Rod element for linking bone anchor elements, and stabilisation device with such a rod element

The invention relates to a rod-shaped element for use in spinal or trauma surgery and a stabilization device with such a rod-shaped element.

From the <patcit id="pcit0001" dnum="EP0669109B1"><text>EP 669 109 B1 0</text></patcit> is a stabilization device for stabilizing adjacent vertebrae is known which comprises two monoaxial pedicle screws and a strap 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. However, this stabilization device is not torsion. The use of mono-axial pedicle screws further limits the use of this stabilizer. A similar stabilization device is to be used in place of polyaxial pedicle screws monoaxial pedicle screws from the<patcit id="pcit0002" dnum="EP1188416A1"><text>EP 1188416 A1</text></patcit> known.

From the <patcit id="pcit0003" dnum="US6162223A"><text>US 6,162,223</text></patcit> is a fixation device for a joint, for example for a wrist or a knee joint, is known in which one of its ends with bone anchoring elements connected fixation rod is constructed in two parts, the two parts of the fixation rod are connected to one another via a flexible coupling member, and wherein said fixation rods and coupling part are mounted outside the body. The facing ends of the two parts of the fixation rod are hemispherical and abut, so as to simulate a kind of joint that is limited in its freedom of movement by the flexible coupling member. The known fixing device is not suitable due to their complicated and bulky structure for use in the spine.

From the <patcit id="pcit0004" dnum="US20030109880A1"><text>US 2003/0109880 A1</text></patcit> is a dynamic stabilization device for vertebrae known, first and second in the vortex to be anchored screw includes each with a receiving part for inserting a connecting the coil spring and such a spring. The spring itself is designed as a whole in the form of a coil spring with closely adjacent windings in the manner of a tension spring and is fixed by clamping screws in the receiving parts. There is in this case, however, the risk that the spring because of its elasticity the pressure of the clamping screw and therefore deflects the fixation between the bone screw and the spring is relaxed.

From the <patcit id="pcit0005" dnum="US20030191470A1"><text>US 2003/0191470 A1</text></patcit> is a dynamic fixation device is known which allows flexion of the vertebrae to which it is attached, and limits the amount of translational motion. The device comprises a flexible portion and adapted to two of the connection with the pedicle screws ends. The preamble of claim 1 is based on this device.

From the <patcit id="pcit0006" dnum="FR2717370A1"><text>FR 2717370 A1</text></patcit> is a stabilizing intervertebral prosthesis which comprises a hollow cylindrical body which is slotted. The slots are filled with a viscoelastic material.

The object of the invention to provide a rod-shaped element for the stabilization and movement limitation of to be joined vertebrae or bones, which constructed simple and compact, easy to handle and versatile with high safety in use. It is another object of the invention, a dynamic stabilization device with a compact design that uses such a rod-shaped element to provide.

The object is solved by a rod-shaped element according to the patent claim 1 and a dynamic stabilization device according to claim 9th

Further developments of the invention are specified in the subclaims.

The invention has the advantage that the rod-shaped element axial forces, bending and torsional forces receives, and is suitable and safe to fix the known polyaxial or monoaxial bone screws with this. The rod-shaped element is in particular suitable for use in stabilizing and limiting movement of adjacent vertebrae in spinal disc defects of varying severity. These properties are to be implemented in the production in a simple way by changing the dimension of the stick-shaped element.

