Surgery – Instruments – Orthopedic instrumentation
Patent
1996-02-27
1998-03-31
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 74, A61B 1756
Patent
active
057332843
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a device for anchoring spinal instrumentation on a vertebra.
BACKGROUND AND OBJECTS OF THE INVENTION
The known implanted spinal osteosynthesis devices are fixed with respect to the various vertebrae by anchoring elements.
Anchoring elements are already known which are constituted by, or which have, intrapedicular screws. These intrapedicular screws are widely used, in various forms, with different types of osteosynthesis devices (Cotrel-Dubousset, Roy-Camille, etc.).
Anchoring elements in the form of hooks with curved, fixed ends supported on the articular processes, or on the lamina or on a transverse process of the vertebra, are also known. The hook is held in position against the bone and kept there by spinal instrumentation.
Anchoring devices in the form of sub-laminar wires (de Luque-type osteosynthesis devices) are also known.
All these known anchoring elements have disadvantages as regards reliability and longevity and/or the strength of the anchorage thus brought about, especially as they bring about a single anchorage in each of the paravertebral grooves. In actual fact, all these anchoring elements are essentially constituted by a hard, rigid metal element supported on a single localized zone on one side of the vertebra. Now these anchoring elements are intended to transmit extremely high stresses caused by the instrumentation on the various vertebrae. For this reason, one of the greatest risks limiting the longevity and reliability of the spinal instrumentations originates from the fact that the anchoring elements may become detached or break the bone in the event of excessively high mechanical stresses. Hooks and screws, in particular, induce a high degree of discontinuity between the instrumentation and the vertebra, from the point of view of mechanical characteristics. Thus, the local contact surface zone between the anchoring device and the osseous portion of vertebra is subjected to heavy tensile stresses which are liable to give rise to secondary osteolysis.
Moreover, sub-laminar wires have the disadvantage of causing to major neurological risks and cannot be used with all categories of spinal instrumentation.
American patent U.S. Pat. No. 4,836,196 describes a spacer device composed of a plastics material which makes it possible to reduce the stresses transmitted between a screw fitted into the osseous part of the vertebra, and the instrumentation. A device of this kind can nevertheless not be used with most of the known spinal instrumentations and induces a flexibility in the coupling between the instrumentation and the anchoring device which may prove harmful.
French patent application FR-A-2 689 750 describes a spinal osteosynthesis device comprising hooks and/or intrapedicular screws and plates for coupling the instrumentation which are anchored in the vertebra by means of an intrapedicular screw. In that instance, too, the anchorage brought by a single intrapedicular screw proves insufficient.
The aim of the invention is therefore to alleviate the disadvantages of the known anchoring devices.
The general aim of the invention is therefore to propose an anchoring device for implanted spinal instrumentation, such as a spinal osteosynthesis device or a dynamic implanted vertebral orthosis, which offers greater reliability, longevity and strength than the known anchoring devices. The aim of the invention is also to propose a vertebral anchoring device which leaves vertebral, posterior articular and ligamentary systems unaffected, an essential precondition for the insertion of equipment intended to correct and preserve physiological movements of the vertebral column.
DESCRIPTION OF THE INVENTION
The aim of the invention is also to propose an anchoring device of this kind which can be used with, and adapted to, most of the spinal instrumentations.
In order to accomplish this, the invention relates to a device for anchoring spinal instrumentation onto a vertebra, comprising at least one support carrying means for coupling the instrumentation to the said suppor
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Buiz Michael
Dutton, Jr. Harold H.
Fairant Paulette
Woo Julian W.
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