Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Utility Patent
1998-10-14
2001-01-02
Millin, V. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S020140, C623S013160
Utility Patent
active
06168629
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a femoral component for a knee prosthesis.
2. Description of Background and Relevant Information
The conventional femoral component of a knee prosthesis consists, of two lateral condyles, namely an external condyle and an internal condyle which define an intercondylar space. This lateral condyles are intended to cooperate with an insert attached to a tibial plateau, which is itself anchored at the upper end of the tibia.
This type of femoral component is typically used when a knee prosthesis is being fitted on a patient whose ligaments, and in particular the posterior cruciate ligament, are in a correct state, that is to say when they are able to maintain the femoral component on the insert/tibial plateau assembly, thereby preventing any drawer movement.
In case when the posterior cruciate ligament is no longer able to perform its function, the femoral component is replaced with a femoral component in which the intercondylar space is partly obturated by a third condyle, and thus permits posterior stabilization of the prosthesis during flexion of the tibia on the femur.
In view of these two types of cases, there is a need to provide a single femoral component which could be used either in the presence or absence of the posterior cruciate ligament.
One type of femoral component has been described in particular in the document FR-A-2 710 258, which proposes fitting, within the intercondylar space, a retractable support component which is able to receive a third condyle.
In practice, when it is not necessary to replace the posterior cruciate ligament, the surgeon implants the femoral component in a definitive manner, without fixing the third condyle thereto.
However, in the absence of the posterior cruciate ligament, the surgeon fits the third condyle into place before implanting the femoral component.
Unfortunately, once the prosthesis is fitted on a knee which still has its posterior cruciate ligament, this type of femoral component does not allow a third condyle to be fitted in the event of the ligament subsequently rupturing, without completely removing the femoral component from the femur, which causes considerable trauma.
SUMMARY OF THE INVENTION
The object of the invention is therefore to provide a femoral component for a knee prosthesis on which a third condyle can be fitted at any time, such as, before, during, and after the femoral component has been implanted. And such fitting can occur without having to remove the femoral component from the femur.
The invention therefore provides a femoral component for a knee prosthesis intended to cooperate with an insert attached to a tibial plateau which is anchored at the upper end of the tibia, the femoral component itself being anchored at the lower end of the femur and having two lateral condyles which cooperate with the insert and define an intercondylar space which is able to receive a third, removable condyle.
The femoral component provides each of the two lateral condyles with arrangements permitting the fitting or removal of a third condyle even after the anchoring of the femoral component on the femur.
In other words, the invention allows the third condyle to be fitted on a femoral component, even after it has been anchored definitively in the femur. This fitting, for example, will occur when it becomes necessary to remove the posterior cruciate ligament.
According to one embodiment of the invention, the arrangements consist of at least one through orifice formed on the lateral faces of each of the two lateral condyles, the orifices being intended to receive at least one device for securing the third condyle to the two lateral condyles.
Advantageously, there are two orifices and they are formed along a vertical axis.
To allow the third condyle to be fitted in the area of the two lateral condyles, the third condyle has complementary arrangements intended to cooperate with the arrangements on the lateral condyles.
In practice, the complementary arrangements consist of at least one through orifice formed on the lateral faces of the third condyle.
Advantageously, there are two orifices per face and they are aligned with the orifices provided on the lateral faces of the lateral condyles.
In order to obtain posterior stabilization of the knee prosthesis during flexion of the tibia on the femur, the third condyle has a semicylindrical shape with a thickness smaller than that of the intercondylar space, each of the lateral faces of the third condyle being equipped with a protuberance intended to make contact with the inner lateral faces of the lateral condyles, those protuberances having two lateral orifices which are intended to be positioned in alignment with the orifices of the lateral condyles.
To allow the third condyle to be fixed to the lateral condyles in a removable manner, the securing devices consists of at least one screw, one end of which has a thread intended to cooperate with a thread formed in an orifice of one of the two lateral condyles.
Thus, when fitting the third condyle, it suffices to position each of the orifices in line with the other, then to introduce the screw through the orifices, and finally to screw it in so as to fix the third condyle on the femoral component.
REFERENCES:
patent: 3990117 (1976-11-01), Pritchard et al.
patent: 4662889 (1987-05-01), Zichner et al.
patent: 4888021 (1989-12-01), Forte et al.
patent: 5116375 (1992-05-01), Hofmann
patent: 5405398 (1995-04-01), Buford, III et al.
patent: 5549687 (1996-08-01), Coates et al.
Greenblun & Bernstein, P.L.C.
Millin V.
Phan Hieu
Tornier S.A.
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