Surgery – Instruments – Orthopedic instrumentation
Patent
1994-05-25
1997-01-07
Tucker, Guy V.
Surgery
Instruments
Orthopedic instrumentation
606 72, 606 60, A61B 1770
Patent
active
055911650
DESCRIPTION:
BRIEF SUMMARY
This application is a 35 U.S.C. 371 application of PCT/US95/09919, filed Oct. 15, 1993.
BACKGROUND OF THE INVENTION
The present invention concerns an apparatus for spinal osteosynthesis, applicable notably to degenerative or misaligned vertebrae.
It is known that the vertebrae, in particular the lumbar vertebrae, are subjected to a concentration of stresses, in which the discs and the ligaments play a significant compensating part. If these vertebrae belong to a relatively aged body, they undergo a certain degeneration, which makes the discs and the ligaments unable to completely fulfill their role by reason of their aging.
These vertebrae then, are subjected to a certain instability and tend to displace relative to adjacent vertebrae. These displacements are uncontrolled and can be: displacements in angularion and rotation, medio-lateral and antero-posterior displacements, or else the combination of these displacements.
It is therefore necessary to remedy this situation, which risks generating a compression or compromise of the spinal cord of the patient, by endeavoring to put the displaced or misaligned vertebrae back to their positions.
SUMMARY OF THE INVENTION
The spinal osteosynthesis device, according to the invention, comprises at least one longitudinal implant, such as a rod, and by preference two, together with bone anchorage elements joined to the rod, such as screws or hooks.
In accordance with the invention, this device comprises at least one connection element between the rod and a vertebra to be treated, and means for fixation of this element to the vertebra, this element including a body, such as a ring or collar, so dimensioned that the rod can be mounted therein to move freely in rotation and in translation on the rod and outfitted with means for fixing the ring on the rod and extended radially by an arm, this arm and the ring forming a one-piece unit.
In this way the terminal ring of the connection element can be mounted to be trapped on the osteosynthesis rod or longitudinal implant, while being still free in translation and in rotation before its fixation in the chosen position on the osteosynthesis rod, by way of a suitable means for fixing.
According to one aspect of the invention, the means for fixation of the connection element to the vertebra to be treated is advantageously a bone anchorage element, such as a screw or a hook of a known type, and whose body is open in a U-shape in order to permit introduction into it of the free end of the arm of the connection element. The invention contemplates that the anchorage element be free to both translate medio-laterally along and rotate/angulate around the extended radial arm of the connection element. This aspect of the invention can be implemented with a hook having a closed body with the longitudinal implant or rod extending through an opening in the hook body.
In another aspect of the invention, the aforementioned lateral connection element is used in a novel method for correction of a spinal deformity. This method provides for correction segmentally along the entire length of the spine, in all three degrees of freedom and along the three columns (posterior, middle and anterior) of the spine. This method contemplates implanting a strong yet ductile longitudinal implant between several vertebrae. In one embodiment, the implant is an osteosynthesis rod, although this method can be applied using a bar or plate. The vertebrae are instrumented with fixation elements, such as hooks or screws, and the fixation elements are engaged to the longitudinal implant, or rod, in a manner that permits free sliding translation and rotation of the fixation elements with respect to the rod. In the preferred embodiments, this engagement is effected by the lateral connection element.
Once the instrumentation is in position, the spinal rod is contoured within the patient, or in situ, until the rod has assumed the shape of a properly oriented spine. As the rod is contoured in situ, the fixation elements engaged to the vertebrae impart corrective forces
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Sofamor S.N.C.
Tucker Guy V.
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