MXPA01001226A - Self-cutting hollow cylindrical bone anchoring element - Google Patents

Abstract

The invention relates to a bone anchoring element (9) for fixing bone parts to another implant, comprising A) a longitudinal cylindrical anchoring part (1) having a longitudinal axis (2), an upper end (3) and a lower end (4);and B) a connecting element (5) which is fixed to the upper end (3) and designed to be coupled to another implantable element;where C) the outer surface (6) of the anchoring part (1) is provided with an external thread (7);D) the anchoring part (1) has a height H in the direction of the longitudinal axis (2) and is provided with a hole (10) which is concentric in relation to said longitudinal axis (2) and measured from the lower end (4) has a depth T;and E) the anchoring part (1) is configured self-cutting at the lower end (4). The invention also relates to a bone fixing device comprising a) two bone anchoring elements (9);b) at least one plate (14;15) with a central axis (16), said at least one plate (14;15) being provided with means (17) for receiving connecting elements (5) of the two bone anchoring elements (9);and c) means (18) for fixing the bone anchoring elements (9) in the plates (14;15), where d) the two bone anchoring elements (9) can be displaced in the direction of the central axis (16).

Description

ASSEMBLY OF ANCHOR OF BONE, CYLINDRICAL, HOLLOW, AUTOCORTE The invention relates to a bone anchor assembly as defined in the preamble of claim 1 and an apparatus for bone fixation as defined in the preamble of claim 11. Pedicle screws or other anchor mounts Bone fixation to internal plates or bars in the fixation of bone segments or in particular in the fixation of vertebrae. German document 297 10 979 AESCULAP discloses an implant for the relative fixation of bone parts or also vertebral fixation. The implant comprises insertable anchoring elements in each bone segment, connecting elements to which the anchoring elements can be assembled using a removable ball clamp, and longitudinal supports also attached to the connecting elements and by means of which several anchoring elements inserted in several bone segments or also vertebrae can be rigidly connected. The anchoring elements are in the form of bone screws, cylindrical, hollow and externally threaded and are also equipped with radial pass holes between the threads. A settling passage in the bone can be pierced before these hollow cylindrical anchoring elements can be inserted. In U.S. Patent No. 5,015,247 (Michelson) another implant comprising a hollow cylindrical bone screw is described. This bone screw, like the aforementioned anchoring element, is designed above all for insertion into the intervertebral space, and consists of a hollow cylinder with an internal thread and radial passages between the threads. This implant is either screwed into a perforated bone conduit as before or in a bone through hole. In the latter case, the bone screw cavity will be filled with bits of bone from the patient's body, thereby improving fusion between the adjacent vertebrae and between the vertebrae and the implant. Both anterior implants incur the disadvantage that a passage or hole in the bone must be punctured before it can be *? # ti £ c¿s & iSt tiS ». screw the hollow, cylindrical bone screw or the anchoring element into this bone. The object of the invention is the palliation. The purpose is to create a self-cutting anchor element. This self-cutting feature of the bone anchor assembly results in a substantially shortened implantation time. The invention solves this problem by a bone anchoring assembly of the features of claim 1 and with the apparatus for bone fixation having the features of claim 11. Further advantageous embodiments of the invention are set forth in the dependent claims. In a preferred embodiment of the bone anchor assembly of the invention, this consists of a cylindrical, circular anchor portion equipped at one end with a cutting tooth arranged in a tangential manner. The anchoring element is cylindrical, hollow and comprises a thread of self-creation on its outer surface. By means of the cutting or sawing tooth, the anchoring element can be inserted into the hole without drilling *? éb¡ S & *? & k A J before a bone canal. The bits of bone are removed in the hole of the hollow cylinder. The number of cutting teeth is between 10 and 40, preferably between 25 and 35, where the rake is understood to be the angle between the longitudinal axis of the hollow cylindrical anchoring element and the cutting surface of a cutting tooth . Appropriately, the clearance angle is between 5 and 40 °, preferably between 18 and 28 °. The cutting edge also subtends an angle with the perpendicular to the longitudinal axis of 30 to 60 °, preferably between 40 and 50 °, the cutting corner which is on the outer surface of the anchoring element. A set screw having a through hole, a circular cylindrical anchor section, a connecting element at the upper end and an external self-cutting thread on the outer surface of the anchoring section is known from US 4,537,185 of STEDNITZ East Known set screw is axially drilled and is provided with cutting teeth at the front end.

