Two-part articulating joint spacer and method for producing said joint spacer

Abstract

The invention relates to an articulating joint spacer for temporary replacement of a joint, whereby the joint spacer comprises two spacer parts which each comprise one sliding surface on which the spacer parts, in the patient-inserted state, touch against each other in mobile manner and roll off on each other, and the remaining spacer parts are made, at least in part, of a second bone cement that contains at least one water-soluble antibiotic. The invention also relates to a method for producing a two-part articulating joint spacer, in which a sliding surface is formed in both spacer parts from a low-abrasion first bone cement and at least the surfaces of the remaining spacer parts, at least 50% thereof, are formed with a second bone cement that contains at least one water-soluble antibiotic.

Claims

1. An articulating joint spacer for temporary replacement of a joint comprising two spacer parts, wherein each of the two spacer parts comprises (1) a first portion comprising a first layer, which first layer comprises a first bone cement which is a low-abrasion bone cement, and a sliding surface, the sliding surfaces of the two spacer parts being configured to touch against each other in a mobile manner and roll off on each other in a patient-inserted state, and (2) a remaining portion comprising a second layer, which second layer comprises a second non low abrasion bone cement that contains at least one water-soluble antibiotic, wherein the first bone cement and the second bone cement comprise different bone cement materials.

2. The articulating joint spacer according to claim 1, wherein the first layer has a thickness of at least 1 mm and is arranged directly on the second layer.

3. The articulating joint spacer according to claim 2, wherein the first layer has a thickness between 6 and 11 mm.

4. The articulating joint spacer according to claim 1, wherein the first layer comprises at least one anchoring component that extends from a direction of the sliding surface conically into the remaining portion and/or into the second layer.

5. The articulating joint spacer according to claim 1 wherein the remaining portion consists of the second bone cement, and connections of the spacer parts to a patient's bone consist of the second bone cement, and a region of the spacer parts located at a distance from the sliding surface consists of the second bone cement.

6. The articulating joint spacer according to claim 5 wherein the region of the spacer parts is situated at a distance of at least 1 mm from the sliding surface.

7. The articulating joint spacer according to claim 1 wherein the first bone cement comprises a radiopaque powder with a Mohs hardness of less than 8.

8. The articulating joint spacer according to claim 7 wherein the first bone cement comprises a radiopaque powder with a Mohs hardness of less than 4.

9. The articulating joint spacer according to claim 1 wherein the second bone cement comprises a mixture of at least two antibiotics selected from the group consisting of gentamicin, vancomycin, and clindamycin.

10. The articulating joint spacer according to claim 1 wherein a free surface of the first layer is coated by at least one antibiotic.

11. The articulating joint spacer according to claim 1 wherein the first bone cement comprises a calcium carbonate powder and/or barium carbonate powder.

12. A kit for forming an articulating spacer according to claim 1, comprising (1) a cartridge and/or an application system comprising the first bone cement in a pasty form, or starting components for forming the first bone cement, and (2) a second cartridge and/or a second application system comprising the second bone cement, or starting components for forming the second bone cement, and (3) at least two spacer moulds for producing a moulded part from the first bone cement, whereby internal surfaces of the at least two spacer moulds comprise a negative image of the sliding surfaces to be produced.

13. A kit for forming an articulating spacer according to claim 1, comprising (1) at least two spacer components formed from a material which consists of the first bone cement, each of said at least two spacer components comprising one sliding surface, and (2) a cartridge and/or an application system comprising the second bone cement or starting components for forming the second bone cement.

14. The articulating joint spacer according to claim 1 consisting of the first portion and the remaining portion.

15. The articulating joint spacer according to claim 1, wherein the two spacer parts touch only at the sliding surfaces.

Description

(1) Exemplary embodiments of the invention shall be illustrated in the following on the basis of one schematic FIGURE, though without limiting the scope of the invention.

(2) FIG. 1 shows a schematic cross-sectional view of a spacer according to the invention fabricated from two bone cements (6, 7, 12, 13). The spacer shown is a two-part articulating knee spacer intended for temporary replacement of a knee joint. The selected sectional plane shown is a plane of the artificial knee joint that is parallel to the sagittal plane.

