Pedicle screw.

The invention relates to a pedicle screw for stabilizing vertebral column segments, having a threaded shank part and a head end provided for receiving part of a rod. Such screws are used for mono or multisegmental Stabili tion of the spine used.

A pedicle screw of the type described above is known from DE-AS 26 49 042 known. The screw has a threaded portion and a rigid order at the head end provided for receiving part on. There are several pairs of such screws each in a Spaced apart on both sides of the spine into the vortex body screwed. The respective receiving parts have receiving slots on. Through these slots receiving the right and left Group of screws each performed a threaded rod. With Help of fixing screws, the rod then the respective Receiving part fixed. Further, the screw heads are unterlegbare and the shape of the vertebrae approximately matched load distribution flaps provided. A disadvantage of this solution is that it is very is difficult to screw on the one hand firmly into the vertebral bodies and to screw the other hand, the screw in two planes just to provide such a way that the axes of the receiving slots in the above located receiving parts each are aligned so that the Threaded rod without bracing the screws through the recording is slits passed. Even the attempt requires much Time, in an operation on the spine a great disadvantage is. Moreover, such a precise alignment can hardly to accomplish. The result is that significant shear forces on the Threaded rods are exerted, resulting in that later in the even cancel use after completion of the operation, the rods could not allow the full stabilization or. The neces sary pressure distribution plates are also additional moving parts, which complicate the operation.

The object of the invention is to provide a pedicle screw of the initially to create the type described, which facilitates insertion and simultaneously also reduces the risks during subsequent use or excludes.

This object is achieved by a pedicle screw of the initially be dissolved described type which are marked in accordance with the invention by characterized is that the threaded shank part and receiving part are hinged together.

This solution ensures that the screw initially oh screwed ne regardless of the position of the receiving part can be, and the receiving member then easily in a for receiving the threaded rod required position can be brought. Thus, the operation time is substantially ver shortened, and the forces acting on the threaded rod forces substantially reduced.

give Further features and advantages of the invention from the description of embodiments using the Characters. Of the figures:

<b>Fig.</b> 1 a pedicle screw in an exploded view, partially cutaway, in an enlarged representation;

<b>Fig.</b> 2 the receiving part is rotated 90 ° to the in <b>Fig.</b> 1 Position shown; and

<b>Fig.</b> 3 in the <b>Fig.</b> 1 screw shown in composite Representation.

The pedicle screw <b>1</b> comprises a threaded shaft portion <b>2</b> and a receiving part <b>3</b> on.

The threaded shaft portion <b>2</b> has an out in a known manner formed threaded part <b>4</b> for screwing into the vertebral body on. At the head end of the threaded part is a hexagonal head <b>5</b> provided. On the side facing away from the threaded portion endorses an approach <b>6</b> with an outer thread <b>7</b> at. The on sentence <b>6</b> has its threaded portion opposite side a spherical-segment-shaped recess <b>8th</b> on. The threaded portion<b>4</b>. the hexagonal head <b>5</b>, the approach <b>6</b> and the recess <b>8th</b> are in the in <b>Fig.</b> 1 shown coaxially aligned.

belonging to the threaded shaft portion is a lock nut <b>9</b> provided. It is a hexagonal screw, on its side facing the threaded shaft portion <b>2</b> side facing an internal thread <b>10</b> having recess <b>11</b> having. This in female thread is in its dimensions match the outer threaded de <b>7</b> selected. At the bottom of the recess<b>11</b> locks herself spherical segment section <b>12</b> at. The radius of the Kugelseg mentes substantially corresponds to the radius of the recess <b>8th</b>, The open side of the spherical segment-shaped recess is the recess <b>8th</b> opposite. On the approach<b>6</b> facing away Page joins the recess <b>12</b> a bore <b>13</b> at. recess <b>11</b> with the internal thread <b>10</b>, The spherical segment shaped recess <b>12</b> and the bore <b>13</b> are coaxial with aligned to each other.

