Tool for driving pedicle screws

A tool for driving pedicle screws into vertebrae of the human spine has a shaft preferably with a handle at one end and, at the opposite end, a holder for receiving a preferably ring-shaped head which is flattened on opposite sides. The tool has a first clamping jaw (18) secured to the shaft (12), and a second loose clamping jaw (20) including a lateral projection which is tiltably received by the first clamping jaw (18). The tool has an axially slidable actuating member (32) which is guided along the shaft (12). The front end of the actuating member (32) engages the rear end of the second clamping jaw (20) and is preferably axially urged towards the second clamping jaw (20) by a threaded driving means.

The present invention relates to a tool for driving pedicle screws. 
So-called pedicle screws are screwed into the vertebrae of the human spine, 
i.e. in the pedicle area, to form substantial components to support the 
human spine, for example. Generally, pedicle screws are used to exert a 
force on the vertebrae for positioning them with respect to each other to 
give support or the like. In this connection a supporting means is 
disclosed in EP 0 328 883, in which at least a pair of pedicle screws is 
dorsally screwed into the vertebrae. The ring-shaped head end of the 
pedicle screws includes parallel clamping faces on opposite sides, 
including toothing, for example. Two pedicle screws are fixed at a 
distance apart by a clamping means including a pair of threaded bolts 
which cooperate with a threaded sleeve having reverse threaded portions. 
For driving pedicle screws into the vertebrae in the pedicle areas, a high 
skill of the surgeon is necessary since the available space is small. The 
driving operation requires a tool which is suited to safely receive the 
substantially ring-shaped head of the pedicle screws and to transfer the 
driving force onto the screw. 
It is thus an object of the present invention to provide a tool for driving 
pedicle screws into the vertebrae of the human spine, which tool is easily 
operable, affords an easy clamping and removing of these pedicle screws 
and, moreover, ensures the application of the driving force necessary. 
The objects are solved by the device of the invention. 
SUMMARY OF THE INVENTION 
According to the invention, a first clamping jaw is rigidly connected to a 
tool shaft. A second loose clamping jaw is tiltably held by the first jaw 
so that it can be pivoted with respect to the first clamping jaw. An 
axially slidable actuating member is guided along the shaft, the front end 
of the member contacting the rear end of the second clamping jaw and urged 
towards the second clamping jaw by a thread driving means or the like. 
According to the invention the loose clamping jaw may perform a tilting 
motion as well. This is initiated by urging the actuating member towards 
the rear end of the clamping jaw so that the head of the pedicle screw 
received between the clamping jaws is tightly clamped between the clamping 
jaws to be subjected to the necessary driving force. 
According to an embodiment of the invention, the first clamping jaw 
includes a through-going guiding recess, and the projection is defined by 
a hook-shaped portion contacting the outer side of the first clamping jaw. 
The recess has an axial length to accommodate the hook-shaped portion in 
dismounting. 
According to the invention, a particularly simple embodiment of the 
actuating member comprises a sleeve which is axially slidable along the 
shaft to engage the rear side of the movable jaw. The sleeve may be 
displaced by a further sleeve, for example, which threadably engages the 
shaft to apply an axial force to the sleeve when being rotated. According 
to an embodiment of the invention the sleeve includes an internal threaded 
portion cooperating with a threaded portion of the shaft. To simply 
actuate the sleeve, an embodiment of the invention provides an enlarged 
and preferably knurled portion thereon. 
According to a still further embodiment of the invention a spring is 
arranged between the clamping jaws to urge the jaws apart to facilitate 
receiving and releasing the head of the pedicle screw. 
The opposite flatened sides of the pedicle screw head are often roughened 
or toothed. The clamping faces of the jaws are thus preferably formed 
correspondingly. 
The tool according to the invention provides a movable or, respectively, 
loose clamping jaw which is slidable (for dismounting) as well as 
tiltable. However, the scope of protection includes an embodiment in which 
the movable jaw is tiltably mounted merely about an axis passing through 
the stationary clamping jaw. 
According to a further embodiment a thrust member is axially slidably 
mounted on the shaft to engage the movable clamping jaw, whereas the 
actuating sleeve cooperates with the thrust member. As the sleeve is 
displaced towards the handle, the front portion of the tool becomes 
slimmer. 
The movable clamping jaw may be provided with a surface extending under a 
predetermined angle to afford a clamping of angular screws having a flat 
head.

