Pedicle screw

The invention relates to a pedicle screw for implants for correction and stabilization of the spine, with one at the axial end of a threaded shaft arranged head part on which a stirrup part connectable is that a receptacle for a fixable on the head part having rod.

Such pedicle screws are, for example, from DE 41 07 480 A1. In these known Pedicle screw overlaps the arm part the head part with lateral leg portions, where parallel to Longitudinal direction of the rod extending, open on one side Grooves are formed in the head part provided and positively engage corresponding extending strips, wherein to avoid the strips and Abspreizungen Grooves on their adjacent leg parts have dovetailed undercuts. These Pedicle screws are well proven in practice since it is possible with these, a stable and permanent Fixing the position of the rod to allow. though is for placement and mutual fixing of the Pedicle screw and rod during the operation relatively much space is required, which is due to the curvature of Spine and inclined to the longitudinal axis of the Pedicle vertebral employed is possible that the already placed pedicle screws placement the pedicle screws on the immediately adjacent vertebrae hinder or even prevent.

The invention is therefore based on the object, a Pedicle screw of the type mentioned in such a way that the space required for the placement and adjustment of the Pedicle screw is reduced during surgery.

This object is according to the invention at a Pedicle screw of the type mentioned in that the head part by a circular piece and a rotatably on formed the cap round piece mounted, and that the Ironing part by performance in the axial direction Plug movement can be fixed in a snap fit on the cap is.

The invention offers the advantage that after placing the pedicle screws in the vertebral body and the Positioning of the bar the other necessary Actions of the surgeon only in the longitudinal direction of the Threaded shaft must be carried out, ie towards the area of ​​any case of screwing the Pedicle screws is required, no additional space is required. In this case, an individual adaptation to the curve of the generally curved rod possible because in addition to the appropriate choice of the rotational position of the threaded shaft the pedicle screw with the head part, in addition, the cap can be rotated about the round piece.

The so given rotatability is subject to the lowest Restrictions if the round piece as a hemisphere with perpendicular to the threaded shaft oriented, for free End-oriented end face is formed.

If, in addition to the end face a cap with opposite the hemisphere smaller diameter arranged, it is possible, the rod on a support support point directly by the round piece, wherein the rotation due to the small diameter of the Dome of the rod relative to the non-circular piece is impaired.

According to a particularly preferred embodiment of the Invention it is provided that the arm part is U-shaped with a base plate and two side legs is formed, are formed at their free ends latching lugs, which for Forming the latch seat in the plug-in movement on the Cap hook.

In order to prevent unwanted rotation of the cap, there is the possibility, means for blocking the provide rotation of the cap on the round piece. These are expediently designed so that the facing surfaces of the round piece and the Cap have a surface profiling and that in the base of the arm part has a threaded bore formed is serving for the fixation of the rod Locking screw. Once when screwing the Securing screw this comes to the bar for investment, is the rod against the round piece pressed while the Securing screw is supported on the rod and thus also the arm part against the cap clamped, which thus likewise on the opposite side of the bar at the round piece is pressed, what with the appropriate Surface profiling is used, the rotatability to restrict.

To a well-defined seat of the bracket part on the to ensure cap permanently, the pedicle screw designed so that with end plates on the cap respectively one extending axially guide web are arranged, and that each side limb has a having guide for Führunssteg. alternative is to achieve this goal, of course, the Possibility that the guide ribs and the guide grooves to the end plates and the side legs to each other are reversed.

To avoid spreading of the side legs at in the axial direction on the arm part forces acting it is provided that the latching lugs the free edges of End plates engage behind.

With regard to a possible area distributed Introduction of force, it is advantageous if the cap has a groove having as a support for the rod. It is to direct transfer of forces acting on the rod Forces to the pedicle screw or the cap in the Trough an opening formed.

To include the rod in the circumferential direction as far as possible to can, is in the base of the arm part a groove educated.

Plugging the bow part of the cap, a to easy spreading of the side legs is necessary is facilitated by and between the base plate the side legs a groove is formed.

The pedicle screw according to the invention is further designed such that the head portion of a taper at Threaded rod is attached. This provides the advantage that the cap over a larger angular area on the Round piece can be adjusted without the cap to the Threaded shank comes to rest.

