Surgery – Instruments – Orthopedic instrumentation
Patent
1993-08-20
1995-06-20
Graysay, Tamara L.
Surgery
Instruments
Orthopedic instrumentation
A61B 1770
Patent
active
054257328
DESCRIPTION:
BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS
This application is a national phase application corresponding to PCT/DE 93/00033 filed 13 Jan. 1993 and based, in turn, upon a German application P 4200905.7 filed 16 Jan. 1992 under the International Convention.
SPECIFICATION
FIELD OF THE INVENTION
The present invention relates to an implant for the correction and fixation to each other of two bones or bone segments, particularly a spondylodesis implant for the correction and fixation of the position of vertebrae with respect to each other. The invention especially relates to an apparatus of this type having at least two connection pieces guided relatively to each other and adjustable with respect to their distance from each other and with resetting screws which can be screwed into the bones or bone segments, particularly vertebrae, and for which receiving spaces are provided in the connection pieces for the purpose of fastening the connection pieces to the bones or bone segments, especially vertebrae.
BACKGROUND OF THE INVENTION
Spondylodesis implants of this kind are known in various embodiments for instance from DE 31 32 520 C2 or DE 33 06 657 C2 and differ from each other by the type and manner of the relative guiding and distance adjustment of the connection pieces, as well as by design of the receiving pieces for the resetting screws provided at the connection piece. It is common to all these known embodiments that the force-locking between the connection pieces and the resetting screws is basically achieved through the screw heads, which presumes that the resetting screws must have a precisely defined length for each particular case. This insures that within the limits of the acceptable maximal, respectively the required minimal depth of engagement the head of the resetting screw is each time in the correct position for being received in the connection pieces.
Therefore the resetting screws need not only be stored in a variety of lengths, but also must be selected in the precisely correct length prior to being screwed in, which is cumbersome and can create complications. Although it is already known to avoid these drawbacks by using headless resetting screws, so-called SCHANZ screws, which adjacent to the threaded shaft portion have a longer, smooth shaft segment to be shortened to the respective required length after implant, problems arise in these cases when the resetting screws have to be connected rigidly enough for the fixation with the connection pieces, especially then when the inclined position of the resetting screws has to be taken into consideration with respect to the mutual adjustment direction of the connection pieces.
OBJECT OF THE INVENTION
It is the object of the invention to provide an improved implant of the aforementioned kind so that the resetting screws can be reliably fastened in the receiving elements provided at the connection pieces in a quick and handy manner, to a large extent independently of their engagement depth and position on the bone or vertebra.
SUMMARY OF THE INVENTION
According to the invention, this object is achieved in the implant or bone-fixing device of the aforementioned kind by mounting the resetting screws in the respective receiving elements so that they can slide in the longitudinal direction of the screw and are guided to be transversely swingable thereto. The receiving element is equipped with a clamping device actuatable through a clamping member, which in its clamping position secures the resetting screw in the receiving element against sliding, as well as pivoting.
With the device of the invention it becomes possible to keep to a minimum the influence of the receiving element on the positioning of the resetting screw on the bone, namely its engagement depth and direction, since when the clamping device is still open the setting screw is slidable, as well as pivotable in the receiving element. However these movement possibilities are simultaneously blocked, i.e. the resetting screws and the connection piece are rigidly connected to each oth
REFERENCES:
patent: 5047029 (1991-09-01), Aebi et al.
patent: 5084048 (1992-01-01), Jacob et al.
Dubno Herbert
Graysay Tamara L.
Kateshov Yuri
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