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From US 5,129,901 to DECOSTE another orthopedic fixing screw is known which is perforated and has a cylindrical, circular anchoring section and an external self-cutting thread on the outer surface of the anchoring section. This known fixing screw is axially perforated and is also provided with cutting teeth at the front end. Both anterior fixation screws are provided with external threads that reach or are near the tip of the screw and therefore are screwed or also in the cancellous region of the bone. This has the disadvantage that in the case of teoporosis, where the cortical region remains almost normal but the spongy region is removed, an anchor through a thread adapted to the spongy part is not practicable. In the case of both fixing screws mentioned above, the self-cutting quality of the external thread is established by means of axial grooves, such that the fixing screws are not provided with an outer surface having a smooth surface in the present. Here, the objective is the palliation. Its purpose is to create an anchoring element, which j ^^^ dj ^ | fe? ^ g ^^? ^^ a¿ ^ ^ g ^^ ancle with the cortical region of the bone through a cortical thread, particular, individual and allowing a better recovery of blood circulation as well as a better incorporation of the implant by means of a smooth surface on the spongy surface. An elongation of this cortical thread to the spongy region is disadvantageous because in the case of micromotion the stress effects and the dents that arise can damage the spongy region. At its other end, the anchoring element is equipped with a connection element for coupling to another implantable element, for example a connection plate, an adjustment plate or longitudinal supports. In the simplest mode, this connection element is a cylinder insertable in a corresponding passage hole in the plate. However, advantageously, the connecting element is designed to allow the attachment of the anchoring element to the plate in a rotational manner along an angular range. This rotational action can be implemented for example by the connecting element which is a ball seated in the depressions of to «< g, S < fe ^. »? - j» -a or *,. *? < £ «S? ^ '^ Us? - ^^^ SSÁíi ^ i ^ & The correspondence on the plate. In another embodiment, the outer surface of the anchoring element can be smooth, starting from the lower end equipped with cutting teeth, over the part of the length. This embodiment is advantageous because the side wall of the cylindrical, hollow anchoring part can be equipped on this part length with radial passage passages allowing the bone to be fused outside the anchoring element with the bone core. inside the anchoring element. In addition, the through holes save material and in this way can substantially reduce the weight of the implant. The length of part L is appropriately between 60 and 85%, preferably between 70 and 80% of the height H of the anchoring element. A preferred embodiment of the apparatus of the invention comprises at least two bone anchoring mounts, at least one plate with a central axis, which is at least one plate that is equipped with means for receiving the connecting elements of the two anchoring mounts. of bone. The means that receive the means of connection consist essentially of holes of passages of appropriate longitudinal cross-sections in the plate allowing the connection means mounted on the anchoring elements to be supported thereon and fixed in removable form by the fasteners of the bone anchoring assembly on the plate (s). In the preferred embodiments of the apparatus of the invention, the fasteners of the bone anchor assembly are screws or nuts that can be screwed into or on the connecting elements. The means that receive the connection means, for example, elongated slots arranged along the central axis of the plate, is designed in such a way that the two bone anchoring mounts can be moved relatively from a distance Z that can be from 10 to 80 mm, so preferred from 20 to 60 mm. In another embodiment, the apparatus of the invention, this apparatus is equipped with two plates movable in the direction of the central axis, each plate comprising a means for centering a connecting element to a fastener for mutually fixing the two plates. This fastener is a screw in the various modes and passes through a through hole in one of the plates and is screwed into the other plate.

