Surgery – Instruments – Orthopedic instrumentation
Reexamination Certificate
1999-04-07
2001-02-06
Buiz, Michael (Department: 3731)
Surgery
Instruments
Orthopedic instrumentation
C606S075000, C606S104000
Reexamination Certificate
active
06183472
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to a pedicle screw and an assembly aid therefor.
For the replacement of vertebra of the human spinal column, for the distraction of the spinal column, for the stabilization of the vertebrae and likewise, it is known to apply so-called pedicle screws. They are screwed into the pedicle of the vertebra and comprise a head which is connected to suitable provisions, for example to a stabilizing system, to distraction rods and likewise. It is known to provide pedicle screws with a ring-like head which on the end faces comprises a toothing. It is however also known to form the screw head fork-like so that with this it is in the position to accommodate a distraction rod, a connecting rod or likewise. For fastening the rod in the fork-like head a suitable screw element may be brought into engagement with the head. The screw element may be hat-like and be screwed onto outer threaded sections of the head. It is however also known to allocate an inner thread to the head sections for receiving a set screw or likewise with which the applied rod may be fastened in the head.
It is further known for a more simple handling of the pedicle screw to provide this with a head which is movable relative to the shank, preferably pivotable in all directions. For this purpose the head end of the shank may be formed ball-like, wherein the ball surface cooperates with a spherical bearing surface in the head. In this case it is necessary, after the adjustment of the shank and head to one another has been effected, to retain this angular position. This may for example be effected in that the rod accommodated by the head is pressed against the ball-like head of the shank, by which means the parts are fixed in their position to one another.
In the treatment generally first the pedicle screws are rotated in. Subsequently the insertion of the rod is effected. With this however under certain circumstances considerable forces must be applied in order to move the rod into the fork-like head. The introduction force must be maintained for so long until with the help of the screw element a sliding out of the receiver in the head is no longer possible. For this a considerable amount of dexterity and also a considerable force effort must be carried out on the part or the surgeon.
BRIEF SUMMARY OF THE INVENTION
It is therefore the object of the invention to so form a pedicle screw and so design an assembly aid that the insertion and fixing of rods in the pedicle screw heads are simplified.
An important aspect of the pedicle screw design of the present invention is that recesses are formed on the outer surface of the head. The recess serves for receiving gripping sections which are formed at the end of arms, which for their part are connected to a shank. The shank is slidingly, but rotationally rigidly guided in a sleeve and between the sleeve and the shank there acts an adjusting mechanism, which on actuation displaces the shank relative to the sleeve.
The gripping sections acquire the pedicle screw head from the outer side, so that the head may be moved in the direction of the sleeve with the help of the described adjusting mechanism. The rod has firstly been introduced between the arms, before the pedicle screw has been acquired. If now the screw head is moved in the direction of the sleeve, the sleeve presses the rod automatically between the head sections into the recess.
The shank comprises an axial passage through which a relatively thin shank of a rotary tool may be guided. With the help of the rotary tool, on which already a suitable fastening screw is attached, from now on the set screw may be screwed to the inner threaded sections of the head. By way of this the screw presses the rod against the floor of the receiver. With a sufficiently high tightening force therefore also with a two-part design of a pedicle screw, i.e. with a head mounted pivotably to the screw shank, a fixation in the adjusted angular position may be achieved.
The cooperation of the arms with the outer side of the pedicle screw head may be effected in any suitable way and manner. One formation of the invention for this envisages for the outer contour of the head sections to be convexly rounded and the recess to comprise a floor surface running planarly, parallel to the axis, which in the circumferential direction of the head blends into the outer contour. If the gripping means are for example claw-like attachments on the arms, these may be brought into position laterally to the head and subsequently by way of a movement be laterally aligned to the head. If now relative to the head a tension force is applied to the arms, the claw-like sections acquire the upper wall of the recess and by way of this pull the pedicle screw in the direction of the sleeve of the assembly aid.
The adjusting mechanism may likewise be designed in a known way and manner. Particularly advantageous is an embodiment of the type such that the shank at the rear end comprises an outer thread onto which a handle comprising an inner threaded bore can be screwed, bearing onto the rear end of the sleeve.
In order to obtain a guiding of the rod or wire into the receiver of the pedicle screw head, according to one formation of the invention it is provided for the front end of the sleeve to comprise a diametrical recess which is adapted to the circumferential contour of the rod.
REFERENCES:
patent: 5720751 (1998-02-01), Jackson
Buiz Michael
Howmedica GmbH
Lerner David Littenberg Krumholz & Mentlik LLP
Woo Julian W
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