) and particularly preferably from a PETG film and/or a polyamide film and/or a PE film.

12. The device according to claim 1, characterized in that the at least one opening (8, 58, 108, 158) has a minimum cross-sectional length of a maximum of 2.5 mm, preferably a minimum cross-sectional length of a maximum of 2 mm, particularly preferably a minimum cross-sectional length of a maximum of 1.5 mm and very particularly preferably a minimum cross-sectional length of a maximum of 1 mm, and/or the at least one opening (8, 58, 108, 158) has a minimum cross-sectional length of at least 0.2 mm, preferably of at least 0.5 mm and particularly preferably of at least 1 mm.

13. The device according to claim 1, characterized in that, at the end of the casting mold wall (3, 53, 103, 153) opposite from the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), a limit stop (20, 70, 120, 170) is arranged for limiting the movement of the casting mold upper part (5, 55, 105, 155) within the casting mold wall (3, 53, 103, 153) in the direction of the cavity (2, 52, 102, 152), wherein a contact surface is preferably arranged as a limit stop (20, 70, 120, 170) at the end of the casting mold wall (3, 53, 103, 153) opposite from the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), which contact surface particularly preferably projects out at right angles from the casting mold wall (3, 53, 103, 153).

14. The device according to claim 1, characterized in that the device has a metal core (10, 60) which is to be or is arranged in the cavity (2, 52), wherein the device preferably has a plurality of spacing pieces (12, 62) which keep the metal core (10, 60) in the cavity (2, 52) spaced from the internal side of the cavity (2, 52) and from the internal side of the casting mold wall (3, 53), wherein the spacing pieces (12, 62) particularly preferably consist of cured bone cement and in particular of polymethyl methacrylate.

15. The device according to claim 1, characterized in that the casting mold lower part (1, 51, 101, 151) or the casting mold lower part (1, 51, 101, 151) and the casting mold wall (3, 53, 103, 153) or the casting mold lower part (1, 51, 101, 151), the casting mold wall (3, 53, 103, 153) and the casting mold upper part (5, 55, 105, 155) is or are transparent or translucent.

16. The device according to claim 1, characterized in that the at least one opening (8, 58, 108, 158) is arranged in the regions which, in the normal disposition of the casting mold, are the highest points of the hollow space.

17. The device according to claim 1, characterized in that the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) rests with an outer edge internally against the casting mold wall (3, 53, 103, 153) and, when the casting mold upper part (5, 55, 105, 155) is pushed in, the edge slides internally on the casting mold wall (3, 53, 103, 153), wherein the edge preferably has a wiper rim or wiper lip.

18. The device according to claim 1, characterized in that the device has a stand (16, 66, 116, 166), wherein the casting mold lower part (1, 51, 101, 151) is insertable into the stand (16, 66, 116, 166) and the stand (16, 66, 116, 166) is suitable, with the casting mold lower part (1, 51, 101, 151) therein, to be placed on a flat support, wherein the stand (16, 66, 116, 166) preferably substantially or entirely consists of a plastics film or of two or more plastics films which are joined together and are particularly preferably welded or adhesively bonded together.

19. A method for producing a spacer (42, 92, 142, 192) for temporarily replacing a joint or part of a joint, in particular a hip joint, a knee joint or a shoulder joint, comprising an articulating surface of the joint, wherein the method is carried out with the device according to any one of claims 1 to 18, the method having the following chronological steps: A) introduction of flowable bone cement paste (36) into the cavity (2, 52, 102, 152) and the interior (4, 54, 104, 154) delimited by the casting mold wall (3, 53, 103, 153), wherein a larger volume of the flowable bone cement paste (36) is introduced than is required by the spacer (42, 92, 142, 192); B) insertion of the casting mold upper part (5, 55, 105, 155) into the casting mold wall (3, 53, 103, 153), wherein the shaping surface (6, 56, 106, 156) points in the direction of the cavity (2, 52, 102, 152); C) pushing in of the casting mold upper part (5, 55, 105, 155) in the direction of the cavity (2, 52, 102, 152) within the casting mold wall (3, 53, 103, 153); D) emergence of excess bone cement paste (38) through the at least one opening (8, 58, 108, 158) as the casting mold upper part (5, 55, 105, 155) continues to be pushed in, wherein the excess bone cement paste (38) flows into the at least one container (7, 57, 107, 157) for receiving the excess bone cement paste (38); E) completion of pushing in when a limit stop (20, 70, 120, 170) is reached or when a desired height of the spacer (42, 92, 142, 192) is reached; F) curing of the bone cement paste (36) in the hollow space formed by the cavity (2, 52, 102, 152), the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) and the casting mold wall (3, 53, 103, 153) and G) removal of the spacer (42, 92, 142, 192) molded and cured in this manner from the hollow space, wherein sprues (40, 90, 140, 190) of the cured bone cement paste (36) formed in the at least one opening (8, 58, 108, 158) are detached.

20. The method according to claim 19, characterized in that, in step D), the excess bone cement paste (38) flows into a lower container closed by a lid (9, 59, 109, 159) for receiving the excess bone cement paste (38) on the casting mold lower part (1, 51, 101, 151) and is enclosed therein and/or flows into an upper container (7, 57, 107, 157) closed by a lid (9, 59, 109, 159) for receiving the excess bone cement paste (38) on the casting mold upper part (5, 55, 105, 155) and is enclosed therein, wherein, on demolding the cured spacer (42, 92, 142, 192) after step F) or in step G), the cured excess bone cement paste (38) remains in the lower container and/or the upper container (7, 57, 107, 157).

21. The method according to claim 19, characterized in that, before step A), the bone cement paste (36) is mixed from a monomer liquid and a cement powder, in particular until a homogeneous bone cement paste (36) is obtained.

22. The method according to claim 19, characterized in that, before step A), a metal core (10, 60) is arranged in the cavity (2, 52), wherein the metal core (10, 60) is preferably spaced from the internal wall of the cavity (2, 52) and the casting mold wall (3, 53) with the assistance of pin-shaped spacing pieces (12, 62).

23. The method according to claim 19, characterized in that, during step C), the air is expelled through the at least one opening (8, 58, 108, 158) from the hollow space delimited by the cavity (2, 52, 102, 152) of the casting mold lower part (1, 51, 101, 151), the shaping surface (6, 56, 106, 156) of the casting mold upper part (5, 55, 105, 155) and the casting mold wall (3, 53, 103, 153).

24. The method according to claim 19, characterized in that, after step F) and before step G), the casting mold upper part (5, 55, 105, 155) is withdrawn from the open end of the casting mold wall (3, 53, 103, 153).

