Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-09-23
2001-10-09
Snow, Bruce (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
Reexamination Certificate
active
06299646
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a knee prosthesis and more specifically to the device for assembling its tibia plate, which is made of plastic, on its metal base anchored beforehand into the tibia bone tissue.
2. Discussion of Background Information
Knee prostheses which comprise a plastic tibia part which is free to rotate about the tibia bone axis with respect to the metal base secured to the tibia are known.
This freedom of rotation is generally achieved via a male shaft integral with the plastic tibia part which engages with a bore made in the metal base.
Furthermore, this freedom of rotation may be achieved by a male shaft secured to the metal base which engages with a bore made in the plastic tibia part.
These connecting devices have certain drawbacks, namely the difficulty of inserting the plastic tibia plate once the metal base is in place on the tibia. These drawbacks are exacerbated when the posterior cruciate ligament is being kept, as this restricts access to the upper part of the tibia.
Furthermore, it is observed that the center of rotation is necessarily positioned at a point of the device or [sic] the bore can be made, that is to say in a part or [sic] there is enough material to make the said bore. This arrangement of the center of rotation is not strictly anatomical.
It can be seen that the volume generated by the tibia bone axis may prevent a posterior cutout from being made in the plastic tibia plate or in the metal base to allow the posterior cruciate ligament to be kept.
Knee prostheses which comprise a plastic tibia plate which slides freely over the flat surface of the metal base, and the movement of which is limited by one or more cylindrical studs integral with the base communicating with spaces made in the plastic plate are also known.
This type of prosthesis has the drawback of not physically embodying an axis of rotation.
It is these drawbacks which the present invention sets out more particularly to overcome.
SUMMARY OF THE INVENTION
The knee prosthesis according to the present invention is intended to provide a plastic tibia plate which has a degree of freedom in rotation with respect to the metal base.
The knee prosthesis in accordance with the present invention comprises a metal base and a tibia plate which are equipped with guide mechanism defining a center of rotation which may be offset from that of the tibia bone axis, so as to allow the tibia plate to slide in rotation over the base, the guide mechanism being positioned a certain distance away from the center of rotation.
The knee prosthesis has guide mechanism which utilizes at least one upstand in the shape of an arc of a circle secured to the metal base and of a housing with the same radius of curvature made in the plastic tibia plate to allow the latter to slide in rotation about the center of rotation of the upstand.
The knee prosthesis according to the present invention comprises guide mechanism which utilizes an upstand in the shape of an arc of a circle, which upstand is positioned in the anterior part of the metal base and oriented in a substantially medio-lateral direction.
The knee prosthesis according to the present invention comprises additional guide mechanism which is positioned on or near to the center of rotation of the tibia plate on the metal base.
The knee prosthesis according to the present invention comprises additional guide means which are secured to a device making it possible to prevent the tibia plate from lifting from the metal base.
The knee prosthesis in accordance with the present invention comprises guide mechanism which utilizes at least two pegs set out in an arc of a circle and defining a center of rotation, and of a housing of the same radius of curvature formed in the tibia plate.
The knee prosthesis according to the present invention comprises a metal base which comprises an upstand in the shape of an arc of a circle having a central part secured to lateral edges which are not as tall as the said central part, while the tibia plate comprises, on its lower face, a housing in the shape of an arc of a circle.
The knee prosthesis according to the present invention comprises an upstand which has a center of rotation which is borne by the tibia bone vertical axis, while the upstand is a certain distance away from its center of rotation.
The knee prosthesis according to the present invention comprises an upstand which has a center of rotation which is offset from the tibia bone vertical axis, while the upstand is a certain distance away from its center of rotation.
The knee prosthesis according to the present invention comprises a metal base which has two upstands in the shape of an arc of a circle, of constant height and having one and the same center of rotation, while the tibia plate comprises two housings in the shape of an arc of a circle.
The knee prosthesis according to the present invention comprises upstands which are set out opposite one another, and have one and the same center of rotation.
The knee prosthesis according to the present invention comprises a metal base which has, opposite the upstand, a retaining peg borne by a center of rotation so as to engage with a cutout formed in the tibia plate to prevent the latter from lifting off the base as the plate slides in rotation about its center of rotation.
The knee prosthesis according to the present invention comprises a retaining peg which utilizes a cylindrical pin integral with a head which has a larger diameter than the pin so that the head engages with inclined faces made in the cutout.
The knee prosthesis according to the present invention comprises a metal base which has, opposite the upstand, a centering peg borne by the center of rotation so as to engage with a blind hole formed in the tibia plate to guide the latter with respect to the base as the plate slides in rotation about its center of rotation.
The knee prosthesis according to the present invention comprises a metal base and a tibia plate which respectively comprise a cutout through which the posterior cruciate ligament can pass.
The knee prosthesis according to the present invention comprises a metal base which has two upstands in the shape of an arc of a circle curved in the same direction and centered about the same center of rotation, while the tibia plate comprises housings intended to receive the upstands respectively, so as to allow the plate to slide in rotation about the center of rotation.
The knee prosthesis according to the present invention comprises an upstand which is integral with a flange which engages in a slot in the housing to prevent the tibia plate from lifting off the metal base as the plate slides in rotation about the center of rotation.
The knee prosthesis according to the present invention comprises a metal base which comprises two upstands in the shape of an arc of a circle in opposite directions and centered about the same center of rotation, while the tibia plate comprises an element and a housing which are intended to receive the upstands respectively to allow the plate to slide in rotation about the center of rotation.
The knee prosthesis according to the present invention comprises an upstand which is set out on the external periphery of the horizontal disk of the metal base so as to engage with a peripheral recess in the tibia plate.
The knee prosthesis according to the present invention comprises an upstand which is offset from the center of rotation and comprises a flange which snap-fastens into the housing in the tibia plate to, on the one hand, guide the plate as it slides in rotation about its center and, on the other hand, retain the plate so that it does not lift off the metal base.
The knee prosthesis according to the present invention comprises a metal base which comprises a peripheral upstand in the shape of an arc of a circle integral with a flange directed toward the tibia bone vertical axis and a housing set out in the region of the center of rotation, while the tibia plate has, on its external periphery, a r
Chambat Pierre
Deschamps Gerard
Judet Thierry
Neyret Philippe
Greenblum & Bernstein P.L.C.
Snow Bruce
Tornier SA
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