Surgery – Instruments – Orthopedic instrumentation
Patent
1996-01-29
1998-04-14
Buiz, Michael
Surgery
Instruments
Orthopedic instrumentation
606 73, 606 72, 411308, 411426, A61B 1756
Patent
active
057386854
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to an osteosynthesis device having a bone screw, particularly a pedicle screw, a fork head that has a groove and a corrective pin seated in the groove of the fork head.
BACKGROUND OF THE INVENTION
A large number of osteosynthesis devices of this type are known, for example from German Utility Model DE-Gbm 91 04 027, European Patent Application EP-A-346 521, German Patent Application DE-A 39 42 429, European Patent Application EP-A-443 894, European Patent Application EP-A-348 272, European Patent Application EP-A-465 158, European Patent Application EP-A-528 706, European Patent Application EP-A-443 892, German Patent Application DE-A 39 16 198, and German Patent Publication DE-C 41 10 002. Various bone screws with forked heads are known from these references into which a corrective pin can be inserted and fixated. This primarily involves a non-slip bracing against the bone screw. Only a slip-free and twist-free fixation of the corrective pin against the bone screw assures an optimum transfer of pulling and pressing forces onto the individual bones to be corrected and fixated, as well as the transfer of torque and bending moments.
As a rule, a good fixation is achieved in that a fastening screw is screwed into the fork head in such a way that the screw presses on the inserted corrective pin. It has been shown, however, that an upward bending of the fork head is not to be ruled out because of the high forces and moments occurring, so that the fastening of the corrective pin can loosen. Moreover, a clamping fixation of this type does not offer adequate insurance against twisting of the corrective pin around its own axis.
With a clamping osteosynthesis implant (European Patent Application EP-A-528 706), a fixing plate is placed onto the corrective pin inserted into the fork head of the bone screw; the task of this plate on the one hand is to prevent the two legs of the fork head from being pressed apart and, on the other hand, it has longitudinal grooves on its section resting on the corrective pin that engage longitudinal grooves of the corrective pin. By means of this, an increased insurance against twisting of the corrective pin in the fork head is achieved; however, the total torque acting on the corrective pin must be transferred onto the bone screw via the pressing plate, a fastening screw and the two legs of the fork head. At high torques, there is still the danger that the fork head will become deformed and, because of this, the fixation of the corrective pin will be loosened.
OBJECT AND SUMMARY OF THE INVENTION
Therefore an object of present invention is to further develop an osteosynthesis device of the type mentioned at the outset in such a way that the corrective pin can be placed against the bone screw in a manner that is fixed against twisting.
This object is attained in accordance with the present invention in that the bottom of the groove of the fork head is provided with a plurality of longitudinal slots lying parallel to one another.
The longitudinal slots provided at the bottom of the groove of the fork head, that is, at the bottom of the groove into which the corrective pin is inserted, permit, on the one hand, a fixation secure against twisting of the corrective pin against the bone screw and, on the other hand, a direct transfer of force from the corrective pin onto the shaft of the bone screw. When a corrective pin with a smooth surface is placed into the fork head, the longitudinal slots dig into the surface of the corrective pin and fixate it in this manner. If the corrective pin is embodied as a threaded rod, then the longitudinal slots dig into the thread of the threaded rod. In an advantageous manner, the longitudinal slots extend in the direction of the axis of the corrective pin. In other embodiments the longitudinal slots can also extend diagonally or transversely.
The embodiment of the bone screw in accordance with the present invention has the advantage that the transfer of force from the corrective pin onto the shaft
REFERENCES:
patent: 5176680 (1993-01-01), Vignaud et al.
patent: 5226766 (1993-07-01), Lasner
patent: 5261912 (1993-11-01), Frigg
patent: 5306275 (1994-04-01), Bryan
patent: 5443467 (1995-08-01), Biedermann et al.
patent: 5496321 (1996-03-01), Duno et al.
patent: 5499983 (1996-03-01), Hughes
patent: 5562663 (1996-10-01), Wisnewski et al.
Halm Henry
Rehder Gunther
Schafer Bernd
Buiz Michael
SCHAFER micomed GmbH
Woo Julian W.
LandOfFree
Osteosynthesis device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Osteosynthesis device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Osteosynthesis device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-631503