Description

[0131] Further exemplary embodiments of the invention are explained below with reference to thirty-five schematic figures but without thereby limiting the invention. In the figures:

[0132] FIG. 1 shows a schematic perspective external view of a first exemplary embodiment of the present invention as a device for producing a spacer for a hip joint with separately depicted individual parts;

[0133] FIG. 2 shows a schematic plan view onto the open casting mold upper part;

[0134] FIG. 3 shows a schematic perspective external view of the first exemplary embodiment according to FIGS. 1 and 2 prior to arrangement of the metal core in the casting mold lower part;

[0135] FIG. 4 shows a schematic perspective external view of the casting mold of the first exemplary embodiment during the introduction of bone cement paste;

[0136] FIG. 5 shows a schematic perspective external view of the first exemplary embodiment prior to insertion of the casting mold upper part into the casting mold lower part;

[0137] FIG. 6 shows a schematic plan view onto the closed casting mold of the first exemplary embodiment with section plane B indicated;

[0138] FIG. 7 shows a schematic cross-sectional view onto section B according to FIG. 6 of the first exemplary embodiment in the closed state;

[0139] FIG. 8 shows a schematic perspective angled cross-sectional view onto the casting mold filled with bone cement paste of the first exemplary embodiment in the closed state;

[0140] FIG. 9 shows a schematic perspective view onto the device according to FIG. 8 without lid;

[0141] FIG. 10 shows a schematic perspective side view onto a spacer which has been produced using the device of the first exemplary embodiment according to FIGS. 1 to 9;

[0142] FIG. 11 shows a schematic cross-sectional view onto the spacer according to FIG. 10 with detached spacing pieces;

[0143] FIG. 12 shows a schematic perspective view onto the individual parts of a second exemplary embodiment of the present invention as a device for producing a spacer for a shoulder joint;

[0144] FIG. 13 shows a schematic perspective external view of the second exemplary embodiment according to FIG. 12 prior to arrangement of the metal core in the casting mold lower part;

[0145] FIG. 14 shows a schematic perspective external view of the casting mold of the second exemplary embodiment during the introduction of bone cement paste;

[0146] FIG. 15 shows a schematic perspective external view of the second exemplary embodiment prior to insertion of the casting mold upper part into the casting mold lower part;

[0147] FIG. 16 shows a schematic perspective view onto the closed casting mold of the second exemplary embodiment;

[0148] FIG. 17 shows a schematic perspective view of the first exemplary embodiment during removal of the cured spacer;

[0149] FIG. 18 shows a schematic perspective side view onto the spacer which has been produced using the device of the second exemplary embodiment according to FIGS. 12 to 17;

[0150] FIG. 19 shows a schematic plan view onto the closed casting mold of the second exemplary embodiment with section planes A and B indicated;

[0151] FIG. 20 shows a schematic cross-sectional view onto section B according to FIG. 19 of the second exemplary embodiment in the closed state;

[0152] FIG. 21 shows a schematic cross-sectional view onto section A according to FIG. 19 of the second exemplary embodiment in the closed state;

[0153] FIG. 22 shows a schematic perspective cross-sectional view onto the casting mold filled with bone cement paste of the second exemplary embodiment in the closed state;

[0154] FIG. 23 shows a schematic perspective view onto the individual parts of a third exemplary embodiment of the present invention as a device for producing two components of an articulating spacer for a knee joint;

[0155] FIG. 24 shows a schematic perspective external view of the third exemplary embodiment according to FIG. 23 with open casting mold lower parts;

[0156] FIG. 25 shows a schematic perspective external view of the casting molds of the third exemplary embodiment during the introduction of bone cement paste;

[0157] FIG. 26 shows a schematic perspective external view of the third exemplary embodiment prior to insertion of the casting mold upper parts into the casting mold lower parts;

[0158] FIG. 27 shows a schematic perspective external view of the third exemplary embodiment during insertion of the casting mold upper parts into the casting mold lower parts;

[0159] FIG. 28 shows a schematic perspective view onto the closed casting molds of the third exemplary embodiment;

[0160] FIG. 29 shows a schematic perspective cross-sectional view of the casting molds filled with bone cement paste of the third exemplary embodiment in the closed state;

[0161] FIG. 30 shows a schematic perspective external view of the third exemplary embodiment during withdrawal of the casting mold upper parts from the casting mold lower parts;

[0162] FIG. 31 shows a schematic perspective view onto the individual parts of the third exemplary embodiment with the two spacers for the knee joint;

[0163] FIG. 32 shows a schematic perspective view of the third exemplary embodiment with closed casting molds and stands for the casting molds;

[0164] FIG. 33 shows a schematic cross-sectional view of the casting molds of the third exemplary embodiment in the closed state;

[0165] FIG. 34 shows a schematic perspective view onto the two parts of the spacer which have been produced using the device according to the third exemplary embodiment; and

[0166] FIG. 35 shows a schematic plan view onto the casting molds with removed lid of the third exemplary embodiment.

[0167] FIGS. 1 to 9 are drawings showing various views of a first exemplary embodiment of a device according to the invention for producing a spacer for a hip joint and parts of the device. FIGS. 1 to 11 show the course of a first exemplary embodiment of a method according to the invention which is carried out using the device according to the first exemplary embodiment.

[0168] The first device according to the invention is suitable and provided for producing a spacer 42 (see FIGS. 10 and 11) for a hip joint. The device comprises a multipart casting mold. The casting mold has a casting mold lower part 1 and a casting mold upper part 5. A cavity 2 for receiving bone cement paste 36 (see FIGS. 4, 5 and 8) and for forming part of the surface of the spacer 42 to be produced is arranged in the casting mold lower part 1. The cavity 2 can shape one half of the spacer 42. A casting mold wall 3, which extends the hollow space formed by the cavity 2 with an interior 4, may be arranged at the edge of the cavity 2. The casting mold wall 3 may to this end peripherally enclose the edge of the cavity 2. The walls of the casting mold wall 3 may be oriented parallel to one another, such that the casting mold wall 3 has a generally cylindrical geometry, wherein the base area of the general cylinder is defined by the area which delimits the edge of the cavity 2. The interior 4 for introduction of bone cement paste 36 is arranged within the walls of the casting mold wall 3, which interior is connected, and preferably also aligned, with the cavity 2.

[0169] The casting mold upper part 5 may preferably be inserted or pushed into the casting mold lower part 1. The casting mold upper part 5 has at the bottom thereof a shaping surface 6, with which a further part of the surface of the spacer 42 to be produced is shapeable and preferably the remaining part of the surface of the spacer 42 to be produced is shapeable. Together with the cavity 2, the shaping surface 6 may define the entire surface of the spacer 42 or at least 90% of the entire surface of the spacer 42. The shaping surface 6 may form an indentation in the casting mold upper part 5. It is also possible for part of the casting mold wall 3 to form part of the surface of the spacer 42 or for one or more inserts (not shown), which shape part of the surface of the spacer 42, additionally to be inserted into the cavity 2 and/or placed on the shaping surface 6.

