Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
2000-09-22
2004-06-29
Isabella, David J. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S020150
Reexamination Certificate
active
06755864
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a tibia part for a knee joint prosthesis and to a kit for putting together a knee joint prosthesis. Furthermore, the invention relates to a method for implanting and for re-operating a knee joint prosthesis.
Knee joint prostheses usually comprise a tibia part, which is fixed in the tibia, a femur part, which is fixed in the femur, as well as a bearing body which is arranged between them and which is often designated as a meniscus part. The tibia part has a tibia bearing surface for the support of the bearing body. The bearing body is provided on its side which faces away from the tibia bearing surface—that is, on the side facing the femur—with bearing shells which cooperate with condyles (running surfaces) of the femur part.
Nowadays knee joint prostheses are available in a large number of different prosthesis types, the functioning principles of which often differ strongly from one another. This is connected, among other things, with the fact that the prosthesis, depending on the state of the ligaments (cruciate ligaments, collateral ligaments), must wholly or partly take over the various functions of the ligaments in the respective patient.
Thus for example types of prostheses are known (see e.g. EP-A-0,923,916) in which the meniscus part is fixed to the tibia bearing surface of the tibia part, so that the meniscus part is arranged to be immobile relative to the tibia part.
Furthermore, prosthesis types are known in which the meniscus part is journalled on the tibia bearing surface so as to be movable relative to the tibia part, i.e. is thus either slidingly displaceable on the tibia bearing surface or is rotatable on the tibia bearing surface or both.
In EP-A-0,913,132 for example a knee joint prosthesis is shown in which the meniscus part is admittedly slidingly displaceable, but is however substantially rotationally fixedly seated on the tibia bearing surface of the tibia part, so that the meniscus part is admittedly displaceable on the tibia bearing surface in the anterior/posterior direction relative to the tibia part, but is substantially not rotatable.
Furthermore, prosthesis types are known in which the meniscus part is admittedly rotatable, but however not displaceably journalled on the tibia part relative to the tibia bearing surface, so that the meniscus part is only rotatable relative to the tibia part, but cannot be displaced.
Finally, prosthesis types are known from EP-A-0,519,873 in which the meniscus part is both slidingly displaceable and rotatable relative to the tibia bearing surface.
Moreover, prosthesis types are known in which means are provided in order to stabilize the femur part during the flexion (bending) in the posterior position relative to the meniscus part or relative to the tibia part respectively. This prosthesis type is used in particular when the rear cruciate ligament is no longer present or is no longer capable of functioning.
In particular in cases in which the collateral ligaments are no longer present or are no longer sufficiently capable of functioning, prosthesis types are used in which means for the lateral stabilizing (varus/valgus stabilizing) are provided.
From this non-exhaustive listing it is already clear that a large number of different embodiments of the individual components of a knee joint prosthesis, in particular also a large number of different tibia parts, must be provided in order that the respective prosthesis which is ideal for the respective patient can be put together.
For each prosthesis type there exists a tibia part which is specially matched to this type in order to ensure as good a cooperation with the remaining components of the prosthesis as possible. This means: A tibia part which was manufactured for a specific prosthesis type cannot as a rule be used for other prosthesis types. As a result of this there exist in part considerable constructional differences between tibia parts which belong to different prosthesis types.
This is however disadvantageous in particular from the point of view of the manufacturing technology, since for each prosthesis type the tibia part must be produced in accordance with a manufacturing process which is specific to the respective tibia part. Thus in order to provide a plurality of tibia parts for different prosthesis types, a plurality of partly very different, manufacturing processes must also be used, which is very complicated from the technical side and in addition is also economically disadvantageous.
If a kit is to be created by means of which different prosthesis types can be put together, then this kit must comprise a large number of tibia parts which differ from one another in regard to their functional design. Since in addition for each prosthesis type a plurality of tibia parts of different sizes must yet also be present in the kit in order to take into account the different anatomical circumstances of the patients, a kit of this kind necessarily comprises a very large number of individual components.
Here the invention wishes to provide a remedy. It is therefore an object of the invention to propose a tibia part which considerably simplifies the manufacture for different prosthesis types. Furthermore, through the tibia part a kit for the putting together of a knee joint prosthesis should be enabled which comprises considerably fewer different tibia parts without concessions therefore being necessary on the flexibility with respect to the different prosthesis types which can be realized with the kit or concessions on the functioning of the knee joint prosthesis.
SUMMARY OF THE INVENTION
In accordance with the invention thus a tibia part for a knee joint prosthesis is proposed which comprises a tibia bearing surface for the support of a bearing body (meniscus part) and a bore for the reception of a guiding element, with a cut-out for the rear cruciate ligament being provided in the tibia bearing surface and with the bore being formed in such a manner that it can, depending on the design of the guiding element, receive the latter either rotationally fixedly relative to the tibia part or rotatably relative to the tibia part.
These measures enable a tibia part which is suitable for a plurality of functionally different prosthesis types, which means that the same tibia part can be combined with different bearing bodies and/or femur parts and/or guiding elements in order thus to be able to put together different prosthesis types. Through the cut-out for the reception of the rear cruciate ligament the tibia part is suitable for prosthesis types in which the rear cruciate ligament remains intact and is capable of functioning. Through the design of the bore in the tibia bearing surface the tibia part in accordance with the invention is suitable both for prosthesis types in which the bearing body is rotationally fixedly seated relative to the tibia part and for prosthesis types in which the bearing body is rotatably journalled on the tibia bearing surface.
The variability of the tibia part in accordance with the invention or, respectively, its compatibility with different prosthesis types means a considerable simplification of the manufacturing process, since the same tibia part can be used for different prosthesis types.
The tibia part is preferably provided with an extension piece which serves for securing the tibia part in the tibia, with means being provided in order to connect the extension piece firmly to a separate anchoring shaft in the event that a separate anchoring shaft appears indicated as a result of the anatomical circumstances. Through this it is possible to provide the tibia part with differently designed anchoring shafts, in particular anchoring shafts of different lengths (insofar as indicated), in order thus to be able to match the anchoring of the tibia part in the tibia ideally to the special application.
In accordance with a first exemplary embodiment, securing means are provided at the tibia part in order to fix the bearing body on the tibia bearing surface. This exemplary embodiment is suitable in
Brack Rene
Leclercq Vincent
Scherrer Roger
Isabella David J.
Sulzer Orthopedics Ltd.
Townsend and Townsend / and Crew LLP
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