Knee prosthesis

Abstract

A knee prosthesis (1), comprising a tibial component (2) adapted to be implanted in the tibia of a patient, and a femoral component (3) adapted to be implanted in the femur of the patient; the tibial and femoral components (2, 3) are compatible with two different interface elements (4, 5), which are adapted to be interposed between the femoral component (3) and the tibial component (29; one (4) of the two interface elements(4, 5) being associable with the tibial and femoral components (2, 3) with an insert (4a-4c) without interposition of other elements in order to provide the Constrained Condylar Knee (CCK)-type knee prosthesis; the other interface element (5) being associable with the tibial and femoral components (2, 3) with an insert (5a-5b) and a hinge element (5b-5e) which are adapted to be inserted in the femoral component(3) and in the tibial component (2) in order to provide the Hinge Constrained Condylar Knee (HCCK)-type knee prosthesis.

Description

[0001] KNEE PROSTHESIS

[0002] The present invention relates to a knee prosthesis. More specifically, the invention relates to a knee prosthesis for oncological revision or resection operations.

[0003] As is known, there are two different types of knee prosthesis for oncological revision or resection operations:

[0004] - knee prosthesis of the Constrained Condylar Knee (CCK) type

[0005] - knee prosthesis of the Hinge Constrained Condylar Knee (HCCK) type

[0006] The two types of prosthesis are implanted on the basis of a choice made by the surgeon at the time of the operation.

[0007] All prostheses on the market use a prosthesis (femoral component and tibial component) that is "customized" (therefore different) to one of the above two types of knee prosthesis.

[0008] With conventional prostheses the surgeon needs to make the choice of which type of prostheses to implant before carrying out the operation. This entails a final choice made by the surgeon, since the operation is then carried out as a function of the type of prostheses chosen.

[0009] In revision surgery too, i.e. if the prosthesis needs to be revised and be given better stabilization, the passage from one type of prostheses to another, i.e. from CCK to HCCK, is carried out by the surgeon by removing the femoral and tibial components of the prosthesis, therefore with an operation that is extremely invasive for the patient.

[0010] As is known, in fact, the tibial component of the prosthesis is the part of the prostheses that is implanted in the tibia, while the femoral component is the part that is implanted in the femur. Removal of these components from the femur and from the tibia entails surgery that is more complex than the surgery carried out when the prosthesis is first implanted.

[0011] Furthermore, conventional prostheses of the HCCK type have a modular hinge attached to the femoral component of the prosthesis, which is subsequently fixed to the tibial component with an accessory pivot, which is mounted during surgery.

[0012] The aim of the present invention is to provide a knee prostheses that enables the surgeon to choose, at the time of surgery, which type of prostheses, CCK or HCCK, to use during the operation, without needing to change the femoral and tibial components of the prosthesis.

[0013] Within this aim, an object of the present invention is to provide a knee prosthesis that, also in the event of revision surgery of one of the two components of the prosthesis (femoral or tibial) of that prosthesis, does not require the removal of one or both of the femoral and tibial components.

[0014] Another object of the present invention is to provide a knee prosthesis in which the hinge is provided in such a way as to make it possible to connect femur and tibia, with the femoral and tibial components already implanted, without needing to place the femoral and tibial end in stretching traction.

[0015] Another object of the present invention is to provide a knee prosthesis that is highly reliable, is easily and practically implemented, and at low cost.

[0016] This aim and these and other objects which will become more apparent hereinafter are achieved by a knee prosthesis comprising a tibial component adapted to be implanted in the tibia of a patient, and a femoral component adapted to be implanted in the femur of the patient, characterized in that said tibial component and said femoral component are compatible with two different interface elements, which are adapted to be interposed between said femoral component and said tibial component; one of said two interface elements being associable with said tibial and femoral components with an insert without interposition of other elements in order to provide a Constrained Condylar Knee (CCK)-type knee prosthesis; the other one of said two interface elements being associable with said tibial and femoral components with an insert and a hinge element which are adapted to be inserted in said femoral component and said tibial component in order to provide a Hinge Constrained Condylar Knee (HCCK)-type knee prosthesis.

