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

p0001The invention relates to a stabilization device for dynamic stabilization of vertebrae or bones, and a rod-shaped element for such stabilization means.

p0002From the <patcit id="pcit0001" dnum="EP1188416A1"><text>EP 1188416 A1</text></patcit> is a dynamic stabilization device for stabilizing adjacent vertebrae is known which comprises two pedicle screws and a cable-like band which is secured in the receiving parts of pedicle screws each have a clamping screw and which includes a wound-up on the tape support member in the form of a pressure-resistant body.

p0003From the <patcit id="pcit0002" dnum="US20030109880A1"><text>US 2003/0109880 A1</text></patcit> is a dynamic stabilization device for vertebrae known, first and second in a fluid to be anchored screw includes each with a receiving part for inserting a connecting the coil spring and such a spring.

p0004From the <patcit id="pcit0003" dnum="US5415661A"><text>US 5,415,661</text></patcit> and the <patcit id="pcit0004" dnum="US20030191470A1"><text>US 2003/0191470 A1</text></patcit> is respectively a stabilization device for the spine is known comprising a curved elastic rod which is anchored at its ends by means of anchoring elements having a shaft in the extensions of adjacent vertebrae on the same side so that the curved rod and the shafts in substantially parallel planes lie. This curvature is located in the anterior / posterior direction. The curvature fulfills the function of a spring rod.

p0005In the known stabilization devices each two of these stabilizing means for stabilizing two adjacent vertebrae are used which are anchored respectively to the right or left of the center longitudinal axis of the spine.

p0006From the <patcit id="pcit0005" dnum="US6440169B1"><text>US 6,440,169 B1</text></patcit> is a stabilization device for the spine is known which comprises a extending in the adjacent vertebrae between anchoring points elastic body consists of a leaf spring which is shaped so that it forms the wall of an opening, wherein the opening in the anterior / posterior direction with respect to the patient's body and being closed in the medial / lateral direction.

p0007From the <patcit id="pcit0006" dnum="WO02102259A2"><text>WO 02/102259 A2</text></patcit> is a stabilization apparatus for fluidized known which comprises two pedicle screws and a spring member, the spring member connecting the pedicle screws with each other.

p0008From the <patcit id="pcit0007" dnum="EP0667127A1"><text>EP 0667127 A1</text></patcit> is a device for the purpose of restricting the movement between vertebrae is known comprising at least two pedicle screws and a resilient coupling element, the coupling element connecting the pedicle screws with each other.

p0009In particular, the presence of a damaged or an artificial disc, it is desirable to support them through a posterior dynamic stabilization device with respect to the forces to be transferred in a defined manner and to control the movement. Here are flexion and extension of the spine or of the disc in question containing segment, as in<figref idrefs="f0007">FIG. 8a</figref> is seen to be possible, while a lateral translation movement, and a torsion about the central longitudinal axis of the spine, as in <figref idrefs="f0007">Fig. 8b</figref> shown, are undesirable.

p0010The object of the invention to provide a dynamic stabilization device for stabilizing and for limiting movement of adjacent vertebrae or bones, which is simple in construction and with the movement limitation is to the effect achieved in that a flexion and extension is allowed to a limited extent, a lateral translation movement or a rotational movement of the vertebrae or bones, however, another largely prevented.

p0011The object is achieved by a stabilizing device according to claim. 1

p0012Further developments of the invention are specified in the subclaims.

p0013The invention has the advantage that a desired movement limitation can be achieved in a simple manner by selection of appropriately sized rod-shaped elements. The rod-shaped elements of the stabilization device are also easy to prepare. The stabilization device is advantageously applicable to the stabilization of the vertebrae with the use of artificial intervertebral discs.

p0014Further features and advantages of the invention will be apparent from the description of exemplary embodiments with reference to FIGS.

