Surgery – Instruments – Orthopedic instrumentation
Patent
1999-01-08
2000-09-12
Mancene, Gene
Surgery
Instruments
Orthopedic instrumentation
606 69, 606 73, A61B 1770
Patent
active
061171352
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a fixation device for bone surgery including a plate-shaped jaw member configured to permit the use of longitudinal members without undue increase in thickness of the plate-shaped jaw member.
BACKGROUND OF THE INVENTION
Anterior fixations in the area of the spinal column have been achieved with plate-shaped devices, as shown in WO94/17744, for example. Such plate-shaped devices have the great advantage of having very limited thickness (between 1.1 and 2.0 mm), and thus are only slightly invasive.
A drawback of such plate-shaped devices, however, is that the fusion zone of the affected vertebrae cannot be actively placed under pressure, which can lead to instances of pseudo-arthrosis. A further drawback is the great variety of the necessary assortment of instruments with greatly varying dimensions that are available to the surgeon. Typically, depending on the manufacturer, 12 to 23 plate types are required.
Devices with longitudinal members, as used in posterior fixation in the area of the spinal cord, have not been able to be used in clinical practice on account of their considerable thickness imposed by design limitations. However, longitudinal members have the advantage of permitting the application of active compression to the treatment site, and would require only a minimum assortment of instruments.
SUMMARY OF THE INVENTION
In accordance with the principle of the present invention, a device for bone surgery is provided which permits an anterior fixation in the area of the spinal cord and which combines the advantages of plate-shaped devices (having limited thickness) with devices including longitudinal members (which permit the application of active compression).
The device of the present invention has a plate-shaped jaw member with a concave lower surface which rests on the vertebra. Longitudinal members may be positioned through bores extending along the long sides of the plate-shaped device. The seating of the longitudinal members through the plate-shaped device requires a greater thickness of the device according to the diameter of the longitudinal members. However, the concavity of the lower side of the plate-shaped device permits a flat shape of the plate-shaped device in the central area (between the bores through which the longitudinal members are positioned) because the longitudinal members are laterally situated at positions where the thickness of the device is greater due to the concavity of the lower side of the device. Due to the concavity, the longitudinal members laterally situated within the plate-shaped jaw member scarcely contribute to the thickness of the plate-shaped jaw member within the central area of the device (area of the esophagus), in which the bone screws are used, hardly increase its thickness. In this area the thickness of the plate-shaped jaw member can be limited to 2 mm.
The thickness of the plate can be kept limited (about 5 mm) even if fastening screws are used to fix the longitudinal members, thanks to the arrangement of the fastening screws at an acute angle with respect to a plane extending between the longitudinal axes of the longitudinal members. The thickness of the plate-shaped device can even be further reduced if longitudinal members with a reduced diameter are used.
The geometry of the body of a cervical vertebra makes it possible to position the longitudinal members laterally in relation to the front longitudinal fastener so far posterior, that the device according to the invention exhibits a similar thickness toward the front longitudinal fastener, in the area of the esophagus, as a conventional plate. Only in the area of the musculus longus colli, where it is less critical, is the thickness of the device determined by the diameter of the longitudinal members. The lateral arrangement of the longitudinal members also contributes to the stability and firmness of the rotation of the fixation device.
In a preferred embodiment, the fixation device of the present invention includes two plate-shaped
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patent: 5954722 (1999-09-01), Bono
Mancene Gene
Philogene Pedro
Synthes (U.S.A.)
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