Ceramic Spacer for the Two-Sided Replacement of Implants in Shoulder, Knee and Hip as a Result of Infections

Abstract

A spacer comprised of individual components as joint replacement in the arthroplasty of shoulder, knee, and hip for the temporary surgical care of infections in the joint. The problems addressed by the invention are those of avoiding an adhesion of the bone to the spacer and a release of wear products, achieving that the patient does substantially not experience any mobility restriction, and keeping the wear and tear of the spacer as little as possible. These problems are solved in that at least one component of the spacer is made of a ceramic material, of a plurality of ceramic materials, or of a non-ceramic material having a ceramic coating.

Claims

1. A spacer having individual components as a joint replacement in the arthroplasty of the shoulder, knee and hip for the temporary surgical care of infections in the joint, characterized in that the spacer comprises at least one component that is composed of one or more ceramic substances or of a non-ceramic substance with a ceramic coating.

2. The spacer according to claim 1, wherein all exposed surfaces of the at least one ceramic component that are in contact with biological tissue are polished or processed such that their surface roughness Ra is less than 0.35 μm.

3. The spacer according to claim 1, wherein at least some regions of the at least one ceramic component have a coating or multiple coatings with one or more antibiotic agents.

4. The spacer according to claim 1 for a joint replacement in the arthroplasty of the hip and the shoulder, wherein the spacer consists of a ceramic stem with a projecting retainer element, a metallic sleeve being attached to said retainer element, and a ceramic ball head being anchored to the sleeve.

5. A spacer according to claim 4, wherein the coupling between the stem and sleeve and between the sleeve and ball head is preferably established by a conical clamping connection, or the coupling between the stem and sleeve is established as a clamping connection based on frustum geometries or in a form-fitting manner based on a square geometry, e.g. in order to promote the shaping of the stem by the single-axis dry pressing of ceramic powder, or the coupling is established in a firmly bonded or form-fitting way by using bone cement.

6. The spacer according to claim 4, wherein the sleeve can also be clamped to the retainer element by one or more stops.

7. The spacer according to claim 1, wherein the section of the stem that engages in the bone has a rectangular or oval shape in cross-section.

8. The spacer according to claim 1 for a joint replacement in the arthroplasty of the knee, wherein the spacer consists only of two components, namely a femur component composed of bone cement or a ceramic substance and a tibia component composed of a ceramic substance, said femur component having two parallel sliding surfaces that are mounted on two parallel curved regions on the tibia component.

9. The spacer according to claim 8, wherein the femur component is closed between the sliding surfaces.

10. The spacer according to claim 8, wherein the tibia component has a pin on the lower side opposite the curved regions, which protrudes at a right angle and which is non-circular in cross-section and which preferably has an angular or oval cross-section.

Description

[0051] The invention will be further explained below on the basis of drawings.

[0052] FIG. 1 shows a claimed spacer 1, consisting of a stem 2 with a projecting retainer element 13 for a sleeve 3 and a head 4. The stem 2 and the head 4 consist of a ceramic material. In the present embodiment, the sleeve 3 consists of a metal. The cross-section has a rectangular or oval shape so that the stem 2 can be implanted such that it does not rotate in the bone.

[0053] FIG. 2 shows the stem 2 alone. It has an anatomical design at the position indicated A1. The stem has large radii at indicated position A2. In region A3, there are only smooth transitions in the cross-section. The stem has a maximum cross-section of 14*14 mm in region A4.

[0054] FIG. 3 shows various sizes of the stem 2. FIG. 4 shows conventional ball heads 5 compared with the ball heads 4 for the spacers including the sleeves 3. The ball heads 4 are larger than the conventional ball heads 5 in the hip prosthesis.

[0055] The surface roughness Ra of the stem 2 after sintering is 0.25 to 0.35. The ball head 4 of the spacer 1 has a surface roughness of preferably 0.1 μm.

[0056] Embodiment for use in arthroplasty of the knee:

[0057] FIGS. 5a and 5b show the prior art of knee joint prostheses. This prosthesis consists of a ceramic femur component 6, a PE component 7 and a ceramic tibia component 8. FIG. 5a shows the prosthesis implanted and FIG. 5b shows it not yet implanted.

[0058] Claimed spacers for the knee are depicted in FIGS. 6 and 7.

[0059] FIG. 6a shows a femur component 9 that consists of bone cement and is mounted on a claimed tibia component 10 composed of a ceramic material. The tibia component 10 consists substantially of a rectangular plateau composed of a ceramic material with curved regions 15, on which the femur component 9 is mounted by its sliding surfaces 14. The tibia component 10 has a pin 11 on its lower side, said pin being non-circular, e.g. with an angular or oval cross-section, to secure it against rotation. Both the femur component 9 and the tibia component 10 are anchored in the bone with bone cement.

[0060] An alternative spacer is shown in FIGS. 7a and 7b. Like the tibia component 10, the femur component 12 in this embodiment consists of a ceramic material. The tibia component 10 is identical in configuration to the tibia component 10 according to FIG. 6b.

[0061] Advantageously: [0062] the femur component 9, 12 of the spacer has simplified geometry and is modelled on existing spacers composed of PMMA materials—alternatively, a universal geometry can be implemented, which represents the average of the inner contour of the most common implant systems on the market or the minimal geometry (minimum material condition) of an overlap between these systems; [0063] the tibia component 10 is executed in the form of a simplified plateau of ceramic, where the joint space is created by inserting one or more stackable spacer plates; [0064] the spacer plates consist of ceramic material or a low-abrasion polymer, e.g. PE, XPE, vitamin E XPE, wherein the polymer could additionally be filled with one or more antibiotic agents, which are released in vivo.

[0065] Production of the ceramic components:

[0066] The articulating components can be produced by the known production methods, such as uniaxial or isostatic dry pressing, shape cutting, single or multi-stage sintering (hot isostatic pressing is possible but may not be necessary), grinding and polishing in the sintered state, wherein processing by grinding and polishing can be reduced or sub-steps omitted owing to lower requirements regarding tolerances and surface finishes.

[0067] The articulating components could likewise be shaped by ceramic injection molding (CIM or LIM).

[0068] For applications in hip or shoulder arthroplasty, the following methods for producing the stem 2 are possible: [0069] slip casting [0070] dry pressing [0071] wet pressing [0072] true net-shape CIP (cold isostatic pressing) [0073] CIM (ceramic injection molding) [0074] gel casting [0075] LIM (low pressure injection molding)

[0076] After sintering, the surface of the ceramic stem is mechanically reprocessed, optionally by grinding and/or vibratory grinding and/or polishing, until the smoothest possible surface is obtained, which undergoes little or no osseointegration into the bone and prevents bacterial colonization but which permits sufficient adherence of the coating, if needed.

[0077] For applications in hip or shoulder arthroplasty, the metallic sleeve 3 is advantageously produced in a cost-saving manner by deep-drawing from sheet metal blanks.