p0015Of the figures:<dl id="dl0001"><dt>Fig. 1</dt><dd>a plan view of the invention stabilizing device according to a first embodiment of the posterior side of the vertebral column seen;</dd><dt>Fig. 2A</dt><dd>a perspective view of a rod-shaped element of the stabilization device according to <figref idrefs="f0001">Fig. 1</figref>;</dd><dt>FIG. 2b</dt><dd>a perspective view of the stabilization device of <figref idrefs="f0001">Fig. 1</figref> from above with preferred formation of rod-shaped elements without showing the top two anchoring elements; </dd><dt>FIG. 3</dt><dd>a partial sectional view of an anchoring element for anchoring the rod-like element of <figref idrefs="f0002">FIG. 2</figref> according to a first embodiment;</dd><dt>Fig. 4</dt><dd>a partially sectioned exploded view of an anchoring element for anchoring the rod-like element of <figref idrefs="f0002">FIG. 2</figref> according to a second embodiment;</dd><dt>Figure 5</dt><dd>a partial sectional view of the anchoring element of <figref idrefs="f0004">Fig. 4</figref> in connection with the rod-shaped element;</dd><dt>Fig. 6a</dt><dd>a schematic representation of the movement is a rod-shaped element of the stabilization device of <figref idrefs="f0001">Fig. 1</figref>;</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 stabilization device is not an embodiment of the invention;</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>

p0016As from <figref idrefs="f0001">Fig. 1</figref> It 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, ', 3' connected in the illustrated application example with pedicle screws 2, 3 and 2, which are anchored in the pedicles of two adjacent vertebrae 4; 5. The first pedicle screw 2 of the rod-shaped element 1 is anchored in the right pedicle of lower vertebra 4, while the second pedicle screw 3 of the rod-shaped element 1 is anchored in the left pedicle of the upper vertebra. 5 Symmetrically, the first pedicle screw 2 'of the rod-shaped element 1' in the left pedicle of lower vertebra 4 is anchored, while the second pedicle screw 3 'of the rod-shaped element 1' is anchored in the right pedicle of the upper vertebra fifth Thus, the rod-shaped elements 1, 1 tick 'at a point K in the plane of symmetry.

p0017As from <figref idrefs="f0002">Fig. 2A</figref> It can be seen, the first rod-shaped element 1 is formed as a curved rod with a rectangular cross section. The rod-shaped element 1 has a first straight portion 6 having a length L1, adjacent thereto a curved portion 7 having a length L2 and adjacent thereto once again a straight portion 8 having a length L3. The central longitudinal axes M1 and M2 of the straight sections include in the illustrated embodiment, an obtuse angle α with each other a. The length L1 of the first straight portion is in the embodiment shown, about three times the length L3 of the second straight portion 8. The curvature extends over the broad side B of the rod-shaped element. The flexural rigidity against a force component which acts normal to its broad side B is less than against a force component which acts vertically on its narrow side S. Further, the flexural rigidity of the rod-shaped member due to the leverage effect due to the different lengths L1 and L3 of the straight portions 6, 8 against a force component which perpendicularly engages the end of the long portion 6 to the bar, less than against a force component of the end short section 8 engages vertically.

p0018Thus, the rod-shaped element has an oriented bending stiffness that is adjustable in the production in the desired manner by choice of the cross section, the curvature and length. The rod-shaped element 1 is also integrally from a body-friendly material such as made of titanium and preferably milled from solid.

p0019The second rod-shaped element 1 'is mirror-symmetrically mounted in the simplest embodiment to the first rod-shaped element 1, so that the curved portions pointing in opposite directions.

p0020<figref idrefs="f0002">FIG. 2b</figref> shows the stabilizing device of <figref idrefs="f0001">Fig. 1</figref> from above with a preferred embodiment of the rod-shaped elements 1, 1 ', in each case the upper anchoring elements are not shown. The rod-shaped elements 1, 1 'are in a range 1a, 1a' adjacent to the section with which they are fastened in the anchoring element, in such a way from the plane which is defined by the joints bent outwardly that they together in the operating state of the stabilization device are passed, without interfering. This enables the connection points of the anchoring elements to the rod-shaped elements, all in a plane perpendicular to the in<figref idrefs="f0007">FIG. 8a</figref> indicated median plane lying.