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

Of the figures:<dl id="dl0001"><dt>Fig. 1</dt><dd>is a schematic perspective view of a stabilization device with bar-shaped element in a first application;</dd><dt>FIG. 2</dt><dd>a perspective view of the rod-shaped element;</dd><dt>Fig. 3a</dt><dd>a side view of the rod-shaped element;</dd><dt>FIG. 3b</dt><dd>a sectional view of the rod-shaped element; </dd><dt>FIG. 4a</dt><dd>a perspective view of the connection between the rod-shaped element and bone anchorage elements;</dd><dt>Figure 4b</dt><dd>a sectional view of the connection between the rod-shaped element and bone anchorage elements;</dd><dt>Fig. 5</dt><dd>a side view of a second rod-shaped element;</dd><dt>Fig. 6</dt><dd>a side view of a third rod-shaped element;</dd><dt>Fig. 7</dt><dd>rotated by 90 ° side view of the third rod member of Fig. 6;</dd><dt>Fig. 8</dt><dd>a perspective view of a fourth rod-like element;</dd><dt>Fig. 9</dt><dd>a side view of the rod-shaped element according to FIG. 8;</dd><dt>Fig. 10</dt><dd>a sectional view of a fifth rod-shaped element;</dd><dt>Fig. 11</dt><dd>the operation of the stabilizing device to the fourth rod-like element in a first state;</dd><dt>Fig. 12</dt><dd>a side view of the rod-shaped element according to Fig 11 in the first state. </dd><dt>Fig. 13</dt><dd>a perspective view of the stabilization device to the fourth rod-like element in a second state;</dd><dt>Fig. 14</dt><dd>a side view of the rod-shaped member of Figure 13 in the second state.</dd><dt>Fig. 15</dt><dd>a second application example of the stabilization device;</dd><dt>Fig. 16</dt><dd>a third application example of the stabilization device;</dd><dt>Fig. 17</dt><dd>a fourth application example of the stabilizer;</dd><dt>Fig. 18a</dt><dd>a perspective view of a sixth rod-shaped element;</dd><dt>Fig. 18b</dt><dd>a side view of the sixth rod-like element shown in dashed hidden lines;</dd><dt>Fig. 18c</dt><dd>. A rotated to Figure 18b by 90 ° side view of the sixth rod-shaped element;</dd><dt>Fig. 18d</dt><dd>a section of the sixth rod-shaped element perpendicular to the core axis in the elastic portion;</dd><dt>Fig. 19a</dt><dd>a perspective view of a seventh rod-shaped element; </dd><dt>Fig. 19b</dt><dd>a side view of the seventh rod-shaped element;</dd><dt>Fig. 19c</dt><dd>a section of the seventh rod-shaped element along the rod axis;</dd><dt>Fig. 20a</dt><dd>a view of the lower portion of Figure 19c. and</dd><dt>Fig. 20b</dt><dd>a perspective view of the head portion 134 of FIG. 20a</dd></dl>

1 as is seen from Fig., Comprises the stabilization device in a first application, a rod-shaped element 1 and two pedicle screws 2, 3 which are connected via the rod-shaped element. The pedicle screws 2, 3 are anchored in the pedicles of two adjacent vertebrae 4, 5, between which a damaged disc is located. 6

The rod-shaped element 1 is integrally formed. It has, as shown in FIG. 2, shown 3a and 3b, one from its first end over a predetermined length extending first rigid section 7, and extending from its second end over a predetermined length second rigid portion 8 and a between rigid portions 7, 8 provided on the elastic portion 9 of predetermined length, wherein all the sections have the same outside diameter. By the rod-shaped member 10 also extends a coaxial hole of a predetermined diameter. The elastic portion 9 is formed as a helical spring 11 having turns with a predetermined pitch. The height of the windings 11 of the elastic portion 9 in the direction of the longitudinal axis A of the rod-shaped element, the diameter of the coaxial bore 10, 11 determines the thickness of the windings in the radial direction, as well as the pitch are selected so that a desired stiffness towards axial forces , bending forces and torsional forces acting on the rod-like element 1, can be achieved.

4b is as shown in FIG. 1, FIG. 4a and FIG. Can be seen, a pedicle screw 2, 3 of the stabilization device a threaded shank 12 of the in known manner with a bone thread and a substantially cylindrical receiving part 13 having a U-shaped recess 15 for inserting rod-shaped element on. For fixing the rigid portions 7, 8 in the receiving part 13 screw-female screw 14 are provided in a known manner into the receiving part. Preferably, the pedicle screws are designed as polyaxial screws. The axial length and the diameter of the rigid sections 7, 8 of the rod-shaped element 1 is dimensioned such that the rod-shaped element 1 with its rigid portions 7, 8 with the pedicle screws 2, 3 can be connected. The length of the rigid portions 7, 8 thus corresponds at least approximately to the diameter of the female screw, which is provided for fixing the rod-shaped element. In receiving portions 13 'of a pedicle screw 20 into which the rod-shaped element is not loaded from above, but will be pushed laterally into an opening 21, the length of the rigid portion is also at least approximately to the diameter of a fixing member 14, the rod-shaped element in the receiving part 13 'fixes.

In the example of the stabilization device shown in Fig. 1, the length of the elastic portion 9 of the rod-shaped element 1 is chosen such that it corresponds substantially to the distance between the pedicle screws 2, 3 in the unloaded state of the disc. 6 However, the elastic portion 9 can be shorter or longer.

