Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Reexamination Certificate
1998-03-09
2001-02-06
Willse, David H. (Department: 3738)
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
C623S021110
Reexamination Certificate
active
06183519
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to ankle prostheses.
2. Brief Description of the Related Art
Numerous prostheses were put forth that comprise a tibial and a talar element, each provided with an articular surface; these articular surfaces are shaped in such a manner that, by interacting as a whole, they provide the necessary articulation between the foot and the leg. Several shapes of articular surfaces were contemplated, some of which were spherical while others were constituted by surfaces of revolution around an axis essentially perpendicular to the tibial axis, allowing a rotary motion only around this one axis. Furthermore, one or the other of the tibial and talar elements can be provided with a plane interface, which allows a sliding between two elements, one of which is secured to the bone while the other one delimits the articular surface.
It must be noted, however, that in all the various currently used prostheses the obtained movement of the articulation does not correspond to the natural articular movement of the ankle, a fact that manifests itself in an inadequacy between the movement allowed by the articular surfaces and the movement the various ligaments tend to impose upon the foot. This inadequacy is evidenced by the appearance of limitations and stresses on the prosthesis which, in turn, can give rise to wear and tear, a loss of mobility or even a loosening of the prosthesis. Furthermore, it can cause discomfort and unpleasant pains to the patient.
SUMMMARY OF THE INVENTION
Thus, the object of the present invention is to present an ankle prosthesis that allows an improvement of this situation and to obtain an ankle kinematics that comes very close to that of a regular ankle.
To this effect, the object of the present invention is an ankle prosthesis, comprising a tibial element and an talar element, each one provided with anchoring means at the lower extremity of the tibia and at the astragalus, respectively, and each delimiting an articular surface; these two articular surfaces are shaped in such a manner as to interact as a whole and to provide a relative movement between the tibial and the talar elements around at least one axis, characterized by the fact that, taking as reference direction the orientation of the axis of the tibia at which the tibial element is to be anchored, when seen in projection on a plane that is essentially perpendicular to this reference direction, the articular surfaces are curved with a concavity oriented toward the inside of the foot on which the talar element is to be anchored.
In accordance with other characteristics
each of the articular surfaces is provided with a central bearing surface and two lateral abutting surfaces, with play between the lateral abutting surfaces of the two articular surfaces, allowing a limited lateral deflection between these two articular surfaces;
the play between the lateral abutting surfaces varies according to the length of the articular surfaces;
the play between the lateral abutting surfaces is grater in the back of the prosthesis than in its front;
the play between the lateral abutting surfaces corresponds to an angular deflection of less than 5° on both sides of a medial position;
each of the articular surfaces is provided with a central surface and two lateral bearing surfaces; these two latter are at different levels than that of the central bearing surface, being the lateral abutting surfaces formed by connecting areas between the central and the lateral bearing surfaces;
each articular surface can be defined as being produced by the rotating of a plane directrix line, comprising at least one circular arc, around at least one axis in its plane and running in an oblique direction with respect to the mean or median radius of said circular arc;
the axis around which the directrix is rotated, being the directrix supposedly located on an essentially vertical plane, is directed towards the inside and upwards with respect to the mean or median radius of this directrix;
the directrix is formed by three circular arcs, one central and two lateral arcs, connected by two curves, each of which includes a point of inflection;
the talar element of the prosthesis comprises a lateral S-curved articular surface, which curvatures are convex in a front-to-back direction and concave in a vertical direction, adapted to interact with the area adjacent to the lower extremity of the fibula.
REFERENCES:
patent: 3896502 (1975-07-01), Lennox
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patent: 4069518 (1978-01-01), Groth, Jr. et al.
patent: 4156944 (1979-06-01), Schreiber et al.
patent: 4232404 (1980-11-01), Samuelson et al.
patent: 4792340 (1988-12-01), Aule et al.
patent: 5766259 (1998-06-01), Sammarco
patent: 5824106 (1998-10-01), Fournol
patent: 2401481 (1974-07-01), None
patent: 2370465 (1978-06-01), None
patent: 2684291 (1993-06-01), None
patent: 2700462 (1994-07-01), None
patent: 2724108 (1996-03-01), None
Bonnin Michel
Colombier Jean-Alain
Judet Thierry
Tornier Alain
Dowell & Dowell , P.C.
Jackson Suzette J.
Tornier SA
Willse David H.
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