Apparatus for dynamic stabilisation of the spine or bones and rod-like element for same

The invention relates to a stabilization device for dynamic Stabilization of vertebrae or bones and a rod-shaped Element for such a stabilization device.

From EP 1188416 A1 is a dynamic stabilization device for stabilizing adjacent vertebrae known the two pedicle screws and a rope-like band comprises, which in the receiving parts of the pedicle screws each on a clamping screw is attached and which one to the tape reared support member includes in the form of a pressure-resistant body.

From US 2003/0109880 A1 is a dynamic stabilization device vertebra known that a first and a second in a fluid to be anchored screw each with a receiving part for inserting a spring connecting the screws and includes such a spring.

From US 5,415,661 and US 2003/0191470 A1 is a respective Stabilization device for the spine known has a curved elastic rod, which at its ends through anchoring elements having a shank in the extensions adjacent vertebrae is anchored on the same side so that the curved bar and the shafts substantially in each other parallel planes. Thus, the curvature is in the anterior / posterior direction. The curvature has the function a spring bar.

In the known stabilizers are each two of these stabilizing means for stabilizing two adjacent vertebrae used, each of the right or are anchored to the left of the central longitudinal axis of the spine.

From US 6,440,169 B1 discloses a stabilizing device for known the spine, between one to anchorage points extending into adjacent vertebrae elastic body having a leaf spring which is so shaped as to the wall of an aperture forms, wherein the opening in the anterior / posterior direction with respect to the body of the extends patients and closed in the medial / lateral direction is.

In particular, the presence of a damaged or artificial intervertebral disc, it is desirable, this by a posterior dynamic stabilization device with respect to support the forces to be transferred in a defined manner and to control the movement. Here are a flexion and an extension of the spine and of the relevant Disc containing segment, as in Fig. 8a visible is to be possible, while a lateral translation movement, and a torsion about the central longitudinal axis of the spine, As shown in Fig. 8b, are undesirable.

The object of the invention, a dynamic stabilization device to stabilize and to limit the movement of provide adjacent vertebrae or bones which are easily is constructed and with which a movement limiting to the effect is achieved in that a flexion and extension limited Dimensions is allowed a lateral translational motion or a rotational movement of the vertebrae or bones to each other, however, is largely prevented.

The object is achieved by a stabilizing device according to the Claim 1 dissolved.

Further developments of the invention are specified in the subclaims.

The invention has the advantage that a desired movement limitation simply by selection of appropriately sized rod-shaped elements can be achieved. The rod-shaped elements of the stabilization device are further easy to manufacture. The stabilization device is advantageous applicable for stabilizing the vertebrae in use of artificial intervertebral discs.

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

Of the figures:<dl tsize="7"><dt>Fig. 1</dt><dd>a plan view of the inventive Stabilization device after a first embodiment of the posterior side of the spine seen;</dd><dt>Fig. 2A</dt><dd>a perspective view of a rod-shaped element of the stabilization device according to Fig. 1;</dd><dt>FIG. 2b</dt><dd>a perspective view of the stabilization device FIG. 1 from above with preferred training the rod-shaped elements without representation the upper two anchoring elements; </dd><dt>FIG. 3</dt><dd>a partially sectioned view of a Anchoring element for anchoring the rod-shaped member of Fig. 2 according to a first embodiment;</dd><dt>Fig. 4</dt><dd>a partially sectioned exploded view an anchoring element for anchoring the rod-shaped element of Fig. 2 according to a second embodiment;</dd><dt>Figure 5</dt><dd>a partial sectional view of the Anchoring element of Fig. 4 in Connection with the rod-shaped element;</dd><dt>Fig. 6a</dt><dd>a schematic representation of the movement possibility a rod-shaped Elements of the stabilization device of FIG. 1;</dd><dt>Fig. 6b</dt><dd>a schematic representation of the Operation of the stabilizing device according to the first embodiment;</dd><dt>Fig. 7</dt><dd>a modification of the stabilizing device the first embodiment;</dd><dt>Fig. 8a</dt><dd>a representation of a portion of the Spine from the side; and</dd><dt>Fig. 8b</dt><dd>a representation of a portion of the Spine from behind.</dd></dl>

As shown in FIG. 1 can be seen, the stabilizing device comprises in a first embodiment of a first and a second rod-shaped element 1, 1 '. These are each provided with two Anchoring elements, in the illustrated application example with pedicle screws 2, 3 and 2 ', 3', respectively, which in the pedicles two adjacent vertebrae 4, 5 are anchored. The first Pedicle screw 2 of the rod-shaped element 1 is in right pedicle of lower vertebra 4 anchored, while the second pedicle screw 3 of the rod-shaped element 1 in the left Pedicle of the upper vertebra is 5 anchored. Symmetrically is the first pedicle screw 2 'of the rod-shaped element 1' anchored in the left pedicle of lower vertebra 4, while the second pedicle screw 3 'of the rod-shaped element 1' in the right Pedicle of the upper vertebra is 5 anchored. Thus cross the rod-shaped elements 1, 1 'at a point K in the Plane of symmetry.