By appropriately configuring the connecting elements, for example, as ball connecting elements, an angle between 60 to 120 °, preferably between 70 and 110 °, can be established between the central axis of at least one plate and each one of the longitudinal seals of the anchor parts. In another embodiment, the apparatus of the invention, the two plates are toothed on the surfaces in mutual contact. Accordingly, the apparatus is secured against relative sliding of the two plates and becomes more stable. In addition, the two plates are made non-rotational by lateral handles or guide pincers. In another embodiment of the apparatus of the invention, two annular discs are used instead of a second plate, a disc that is mounted below the plate and that seats the connecting means of the anchoring element, the other disc together with a screw insertable therein is used to hold in place the first anchoring element relative to the plate. The second anchoring element is fixed on the plate. To implement the variable spacing between the two anchoring elements, at least one of the pass holes that receive the connection elements is an elongated slot. The disc below the plate and the plate itself can also be equipped with a grid on the two contact surfaces. The spherical connection element can be replaced by a unilaterally convex disk resting on the plate and with a concave upper end of coupling the anchoring element to allow rotation of the anchoring element. Essentially, the advantages of the invention are thanks to the bone assembly of the invention which does not require that the perforation be carried out in the bone before inserting the implant. The invention and additional embodiments of this invention will be made clear later with respect to the partially schematic figures of an illustrative embodiment. Figure 1 is a perspective, schematic view of one embodiment of the bone anchoring assembly of the invention, Figure 2 is a detail of a cutting tooth in one embodiment of the device of the invention, Figure 3 is a front view of a embodiment of an apparatus of the invention, and Figure 4 is a top view of the embodiment of the apparatus of the invention shown in the top view in Figure 3. Figure 1 schematically shows an embodiment of the assembly 9 of bone anchor of the invention. This assembly comprises a circular cylindrical anchor element 1 of height H equipped with a connecting element 5 coaxial to the longitudinal axis 2 of the element 1 and in this embodiment shown as being a simple cylindrical joint. Instead of the cylindrical joint, the connecting element 5 can also be spherical. The connection element is connected directly, in the direction of the longitudinal axis 2, to the upper end 3 of the anchoring element 1. A through hole 10 of a depth T smaller than the height H enters concentrically at the lower end 4 of the anchoring element 1. As a result, the cross section of the anchoring element 1 is cylindrical, hollow on a length corresponding to the depth T. The cutting or sawing teeth 8 are configured tangentially at the lower end 4 in the hollow cylinder. In In this embodiment, the cutting edges 11 of the cutting teeth 8 configured tangentially, run radially. The outer surface 6 of the anchoring element 1 is smooth over a partial length L also smaller than the height H and starting at the lower end 4, while the rest of the height H is provided with an external thread 7. The mounting 9 Bone anchor can be equipped on the end surface of the connecting part 5 with a hexagonal socket to simplify, using a coupling tool, the insertion of the bone anchor assembly 9 into the bone. Additionally, the hexagonal plug can be replaced by a hexagonal head in the connecting part 5 or in the portion of the anchoring element 1 joining the upper end 3. Figure 2 shows a detail of a cutting tooth 8. The Figure also shows a 3-D coordinate system with a z axis parallel to the longitudinal axis 24, a radial x axis 25 and an y axis 26 tangential to the outer surface 6 and orthogonal to this radius. The nose 27 is located on the outer surface 6 of the anchoring part 1. The nose angle 27 supported by the z-axis 24 and the surface *, * #? us? . , ",.» * ^ I,. . ^ ^ l ^ ^ »A ^ & ^ ^?. ^ s¡ ^^^ d- ^ l. ^. ^? ^ & ^^^ ^ ^ ^ 32 of the cutting teeth in which the bits run, is 30 °. The clearance angle 29 of the edge 33 of the cutting teeth on the outer surface 6 and the plane 31 determined by the x-axis 25 and the y-axis 26 is 22.5 °. The angle 30 between the