[0170] A container 7 for receiving excess bone cement paste 38 (see FIGS. 8 and 9) may be arranged on the side of the casting mold upper part 5 opposite from the shaping surface 6. Openings 8, which provide a through-connection for the excess bone cement paste 38 from the side of the shaping surface 6 to the container 7, may be present in the shaping surface 6. The openings 8 are preferably arranged at the points of the shaping surface 6 which, in the proper disposition of the device, are the highest shaping points of the casting mold. In this way, gases entrapped in the casting mold may escape through the openings 8 such that entrapped air is avoided in the spacer 42 to be produced.

[0171] The container 7 may have been or be impermeably closed to the outside for the bone cement paste 36 with a lid 9. An internal wall 11, which delimits the container 7, may start from and extend away from the back face of the shaping surface 6. The internal wall 11 may align externally with a perfect fit with the casting mold wall 3. In this way, the casting mold upper part 5 can be inserted with a perfect fit into the casting mold wall 3 of the casting mold lower part 1 and the bone cement paste 36 accordingly collected from the inside of the casting mold wall 3 and pressed into the cavity 2 and the shaping surface 6. It may also be sufficient to this end if the casting mold wall 3 tapers in the direction of the cavity 2, wherein the taper must to this end have an acute angle.

[0172] The container 7 may be gas-permeably connected with the surroundings. Provision may be made to this end for the lid 9 not to close pressure-tightly and/or for small vent openings (not visible in the figures) to be arranged in the lid and/or the internal wall 11.

[0173] A metal core 10 may be provided as reinforcement for the spacer 42. The metal core 10 may to this end be held spaced from the internal side of the cavity 2 and from the casting mold wall 3 with the assistance of pin-shaped spacing pieces 12 of cured PMMA, such that the bone cement paste 36 can flow completely around the metal core 10 between the metal core 10 on the one hand and the internal side of the cavity 2 and the shaping surface 6 on the other. In order to position the spacing pieces 12, bores 14 may be provided in the metal core 10 for receiving one end of the pin-shaped spacing pieces 12. Matching indentations for receiving the opposite end of the pin-shaped spacing pieces 12 may likewise be arranged in the internal side of the cavity 2.

[0174] A stand 16, into which the casting mold lower part 1 may be placed or inserted, may be provided in order to position the casting mold correctly with the casting mold lower part 1 underneath and the casting mold wall 3 perpendicularly on top. The stand 16 may be provided for placement on a flat surface such as a table.

[0175] The casting mold lower part 1, the casting mold upper part 5, the lid 9 and the stand 16 may be inexpensively produced from a plastics film or a plurality of joined together plastics films, in particular by injection molding or by thermoforming. In the assembled state, the parts of the device produced from the plastics films stabilize one another mechanically. The plastics film(s) preferably consist of a polyolefin, a polyethylene (PET) or a glycol-modified PET (PETG). When a plurality of films are used, they may be laminated together with an adhesive or by elevated temperature.

[0176] Internally located grooves 18 and externally located sprues 19, which extend from a limit stop 20 on the side of the casting mold wall 3 opposite from the cavity 2 down to the edge of the cavity 2, may be arranged in the casting mold wall 3. The sprues 19 may contain the volume for forming the grooves 18. The ends of the pin-shaped spacing pieces 12, which have been inserted into the bores 14 of the metal core 10 and project out therefrom, may be guided to the cavity 2 along these grooves 18.

[0177] Grooves 21 matching the sprues 19 may be provided internally in the stand 16. As a result, the casting mold lower part 1 can be pushed in guided manner into the stand 16 and the casting mold lower part 1 does not so readily become detached from the stand 16 and does not move so easily relative to the stand 16.

[0178] In order to fix the spacing pieces 12 and thus the metal core 10 in place, matching recesses 23 may be arranged at the edge of the shaping surface 6 of the casting mold upper part 5. The recesses 23 may be arranged at the edge of the shaping surface 6 in such a manner that they are moved along the grooves 18 of the casting mold wall 3 when the casting mold upper part 5 is pushed into the casting mold wall 3 of the casting mold lower part 1. The ends of the spacing pieces 12 which project out from the metal core 10 are accordingly clamped in place in the casting mold between the casting mold upper part 5 and the casting mold lower part 1.

[0179] The limit stop 20 may be arranged as a peripheral strip-shaped edge projecting out perpendicularly from the casting mold wall 3 on the side of the casting mold wall 3 remote from the cavity 2. The limit stop 20 can limit how far the casting mold upper part 5 can be pushed into the casting mold lower part 1. The casting mold upper part 5 may to this end have a mating stop 22 in the form of a peripheral edge which projects out perpendicularly from the internal wall 11 and is arranged on the side of the internal wall 11 opposite from the shaping surface 6. When the casting mold upper part 5 has been completely pushed into the casting mold lower part 1, the mating stop 22 rests against the limit stop 20. In the same way, a lid edge 24 which can be placed on the side of the mating stop 22 opposite from the limit stop 20 may be arranged on the lid 9. Because the limit stop 20, the mating stop 22 and the lid edge 24 project out from the adjoining parts at an angle, the shape of the casting mold lower part 1, the casting mold upper part 5 and the lid 9 is mechanically stabilized in the assembled state. This is in particular helpful if these parts have been fabricated from a plastics film or a plurality of plastics films by thermoforming.

[0180] The device may furthermore include a mixing cup 26 with a spout 28 for pouring bone cement paste 36 from the mixing cup 26 (see FIG. 3) and a film pouch 30 containing cement powder, an ampoule 32 containing monomer liquid and a spatula 34 for mixing the cement powder with monomer liquid in the mixing cup 26. The bone cement paste 36 may then be mixed in the mixing cup 26 before it is introduced into the casting mold or into the casting mold lower part 1. The bone cement paste 36 may, however, also be produced in another way before it is introduced into the casting mold. The device thus does not necessarily require the mixing cup 26 and also not the bone cement paste 36 or the starting components thereof. The device may in principle be applied and used with any other known system for producing a bone cement paste, such as for example with a suitable cartridge system for storing and mixing bone cement paste.

[0181] The course of a first exemplary embodiment of a method according to the invention is described below with reference to FIGS. 1 to 11.

[0182] The device may firstly be removed from a package (not shown) in a sterile state and may then be present as shown in FIG. 1 or in FIG. 3 or 4. If the casting mold lower part 1 has not already been inserted into the stand 16, the casting mold lower part 1 may be pushed into the stand 16 via the grooves 21. If not already present therein, the metal core 10 may be inserted into the cavity 2 (see FIG. 3). In so doing, the projecting ends of the spacing pieces 12 slide in the grooves 18 of the casting mold wall 3.