FIG. 1 shows a screw driver 10 for pedicle screws, comprising a shaft 12 at 
one end of which a handle 14 and at the other end of which a receiving and 
clamping portion 16 are provided. A fixed clamping jaw 18 is rigidly 
secured to the shaft 12 to cooperate with a movable clamping jaw 20. The 
movable clamping jaw 20 is shown in FIG. 3. It comprises a clamping 
portion 22 and a lateral projection 24 at the rear which is shaped like a 
hook at 26. The lateral projection 24 extends through an elongated opening 
(not shown) in the fixed jaw 18. A spring 25 is positioned so as to urge 
the jaws 18 and 20 apart. 
FIG. 4 shows a plate-like thrust member 50 having an open slot 52 at the 
front end and a pair of shoulders 54, 56 at the rear end. A pin 58 extends 
across the shaft 12, said pin extending through the slot 52 of the thrust 
member 50 when the thrust member 50 is received in a slot 13 (shown in 
FIG. 6) in the shaft 12. 
FIG. 5 shows a sleeve 32 including an inner thread 33. An enlarged end 
portion of the shaft 12 includes a threaded portion 15 including a flange 
17 from which a more slender portion extends rearwardly receiving the 
handle 14. The threaded portion 33 of the sleeve 32 cooperates with the 
threaded portion 15 of the shaft 12, whereas the right end of the thrust 
member 50 as shown in FIG. 4 extends through the sleeve 32 when the parts 
are mounted on the shaft 12 according to FIG. 1, wherein the shoulders 54, 
56 contact the adjacent end of the sleeve 32. The outer surface of sleeve 
32 is a knurled portion 34, shown in FIG. 5. 
The head of a pedicle screw (not shown) is received in the mouth of the 
clamping jaws 18, 20, wherein FIG. 1 shows the receiving position. When 
the sleeve 32 is rotated it is displaced forwardly and moves thus the 
thrust member 50 to the front end to engage the rear end of the movable 
jaw 20. It tilts forwardly and thus urges the head of the pedicle screw 
towards the fixed clamping jaw 18. Thereby the head of the pedicle screw 
is safely held in the tool 10 and may be screwed into a vertebra. After 
screwing-in, the sleeve 32 is counter-rotated so that the tool may be 
removed by releasing the head of the pedicle screw. 
As shown, the tilting axis is located outside the axis of the shaft 12. The 
contact point of the movable clamping jaw 20 is axially off-set alike so 
that the clamping jaw 20 is subjected to a torque anti-clockwise to thus 
approach the front region of the clamping jaw 18. This geometry is used to 
apply the clamping force mentioned before. 
By correspondingly modifying the clamping face of the movable jaw 20, for 
example by an angular face in the front area, angular screws having a flat 
head may be clamped as well. 
It should be understood that the thrust member 50 may be eliminated when 
the sleeve 32 directly engages the movable clamping jaw 20. In this 
embodiment the front portion of the tool is thicker which could be 
objectionable because of a worsened view. 
FIG. 6 is a plan view of the device shown in FIG. 2, viewed from above, 
showing the slot 13 in the shaft 12, in which the thrust member 50 (shown 
in FIG. 4) is positioned and centered (as shown in FIG. 1). Spring 25 with 
attachment screws 27 and pin 58 are also shown. 
FIG. 7 is a part of FIG. 1 drawn at a larger scale and wherein the front 
part of clamping jaw 18 is shown in cross-section. Shown are two prongs 49 
and 51 and shoulders 54 and 56 of thrust member 50 (which is also shown in 
FIG. 4). The lateral projection 24 (of movable clamping jaw 20) extends 
through an elongated opening 60 in the fixed jaw 18. Elongated opening 60 
is preferably a continuation of slot 13. As can be seen in FIG. 1 the hook 
portion 26 of projection 24 engages with a portion of fixed jaw 18. Hook 
portion 26 grips a portion of the lower side of fixed clamping jaw 18. 
Movable jaw 20, thus, may pivot as indicated by double-arrow A. 
As can now be clearly seen in FIG. 7, the rear edge of projection 24 is 
rounded. Thus, a space 60 is left between the lower prong 49 of the 
bifurcated thrust portion 50 and projection 24, even when the upper prong 
51 of thrust member 50 engages jaw 20. From FIG. 7, it is also clear that 
movable jaw 20 may tilt with respect to fixed jaw 18 when thrust member 50 
is axially moved. In other words, an axial movement of thrust element 50 
(indicated by double-arrow B) such that prong 51 thereof engages movable 
jaw 20 leads to a tilting of jaw 20. The axial movement of thrust element 
50 (indicated by double-arrow B) is achieved by an axial movement of 
sleeve 32. This axial movement of sleeve 32 is achieved by turning sleeve 
32 (as indicated by double-arrow C). The threads of sleeve 32 interengage 
with the threads of shank 12 (see FIG. 5 and FIGS. 8-11). Thus, movable 
jaw 20 pivots about the point where the end of hook portion 26 grips the 
lower side of fixed clamping jaw 18. 
In assembling the four main parts (described above) of the device of the 
invention together, the following procedure will be carried out. As shown 
in FIG. 8, the shaft 12 with handle 14 attached thereto has a threaded 
portion 33 (see FIG. 5) which is threaded with the threads of sleeve 32. 
Next, thrust portion 50 is inserted into slot 13 and adjusted so that 
prongs 49 and 51 of the bifurcated portion fit with pin 58 located within 
open slot 52. Then, the rear portion (shaped like a hook 26) of lateral 
projection 24 is inserted into an elongated opening 60 (which is connected 
with slot 13) in fixed clamping jaw 18, and hook portion 26 engages and 
grips the lower side of fixed clamping jaw 18 at opening 15 (shown at 
FIGS. 10 and 16). Next, threaded sleeve 32 is moved so that thrust portion 
50 engages movable jaw 20 at prong 51 of thrust member 50. Movable jaw 20 
tilts, and jaw 20 and jaw 18 are in their closed position (as seen in 
FIGS. 20 and 21). A pedicle screw will be able to be firmly clamped 
between jaws 18 and 20 in the device of the invention.