Pedicle screw.

The invention relates to a pedicle screw having a threaded shank part and a head side receiving part provided on a rod. Such screws are used for mono or multisegmental stabilization of the spine.

Such pedicle screw is known from DE-AS 26 49 042nd The screw has a threaded portion and a rigid so that at the head end provided for receiving part. In each case, screwed several pairs of such screws in a distance from each other on both sides of the spinal column into the vertebral bodies. The respective receiving parts have receiving slots. This receiving slots of the right and left set of screws, a threaded rod is guided in each case. With the help of fixing screws, the rod is then fixed to the respective receiving part. A disadvantage of this solution is that it is very difficult, on the one hand firmly screwing the screws into the vertebral body and the other hand to put the screws in two planes just so that the axes of the receiving slots are aligned in the superimposed located receiving parts so that the threaded rod without distortion of the coil can be passed through the receiving slots. Even the attempt requires a lot of time, which is a big disadvantage in an operation on the spine. In addition to such a precise alignment can hardly reach. The result is that significant shear forces are exerted on the threaded rods, which results in that in the later use after completion of the operation, the rods could even break off and not allow full stabilization.

The object of the invention is to provide a pedicle screw of the type described above, which facilitates insertion and at the same time also reduces the risks during subsequent use or exclude.

This object is achieved by a pedicle screw of the type described initially, which is characterized according to the invention characterized in that the threaded shank part and the receiving part are hinged together.

By this solution it is achieved that the screw can be screwed first without regard to the position of the receiving part and the receiving part then easily in a time required for receiving the threaded rod position can be brought. Thereby, the operation time is substantially shortened, and the force acting on the threaded rod forces are substantially reduced.

Further features and advantages of the invention will be apparent from the description of exemplary embodiments with reference to FIGS. Of the figures:<ul><li>1 shows a first embodiment of a pedicle screw in an exploded view, partly in section, in an enlarged view.</li><li>FIG. 2 shows the receiving part rotated by 90 ° to the position shown in Fig. 1;</li><li>Fig. 3, the screw shown in Figure 1 in an assembled view; FIG.</li><li>Figure 4 shows a second embodiment in side view, partially cut.</li><li>5 shows a part of Figure 4 on an enlarged scale. FIG.</li><li>Figure 6 is a plan view of the part shown in FIG. 5. FIG.</li><li>Fig. 7 is a portion of Figure 4 in a different scale.</li><li>Figure 8 the part shown in Figure 7, rotated by 90 ° view, partly in section..;</li><li>9 shows the part of the back shown in FIG. 7. FIG.</li><li>Fig. 10, the part from the top shown in Fig. 8; and</li><li>Fig. 11 is a ring member of the illustration shown in Fig. 4 in an enlarged scale.</li></ul>

In the first embodiment shown in Figures 1 to 3 embodiment, the pedicle screw 1 a threaded shank portion 2 and a receiving part 3.

The threaded shaft portion 2 has a sold out in a known manner ildeten threaded portion 4 for screwing into the vertebral body. At the head end of the threaded part is a hexagonal head 5 is provided. On the side facing away from the threaded part has a crown 6 concludes with an external thread 7 am. The approach 6 has a spherical segment-shaped recess 8 on its side facing the threaded portion on the opposite side. The threaded portion 4, the hexagonal head 5, the projection 6 and the recess 8 are coaxially aligned in the manner shown in FIG. 1 to each other.

belonging to the threaded shaft portion a Sichterungsmutter 9 is provided. It is a hexagonal screw having on its side facing the threaded shaft portion 2 side facing an internal thread 10 having recess 11th The internal thread is selected in its dimensions to fit the external thread 7th At the bottom of the recess 11, a spherical segment-shaped section 12 connects. The radius of the spherical segment corresponds substantially to the radius of the recess 8. The open side of the spherical segment-shaped recess, the recess 8 in opposite directions. On the approach to the opposite side 6 adjoins the recess 12 to a bore. 13 The recess 11 with the internal thread 10, the spherical segment-shaped recess 12 and the bore 13 are coaxially aligned with each other.