[0183] The bone cement paste 36 may be mixed by mixing the cement powder from the film pouch 30 and the monomer liquid from the ampoule 32 in the mixing cup 26 with the assistance of the spatula 34. Alternatively, the bone cement paste 36 may also be produced in any other manner.

[0184] When the metal core 10 is inserted into the cavity 2 or into the interior 4, the bone cement paste 36 can be introduced in excess into the interior 4 and the cavity 2 (see FIG. 4). The casting mold upper part 5 may then be inserted and pushed into the casting mold lower part 1 or into the casting mold wall 3. The container 7 may to this end be closed with the lid 9 (see FIG. 5).

[0185] The casting mold upper part 5 may be pushed into the interior 4 of the casting mold lower part 1 until the mating stop 22 rests against the limit stop 20 (see to this end FIGS. 6 and 7, which do not show the bone cement paste enclosed in the casting mold). When the casting mold upper part 5 is pushed in, the bone cement paste 36 which is present may be pressed into the cavity 2 and the volume within the casting mold continuously decreases. Excess bone cement paste 38 is pressed out through the openings 8 into the container 7 (see FIGS. 8 and 9). The excess bone cement paste 38 can be enclosed in the container 7 with the assistance of the lid 9.

[0186] The bone cement paste 36 can then cure in the casting mold, wherein the surface thereof is molded by the surface of the cavity 2 of the casting mold lower part 1 and the shaping surface 6 of the casting mold upper part 5. The spacer 42, as shown for example in FIGS. 10 and 11, is obtained as a result. During curing of the bone cement paste 36, sprues 40, which connect the spacer 42 with the cured excess bone cement paste 38 in the container 7, may be formed in the openings 8. The spacer 42 is demolded by being detached from the casting mold lower part 1 and the casting mold upper part 5. In so doing, the sprues 40 may be sheared off or broken off. In order to ensure straightforward demolding, the sprues 40 must be of such a small diameter that they can be broken off or sheared off manually when the spacer 42 is separated from casting mold upper part 5. It has proven effective to this end for the sprues 40 to have a diameter of a maximum of 2.5 cm and preferably of a maximum of 2 cm. Accordingly, the openings 8 should have an internal diameter of a maximum of 2.5 cm and preferably a maximum of 2 cm. Smaller diameters may also be selected in order to further simplify separation of the sprues 40. The openings 8 should, however, not have a diameter of less than 0.2 mm so that the bone cement paste 36 can still be pressed out through the openings 8 without excessive resistance. Otherwise, depending on the viscosity of the bone cement paste 36, the resistance when pushing the casting mold upper part 5 into the casting mold lower part 1 may become too great for it still to be possible to be carried out manually or for damage to or destruction of the casting mold to be avoided. The optimum diameter of the openings 8 here depends on the viscosity of the bone cement paste 36 which is used. Highly suitable diameters for typical bone cements are between 1 mm and 20 mm. As a rule of thumb, the higher the viscosity of the bone cement paste 36, the larger the selected internal diameter of the openings 8 should be.

[0187] After demolding, the projecting spacing pieces 12, any flash which has formed at the junction between the casting mold lower part 1 and the casting mold upper part 5, and protruding residues of the sprues 40 may be removed, for example by being trimmed off with a knife or scalpel or by being ground off with a grinding head. The spacer 42, as shown in FIG. 11, is obtained as the final result.

[0188] FIGS. 12 to 22 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, parts of the device and a spacer produced using the device. FIGS. 12 to 18 and 22 show the course of a second exemplary embodiment of a method according to the invention which is carried out using the device according to the second exemplary embodiment.

[0189] The second device according to the invention is suitable and provided for producing a spacer 92 (see FIGS. 17 and 18) fora shoulder joint. The device comprises a multipart casting mold. The casting mold has a casting mold lower part 51 and a casting mold upper part 55. A cavity 52 for receiving bone cement paste 36 (see FIGS. 12 to 15) and for forming part of the surface of the spacer 92 to be produced is arranged in the casting mold lower part 51. The cavity 52 can shape one half of the spacer 92. A casting mold wall 53, which extends the hollow space formed by the cavity 52 with an interior 54, may be arranged at the edge of the cavity 52. The casting mold wall 53 may to this end peripherally enclose the edge of the cavity 52. The walls of the casting mold wall 53 may be oriented parallel to one another, such that the casting mold wall 53 has a generally cylindrical geometry, wherein the base area of the general cylinder is defined by the area which delimits the edge of the cavity 52. The interior 54 for introduction of bone cement paste 36 is arranged within the walls of the casting mold wall 53, which interior is connected, and preferably also aligned, with the cavity 52.

[0190] The casting mold upper part 55 may preferably be inserted or pushed into the casting mold lower part 51. The casting mold upper part 55 has at the bottom thereof a shaping surface 56, with which a further part of the surface of the spacer 92 to be produced is shapeable and preferably the remaining part of the surface of the spacer 92 to be produced is shapeable. Together with the cavity 52, the shaping surface 56 may define the entire surface of the spacer 92 or at least 90% of the entire surface of the spacer 92. The shaping surface 56 may form an indentation in the casting mold upper part 55. It is also possible for part of the casting mold wall 53 to form part of the surface of the spacer 92 or for one or more inserts (not shown), which shape part of the surface of the spacer 92, additionally to be inserted into the cavity 52 and/or placed on the shaping surface 56.

[0191] A container 57 for receiving excess bone cement paste 38 (see FIG. 22) may be arranged on the side of the casting mold upper part 55 opposite from the shaping surface 56. Openings 58, which provide a through-connection for the excess bone cement paste 38 from the side of the shaping surface 56 to the container 57, may be present in the shaping surface 56. The openings 58 are preferably arranged at the points of the shaping surface 56 which, in the proper disposition of the device, are the highest shaping points of the casting mold. In this way, gases entrapped in the casting mold may escape through the openings 58 such that entrapped air is avoided in the spacer 92 to be produced.

[0192] The container 57 may have been or be impermeably closed to the outside for the bone cement paste 36 with a lid 59. An internal wall 61, which delimits the container 57, may start from and extend away from the back face of the shaping surface 56. The internal wall 61 may align externally with a perfect fit with the casting mold wall 53. In this way, the casting mold upper part 55 can be inserted with a perfect fit into the casting mold wall 53 of the casting mold lower part 51 and the bone cement paste 36 accordingly collected from the inside of the casting mold wall 53 and pressed into the cavity 52 and the shaping surface 56. It may also be sufficient to this end if the casting mold wall 53 tapers in the direction of the cavity 52, wherein the taper must to this end have an acute angle.