radial cutting edge 11 and the plane 31 determined by the x-axis 25 and the y-axis 26 is 45 °, as a result of which the noses 27 of the cutting teeth 8 constitute the lower end 4 ( Figure 1) of the anchoring part 1 and are located on the outer circumference. Figures 3 and 4 show an embodiment of the apparatus of the invention with two bone anchoring assemblies 9. The two bone anchoring assemblies 9 are equipped in their hollow cylindrical portions with radial passages 13. The two bone anchoring mounts 9 are connected by two plates 14; 15 of a central axis, common. The two plates 14; 15 overlap on mutually contacting surfaces 21, 22 running along the central axis 16. These two surfaces 21; 22 that contact each other are equipped with serrated edges 23 to prevent the two plates 14; 15 slide relatively ^ »^ ÁáSm ^ Á ^ 3 ^ ¡^ ?. under the load. Additionally, the two plates 14; 15 are equipped at their mutually opposite ends with lateral lugs 43 and extending beyond the thickness of the other particular plate 14; 15. These handles prevent the plates 14; 15 rotate relative to each other, as a result of which they will become aligned with respect to the central axis 16. The means 17 that receives the connecting elements 9 are spherical through holes. The connecting elements 5 are spherical covers and of a diameter corresponding to that of the spherical passage holes. The spherical cover connecting elements 5 are equipped with through holes 37 comprising an internal thread 38 and conically shaped geometry 39 tapering away from the upper end 3. Turned geometries (39) receive the heads 40 of tapered screws of the screws 18 used to fix the bone anchoring mounts 9 to the plates 14; 15. When tightening the screws, the connection elements 5 equipped with grooves 36 and with a turned geometry 39 are clamped against the wall of the spherical pitch holes which serve as a means 17 for seating the connecting elements 5 by the 40 screw heads. In this regard, the conical angle of the screw head 40 need not be identical with the conical, turned geometry 39. In this way, the bone anchor assembly 9 can be fixed with respect to the perpendicular of the plates 14; 15 at an angle 44 of 16 ° on the inside to 19 ° on the outside on the plate 14; 15. The fastening means 20 that fix the plates 14, 15 relative to each other is a screw that is rotated in the lower plate 14 towards a threaded hole 41 and passes through an elongated slot 42 in the upper plate 15. To allow the displacement of the two plates relative to one another, thereby changing the distance between the two bone anchor assemblies 9 along the central axis 16, the elongated slot 42 in the plate 15 is used as the step hole for the screw. The anchoring part 1 comprises a larger diameter at its upper end 3 than the flange 34 comprising the anchoring part 1. This flange 34 comprises six semicircular notches 35 that support an angle of 60 ° between the joining notches. By means of these notches 35 and a coupling tool, the bone anchor assembly 9 can be rotated in the bone. Instead of the notches 35, the flange 34 can also be equipped with an external hexagonal head. In addition, the tab 34 acts as a touch to prevent the bone anchor assembly 9 from turning excessively in the bone or vertebra. The insertion of the implant described above does not require that a reception duct be molded in advance in the bone. further, the bone anchor assembly is inserted into the bone, first a Kirschner wire is concentrically inserted into the bone. After which, the bone anchor assembly is rotated directly, by a key that presses the ball head of the connecting part and which externally engages the six notches, in the bone or also vertebra. The key comprises a through hole and in this way is guided to the Kirschner wire previously inserted. The conduit for receiving the hollow cylindrical anchor portion 1 is pierced from the bone by the cutting teeth 8. The bone chips created in this way are removed inside the hollow cylindrical anchor part 1. After the bone anchor assembly 9 has been screwed in, the Kirschner wire can be removed. The second bone anchor assembly 9 is inserted into the bone in the same manner. After the bone anchor mounts 9 have been inserted into the bone portions or into the vertebrae, the plates 14; 15 are pressed in the connecting part 5. The implant as a whole can be secured in a desired position by screwing and tensioning the screws with the conical screw heads 40 and by means of a set screw 20.