The rod-shaped element 1 is formed of a biocompatible material such as titanium or a biocompatible plastic, but which has no or low elastomeric properties.

In operation, the pedicle screws 2, 3, 20 are first screwed adjacent vertebrae in the pedicle and then inserted the rod-shaped element 1 with its rigid sections 7, 8 each in one of the receiving portions 14 of the pedicle screws 2, 3, 20th After positioning of the vertebrae 4, 5 to each other and the adjustment of the pedicle screws 2, 3, 20 relative to the rod-shaped element, the rigid sections 7, 8 is fixed in the receiving parts 13, 13 '. The positioning of the vertebra 4, 5 to each other is carried out in an application so that the elastic section 9 of the rod-shaped element 1 in the unloaded condition of the disc 6 is at rest. Under load act on the vertebrae and the ligaments forces on the disc 6. The rod-shaped element 1 limits on the elastic portion 9, the multi-axis movement of the vertebrae relative to each other, thereby preventing the action of excessively large forces on the intervertebral disc. Thus the process of degeneration of a slightly or moderately defective intervertebral disc can be stopped. Alternatively, depending on the indication is performed already in the unloaded state of the spine on the stabilization device a predetermined distraction of the vertebrae so as to relieve the disc. Alternatively, bone screws can be laterally anchored directly into the vertebral bodies.

In the second example shown in FIG. 5 has a rod-like member 100 as in the first example on the rigid portions 7, 8 as well as a lying with these integrally connected between the rigid portions 7, 8 elastic portion 90 in the form of a coil spring. The difference from the first example is that the diameter of the elastic portion 90 is larger than the diameter of the rigid portions 7, 8. As a result, a higher stiffness compared to the stiffness of the first rod-shaped element. The operation is as in the first example.

In the figures 6 and 7 a third rod-like element 101 is shown. This differs from the rod-shaped elements 1, 100 in that the envisaged between the rigid portions 7, 8 elastic portion 900 two 180 ° staggered concave to the rod axis toward molded areas having 901. The length L of the areas 901 in the direction of the rod axis is at most equal to the length of the elastic portion 901 and the radius of curvature is such that the turns of the helical spring are not broken. This configuration of the elastic portion 900 is formed in a direction perpendicular to the rod axis B A fitted and thus has a lower stiffness in this direction. So that an oriented stiffness is given, which is advantageous for certain applications.

The operation is as for the first and second example with the only difference that the rod-shaped element 101 is oriented in the circumferential direction can be fixed in the pedicle screws. By choosing the dimensions of the spring portion, a desired rigidity can be precisely selected and set.

In a fourth, in Figures 8 and 9 example, as representing embodiments of the invention in all examples, has the rod-shaped element 102 a through the elastic portion 902 coaxially extending therethrough core 110 which is cylindrical in this example and a certain bending elasticity. The diameter of the core 110 is dimensioned so that the core is held in register 110 upon insertion in the bore in this 10th The core is preferably made of the same material as the rod-shaped element, but it can also consist of a flexible plastic.

In a modification of the core 110 is integrally connected to the rigid portions 7, 8 and with the turns of the coil spring of the elastic portion 902nd

The core 110 provides a higher bending stiffness of the rod-shaped element 102 as compared with the first example. Thus, in this example, a rigidity similar to that of the second rod-shaped element 100, which has the larger diameter of the resilient portion can be obtained. The bending rigidity is further adaptable by selection of the diameter and / or material of the core. For example, a shape memory alloy can be used with the known property of superelasticity.

The operation takes place as in the previous examples out. In contrast to the previous examples, however, a compression or extension of the elastic portion 902 in the axial direction, and a torsion are dimensionally reduced. There are then preferably only flexion, which is positive for certain applications an advantage.

In a fifth, in FIG. 10 example shown, the rod-shaped element 103 as in the first example on the rigid portions 7, 8 and the elastic portion 9. In the preferably coaxial bore 10 a tension member 112, such as a wire, is provided on the fixing elements, such as clamping screws 13 is fixed to the rigid portions 7, eighth In operation can thus be to provide a preload of the elastic portion. 9

The features of the embodiments described can be combined. For example, and the second rod-shaped element has a core and / or integrally formed sections to achieve an oriented stiffness have. In a modification of the third example of the elastic part is formed Fitted evenly at one point or there are more evenly spaced circumferentially concave molded portions provided to obtain a certain rigidity in defined directions.