[0193] The container 57 may be gas-permeably connected with the surroundings. Provision may be made to this end for the lid 59 not to close pressure-tightly and/or for small vent openings (not visible in the figures) to be arranged in the lid and/or the internal wall 61.

[0194] A metal core 60 may be provided as reinforcement for the spacer 92. The metal core 60 may to this end be held spaced from the internal side of the cavity 52 and from the casting mold wall 53 with the assistance of pin-shaped spacing pieces 62 of cured PMMA, such that the bone cement paste 36 can flow completely around the metal core 60 between the metal core 60 on the one hand and the internal side of the cavity 52 and the shaping surface 56 on the other. In order to position the spacing pieces 62, bores (not visible) may be provided in the metal core 60 for receiving one end of the pin-shaped spacing pieces 62. Matching indentations for receiving the opposite end of the pin-shaped spacing pieces 62 may likewise be arranged in the internal side of the cavity 52.

[0195] A stand 66, into which the casting mold lower part 51 may be placed or inserted, may be provided in order to position the casting mold correctly with the casting mold lower part 51 underneath and the casting mold wall 53 perpendicularly on top. The stand 66 may be provided for placement on a flat surface such as a table.

[0196] The casting mold lower part 51, the casting mold upper part 55, the lid 59 and the stand 66 may be inexpensively produced from a plastics film or a plurality of joined together plastics films, in particular by injection molding or by thermoforming. In the assembled state, the parts of the device produced from the plastics films stabilize one another mechanically. The plastics film(s) preferably consist of a polyolefin, a polyethylene (PET) or a glycol-modified PET (PETG). When a plurality of films are used, they may be laminated together with an adhesive or by elevated temperature.

[0197] Internally located grooves 68 and externally located sprues 69, which extend from a limit stop 70 on the side of the casting mold wall 53 opposite from the cavity 52 down to the edge of the cavity 52, may be arranged in the casting mold wall 53. The sprues 69 may contain the volume for forming the grooves 68. The ends of the pin-shaped spacing pieces 62, which project out of the metal core 60, may be guided to the cavity 52 along these grooves 68.

[0198] Grooves 71 matching the sprues 69 may be provided internally in the stand 66. As a result, the casting mold lower part 51 can be pushed in guided manner into the stand 66 and the casting mold lower part 51 does not so readily become detached from the stand 66 and does not move so easily relative to the stand 66.

[0199] In order to fix the spacing pieces 62 and thus the metal core 60 in place, matching recesses 73 may be arranged at the edge of the shaping surface 56 of the casting mold upper part 55. The recesses 73 may be arranged at the edge of the shaping surface 56 in such a manner that they are moved along the grooves 68 of the casting mold wall 53 when the casting mold upper part 55 is pushed into the casting mold wall 53 of the casting mold lower part 51. The ends of the spacing pieces 62 which project out from the metal core 60 are accordingly clamped in place in the casting mold between the casting mold upper part 55 and the casting mold lower part 51.

[0200] The limit stop 70 may be arranged as a peripheral strip-shaped edge projecting out perpendicularly from the casting mold wall 53 on the side of the casting mold wall 53 remote from the cavity 52. The limit stop 70 can limit how far the casting mold upper part 55 can be pushed into the casting mold lower part 51. The casting mold upper part 55 may to this end have a mating stop 72 in the form of a peripheral edge which projects out perpendicularly from the internal wall 61 and is arranged on the side of the internal wall 61 opposite from the shaping surface 56. When the casting mold upper part 55 has been completely pushed into the casting mold lower part 51, the mating stop 72 rests against the limit stop 70. In the same way, a lid edge 74 which can be placed on the side of the mating stop 72 opposite from the limit stop 70 may be arranged on the lid 59. Because the limit stop 70, the mating stop 72 and the lid edge 74 project out from the adjoining parts at an angle, the shape of the casting mold lower part 51, the casting mold upper part 55 and the lid 59 is mechanically stabilized in the assembled state. This is in particular helpful if these parts have been fabricated from a plastics film or a plurality of plastics films by thermoforming.

[0201] The device may furthermore include a mixing cup 26 with a spout 28 for pouring bone cement paste 36 from the mixing cup 26 (see FIG. 14). The device may also include the starting components (not shown) of the bone cement paste 36 in separate containers. The bone cement paste 36 may then be mixed in the mixing cup 26 before it is introduced into the casting mold or into the casting mold lower part 51. The bone cement paste 36 may, however, also be produced in another way before it is introduced into the casting mold. The device thus does not necessarily require the mixing cup 26 and also not the bone cement paste 36 or the starting components thereof. The device may in principle be applied and used with any other known system for producing a bone cement paste, such as for example with a suitable cartridge system for storing and mixing bone cement paste.

[0202] The course of a first exemplary embodiment of a method according to the invention is described below with reference to FIGS. 12 to 22.

[0203] The device may firstly be removed from a package (not shown) in a sterile state and may then be present as shown in FIG. 12 or in FIG. 13. If the casting mold lower part 51 has not already been inserted into the stand 66, the casting mold lower part 51 may be pushed into the stand 66 via the grooves 71. If not already present therein, the metal core 60 may be inserted into the cavity 52 (see FIG. 13). In so doing, the projecting ends of the spacing pieces 62 slide in the grooves 68 of the casting mold wall 53.

[0204] When the metal core 60 is inserted into the cavity 52 or into the interior 54, the bone cement paste 36 can be introduced in excess into the interior 54 and the cavity 52 (see FIG. 14). The casting mold upper part 55 may then be inserted and pushed into the casting mold lower part 51 or into the casting mold wall 53. The container 57 may to this end be closed with the lid 59 (see FIG. 15).

[0205] The casting mold upper part 55 may be pushed into the interior 54 of the casting mold lower part 51 until the mating stop 72 rests against the limit stop 70 (see to this end FIGS. 16, 20 and 21, which either do not show the bone cement paste enclosed in the casting mold (FIGS. 20 and 21) or in which it is not visible (FIG. 16)). When the casting mold upper part 55 is pushed in, the bone cement paste 36 which is present may be pressed into the cavity 52 and the volume within the casting mold continuously decreases. Excess bone cement paste 38 is pressed out through the openings 58 into the container 57 (see FIG. 22). The excess bone cement paste 38 can be enclosed in the container 57 with the assistance of the lid 59.