[0017] Further characteristics and advantages of the invention will become more apparent from the detailed description of a preferred, but not exclusive, embodiment of the prosthesis according to the invention, illustrated for the purposes of non-limiting example in the accompanying drawings wherein:

[0018] Figure 1 is a perspective view of a first interface element of the knee prosthesis according to the present invention;

[0019] Figure 2 is a rear view of the first interface element of the knee prosthesis according to the present invention;

[0020] Figure 3 is a side view of the first interface element of the knee prosthesis according to the present invention;

[0021] Figure 4 is a cross-sectional front elevation view of the first interface element of the knee prosthesis according to the present invention;

[0022] Figure 5 is a cross-sectional side view of the first interface element of the knee prosthesis according to the present invention;

[0023] Figure 6 is a perspective view of the knee prosthesis according to the present invention with interface element decoupled;

[0024] Figure 7 is a cross-sectional side view of the knee prosthesis according to the present invention, with the interface element in the coupled configuration;

[0025] Figure 8 is a perspective view of a second interface element of the knee prosthesis according to the present invention;

[0026] Figure 9 is a rear view of the second interface element of the knee prosthesis according to the present invention;

[0027] Figure 10 is a side view of the second interface element of the knee prosthesis according to the present invention;

[0028] Figure 11 is a cross-sectional front elevation view of the second interface element of the knee prosthesis according to the present invention; Figure 12 is a cross-sectional side view of the second interface element of the knee prosthesis according to the present invention;

[0029] Figure 13 is an exploded perspective view of the knee prosthesis according to the present invention with an interface element;

[0030] Figure 14 is a perspective view of the knee prosthesis according to the present invention with the interface element;

[0031] Figure 15 is a cross-sectional perspective view of the knee prosthesis according to the present invention with the interface element.

[0032] With reference to the figures, the knee prosthesis according to the invention, generally designated by the reference numeral 1, comprises a tibial component 2, adapted to be implanted in the tibia of a patient, a femoral component 3, adapted to be implanted in the femur of a patient; the femoral component 3 is provided with a stem 6a that makes it possible to implant the femoral component 3 in the femur, similarly the tibial component 2 is provided with a stem 6b that makes it possible to implant the tibial component in the tibia.

[0033] The prosthesis is completed by two interface elements 4 (Figure 7) (CCK), 5 (Figure 15) (HCCK), which need to be inserted between the tibial component 2 and the femoral component 3. The interface elements differ in relation to the type of prosthesis, CCK or HCCK.

[0034] In the CCK prosthesis, the component 4 has a “cam” 4c in the part directed toward the femoral component 3 and has a cylindrical element or shank 4b.

[0035] In the HCCK prosthesis, the component 5 is composed of an insert and a hinge element (hereinafter hinge). The insert has an articular part 5a and a cylindrical element or shank 5b which conveniently is hollow in order to receive a long and angled element 5c of the hinge.

[0036] The hinge is then inserted in the internally hollow shank 5b of the insert, which in turn is inserted in the tibial part 2; the hinge, with a part 5e, is then inserted in a seat or hole, defined with Morse taper, in the femoral component 3.

[0037] By changing the interface element 4 (CCK) for the element 5 (HCCK), which comprises the insert and the hinge, inserted between the tibial component 2 and the femoral component 3, it is therefore possible to decide which type of knee prosthesis to obtain: CCK or HCCK. In fact, it will be sufficient to replace the interface element 4 with the interface element 5 in order to be able to pass from one type of prostheses (CCK) to the other (HCCK).

[0038] All this occurs without needing to re-implant the tibial 2 and femoral 3 components in contact with the bone.

[0039] In substance, the interface element 4 for CCK prostheses is therefore formed by the insert with articular surfaces 4a, with the shank 4b and cam 4c being connectable to the tibial component 2.

[0040] The interface element 5 for HCCK prostheses is formed by the insert 5a, 5b and by a hinge that comprises the elements 5c, 5d, 5e, being connectable to the tibial component and being connectable to the femoral component by way of the hinge adapted to be inserted in the femoral component and in the insert 5a, 5b; the insert is adapted to be inserted in the tibial component 2.

[0041] Moreover, in the knee prosthesis according to the invention, as mentioned, the hinge 5c-e is supplied already fully assembled i.e., complete with a polyethylene bushing 5f for a pivot 5g which connects the long and conveniently angled component 5 c with a metal liner 5e which enters the femur 3, as well as for a part 5d interposed between the part 5c and the part 5f in order to reduce the friction thereof in movements of the hinge. This hinge makes it possible to connect femur 3 and tibia 2 with the femoral and tibial components already implanted, without needing to place the femoral and tibial ends in stretching traction.

[0042] The surgeon sinks the long and angled part 5c of the hinge into the cavity 5h of the polyethylene insert 5b and then proceeds with the insertion of the femoral part 5e of the hinge in the femur 3, then laying the joint out extended, in order to bring the femoral and tibial components of the prosthesis "into phase". Then, repositioning the knee at 90°, the surgeon proceeds to fix, using an adapted screw, the femoral part 5e of the hinge to the femoral component of the prosthesis 3.