As shown in Fig. 2a can be seen, the first rod-shaped element 1 as a curved rod with a rectangular cross-section educated. The rod-shaped element 1 has a first straight section 6 with a length L1, adjacent thereto a curved portion 7 having a length L2 and adjacent thereto again a straight portion 8 having a length L3 on. The central longitudinal axes M1 and M2 of the straight portions close in the illustrated embodiment, an obtuse Angle α with each other. The length L1 of the first straight portion is in the embodiment shown about the Three times the length L3 of the second straight portion 8. Curvature extends over the broad side B of the rod-shaped element. The flexural rigidity against a force component, acting perpendicular to its broad side B, is less than against a force component perpendicular to its narrow Page S acts. Further, the flexural rigidity of the rod-shaped Element due to the leverage effect through the different Lengths L1 and L3 of the straight portions 6, 8 against a force component at the end of the long section 6 vertical attack to the bar, lower than compared to a Force component which is perpendicular to the end of the short portion 8 attacks.

Thus, the rod-shaped element has an oriented bending stiffness, by the choice of the cross section, the curvature, and adjustable length in the desired way in the manufacture is. The rod-shaped element 1 is further integrally formed from a body-friendly material, such as made of titanium and preferably milled from solid.

The second rod-shaped element 1 'is in the simplest embodiment, mirror symmetry to the first rod-shaped element 1 is fixed so that the curved sections in opposite show directions.

FIG. 2b shows the stabilization device of Fig. 1 from above with a preferred embodiment of the rod-shaped elements 1, 1 ', in each case the upper anchoring elements not shown are. The rod-shaped elements 1, 1 'are in a Section 1a, 1a 'adjacent to the portion with which they in the anchoring element are mounted in such a way from the plane is defined by the joints, bent outwardly, they each other in the operating state of the stabilization device are passed, without interfering. This makes possible, that the joints of the anchoring elements perpendicular to the rod-shaped elements all in one plane the direction indicated in Fig. 8a median plane lying.

As shown in Fig. 3, in a first embodiment, the rod-shaped element 1, 1 'in a monoaxial pedicle screw fixed. This has a threaded shank 10 with a Bone thread and a rigidly connected receiving part 11 on. The Aufnahemteil 11 is a substantially cylindrical configuration and has a facing away from his the threaded shaft 10 free end to the threaded shank toward extending recess 12 with a rectangular cross-section, the so dimensioned is that in it the rod-shaped element 1, 1 'inserted and yet is displaceable in the direction of its longitudinal axis. recess 12 is formed so that the narrow side S of the rod Element 1 rests in the bottom of the recess. Based on its free end, the receiving part an external screw thread 13 which extends over a predetermined length dimensioned so is that the male thread when inserted rod-shaped element to below its top ranges. To fix the rod-shaped Element in the receiving part is a onto the external thread screw-nut 14.

In another embodiment, a is shown in Figures 4 and 5 polyaxial screw shown for connecting to the rod-shaped Element 1, 1 'are provided. This includes a screw member 15 with a threaded shank 16 with a bone thread and a spherical segment-shaped head 17 with a not shown recess for screwing on. Further, an element with the screw 15 connectable receiving part 18 is provided. The receiving part 18 is substantially cylindrical and has at one end an axially symmetric aligned first Bore 19 whose diameter is smaller than that of the head 17 is. Further, the receiving portion 18 has a coaxial second bore 20 which on the opposite of the first bore 19 End is open and whose diameter is so great that the Screw element 15 through the open end with its thread shaft through the first bore 19 therethrough, with the top 17 be guided to the bottom of the second bore 20th Between the first and second bore portion 21 is a spherical provided for abutting the head 17th

The receiving part 18 also has a symmetrical to the center of the part arranged recess 22 with a rectangular cross section for receiving the rod-shaped element 1, 1 ', through the two free legs 23, 24 are formed. In a region adjacent to its free end, the legs 23, 24 in this embodiment, an external thread 25 and an internal thread 26.

It is also in the bore 20 toward the head sliding Pressure element 27 is provided. The pressure element 27 has a coaxial bore 28 for passage of a screwdriver, and at its head 17 side facing a spherical Recess 29 for the head 17. At its head side facing away from the pressure element 27 a recess 30 of rectangular cross section for receiving the rod-shaped element 1, 1 '. The width of the recess 30 is just a slightly larger than the narrow side S of the rod-shaped element 1, 1 ', so that this with his narrow side S to the base Recess toward insertable and in the recess in the longitudinal direction is slidable. The depth of the recess 30 is slightly smaller than the height B of the rod-shaped element.

