Knee hinge prosthesis with wear-resistant device for guiding...

Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone

Reexamination Certificate

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C623S020310, C623S020330

Reexamination Certificate

active

06383222

ABSTRACT:

The invention relates to a knee-joint prosthesis according to the preamble of claim 1.
BACKGROUND OF THE INVENTION
A knee-joint prosthesis having a tibial component, which is fixed to the proximal tibia, and a femoral component, which is fixed to the distal femur and has condylar bearing sections which cooperate in an articulated manner with condylar bearing sections of the tibial component, is known from German Utility Model 89 01 097.3. Apart from this, this knee-joint prosthesis comprises a patellar component, which is fixed to the patella and has a patellar bearing surface which touches an anterior plate section of the femoral component when the prosthetic knee-joint is fully extended. The femoral component with the anterior plate section is a one-piece item made of a metal or a metal alloy such as a cobalt-chromium-molybdenum alloy, titanium or a titanium alloy. The patellar bearing surface is made of a plastic, for example ultra-high molecular weight polyethylene.
Knee-joint prostheses which have no patellar component are also known. In this case, the natural patella, i.e. the bone, touches an anterior plate section of the femoral component directly when the prosthetic knee-joint is fully extended.
A disadvantage of this is that the patellar bearing surface or the natural patella often wears to a great extent, with the result that an exchange operation can become necessary.
SUMMARY OF THE INVENTION
The underlying object of the invention is to improve a knee-joint prosthesis according to the preambles of claims 1 or 3 in such a way that less wear occurs at the patellar bearing surface or the natural patella.
In accordance with the invention, this object is achieved in a first embodiment by the features of claim 1.
Because the anterior plate section and the bearing surface of the patellar component consist of one of the following sliding pairs:
metallic anterior plate section and metallic bearing surface of the patellar component, or
ceramic anterior plate section and ceramic bearing surface of the patellar component, or
ceramic anterior plate section, and bearing surface of the patellar component made of plastics,
a low-wear sliding pair is found, which makes an exchange operation necessary substantially less frequently.
Advantageously, the anterior plate section is constructed as an insert in the femoral component.
In accordance with the invention, the underlying object of the invention is achieved in a second embodiment by the features of claim 3.
Because the anterior plate section is a ceramic insert, the wear is likewise reduced, so that an exchange operation is necessary substantially less frequently. In this embodiment, the knee-joint prosthesis has no patellar component. The natural patella, i.e. the bone, touches the anterior plate section of the femoral component directly.
Advantageously, the ceramic material in all embodiments consists of aluminium oxide, zirconium oxide, mixed ceramic material of aluminium oxide or zirconium oxide, or other biocompatible ceramic materials or coatings.
Further features of the invention are evident from the figures, which are described in the following.


REFERENCES:
patent: 4355429 (1982-10-01), Mittelmeier et al.
patent: 5021061 (1991-06-01), Wevers et al.
patent: 5171282 (1992-12-01), Pequignot
patent: 0 681 815 (1995-11-01), None
patent: WO 95 23567 (1995-09-01), None

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