(3) The two parts of the knee spacer are a tibial part 1 (on the bottom in FIG. 1) and a femoral part 2 (on the top in FIG. 2). The tibial part 1 is attached to a tibial bone 4 of a patient. The tibial part 1 comprises an articular head with an articular socket. The articular head is fabricated from a first bone cement 6 possessing sufficient hardness to prevent abrasion through the use of barium carbonate powder and/or calcium carbonate powder as radiopaquer andoptionallycan contain antibiotics/be antibiotics-containing. This renders the first bone cement 6 a low-abrasion bone cement. The remaining tibial part 1 is fabricated from a second bone cement 7 that contains a mixture of two water-soluble antibiotics that are matched to the manifest treatment setting of the patient.

(4) The articular head is anchored in the tibial bone 4 by means of a conical peg 8. This attains a stable connection of the tibial part 1 to the bone 4 and reduces the quantity of antibiotic-containing bone cement 7 used in the process and thus saves antibiotics. Besides, further anchorings 8 made of the second bone cement 7 are anchored in matching conical recesses in the tibial bone 4 in order to attain a more stable connection of the tibial part 1 of the spacer to the tibial bone 4.

(5) The femoral part 2 of the spacer is structured alike. An articular head is formed on the femoral bone 10 of a patient from a low-abrasion bone cement 12 and attached by means of an antibiotics-containing bone cement 13. The first bone cement 12 of the femoral part 2 of the spacer is preferably the same as the first bone cement 6 of the tibial part 1 and the second bone cement 13 of the femoral part 2 of the spacer is preferably the same as the second bone cement 7 of the tibial part 1 of the spacer. A stable connection of the articular head to the femoral bone 10 is attained by means of a conical anchoring 14.

(6) With the exception of the articular heads, the surfaces of the two spacer parts 1, 2 are implemented by means of the second bone cement 7, 13 and can therefore release antibiotics in the patient-inserted state, in particular in the direction of the bones 4, 10 of the patient.

(7) In the state intended, i.e. in the patient-inserted state shown in FIG. 1, the two spacer parts 1, 2 touch against each other by means of the articular heads. For this purpose, similar to a natural knee joint, sliding surfaces 16, 18 are provided at the surfaces of the articular heads by means of which the two spacer parts 1, 2 can roll off on each other and/or slide over each other.

(8) As a result, articulation of the spacer parts 1, 2 and thus replication of the functional mechanism of the knee is feasible.

(9) Since the sliding surfaces 16, 18 are fabricated from the low-abrasion first bone cement 6, 12, the sliding surfaces 16, 18 remain intact during the dwell time of the temporary knee spacer such that no (or only very few) particles detach from the sliding surfaces 16, 18. As a result, the mobility of the knee spacer is kept intact and there is no adverse abrasion effect on the healing process.

(10) Concurrently, the mixture of antibiotics is continually eluted by dissolution out of the second bone cement 7, 13 of the two spacer parts 1, 2 in order to support healing and is thus available for infection control.

(11) The example shown relates to a knee spacer that is preferred according to the invention. However, the invention is not limited to knee spacers, but also relates to any other form of two-part temporary joint spacers, such as, for example, elbow spacers, hip spacers, ankle spacers or shoulder spacers. It is obvious to a person skilled in the art to apply the example described by means of FIG. 1 to spacers for other joints.

(12) The features of the invention disclosed in the preceding description and in the claims, figures, and exemplary embodiments, can be essential for the implementation of the various embodiments of the invention both alone and in any combination.

LIST OF REFERENCE NUMBERS

(13) 1 Spacer part/tibial part

(14) 2 Spacer part/femoral part

(15) 4 Bone (tibia)

(16) 6 Low-abrasion bone cement (tibial part)

(17) 7 Antibiotics-containing cement (tibial part)

(18) 8 Anchoring

(19) 10 Bone (femur)

(20) 12 Low-abrasion bone cement (femoral part)

(21) 13 Antibiotics-containing cement (femoral part)

(22) 14 Anchoring

(23) 16 surface (tibial part)

(24) 18 Sliding surface (femoral part)