For fixing the rod-shaped element 1, 1 'in the receiving part and for fixing the angular position of the screw member 15 relative to the receiving part are also one between the Legs screwed inner screw 31 and to ensure a provided on the legs can be screwed nut 32nd

In operation, first the pedicle screws 2, 3, 2 ', 3' in to be connected with the vortex stabilizer 4, 5 screwed. In the case of monoaxial of FIG. 4 the threaded shafts 10 are screwed in to the receiving parts 11 of each having a rod-shaped element 1, 1 ' to be connected to pedicle screws 2, 3 or 2 ', 3' to each other so are aligned so that the rod-shaped element without tilting can be inserted. Then, the rod-shaped element is Screwing the nut 14 is fixed.

In the case of polyaxial screws according to FIGS 4 and 5 until the screw member 15 is inserted into the receiving part 18, Then the pressure element 27 inserted, and then the Screw member screwed into the pedicle. subsequently is the rod-like element 1 or 1 'in the receiving parts used. The receiving parts 18 of two with the rod-shaped Element 1 or 1 'to be connected to pedicle screws 2, 3 and 2 ', 3' shall do so due to the articulated connection between the head 17 and the receiving member 18 itself properly for Rod out of what at the crossed arrangement of the rod-shaped Elements is advantageous. Subsequently, the receiving parts are relative to the head and to the bar through the inner screw and the mother fixed.

Figures 6a and 6b schematically show the functioning of the Stabilization device. As shown in FIG. 6a, the rod-shaped element 1 in the unloaded state in an idealized Than as a lever with a long lever arm 6 and a short lever arm be considered. 8 With exposure to flexion or extension of the spinal segment carries a small to the anchorage points perpendicular to the long lever arm 6 attacking Force component and the elastic deformation of the rod-shaped Element 1 by the long lever arm is deflected and the radius of curvature relative to the rest position in the Flexion increased and decreased in the extension.

In Fig. 6B, the solid lines show the rod-shaped Elements 1, 1 'in a first state and the dashed Lines in a second state, which in this case, a flexion the spine segment. have in the first state the pedicle screws 2 ', 3 with which the rod-shaped element 1 is connected, in the direction of the central longitudinal axis M of the spine a distance H from each other. In the flexion of the spinal segment there is a deflection of the rod-shaped element 1, wherein the radius of curvature thereby becomes larger and thus shown in the second state, the distance between the pedicle screws is enlarged in direction of the central longitudinal axis H '. Conversely, if an extension of the spinal column segment of the Radius of curvature of the rod-shaped elements reduced. In order to reduces the distance between the pedicle screws.

In application of a force component perpendicular to the short Lever arm, is to change the curvature of the rod-shaped elements difficult because of the required higher force or impossible. Thus, a lateral translational motion prevented. Due to the elongated design of the rod-shaped Elements further consists largely rotational stability to each other with respect to a rotational movement of the vertebrae.

Fig. 7 shows a second embodiment. The stabilization device covers two motion segments consisting each of the vertebrae 4, 5 and 5, 5 '. There are rod-shaped Elements 101, 101 'are provided which have a shape which first by mirroring a rod-shaped element 1, 1 'of the Embodiment of a free on the end of the short portion plane perpendicular arises. The rod-shaped Elements 101, 101 'are respectively through the pedicle screws 2, 2' ' or 2 ', 3' 'at their ends in the pedicles on the same side the respective next vertebrae 4, 5 'anchored and with her central portion on pedicle screws 3 and 3 'in the pedicles the opposite side of the intermediate Vertebra 5 anchored.

A multisegmental training is also possible.

Modifications of the embodiments described above are possible. Thus, the lengths of the individual sections of rod-shaped elements according to the dimensions of connecting to Eddy selected. The invention is not limited to, that the rod-shaped elements of the stabilization device the first embodiment of a long and a short have straight section. It is also only a long his and a curved portion present. In the stabilizing device the second embodiment, the straight Sections be different lengths, critical is that the rod-shaped element between the one mounting point and the other mounting point has a curvature, so that the rod-shaped element under the effect of bending moments a change in distance of the fixing points causes.

Further, the features of the embodiments described combined. The stabilization device of first embodiment may also be rod-shaped elements having circular cross section. Also, a square Rod cross-section is possible, but in which case a degree of freedom in the choice of the bending-elastic properties of the rod-shaped Element will be invisible.

Instead of the monoaxial and polyaxial screws can also monoaxial and polyaxial screws be used, in which the head or the rod fixation takes place in other ways.

The invention is also not limited to a stabilization device limited to the spine, but can also for stabilizing are used by bone.