Claims (17)

1. CLAIMS 1. A bone anchor assembly, comprising: (a) a cylindrical, circular, longitudinal anchor portion having a longitudinal axis with an upper end and a lower end, in addition, (b) a connection element mounted in the upper part for the coupling to the internal parts or longitudinal supports; where (c) an external thread present on the outer surface of the anchoring part; (d) the anchoring part which is of height H in the direction of the longitudinal axis and which is equipped with a through hole concentric to the longitudinal axis and of a depth T < H from the lower end and (e) the anchoring part is self-cutting at the lower end, characterized in that (f) the outer surface is smooth over a partial length L < H that starts at the lower end.
2. 2. The bone anchor assembly according to claim 1, characterized in that the Partial length L is between 40% and 90% of the height H.
3. The bone anchor assembly according to claim 2, characterized in that the partial length L is between 50% and 80% of the height H.
4. The bone anchor assembly according to claim 2, characterized in that the cutting teeth are tangentially driven on the end surface of the lower end of the anchoring part.
5. The bone anchor assembly according to claim 4, characterized in that the cutting edges of the cutting teeth form an angle between 30 and 60 ° relative to a given plane with a radius and the associated tangent.
6. The bone anchor assembly according to one of claims 1 to 5, characterized in that the cutting teeth support a range of 10 to 40 °.
7. The bone anchor assembly according to one of claims 1 to 5, characterized in that the range of the cutting teeth is between 25 and 35 °.
8. 8. The bone anchor assembly according to felfea »- one of claims 1 to 7, characterized in that the clearance angle of the cutting teeth is between 15 and 30 °.
9. The bone anchor assembly according to one of claims 1 to 8, characterized in that the thread is self-forming.
10. The bone anchor assembly according to one of claims 1 to 8, characterized in that the cylindrical, hollow side walls of the anchoring part are equipped with radial passages.
11. 11. An apparatus for bone fixation comprising two bone anchoring assemblies as claimed in one of claims 1 to 12, characterized in that: (a) it is equipped with at least one plate having a central axis, this is at least one plate comprising a means that seats the connecting elements of the two bone anchoring mounts, and (b) comprises a means that fixes the bone anchoring mounts on the plates, where (c) the two mounts of bone anchor can move in the direction of the central axis. * ^ *, ^ ^ && amp; tj-a »12.
12. The apparatus according to claim 11, characterized in that it comprises two plates movable in the direction of the central axis, each plate that is equipped with means that seat a connecting element, and a fastener for fixing the two plates with relationship to each other.
13. The apparatus according to any of claims 11 and 12, characterized in that the two bone anchoring mounts can be mutually displaced by a distance Z along the central axis.
14. 14. The apparatus according to claim 13, characterized in the distance Z is between 20 and 60 mm.
15. 15. The apparatus according to claim 14, characterized in that the distance Z is between 35 and 55 mm. The apparatus according to one of claims 11 to 15, characterized in that the two plates are equipped with a serrated edge to the surfaces in mutual contact. The apparatus according to one of claims 11 to 16, characterized in that an angle of 70 to 110 ° can be established between the central axis of at least one plate and each of the longitudinal axes of the anchoring parts. SUMMARY OF THE INVENTION A bone anchoring assembly (9) for securing bone portions to another implant, comprising (a) a circular, longitudinal cylindrical anchor portion (1) having a longitudinal axis (2), one end (3) superior and one extreme (4) lower; and (b) a connecting element (5) mounted on the end (3) for coupling to another implantable element; where (c) an external thread (7) is present on the outer surface (6) of the anchoring part (1); (d) the anchoring part (1) is of height H in the direction of the longitudinal axis (2) and is equipped with a hole (10) of concentric passage to the longitudinal axis (2) and of a depth T starting at the lower end (4); and (e) the anchoring part (1) at the lower end (4) is aut ocort ant e. The apparatus for bone fixation comprises (a) two bone anchoring mounts (9); (b) at least one plate (14; 15) having a central axis (16) where at least one plate (14; 15) is equipped with means (17) that seat the elements (5) connecting the two bone anchoring assemblies (9); and (c) means (18) for fixing the bone anchoring mounts (9) on the plates (14; 15), wherein (d) the two bone anchoring mounts (9) can be moved in the direction of the axis central (16). ^^ ^ Bj ^^ g | ^^^