[0206] The bone cement paste 36 can then cure in the casting mold, wherein the surface thereof is molded by the surface of the cavity 52 of the casting mold lower part 51 and the shaping surface 56 of the casting mold upper part 55. The spacer 92, as shown for example in FIGS. 17 and 18, is obtained as a result. During curing of the bone cement paste 36, sprues 90, which connect the spacer 92 with the cured excess bone cement paste 38 in the container 57, may be formed in the openings 58. The spacer 92 is demolded by being detached from the casting mold lower part 51 and the casting mold upper part 55. In so doing, the sprues 90 may be sheared off or broken off. In order to ensure straightforward demolding, the sprues 90 must be of such a small diameter that they can be broken off or sheared off manually when the spacer 92 is separated from casting mold upper part 55. It has proven effective to this end for the sprues 90 to have a diameter of a maximum of 2.5 cm and preferably of a maximum of 2 cm. Accordingly, the openings 58 should have an internal diameter of a maximum of 2.5 cm and preferably a maximum of 2 cm. Smaller diameters may also be selected in order to further simplify separation of the sprues 90. The openings 58 should, however, not have a diameter of less than 0.2 mm so that the bone cement paste 36 can still be pressed out through the openings 58 without excessive resistance. Otherwise, depending on the viscosity of the bone cement paste 36, the resistance when pushing the casting mold upper part 55 into the casting mold lower part 51 may become too great for it still to be possible to be carried out manually or for damage to or destruction of the casting mold to be avoided. The optimum diameter of the openings 58 here depends on the viscosity of the bone cement paste 36 which is used. Highly suitable diameters for typical bone cements are between 1 mm and 20 mm. As a rule of thumb, the higher the viscosity of the bone cement paste 36, the larger the selected internal diameter of the openings 58 should be.

[0207] After demolding, the projecting spacing pieces 62, any flash which has formed at the junction between the casting mold lower part 51 and the casting mold upper part 55, and protruding residues of the sprues 90 may be removed, for example by being trimmed off with a knife or scalpel or by being ground off with a grinding head. The spacer 92, as shown in FIG. 18, is obtained as the final result.

[0208] FIGS. 23 to 35 are drawings showing various views of a third exemplary embodiment of a device according to the invention for producing a spacer for a knee joint, parts of the spacer and parts of the device. FIGS. 23 to 31 show the course of a third exemplary embodiment of a method according to the invention which is carried out using the device according to the third exemplary embodiment.

[0209] The third device according to the invention is suitable and provided for producing a two-part articulating spacer with a spacer 142 for the femur and a spacer 192 for the tibia (see FIGS. 31 and 34) for replacing a knee joint. The device has two multipart casting molds, a femoral component casting mold for producing the spacer 142 for the femur (on the left in FIGS. 23 to 28 and 30 to 32 and 35 and at the top in FIGS. 29 and 33) and a tibial component casting mold for producing the spacer 192 for the tibia (on the right in FIGS. 23 to 28 and 30 to 32 and 35 and at the bottom in FIGS. 29 and 33). The third exemplary embodiment may for the purposes of the present invention also be understood as two different devices according to the invention, namely as a fourth device for producing a spacer 142 for the femur and a fifth device for producing a spacer 192 for the tibia.

[0210] The femoral component casting mold has a casting mold lower part 101 and a casting mold upper part 105. A cavity 102 for receiving bone cement paste 36 (see FIGS. 23 to 25, 29 and 33) and for forming part of the surface of the spacer 142 to be produced is arranged in the casting mold lower part 101. The cavity 102 can shape one half of the spacer 142. A casting mold wall 103, which extends the hollow space formed by the cavity 102 with an interior 104, may be arranged at the edge of the cavity 102. The casting mold wall 103 may to this end peripherally enclose the edge of the cavity 102. The walls of the casting mold wall 103 may be oriented parallel to one another, such that the casting mold wall 103 has a generally cylindrical geometry, wherein the base area of the general cylinder is defined by the area which delimits the edge of the cavity 102. The interior 104 for introduction of bone cement paste 36 is arranged within the walls of the casting mold wall 103, which interior is connected, and preferably also aligned, with the cavity 102.

[0211] The casting mold upper part 105 may preferably be inserted or pushed into the casting mold lower part 101. The casting mold upper part 105 has at the bottom thereof a shaping surface 106, with which a further part of the surface of the spacer 142 to be produced is shapeable and preferably the remaining part of the surface of the spacer 142 to be produced is shapeable. Together with the cavity 102, the shaping surface 106 may define the entire surface of the spacer 142 or at least 90% of the entire surface of the spacer 142. The shaping surface 106 may form an indentation in the casting mold upper part 105. It is also possible for part of the casting mold wall 103 to form part of the surface of the spacer 142 or for one or more inserts (not shown), which shape part of the surface of the spacer 142, additionally to be inserted into the cavity 102 and/or placed on the shaping surface 106.

[0212] A container 107 for receiving excess bone cement paste 38 (see FIG. 29) may be arranged on the side of the casting mold upper part 105 opposite from the shaping surface 106. Openings 108, in the form of channels in an internal wall 111 of the casting mold upper part 105, which provide a through-connection for the excess bone cement paste 38 from the side of the shaping surface 106 to the container 107, may be present in the shaping surface 106. The openings 108 are preferably arranged at the points of the shaping surface 106 which, in the proper disposition of the device, are the highest shaping points of the femoral component casting mold. In this way, gases entrapped in the femoral component casting mold may escape through the openings 108 such that entrapped air is avoided in the spacer 142 to be produced.

[0213] The container 107 may have been or be impermeably closed to the outside for the bone cement paste 36 with a lid 109. The internal wall 111, which delimits the container 107, may start from and extend away from the back face of the shaping surface 106. The internal wall 111 may align externally with a perfect fit with the casting mold wall 103. In this way, the casting mold upper part 105 can be inserted with a perfect fit into the casting mold wall 103 of the casting mold lower part 101 and the bone cement paste 36 accordingly collected from the inside of the casting mold wall 103 and pressed into the cavity 102 and the shaping surface 106. It may also be sufficient to this end if the casting mold wall 103 tapers in the direction of the cavity 102, wherein the taper must to this end have an acute angle.

[0214] The container 107 may be gas-permeably connected with the surroundings. Provision may be made to this end for the lid 109 not to close pressure-tightly and/or for small vent openings (not visible in the figures) to be arranged in the lid and/or the internal wall 111.

[0215] According to a preferred variant of the third exemplary embodiment, a stand 116, into which the casting mold lower part 101 may be placed or inserted, may be provided for correctly positioning the femoral component casting mold with the casting mold lower part 101 underneath and the casting mold wall 103 perpendicularly on top (see FIGS. 32 and 33). The stand 116 may be provided for placement on a flat surface such as a table.

