Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-12-06
2001-10-30
Mancene, Gene (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06309389
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates in general to implants for osteosynthesis, particularly of the spine.
It relates more specifically to a new ring of spherical type intended to allow angular orientation between two components of the implant prior to tightening, and to an implant equipped with such a ring.
BACKGROUND OF THE INVENTION
Document FR-A-2 659 546 discloses a spinal osteosynthesis system which comprises a collection of pedicle screws, each having a spherical seat made in a so-called “forked” head and in which a split ring can be housed. Passing through this ring itself is a rod intended to connect the various screws together, and the ring offers a possibility of angularly orientating the axis of the pedicle screw and the axis of the rod in one or two planes. Once this angular adjustment has been performed, a threaded cap compresses the ring and locks the assembly firmly in position.
The known ring is made of one single piece, with a spherical outer face, a cylindrical inner face with symmetry of revolution, and a slot directed radially and extending between the inner and outer faces.
This slot gives the ring the required deformability so that when clamped into the seat in the pedicle screw using an appropriate threaded member, it can be compressed firmly against the rod, so that once the angular adjustment has been performed, the assembly is held perfectly immobilized.
This known ring does, however, have a limitation: when preparing the implant system prior to or during fitting, it is necessary to slip as many split rings as are needed over the rod from one of its ends.
This is because the deformability of the ring which is afforded by its slot is far from sufficient to allow this slot to be parted temporarily to allow the rod to be introduced radially into the cylindrical passage through the ring. Thus, the practitioner attempting to proceed in this manner would inevitably cause breakage or significant damage to the mechanical qualities or the shape of the ring.
The use of this kind of known ring is therefore restricted to scenarios in which the rod is accessible from at least one of its ends.
SUMMARY OF INVENTION
The present invention aims to alleviate this drawback of the state of the art and to propose a new deformable ring which can be fitted onto a rod even when the latter has neither end free for the said ring to be slipped over it.
Thus the present invention proposes an angular orientation ring for an osteosynthesis device, particularly for the spine, of the type comprising an essentially spherical outer face and an essentially cylindrical inner face intended to take a rod of the device, the ring being characterized in that it is made in two mating parts, each part being substantially U-shaped with a bottom and at least one pair of branches occupying a fraction of the axial dimension of the bottom, the distance between the two branches of one same pair being close to the diameter of a rod intended to take the ring, and the two parts being designed to be inserted over the rod from its side in such a way that their respective bottoms come to substantially face each other, enclosing the rod, and such that their pairs of branches come to be side by side, the said two parts therefore jointly defining an essentially spherical outer face and an essentially cylindrical inner face.
Preferred but non-limiting aspects of the ring according to the invention are as follows:
each part has a pair of branches and each of the said branches occupies substantially half of the axial dimension of the ring.
each of the said branches has, at its free end, a projecting shape able to be received in an essentially complementary housing provided in the bottom of the other part.
the projecting shape of each of the branches of one part is defined by the intersection of a spherical contour of the branch with an end face essentially parallel to the axis of the ring and forming an extension of a semi-cylindrical inner surface defined by the bottom of this same part.
the said end face of each branch extends slightly obliquely with respect to the axis of the ring.
the two branches are separated from the bottom by two shoulders extending in planes which, with respect to the axis of the ring, have an obliqueness similar to that of the said end faces.
the branches of each part are delimited, on a face facing towards the branches of the other part, by a plane perpendicular to the axis of the ring.
the minimum distance between the two branches of one same pair is locally slightly shorter than the diameter of a rod intended to take the said ring.
The invention also proposes an osteosynthesis device, particularly for the spine, comprising a bone fixation part which has an essentially spherical seat, a ring housed in the said seat, an element for clamping the ring into its seat, and a rod passing through an essentially cylindrical passage formed in the ring, characterized in that the rod forms part of a component comprising, at the two ends of the rod, two parts which are wider than the said rod, and in that the ring is made as defined above, its two parts being fitted onto the rod from the side thereof.
REFERENCES:
patent: 4065221 (1977-12-01), Cawthorne
patent: 4127119 (1978-11-01), Kronner
patent: 5176680 (1993-01-01), Vignaud et al.
patent: 5242445 (1993-09-01), Ashman
patent: 5584833 (1996-12-01), Fournet-Fayard et al.
patent: 487895 (1992-06-01), None
patent: 2659546 (1991-09-01), None
patent: 2682280 (1993-04-01), None
Blakely & Sokoloff, Taylor & Zafman
Mancene Gene
Robert Eduardo C.
Stryker France S.A.
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