p0021As in <figref idrefs="f0003">Fig. 3</figref> As shown, the rod-shaped element 1, 1 'in a monoaxial pedicle screw is fixed in a first embodiment. This has a threaded shank 10 with a bone thread and a rigidly connected receiving part 11th The Aufnahemteil 11 is substantially cylindrical and has a a 10 facing away from its threaded shank the free end of the threaded shank toward extending recess 12 having a rectangular cross-section which is so dimensioned such that the rod-shaped element 1, 1 'inserted and still in direction its longitudinal axis is displaced. The recess 12 is formed so that the narrow side S of the rod-shaped element 1 rests in the bottom of the recess. Starting from its free end, the female member to a male screw 13, which extends over a predetermined length which is dimensioned such that the external thread extends at an inserted rod-shaped element to below the top thereof. For fixing the rod-shaped element in the receiving part a can be screwed onto the external thread nut 14 is provided.

p0022In another embodiment, a is in the <figref idrefs="f0004">Figures 4 and 5</figref> Polyaxial screw shown for connecting to the rod-like element 1, 1 'provided. This comprises a screw element 15 with a threaded shank 16 with a bone thread and a spherical segment-shaped head 17 with a not shown recess for screwing. Further, be connected to the screw member 15 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 17th Further, the receiving portion 18 has a coaxial second bore 20 which is open on the side opposite to the first hole 19 end and the diameter of which is so great that the screw element 15 with its threaded shaft through the first bore 19 therethrough and the through the open end head 17 to the bottom of the second bore 20 is feasible. Between the first and the second hole, a spherical portion 21 is provided for abutment of the head 17th

p0023The receiving part 18 further has a symmetrically arranged to the center part of the recess 22 with a rectangular cross section for receiving the rod-shaped element 1, 1 on ', formed by the two free legs 23, 24th In a region adjacent to its free end 24, the legs 23, in this embodiment, an external thread 25 and an internal thread 26.

p0024It is a further provided in the bore 20 toward the head movable pressure element 27th The pressure element 27 has a coaxial bore 28 for passage of a screwdriver, and on its side facing the head 17, a spherical recess 29 for the head 17. On its side facing away from the head of the pressure element 27 has a recess 30 with a rectangular cross section for receiving the rod-shaped element 1, 1 '. The width of the recess 30 is just a little bigger than the narrow side S of the rod-shaped element 1, 1 ', so that this the base of the recess is inserted through with its narrow side S and is movable in the recess in the longitudinal direction. The depth of the recess 30 is somewhat smaller than the height B of the rod-shaped element.

p0025For fixing the rod-shaped element 1, 1 'in the receiving part and for fixing the angular position of the screw element 15 relative to the receiving part a screw-in between the legs of the female screw 31 and to secure a screw on the leg nut 32 are further provided.

p0026In operation, first the pedicle screws 2, 3, 2 ', 3' is screwed into the stabilization device to be connected with the vertebra 4, 5th In the case of monoaxial after<figref idrefs="f0004">Fig. 4</figref> the threaded shafts 10 are screwed in to the receiving parts 11 of the are, 3 'each aligned with a respective rod-like element 1, 1' to be joined pedicle screws 2, 3 or 2 ', that the rod-shaped element to tilt without being insertable. Then, the rod-shaped element is fixed by screwing the nut fourteenth

p0027In the case of polyaxial screws after the <figref idrefs="f0004">Figures 4 and 5</figref> is only the screw member 15 is inserted into the receiving part 18, then the pressure element 27 inserted and subsequently screwed in the screw member in the pedicle. Subsequently, the rod-shaped element 1 or 1 'is inserted into the receiving parts. The receiving parts 18 of two with the rod-shaped element 1 or 1 'to be connected to the pedicle screws 2, 3 or 2', 3 'shall do so on the basis of the articulated connection between the head 17 and the receiving member 18 itself properly toward the rod from what is in the crossed arrangement of the rod-shaped elements beneficial. Subsequently, the receiving parts are fixed relative to the head and to the bar through the inner screw and the nut.

