Surgery – Instruments – Orthopedic instrumentation
Patent
1993-08-20
1995-04-25
Graysay, Tamara L.
Surgery
Instruments
Orthopedic instrumentation
A61B 1756
Patent
active
054094887
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This is national phase application PCT/DE93/00031 filed 13 Jan. 1993 and based in turn, upon German national application P 42 00 904.9 filed 16 Jan. 1992 under the International Convention.
FIELD OF THE INVENTION
The invention relates to a spondylodesis implant for the correction and fixation of the relative position of vertebrae, with two connection pieces guided in threaded spindles in the longitudinal direction of the spinal column and adjustable as to their distance from each other, and with resetting screws which can be screwed into the vertebrae, for which receiving elements are provided in the connection pieces for the purpose of fastening the connection pieces to the vertebrae.
BACKGROUND OF THE INVENTION
The spondylodesis implant of this kind known from DE 31 32 520 A1 serves for the adjustable fixation of two immediately adjacent vertebrae. The threaded spindles assigned to the two connection pieces are made in one piece in a coaxial arrangement, whereby between the two threaded spindles a connecting outer hexagonal piece is provided, which serves for the application of a turning tool for the common rotation of the threaded spindles. The threaded spindles as well as the corresponding threaded nuts by means of which the connection pieces are guided on their respective threaded spindles rotate in opposite senses, so that during the concurrent rotation of the threaded spindles the two connection pieces are either moved towards each other or away from each other according to the direction of rotation.
OBJECTS OF THE INVENTION
It is the object of the present invention to provide a spondylodesis implant so that three successive vertebrae can be corrected and fixated still another object is to provide a spondylodesis implant for the mutual displacement of the vertebrae.
SUMMARY OF THE INVENTION
According to the invention an implant provides between the two connection pieces a further connection also equipped with a receiving element for a resetting screw, whereby on this median connection piece the threaded spindles for the two outer connection pieces are supported so that they are independently rotatable and axially nondisplaceable. The two threaded spindles are inclined with respect to each other in the common plane of their axes thereby adjusting the implant to the sagittal curvature of the spinal column. Preferably the mutual inclination of the threaded spindles is of approximately 15.degree..
When such implant is affixed with each of its connection pieces to one of three successive vertebrae, by rotating the threaded spindles, the two outer vertebrae can be independently set and fixated with respect to the middle vertebra mutual inclination of the two threaded spindles takes into account to follow the natural curvature of the spinal column in the area of the three vertebrae interconnected by the implant.
The preferred embodiment is characterized in that the threaded spindles are guided each by a pivot pin in a pivot opening of the median connection piece and have on the pivot pin an annular groove coaxial with the spindle axis. A projection on the side of the connection piece engages in the groove to secure the threaded spindle against axial displacements. This projection consists suitably of a cross pin stuck into the connection piece and tangentially reaching into the annular groove. It is therefore advisable that each threaded spindle be equipped with key faces for the application of turning tools between its threaded shaft and the connection piece supporting it. Suitably the key faces on each threaded spindle form an outer hexagon in one piece with the threaded spindle.
The resetting screws can be the usual bone screws provided with a screw head, whereby the screw head comes to lie on the connection piece when the screw is tightened. However, more frequently the headless resetting screw with a smooth shaft segment succeeding the threaded shaft portion will be used within the framework of the invention, since, after being screwed into the resp
REFERENCES:
patent: 5176679 (1993-01-01), Lin
Dubno Herbert
Graysay Tamara L.
Kateshov Yuri
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