In another example, the rod has a plurality of rigid segments having a plurality of respectively intermediate elastic portions so that a plurality can be connected to each other partly rigid and partly elastically of pedicle screws in this way.

In another example, a coating or a sleeve made of a biocompatible material is provided around the elastic part so that no tissue or blood vessels or other body material can pass between the turns and thus can be injured or may impair the function of the rod-shaped element.

In another example, monoaxial are instead of polyaxial screws provided or it is for the stabilization device a combination of a polyaxial screw and a monoaxial or combinations of several of these screws are used. Also, the use of hooks instead of bone screws is also conceivable. In another example, the rigid portions and / or the elastic portion are curved.

Figures 11 to 17 show preferred applications of the stabilization device with the rod-shaped element. In the stabilization device according to the figures 11 to 14 the rod-shaped element according to the fourth example is used, which has the core 110th The stabilizer is used, for example, if a slightly or moderately defective intervertebral disc is to be 6 supports and exposure to harmful forces should be avoided on the disc by movement limitation of the vertebrae. The rod-shaped element 102 is rigid in the axial direction and allows neither a compression nor an extension in the axial direction. Flexion at an angle α to the rod axis, which amounts, for example up to ± 8 °, however, are possible.

Fig. Figure 15 shows the application of the stabilization device with the rod-shaped element at a fusion of two vertebrae 4, 5 by means of a rigid member 200, such as a titanium cylinder, after removal of the natural disc. Here, a higher stiffness of the rod is desired in order to achieve a sufficient movement limitation. However, the slight possibility of movement of the vertebrae to each other as compared to a rigid connection only beneficial because bone growth is stimulated by the increased cyclic partial load and thus the ossification proceeds more rapidly.

FIG. 16 illustrates the application of dynamic stabilization device as a flexible end of a long segment fusion, in which a plurality, in the example shown three vertebrae 5, 5 ', 5' are fused together via rigid elements 200 and posterior connected via a rigid rod 300th The adjoining the last vertebra 5 of the merged chain natural disc 6, and the next vertebrae 4 subject to above-average stress, which lead to increased wear of the disc. 6 To protect this neighboring segment before unusual movements and thus increased loads, the stabilizing device is provided as movement limitation. The rod 300 in this example has a rigid portion 308, which is dimensioned such that this three pedicle screws 2, 2 ', 2 "can be connected, adjacent thereto, the elastic portion 309 is provided, and at the end again a rigid section 307 for connecting to the pedicle screw third

Fig. Figure 17 shows the use of the rod-shaped element 1 in a stabilization device according to an external fixator for stabilizing bone, for example, tube. Bone parts 30, 31 are bone screws 32 which are connected, for example via a connecting element 33 with a rigid rod 34 and a rod-shaped element 1, stabilized.

In a manufacturing method for the rod-shaped element is in a first step, a rigid rod of a desired diameter from a biocompatible material such as titanium is provided. Then, the elastic portion 9, 900, 902 is generated in the form of a coil spring at a portion intermediate the ends of the rod by means of milling. The passing through the spring portion 110 core is then, if desired, drilled out, with which the rod is produced according to the first example.

For generating the rod according to the fourth example, the core 110 is either left or inserted a separate core subsequently.

For generating the rod according to the second example is a rod with a diameter corresponding to the diameter of the desired elastic portion 90 provided, as a starting material. Subsequently, the coil spring is produced by milling. Then, the rigid end portions 7, 8 turned to the desired diameter.

For manufacturing the rod according to the third example is at locations of the elastic portion, which are offset by 180 ° in the circumferential direction from each other, so as to produce an oriented sidecut in a range Distant.

Another example is shown in Figs. 18a to 18d shown. In this embodiment, the core 120 is formed such that it in a part of the elastic portion 9 in the plane perpendicular to the axis of the rod having at least a rectangular cross section (see FIG. 18). The rectangular cross-section is as shown in Fig. 18d is shown, formed with one long side 120a and one short side 120b. As shown in FIG. 18b, the core 120 preferably in the areas that are located in an inserted core 120 in the rigid portions 7, 8 a the inner diameter of the bore 10 adapted round cross-section, so that a fixing of the bar as in ensures the aforementioned embodiments. The attachment can be achieved for example by extending through a transverse bore 122 pin.

