Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
2000-03-07
2001-10-30
Mancene, Gene (Department: 3732)
Surgery
Instruments
Orthopedic instrumentation
Reexamination Certificate
active
06309390
ABSTRACT:
The present invention relates in general terms to devices for osteosynthesis of the spine.
BACKGROUND OF THE INVENTION
An implant for osteosynthesis of the spine is already known, in particular from document FR-A-2 659 546, which implant comprises a pedicular screw provided with a head that is generally tuningfork-shaped, capable of directly receiving a cylindrical rod for linking vertebrae together. A split ring and a threaded clamping plug acting between the two branches of the head enable the assembly to be locked with angular adjustment being possible between the rod and the axis of the pedicular screw.
Installing that type of implant does not present the surgeon with any major difficulty, providing the heads of the various pedicular screws are sufficiently well aligned with one another, since under those circumstances the intervertebral link rod can be put into place relatively easily in said heads, without excessive stresses or twisting.
However, particularly depending on the type of pedicular aiming performed by the surgeon, and also depending on the orientation of the pedicles specific to each patient, it often happens that the axes of the pedicular screws are significantly inclined relative to the sagittal plane, and as a result, the housings for receiving the intervertebral link rod and as defined by the heads of the various screws can be very significantly out of alignment.
Under such circumstances, the solution which consists in deforming the rod very significantly so as to force it to follow the imposed path is either impracticable because of the considerable deformation forces that would be required, or else dangerous because it runs the risk of weakening the rod.
Various other devices are known for the purpose of making it possible to fix and lock a rod that is laterally offset relative to a pedicular screw.
Examples of such devices are given in the following documents: DE-A-195 12 709, U.S. Pat. Nos. 5,575,791, 5,002,542, WO-A-95 02372, and WO-A-96 29947.
Nevertheless, all of those known devices suffer from drawbacks. Thus, some of them are of considerable size, particularly in height, which is quite undesirable and considerably reduces the advantage in terms of compactness of “tuningfork”-type screw devices of the kind described above. Others are complex in structure, having numerous parts. Others are structurally incapable of receiving rods at an appropriate distance from the pedicles, which distance is moreover imposed by the “tuningfork”-type screws. Finally, some of those known devices are unsuitable for locking the rod relative to its anchor point in the bone in a manner that is sufficiently firm and strong.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is thus to mitigate those drawbacks and to propose means that are simple, and therefore do not significantly complicate installation operations, making it possible to connect a bone implant of conventional type rigidly to an intervertebral link rod while the rod is significantly off-axis relative to the bone implant.
Another object of the invention is to be able to use the same type of pedicular screw in all of the vertebrae regardless of the sizes of such offsets.
Yet another object is also to propose off-axis fixing for a link rod on a particular type of sacral fixing.
Thus, the present invention provides an osteosynthesis device for the spine, the device comprising a bone anchor element, an intervertebral link rod suitable for connecting said bone anchor element to other anchor elements, an intermediate element, a ball-and-socket link between a first portion of the intermediate element and the bone anchor element, a clamping link between a second portion of the intermediate element and the intervertebral link rod, and locking means for locking the ball-and-socket link and the clamping link, which device is characterized in that said clamping link is constituted by a clamp having two branches extending laterally from the ball-and-socket link and open away therefrom, and in that the means for locking the clamping link include a clamping member acting on said branches in the region of their free ends in such a manner as to urge said ends towards each other.
Preferred, but non-limiting, features of the device of the invention are as follows:
the ball-and-socket link comprises a generally spherical seat provided in a head of the bone anchor element and an essentially complementary compressible ring received in said seat, and said first portion of the intermediate element comprises a cylindrical appendix received in said ring;
said cylindrical appendix is of circular section;
said cylindrical appendix is of a length such that prior to locking, it is capable of sliding relative to the ring to vary the axial offset between the bone anchor element and the intervertebral link rod;
said cylindrical appendix, in the region of its free end, presents an enlargement for preventing said appendix from escaping freely from the ring prior to locking;
the ring is a split ring, and the enlargement has a diameter such that the appendix can be engaged by force through the ring with temporary elastic deformation thereof;
said first portion of the intermediate element has a housing for a head of a bone anchor element, and the ball-and-socket link has a generally spherical seat defined in said housing and an essential complementary spherical wall formed on said head;
the means for locking the ball-and-socket link comprise a threaded plug screwed into an opening of said housing remote from its seat; and
said branches of the clamp define an empty passage between them suitable for receiving the intervertebral link rod, and said clamping member is constituted by a screw.
REFERENCES:
patent: 5254118 (1993-10-01), Mirkovic
patent: 5437669 (1995-08-01), Yuan et al.
patent: 5474551 (1995-12-01), Finn et al.
patent: 5584831 (1996-12-01), McKay
patent: 5776135 (1998-07-01), Errico et al.
Baccelli Christian
Conchy Frederic
Le Couedic Regis
Blakely & Sokoloff, Taylor & Zafman
Mancene Gene
Robert Eduardo C.
Stryker France S.A.
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