[0216] The casting mold lower part 101, the casting mold upper part 105, the lid 109 and the stand 116 may be inexpensively produced from a plastics film or a plurality of joined together plastics films, in particular by injection molding or by thermoforming. In the assembled state, the parts of the device produced from the plastics films stabilize one another mechanically. The plastics film(s) preferably consist of a polyolefin, a polyethylene (PET) or a glycol-modified PET (PETG). When a plurality of films are used, they may be laminated together with an adhesive or by elevated temperature.

[0217] A limit stop 120 may be arranged as a peripheral strip-shaped edge projecting out perpendicularly from the casting mold wall 103 on the side of the casting mold wall 103 remote from the cavity 102. The limit stop 120 can limit how far the casting mold upper part 105 can be pushed into the casting mold lower part 101. The casting mold upper part 105 may to this end have a mating stop 122 in the form of a peripheral edge which projects out perpendicularly from the internal wall 111 and is arranged on the side of the internal wall 111 opposite from the shaping surface 106. When the casting mold upper part 105 has been completely pushed into the casting mold lower part 101, the mating stop 122 rests against the limit stop 120. In the same way, a lid edge 124 which can be placed on the side of the mating stop 122 opposite from the limit stop 120 may be arranged on the lid 109. Because the limit stop 120, the mating stop 122 and the lid edge 124 project out from the adjoining parts at an angle, the shape of the casting mold lower part 101, the casting mold upper part 105 and the lid 109 is mechanically stabilized in the assembled state. This is in particular helpful if these parts have been fabricated from a plastics film or a plurality of plastics films by thermoforming.

[0218] The tibial component casting mold is of similar construction to the femoral component casting mold and has a casting mold lower part 151 and a casting mold upper part 155. A cavity 152 for receiving bone cement paste 36 (see FIGS. 23 to 25, 29 and 33) and for forming part of the surface of the spacer 192 to be produced is arranged in the casting mold lower part 151. The cavity 152 can shape one half of the spacer 192. A casting mold wall 153, which extends the hollow space formed by the cavity 152 with an interior 154, may be arranged at the edge of the cavity 152. The casting mold wall 153 may to this end peripherally enclose the edge of the cavity 152. The walls of the casting mold wall 153 may be oriented parallel to one another, such that the casting mold wall 153 has a generally cylindrical geometry, wherein the base area of the general cylinder is defined by the area which delimits the edge of the cavity 152. The interior 154 for introduction of bone cement paste 36 is arranged within the walls of the casting mold wall 153, which interior is connected, and preferably also aligned, with the cavity 152.

[0219] The casting mold upper part 155 may preferably be inserted or pushed into the casting mold lower part 151. The casting mold upper part 155 has at the bottom thereof a shaping surface 156, with which a further part of the surface of the spacer 192 to be produced is shapeable and preferably the remaining part of the surface of the spacer 192 to be produced is shapeable. Together with the cavity 152, the shaping surface 156 may define the entire surface of the spacer 192 or at least 90% of the entire surface of the spacer 192. The shaping surface 156 may form an indentation in the casting mold upper part 155. It is also possible for part of the casting mold wall 153 to form part of the surface of the spacer 192 or for one or more inserts (not shown), which shape part of the surface of the spacer 192, additionally to be inserted into the cavity 152 and/or placed on the shaping surface 156.

[0220] A container 157 for receiving excess bone cement paste 38 (see FIG. 29) may be arranged on the side of the casting mold upper part 155 opposite from the shaping surface 156. Openings 158, which provide a through-connection for the excess bone cement paste 38 from the side of the shaping surface 156 to the container 157, may be present in the shaping surface 156. The openings 158 are preferably arranged at the points of the shaping surface 156 which, in the proper disposition of the device, are the highest shaping points of the tibial component casting mold. In this way, gases entrapped in the tibial component casting mold may escape through the openings 158 such that entrapped air is avoided in the spacer 192 to be produced.

[0221] The container 157 may have been or be impermeably closed to the outside for the bone cement paste 36 with a lid 159. An internal wall 161, which delimits the container 157, may start from and extend away from the back face of the shaping surface 156. The internal wall 161 may align externally with a perfect fit with the casting mold wall 153. In this way, the casting mold upper part 155 can be inserted with a perfect fit into the casting mold wall 153 of the casting mold lower part 151 and the bone cement paste 36 accordingly collected from the inside of the casting mold wall 153 and pressed into the cavity 152 and the shaping surface 156. It may also be sufficient to this end if the casting mold wall 153 tapers in the direction of the cavity 152, wherein the taper must to this end have an acute angle.

[0222] The container 157 may be gas-permeably connected with the surroundings. Provision may be made to this end for the lid 159 not to close pressure-tightly and/or for small vent openings (not visible in the figures) to be arranged in the lid and/or the internal wall 161.

[0223] According to a preferred variant of the third exemplary embodiment, a stand 166, into which the casting mold lower part 151 may be placed or inserted, may be provided for correctly positioning the tibial component casting mold with the casting mold lower part 151 underneath and the casting mold wall 153 perpendicularly on top (see FIGS. 32 and 33). The stand 166 may be provided for placement on a flat surface such as a table.

[0224] The casting mold lower part 151, the casting mold upper part 155, the lid 159 and the stand 166 may be inexpensively produced from a plastics film or a plurality of joined together plastics films, in particular by injection molding or by thermoforming. In the assembled state, the parts of the device produced from the plastics films stabilize one another mechanically. The plastics film(s) preferably consist of a polyolefin, a polyethylene (PET) or a glycol-modified PET (PETG). When a plurality of films are used, they may be laminated together with an adhesive or by elevated temperature.

[0225] A limit stop 170 may be arranged as a peripheral strip-shaped edge projecting out perpendicularly from the casting mold wall 153 on the side of the casting mold wall 153 remote from the cavity 152. The limit stop 170 can limit how far the casting mold upper part 155 can be pushed into the casting mold lower part 151. The casting mold upper part 155 may to this end have a mating stop 172 in the form of a peripheral edge which projects out perpendicularly from the internal wall 161 and is arranged on the side of the internal wall 161 opposite from the shaping surface 156. When the casting mold upper part 155 has been completely pushed into the casting mold lower part 151, the mating stop 172 rests against the limit stop 170. In the same way, a lid edge 174 which can be placed on the side of the mating stop 172 opposite from the limit stop 170 may be arranged on the lid 159. Because the limit stop 170, the mating stop 172 and the lid edge 174 project out from the adjoining parts at an angle, the shape of the casting mold lower part 151, the casting mold upper part 155 and the lid 159 is mechanically stabilized in the assembled state. This is in particular helpful if these parts have been fabricated from a plastics film or a plurality of plastics films by thermoforming.