p0028The <figref idrefs="f0005">Figures 6a and 6b</figref> schematically show the operation of the stabilizing device. As in<figref idrefs="f0005">Fig. 6a</figref> As shown, the rod-shaped element 1 are considered in an idealized manner as a lever with a long lever arm 6 and a short lever arm 8 in the unloaded condition. With exposure to flexion or extension of the spinal segment a small perpendicular to the long lever arm 6 acting on the anchorage points force component leads to elastic deformation of the rod-shaped element 1 by the long lever arm is deflected and the radius of curvature is increased relative to the rest position during flexion and during the extension reduced.

p0029In <figref idrefs="f0005">Fig. 6b</figref> show the solid lines, the rod-shaped elements 1, 1 'in a first state, and the dashed lines in a second state, which is a flexion of the spinal segment in this case. 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 at a distance H from one another. During flexion of the spinal segment, there is a bending of the rod-shaped element 1, wherein the radius of curvature thereby becomes larger and thus increases in the shown second state, the distance of the pedicle screws in the direction of the central longitudinal axis to H '. Conversely, at a reduced extension of the spinal column segment of the curvature radius of the rod-shaped elements. This reduces the distance between the pedicle screws.

p0030In application of a force component perpendicular to the short lever arm, a change in the curvature of the rod-shaped elements due to the required larger force is difficult or even impossible. Thus, a lateral translation movement is prevented. Due to the elongated design of the rod-shaped elements to one another is largely further rotational stability compared to a rotational movement of the vertebrae.

p0031<figref idrefs="f0006">Fig. 7</figref> shows a modification of the stabilization device. This stabilizing device extends over two motion segments, each consisting of the vertebrae 4, 5 and 5, 5 '. There are rod-shaped elements 101, 101 'are provided which have a shape obtained by reflection of a bar-shaped member 1, 1' is formed of the first embodiment to a to the free end of the short portion perpendicular plane. The rod-shaped elements 101, 101 'are respectively through the pedicle screws 2, 2' ', 2', 3 '' at their ends in the pedicles on the same side of the respectively next fluidized 4, 5 'anchored and at its central portion via pedicle screws 3 or 3 'anchored in the pedicles of the opposite side of the intermediate vertebra. 5

p0032A multisegmental training is also possible.

p0033Modifications of the embodiments described above are possible. Thus, the lengths of the individual portions of the rod-shaped elements are chosen according to the dimensions of the vertebrae to be connected. The invention is not limited to, that the rod-shaped elements of the stabilization device of the first embodiment have a long and a short straight section. It can only be a long and a curved portion may be present. In the stabilization device according to<figref idrefs="f0006">Fig. 7</figref> can also be of different length, the straight portions, it is essential that the rod-shaped element between the one mounting point and the other mounting point has a curvature so that the bar-shaped element under the effect of bending moments causes a change in spacing of the fastening points.

p0034Further, the features of the embodiments described can be combined each other. The stabilization device of the first embodiment may also have rod-shaped elements having a circular cross-section. Also, a square rod cross-section is possible, but then falls away a degree of freedom in the choice of the bending-elastic properties of the rod-shaped element.

p0035Instead of the monoaxial and polyaxial screws and monoaxial and polyaxial screws can be used, in which the head or the rod fixation takes place in other ways.

p0036The invention is also not limited to a stabilization device for the spine, but may also be used for stabilizing bone.