Through the rectangular embodiment of the core 120 in the area of ​​the resilient portion 9 a large bending rigidity in the direction of the long side 120a of the rectangular cross-section and a smaller flexural rigidity in the direction of the short side 120b of rectangular cross section is produced. can be made possible perpendicular to this, depending on the orientation of the core 120 thus for certain applications increased mobility in one direction and in relation to restricted mobility in the direction. Compared to the examples in which no core or a wire are provided in the bore, while the tensile and compressive strength is increased. Furthermore, the torsional stiffness can be adjusted by selecting a suitable core.

In order to achieve the effect described, the portion of the core does not necessarily have a rectangular cross section, but other cross-sectional shapes such as an oval cross-section, a substantially rectangular cross-section with a partially concave or convex sides, or even a substantially triangular cross-section can be selected depending on desired properties. It is important that the cross-section in two mutually perpendicular axes (or at least in two different directions) perpendicular to the rod axis different dimensions in the plane. This directional bending stiffness can be achieved.

The core 120 may, in this example as in the other examples be again either integral (on the geometry dependent) with the rod or separately formed and inserted in these. A combination of this core 120 with the other examples, it is possible to adjust the properties of the rod-shaped element to the respective requirements.

When in Figs. 19A to 19C and Figs. 20a illustrated embodiment, a special mounting for the core is provided. As shown in Fig. 19c, 7, 8 closes in the rigid portions respectively in the direction of the free end of the rod-shaped element to the bore 10 is a coaxially thereto disposed second bore 10a, 10b. In the illustrated embodiment, the rigid sections 7, 8 formed on both sides of the elastic portion 9 symmetrical, for which reason hereinafter reference to FIG. 20a, only the portion 8 will be described.

In the second bore 10b is a head receiving portion 131 is provided adjacent the bore 10 which is perpendicular to the axis of the second bore 10b has an outer diameter which in the direction which corresponds substantially to the inner diameter of the second bore 10b. The head receiving portion consists of two shells 131a, 131b which are arranged in the direction of the axis of the bore 10 and together enclose a cavity 133 having the form of a stretched in the direction of the axis of the bore 10 is substantially spherical. In the end surfaces of the shells 131a, 131b are coaxially 10b holes 132a and 132b provided to the second hole, whose diameter increases from the cavity 133 to the respective end face and is slightly larger than the diameter of the core 130th

The outer diameter of the core 130 is substantially smaller than the inner diameter of the bore 10. The the rigid portion 8 facing the end of the core 130 is provided with an external thread 137 which cooperates with a female thread 138 in a bore of a head part 134th The head part 134 is shown in Fig. 20b. It consists of two substantially hemispherical halves 134a and 134b assembled to a substantially spherical outer surface having a diameter comprise greater than the smallest diameter of the bore 132b and smaller than the smallest diameter of the cavity 133rd The provided with the outer thread-free end of the core 130 is passed through the hole 132b and screwed into the cavity 133 disposed in the halves 134a and 134b of the head part 134, which together act as a nut and locknut.

The other free end of the core 130 is added to the rigid portion 7 in a similar manner. Depending on how far the head portions 134 are screwed onto the two free ends of the core 130 are the head portions 134 on the inner sides of the head receiving parts 131, which are facing the bore 10 are located on the facing free ends of the second holes 10a, 10b insides or reject these interior pages on each little game.

In this embodiment 131, the head portions 134 glide into the head receiving parts 131 through the spherical formation of the head members 134 in cooperation with the substantially spherical shape of the head receiving parts. In an applied external bending load by bending stress of the core 130 for small displacements is prevented. By screwing the head portions 134 so that they abut the core-side inner faces of the head receiving parts 131 and to the core facing away from inner sides of the head receiving parts 131, a tensile or compressive reinforcement for the rod-shaped element can be achieved. By sided game of the headers 134 in the receiving parts 131 can be set so that an effect of the nucleus occurs only above a certain lengthening of or shortening of the outer region of the rod-shaped element.

In Figs. 19 to 20a is exemplified that the receiving members 131 are attached with screws 135 into the second holes 10a, 10b; however, it is for example also possible to provide for fastening lateral screws as in other examples, or press-fit connection between the head receiving parts and the second holes.

Furthermore, combinations of parts of these embodiments, other examples are possible. Such combinations are according to the invention if they have to be the features of claim 1.