Surgery – Instruments – Orthopedic instrumentation
Patent
1995-10-03
1997-04-15
Tucker, Guy V.
Surgery
Instruments
Orthopedic instrumentation
606 73, A61B 1770
Patent
active
056204442
DESCRIPTION:
BRIEF SUMMARY
This application is filed under 35 USC 371 based on PCT/EP94/02906 which was filed on Sep. 1, 1994.
BACKGROUND OF THE INVENTION
The present invention relates to a spine osteosynthesis device, in particular a clamp for stabilizing a cervical spine segment, such as the cervical vertebrae C1 and C2.
It is known that certain cervical segments are unstable owing in particular to fractures of cervical vertebrae resulting from accidents on the road or injuries undergone by the intervertebral connections such as the ligaments. Various devices for stabilizing the unstable vertebral segment have therefore been proposed which also permit reducing the time the patient spends in hospital and protecting his nervous system. A known arrangement consists in achieving the stabilization by means of wires binding two cervical vertebrae together. In other known arrangements, the stabilization is achieved by means of two elements hooking onto the vertebrae, interconnected by a screw threaded rod and tightened by nuts, or by means of vertebral screws.
These various techniques present the following drawbacks: first, the stability obtained is insufficient, since the wires are not necessarily tightened in their stable position on the vertebrae. The screw threaded rods interconnecting the hooks to form a clamp stabilizing the vertebral segment may gradually unscrew, since nothing opposes the gradual unscrewing of their tightening nuts. A second drawback resides in the difficulty of placing these devices in position owing to the very deep field of operation due to the flesh covering the vertebrae. A third drawback resides in the inconvenient size of the devices employing screws, hooks and clamps which also present serious neurological risks.
As concerns the wires, their obligatory passage behind the posterior elements of the cervical vertebrae is delicate and involves risks which are well noted in the literature. Further, as the surface of contact between the wires and the bone is small, the "butter cutting wire" phenomenon is frequently observed, and a steel wire has the particularity of easily breaking within a short period, whence a risk of a secondary instability or pseudoarthrosis.
The other implants existing on the market pose the problem of the difficulty of inserting them and often of their overall size and the reliability of the connection between implants.
Besides, the usual connection means between an osteosynthesis rod and spinal anchorage hooks or screws comprise screws, which are not easy to correctly put in place by the surgeon.
SUMMARY OF THE INVENTION
An object of the invention is to provide a clamp for stabilizing a cervical spine segment which reduces or completely eliminates these drawbacks, above all for the cervical segment C1-C2 which is concerned in the most frequent cases of instability pathology.
Another object of the invention is to design a spinal osteosynthesis device whose components, in particular the attachment means between the longitudinal rods and the anchorage members in the vertebrae, are easy to assemble and correctly position.
According to the invention, the clamp comprises a pair of hooks adapted to bear against two cervical vertebrae and each comprising a tubular portion, the diameters of these tubular portions being such as to permit the fitting together and the sliding of one tubular portion in the other and consequently the adjustment of the relative position o the two hooks which may be fixed in this position by a permanent deformation of the walls of the tubular portions.
The clamp arranged in this way provides an improved stability over the aforementioned prior structures, since the two hooks which are part of this clamp cannot move apart owing to the fact that they are interconnected by a permanent deformation of material which clamps them in the chosen relative position. This connection may be achieved by means of a clamp, one of the branches of which is provided with a boss at its end. The clamping of the latter on the two tubular portions fitted one inside the other radially de
REFERENCES:
patent: 4041939 (1977-08-01), Hall
patent: 4257409 (1981-03-01), Bacal et al.
Reip David O.
Sofamor S.N.C.
Tucker Guy V.
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