There is a connection element <b>14</b> provided. This includes a spherical segment or spherical portion <b>15</b> and one adjoining and trained with this in one piece cylindrical portion <b>16</b> on. In the cylindrical portion is a perpendicular to the axis of the cylindrical portion extending bore <b>17</b> for receiving a locking pin <b>18</b> in front seen. The radius of the portion<b>15</b> is almost equal and only slightly smaller than the radii of the two recesses <b>8th</b> and <b>12</b>, The diameter of the cylindrical portion<b>16</b> is smaller than the diameter of the bore <b>13</b>So that the Ver connecting element to the cylindrical portion preceded by the recess <b>11</b> and through the bore <b>13</b> can be plugged and of the bore <b>13</b> protrudes outward. The thread<b>7</b> and <b>10</b> are in Abhähgigkeit of the diameters of the recesses <b>8th</b> and <b>12</b> and the spherical-segment-shaped portion <b>15</b> selected, that in connection element and screw inserted the locknut <b>9</b> in a position just a movement the cylindrical portion within a cone around the Center of the spherical segment-shaped section <b>15</b> possible is. The amount of movement is predetermined by the extent to which the bore <b>13</b> greater than the outside diameter of the cylindrical portion <b>16</b>,

The locknut <b>9</b> can be tightened so that the substantially rigid connection between the connecting element <b>14</b> and the threaded portion <b>4</b> arises.

The receiving part <b>3</b> is cylindrical, with its Symmetry axis coincides with the symmetry axis of the threaded shank portion <b>2</b> is balanced. On the threaded shaft portion facing Be te is a coaxially extending inner bore <b>19</b> pre see whose diameter is so large that the cylindrical From cut <b>16</b> just fits. Perpendicular to the direction of the In nenbohrung <b>19</b> is a cross bore <b>20</b> provided, which in its Dimension is selected so that the pin <b>18</b> with a snug fit is settable. The depth of the internal bore<b>19</b> and the location of drilling <b>20</b> are selected so that the cylindrical portion <b>16</b> in its firmly mounted with the locknut state in the in <b>Fig.</b> 2 manner shown in the inner bore <b>19</b> usable and with the pen <b>18</b> can be fixed. At the bore<b>19</b> from facing end, the receiving part to a vertically its axis of symmetry extending receiving slot <b>21</b> on to its two outer sides sinkings <b>22</b> and <b>23</b> scheduled are. The width of the receiving slot<b>21</b> is selected so that the male threaded rods loosely therethrough are feasible.

Between the lock nut <b>9</b> and the receiving part <b>3</b> is still a damping plate <b>24</b> of a damping material as in for example silicone provided.

According to one embodiment, the surfaces of Ausnehmun gene <b>8th</b> and <b>12</b> and / or spherical-segment-shaped portion <b>15</b> polished or coated with a lubricant, such as Teflon, so that even with relatively firm screwing the securing screw <b>9</b> a low damped movement of the cylindrical member is possible. According to another embodiment, the top are surfaces made rough, so that the ball in the inserted State with tight position locknut <b>9</b> quasi seizing and a substantially rigid connection between the Verbin connecting element <b>14</b> and the threaded portion <b>4</b> arises.

To insert the pedicle screws in the respective Wirbelkör via the locknuts <b>9</b> dissolved. After inserting be the receiving parts <b>3</b> oriented in its direction so that the threaded rods without the action of shear forces from are directable. The threaded rods are then each in the sinkings <b>22</b>. <b>23</b> seated fixing screws fixed. At closing the respective locknut <b>9</b> as desired either so tightened that the connecting element <b>14</b> virtually no longer, or no longer moves and thus a substantially rigid connection between the receiving part <b>3</b> and threaded shaft portion <b>2</b> arises or there is only so far drawn that a desired nor damped movement between is the two sections.

With the pedicle screw described above thus is to the axis of symmetry unlimited free movement and in horizon tal and vertical direction of a preset movement, which preferably lies at an angle of 10 ° to 30 °, reached.