There is provided a connecting element 14th This includes a spherical segment or spherical portion 15 and an adjoining cylindrical and with this integral heading 16. In the cylindrical portion a extending perpendicularly to the axis of the bore cylindrical portion 17 is provided for receiving a locking pin 18th The radius of the portion 15 is almost equal and only slightly smaller than the radii of the two recesses 8 and 12. The diameter of the cylindrical portion 16 is smaller than the diameter of the bore 13, so that the connecting element with the cylindrical portion above the recess 11 and can be inserted through the bore 13 and out of the bore 13 projects outward. The threads 7 and 10 are chosen so as a function of the diameters of the recesses 8 and 12 and of the spherical-segment-shaped portion 15 that, when inserted connecting member and screwing the lock nut 9 just the even movement of the cylindrical portion within a cone around the center in a position spherical-segment-shaped portion 15 is possible. The amount of movement is predetermined by the extent by which the bore 13 is larger than the outer diameter of the cylindrical portion sixteenth

The lock nut 9 can be tightened so that a substantially rigid connection between the connecting member 14 and the threaded portion 4 is formed.

The receiving part 3 is cylindrical, with its axis of symmetry is aligned with the axis of symmetry of said threaded shank portion of the second On the threaded shaft portion side facing a coaxially extending inner bore 19 is provided whose diameter is so large that the cylindrical section 16 just fits. Perpendicular to the direction of the internal bore 19 is a transverse bore 20 is provided, which is selected in their dimensions so that the pin 18 can be inserted with a snug fit. The depth of the internal bore 19 and the location of the bore 20 are selected such that the cylindrical portion 16 in its fixed-mounted with the locknut state in the manner shown in Fig. 2 can be fixed inserted into the inner bore 19 and the pin 18. At which the bore 19 end facing away from the receiving part to a vertically extending axis of symmetry to its receiving slot 21, at the two outer sides countersinks 22 and 23 are provided. The width of the receiving slot 21 is chosen so that the male screw rods loosely through these can be guided.

Between the locking nut 9 and the receiving part 3 ei ne damping disk 24 is also provided of a damping material such as silicone.

In one embodiment, the surfaces of the recesses 8 and 12 and / or of the spherical segment-shaped section 15 are polished or coated with a lubricant, such as Teflon, so that even when relatively firm screwing of the locking screw 9 is a low-damped movement of the cylindrical element is possible. According to another embodiment, the surfaces are made rough so that the ball is in the inserted state with tight position lock nut 9 quasi seizing and a substantially rigid connection between the connecting member 14 and the threaded portion 4 arises.

To insert the pedicle screws in the respective vertebrae locknuts 9 are dissolved. After inserting the receiving parts 3 are aligned in their direction so that the threaded rods without the action of shear forces can be aligned. The threaded rods are then fixed with each in the trap doors 22, 23 seated fixing screws. Subsequently, the respective locking nut 9, as desired dressed either determines that the connecting element 14 virtually no more or no longer moved, and thus creates a substantially rigid connection between the receiving part 3 and threaded shank part 2, or there is only so far attracted, that yet a desired damped movement between the two parts is possible.

In the embodiment described in Figures 4-11, the Transpedikelschraube 25 a threaded shank portion 26 and a receiving part 27.

The threaded shank portion 26 includes a threaded portion 28 for screwing into the vertebral body. At the head end of the threaded part is a spherical segment-shaped head 29 is provided. This has, on its side facing away from the threaded portion on a perpendicular to the axis of the threaded part 28 extending flat surface 30 which is formed by a portion of the ball is cut off. The cut area is roughly equivalent to one half the radius of the spherical body.

As can be seen from Figure 6, is provided coaxially to the threaded portion 28 has a hexagonal bore 31st In this action can be taken with an Allen wrench for screwing the threaded shaft portion 26 into the vertebral body. Instead of the hexagonal hole course also possible to provide other forms for engagement by a screwdriver.