[0043] In practice it has been found that the knee prosthesis according to the invention fully achieves the set aim and objects, in that it enables the surgeon to change the Constrained Condylar Knee (CCK) type of knee prosthesis to the Hinge Constrained Condylar Knee (HCCK) type of knee prosthesis both during the implantation surgery, and in the case of subsequent revision, without needing to change the components that are already implanted in the femur and in the tibia.

[0044] Furthermore, the type of hinge used enables mounting without applying traction to the limb.

[0045] The knee prosthesis thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the appended claims.

[0046] Moreover, all the details may be substituted by other, technically equivalent elements.

[0047] In practice, the materials used, as well as the contingent shapes and dimensions, may be any according to the requirements and to the state of the art.

[0048] The disclosures in Italian Patent Application No. 102024000001455 from which this application claims priority are incorporated herein by reference.

[0049] Where technical features mentioned in any claim are followed by reference signs, those reference signs have been included for the sole purpose of increasing the intelligibility of the claims and accordingly, such reference signs do not have any limiting effect on the interpretation of each element identified by way of example by such reference signs.

Claims

CLAIMS1. A knee prosthesis (1) comprising a tibial component (2) adapted to be implanted in the tibia of a patient, and a femoral component (3) adapted to be implanted in the femur of the patient, characterized in that said tibial(2) and femoral (3) components are compatible with two different interface elements (4, 5), which are adapted to be interposed between said femoral component (3) and said tibial component (2); one (4) of said two interface elements (4, 5) can be associated with said tibial (2) and femoral (3) components with an insert (4a-4c) without interposition of other elements in order to provide a Constrained Condylar Knee (CCK)-type knee prosthesis; the other (5) of said two interface elements (4, 5) can be associated with said tibial (2) and femoral (3) components with an insert (5a-5b) and a hinge element (5c-5e) which are adapted to be inserted in said femoral component(3) and said tibial component (2) in order to provide a Hinge Constrained Condylar Knee (HCCK)-type knee prosthesis.

2. The knee prosthesis according to claim 1, characterized in that one(4) of said two interface elements (4, 5) is formed by a polyethylene insert with a horizontal part which is articulated with the tibial and femoral components of the prosthesis, said horizontal part having, in an upper, proximal and central seat, a cam (4c) the dimensions of which are close to the distance between the posterior condyles of the femoral prosthesis (3) and which is adapted to increase the stability of the implant, by preventing its forward sliding, and having, in a lower, distal seat, a cylindrical part, said cylindrical part being adapted to be inserted in a seat provided in the tibial component (2) of the prosthesis.

3. The knee prosthesis according to one or more of the preceding claims, characterized in that the other (5) of said two interface elements (4, 5) comprises said insert (5a-5b) and said hinge (5c-5e).

4. The knee prosthesis according to one or more of the preceding claims, characterized in that said insert of the other (5) of said two interfaceelements (4, 5) has a horizontal shaped part which is adapted to be articulated with the femoral component (3) and the tibial component (2) of the prosthesis; a hollow cylindrical element extends vertically from said shaped part, in a lower (distal) seat, and is adapted to allow the insertion of said hinge, said hollow cylindrical element being configured to be inserted into the seat provided in the tibial component (2) of the prosthesis.

5. The knee prosthesis according to one or more of the preceding claims, characterized in that the hinge (5c-5e) of said other (5) of the two interface elements (4, 5) has a long and angled part made of cobalt chromium alloy which is adapted to be inserted in the hollow cylindrical element of the insert of the other (5) of said two interface elements (4, 5), said long and angled part being connected by means of a cobalt chromium alloy pivot and a polyethylene bushing to a cobalt chromium alloy liner shaped to be connected to the femoral component (3) of the prosthesis; a polyethylene part is interposed between the long and angled part and the liner and is contoured to decrease friction between said pivot and said liner.

6. The prosthesis according to one or more of the preceding claims, characterized in that said hinge of the other (5) of said two interface elements (4, 5) can be fixed by means of a screw to the femoral component (3) of the prosthesis.

7. The prosthesis according to one or more of the preceding claims, characterized in that said hinge (5c-5e) of the other (5) of said two interface elements (4, 5) is made of polyethylene parts and cobalt chromium alloy parts.

8. The prosthesis according to one or more of the preceding claims, characterized in that said hinge (5c-5e) of the other (5) of said two interface elements (4, 5) is adapted to be connected, during prosthesis implantation surgery, to the tibial component (2) and to the femoral component (3) of the prosthesis without the need to place the patient's limb in stretching traction, since it can be inserted first in the tibial component (2) and then, by flexingthe knee by 90°, it can be inserted in the seat of the femoral component (3) of the prosthesis.