[0226] The device may furthermore include a mixing cup 26 with a spout 28 for pouring bone cement paste 36 from the mixing cup 26 (see FIG. 23) and a film pouch 30 containing cement powder, an ampoule 32 containing monomer liquid and a spatula 34 for mixing the cement powder with monomer liquid in the mixing cup 26. The bone cement paste 36 may then be mixed in the mixing cup 26 before it is introduced into the casting mold or into the casting mold lower part 1. The bone cement paste 36 may, however, also be produced in another way before it is introduced into the casting mold. The device thus does not necessarily require the mixing cup 26 and also not the bone cement paste 36 or the starting components thereof. The device may in principle be applied and used with any other known system for producing a bone cement paste, such as for example with a suitable cartridge system for storing and mixing bone cement paste.

[0227] The course of a third exemplary embodiment of a method according to the invention is described below with reference to FIGS. 23 to 35.

[0228] The device may firstly be removed from a package (not shown) in a sterile state and may then be present as shown in FIG. 23 or in FIG. 25. The casting mold lower parts 101, 105 may optionally be inserted into the stands 116, 166, if stands 116, 166 are present.

[0229] The bone cement paste 36 may be mixed by mixing the cement powder from the film pouch 30 and the monomer liquid from the ampoule 32 in the mixing cup 26 with the assistance of the spatula 34. Alternatively, the bone cement paste 36 may also be produced in any other manner.

[0230] The bone cement paste 36 can then be introduced in each case in excess into the interior 104 and the cavity 102 and into the interior 154 and the cavity 152 (see FIG. 25). The casting mold upper part 105 may then be inserted and pushed into the casting mold lower part 101 and the casting mold upper part 155 into the casting mold lower part 151. The container 107 may to this end be closed with the lid 109 and the container 157 with the lid 159 (see FIGS. 26 and 27).

[0231] The casting mold upper part 105 may be pushed into the interior 104 of the casting mold lower part 101 until the mating stop 122 rests against the limit stop 120, and the casting mold upper part 155 may be pushed into the interior 154 of casting mold lower part 151 until the mating stop 172 rests against the limit stop 170 (see in this regard FIGS. 28 and 29). When the casting mold upper parts 105, 155 are pushed in, the bone cement paste 36 which is present may be pressed into the cavities 102, 152 and the volume within the femoral component casting mold and the tibial component casting mold continuously decreases. Excess bone cement paste 38 is pressed out through the openings 108, 158 into the containers 107, 157 (see FIG. 29). The excess bone cement paste 38 can be enclosed in the containers 107, 157 with the assistance of the lids 109, 159.

[0232] The bone cement paste 36 in the femoral component casting mold and the tibial component casting mold may then cure, wherein the surface thereof is molded by the surface of the cavity 102 of the casting mold lower part 101 and the shaping surface 106 of the casting mold upper part 105 or by the surface of the cavity 152 of the casting mold lower part 151 and the shaping surface 156 of the casting mold upper part 155. The spacer 142 for the femur and the spacer 192 for the tibia, as shown for example in FIGS. 31 and 34, are obtained as a result. During curing of the bone cement paste 36, sprues 140, which connect the spacer 142 for the femur with the cured excess bone cement paste 38 in the container 107, may be formed in the openings 108. Likewise during curing of the bone cement paste 36, sprues 190, which connect the spacer 192 for the tibia with the cured excess bone cement paste 38 in the container 157, may be formed in the openings 158. The spacers 142, 192 are demolded by being detached from the casting mold lower parts 101, 151 and the casting mold upper parts 105, 155. In so doing, the sprues 140, 190 may be sheared off or broken off. In order to ensure straightforward demolding, the sprues 140, 190 must be of such a small diameter that they can be broken off or sheared off manually when the spacers 142, 192 are separated from the casting mold upper parts 105, 155. It has proven effective to this end for the sprues 140, 190 to have a diameter of a maximum of 2.5 cm and preferably of a maximum of 2 cm. Accordingly, the openings 8 should have an internal diameter of a maximum of 2.5 cm and preferably a maximum of 2 cm. Smaller diameters may also be selected in order to further simplify separation of the sprues 140, 190. The openings 108, 158 should, however, not have a diameter of less than 0.2 mm so that the bone cement paste 36 can still be pressed out through the openings 108, 158 without excessive resistance. Otherwise, depending on the viscosity of the bone cement paste 36, the resistance when pushing the casting mold upper part 105 into the casting mold lower part 101 or when pushing the casting mold upper part 155 into the casting mold lower part 151 may become too great for it still to be possible to be carried out manually or for damage to or destruction of the femoral component casting mold and the tibial component casting mold to be avoided. The optimum diameter of the openings 108, 158 here depends on the viscosity of the bone cement paste 36 which is used. Highly suitable diameters for typical bone cements are between 1 mm and 20 mm. As a rule of thumb, the higher the viscosity of the bone cement paste 36, the larger the selected internal diameter of the openings 108, 158 should be.

[0233] After demolding, any flash which has formed at the junctions between the casting mold lower parts 101, 151 and the casting mold upper parts 105, 155, and protruding residues of the sprues 140, 190 may be removed, for example by being trimmed off with a knife or scalpel or by being ground off with a grinding head. The spacers 142, 192, as shown in FIG. 34, are obtained as the final result.

[0234] 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 SIGNS

[0235] 1, 51, 101, 151 Casting mold lower part

[0236] 2, 52, 102, 152 Cavity

[0237] 3, 53, 103, 153 Casting mold wall

[0238] 4, 54, 104, 154 Interior

[0239] 5, 55, 105, 155 Casting mold upper part

[0240] 6, 56, 106, 156 Shaping surface

[0241] 7, 57, 107, 157 Container

[0242] 8, 58, 108, 158 Opening

[0243] 9, 59, 109, 159 Lid

[0244] 10, 60 Metal core

[0245] 11, 61, 111, 161 Internal wall

[0246] 12, 62 Spacing piece

[0247] 14 Bore

[0248] 16, 66, 116, 166 Stand

[0249] 18, 68 Groove

[0250] 19, 69 Sprue

[0251] 20, 70, 120, 170 Limit stop/contact surface

[0252] 21, 71 Groove

[0253] 22, 72, 122, 172 Mating stop/contact surface

[0254] 23, 73 Recess

[0255] 24, 74, 124, 174 Lid edge

[0256] 26 Mixing cup

[0257] 28 Spout

[0258] 30 Film pouch containing bone cement powder

[0259] 32 Ampoule containing monomer liquid

[0260] 34 Spatula

[0261] 36 Bone cement paste

[0262] 38 Excess bone cement paste

[0263] 40, 90, 140, 190 Sprue

[0264] 42, 92, 142, 192 Spacer

[0265] 44, 94 Spacer head

[0266] 46, 96 Stem