The receiving portion 27 comprises two head halves 32, 33 and a retaining ring this cohesive 34th

Each half of the head, on its head the other half inside facing a spherical segment shaped portion 35th The inner radius of the sphere corresponds to the outer radius of the head 29 on the ball segment-shaped section is adjoined by a neck portion 36 at. This has the shape of a segment of a cone section and is formed by the spherical segment shaped section proceeding outwardly divergent. The axis of the neck portion passes through the center of the spherical-segment-shaped portion 35. On the side opposite the neck portion side of the spherical segment-shaped portion 35 extends perpendicular to the axis of symmetry of the neck portion and kugelsegmentförmigem section, a receiving slot 37, facing away from the the other half of the head outside a countersink 38 is provided , The width of the receiving slot is selected so that a male threaded rod 39 is loosely guided therethrough, as can be seen from FIG. 4

In the area of ​​the neck portion 36, the head half on a vertically extending axis of symmetry of the neck portion and a spherical segment-shaped section groove-shaped recess 40th

The two head halves 32, 33 are identically formed. Its dimensions are chosen so that the center 41 of the spherical segment shaped portion 35 each a fraction of a millimeter outside the period opposite the respective second half of the head parting plane 42 is such that in parallel with joining the two head halves 32, 33 around the head, a gap 43 between the two halves is produced.

The retaining ring 34 has an inner surface 44 that is substantially the negative of the outer surface of the neck portion 36th In particular, the inner surface 44 at a 40 fitting into the groove-shaped recess projecting bead 45 with each adjoining lateral edge regions 46, 47th The inner diameter of the retaining ring 34, thus in particular of the bead 45 and the edge portions 46, 47 is selected so that the ring 34 such a voltage to the two head halves 32, 33 exerts when used in the manner shown in Figure 4 initially without threaded rod 39 are mounted on the head 29 that it about the longitudinal axis of the threaded shank portion 26 are pivotable within a specified by the taper of the neck portion 36 angle free and 39 sufficiently firmly connected to the insertion of the threaded rod with the head and thus with the threaded shaft portion 26 so are that the two head halves in the area included in the ring portion further together than in the opposite, the receiving slot having area.

As is apparent in particular from Figures 4 and 9, the depth of the receiving slot 37 is selected such that it ends in the assembled state shown in Figure 4 in a distance above the surface 30 so that the free mobility of the receiving part 27 of the about the longitudinal axis threaded shaft portion 26 is not restricted.

To insert the pedicle screw according to the embodiment described in Figures 4 -11 the Transpedikelschraube is first characterized screwed into the respective vertebral body that is engaged with the allen screw through the mounting slots and into the hexagonal hole for screws. After screwing the receiving parts 27, 33 are aligned with the two are held together by the retaining ring 34 halves of the head 32 in its direction, that the threaded rods 39 without the action of shear forces can be used in the receiving slots 37th The threaded rods are then fixed with each seated in the trap doors 38 locking screws 48, 49th The fixing screws may become so tight as desired, either, that the receiving part 27 can no longer be pivoted around the head 29 around and thus creates a substantially rigid connection between the receiving part 27 and threaded shaft portion 26, or the screws only so far attracted that yet a desired damped movement between the two parts is possible.

With both the above described embodiments of the pedicle screws is an unlimited free movement around the symmetry axis and in horizontal and vertical direction, a presets adjustable movement, which is preferably at an angle of 10 ° to 30 °, reached. In the last described embodiment is additionally achieved that the structural length of the pedicle screws is kept particularly short.

In the embodiment shown in Figure 4, the retaining ring 34 on its side facing the threaded portion 28 side rounded about a radius, whose center lies on the the threaded part 28 the opposite side. Accordingly, the threaded portion 4 facing lower side of the hexagon head 5 may be rounded. This rounding is achieved that each vertebral body facing surfaces can not cause any injury to the parts.