In the following the invention will be at a in the drawing Illustrated embodiment explained in more detail; it show:<dl tsize="7"><dt><b>Fig. 1</b></dt><dd>a perspective view of the Pedicle screw according to the invention with the Headboard fixed rod,</dd><dt>FIG. 2</dt><dd>a side view of the pedicle screw,</dd><dt>Fig. 3</dt><dd>the section III-III from Fig. 2,</dd><dt>Fig. 4</dt><dd>a top view of the pedicle screw from FIG. 2</dd><dt>Fig. 5</dt><dd>a side view of the threaded shaft with the Headboard, </dd><dt>Fig. 6</dt><dd>a perspective view of the Rundstück attached cap,</dd><dt>Fig. 7</dt><dd>a further perspective view of the Pedicle screw of Fig. 6 from another Viewpoint,</dd><dt>Fig. 8</dt><dd>the section VIII-VIII of Fig. 7,</dd><dt>Fig. 9</dt><dd>the section IX-IX in FIG. 7</dd><dt>Fig. 10</dt><dd>one of the FIG. 9 illustration corresponding with a comparison with FIG. 9 twisted cap, and</dd><dt>Fig. 11</dt><dd>a perspective view of the U-shaped Bow part.</dd></dl>

The pedicle screw 1 shown in FIG. 1 is used in connection with implants of the correction and stabilization are the spine and its a guided along on the spinal rod 2 use. The pedicle screw 1 consists of a Threaded shank 3, at one axial end by a a round piece 4 and a cap 6 formed headboard 5 is arranged. Here, the round part 4 is a hemisphere 20 formed whose flat surface 22 perpendicular to the Threaded shaft 3 and is oriented facing outward. On the flat surface 22 of the hemisphere 20 is a cap 23 arranged whose diameter is smaller than that of the Hemisphere 20. Because of this structure is evident that the Cap 6 polyaxial to the round piece 4 rotatable and a good adaptability to the position of on the Spine guided rod 2 is given (Fig. 3,8,10).

Which is arranged on the rotary member 4 is driven by a cap 6 U-shaped bow 7 overlapped that of a recording the bar 2 provides. The bracket portion 7 comprises a Base plate 8 and two side limbs 9, free to their Ends detents 10 are formed. To fix the Ironing part 7 this is an exclusively axial direction takes place plug movement to the cap 6 plugged, the detents 10 on the edges of Cap 6 associated end plates 11 in a snap fit Hook. To correct position connecting the arm part 7 with the cap 6 to ensure, and to shifting of the hanger member 7 in the longitudinal direction of the rod 2 to avoid, to the end plates 11 are guide webs 12 formed, which cooperate with a guide groove 13, formed at the side legs 9 of the shackle member 7 are. After itself not in the drawing Embodiment shown, it is understood also possible that the guiding ribs 12 and the Guide grooves 13 on the end plates 11 and the Side arms 9 are interchanged.

A arranged in the base plate 8 of the arm part 7 Threaded hole 18 serves to receive a Locking screw 19, with the rod 2 against Shifts in its longitudinal direction are secured can. This locking screw 19 tightened in Cooperate with the latching lugs 10 and the bracket part 7 respect to the cap 6, which is further exploited to the cap 6 to press against the hemisphere 20th If the facing according to one embodiment, each Surfaces of the round part 4 and the cap 6 a have surface profiling, this acts as a means to block the rotation of the cap 6 and the Round piece 4, wherein the design of the Surface profiling the option leaves open the Rotate fully, in terms of several axes or to stop only with respect to an axis.

In particular from FIG. 7 can be seen, the Cap 6 a groove 14 as a support for the rod. 2 The Embracing the rod 2 through the pedicle screw 1 is by in the base plate 8 of the arm part 7 trained trough 16 rounds.

From FIGS. 1, 3 and 11 it is seen that the Ironing part 7 between the base plate 8 and the Side legs 9 a groove 17 is formed, which the Spreading the bracket part 7 when Aufsteckvorgang facilitated. An undesirable spreading after Attaching the bracket part 7 is prevented by the fact that the latching lugs 10, the free edges of the end plates 11 engage behind.

is from the drawing, especially Figs. 5 to 10 further appreciated that the head part 5 at a Taper 21 of the threaded shank 3 is set, the Angle of rotation of the cap 6 so do not advance through the System is limited to the threaded shaft. 3