US20140222079A1 - Bone anchoring device - Google Patents

Abstract

A bone anchoring device includes a bone anchoring element having a shaft to be anchored in the bone and a head, a receiving part for receiving a rod to be connected to the bone anchoring element, and a pressure member acting onto the head to lock the position of the head relative to the receiving part, the receiving part is formed in one piece and includes an open first bore with a first bore axis, a recess shaped and sized to receive a rod having a longitudinal axis, and a second bore having a second bore axis. The second bore is in communication with the first bore and is sized to receive the head with a part of the shaft extending through the second bore. The second bore axis includes an angle of approximately 90° with a plane defined by the first bore axis and the longitudinal axis of the rod.

Description

CROSS-REFERENCE TO RELATED APPLICATION(S)
• This application is a continuation of U.S. patent application Ser. No. 11/697,220, filed Apr. 5, 2007, which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/790,084, filed Apr. 6, 2006, and claims priority from European Patent Application EP06007324.4, filed Apr. 6, 2006, the entire disclosures of which are incorporated herein by reference.
BACKGROUND
• The invention relates to a bone anchoring device in particular to a bone anchoring device which can be used for stabilization of the spine in the sacro-iliac region.
• Stabilization of the spine in the sacro-iliac region requires in certain constellations that the bone screw which is to be connected with the spinal stabilization rod is screwed laterally into the bone.
• U.S. Pat. No. 6,981,973 discloses a low profile vertebral alignment/fixation assembly which comprises a hemispherical headed pedicel screw disposed within a slotted coupling unit designed to allow angular adjustment of the pedicle screw up to 90° and which may be locked into position via a single internal locking nut once a rod has been inserted into the slotted coupling unit. The nut has an engagement portion designed to engage the rod. The head of the screw is locked by the action of the rod pressing onto the head. The assembly can be anchored in the ileum bone with the screw aligned at a 90° angle with reference to the coupling unit.
• US 2005/0159750 A1 discloses a bone anchor assembly comprising a bone anchor and a receiving member for receiving a spinal rod. The bone anchor can be adjusted in the receiving member such that the longitudinal axis of the bone anchor is at an angle of 0° to 90° relative to the receiving member in a plane which contains the longitudinal axis of the spinal rod. A main application of this anchor assembly is the stabilization of the cervical spine where it can be necessary to pivot the bone anchors out of an alignment to avoid interference due to their close proximity.
• US 2005/0154391 A1 discloses a bone anchor assembly comprising a bone anchor and a receiving member to receive a spinal rod. The receiving member has a first section and a second section which is coupled to the bone anchor. The second section is movably connected to the first section. The bone anchor may be adjusted such that the longitudinal axis of the bone anchor is at an angle of 0° to 90° relative to the receiver member.
• U.S. Pat. No. 6,736,820 discloses a bone screw having a screw member with a threaded section and a head and a receiving part for receiving a rod to be connected to the bone screw. The receiving part has an open first bore and a substantially U-shaped cross-section to receive the rod and a second bore on the opposite end with a seat for the head. In order that the screw member can be pivoted to at least one side by an enlarged angle, the edge bounding the free end of the second bore is of asymmetric construction.
• US 2003/0055426 A1 discloses a biased angulation bone fixation assembly including and anchoring element and a coupling element having a first bore coaxial with a first longitudinal axis and a second bore coaxial with a second longitudinal axis wherein said first and second longitudinal axes are transverse to one another. The coupling element also includes rod receiving openings for receiving a spinal rod.
• Based on the above, there is a need to provide an improved bone anchoring device which allows a lateral fixation of the bone anchoring element in the bone, e.g., at an angle of at least 90° relative to the receiving part in a plane perpendicular to the longitudinal axis of the spinal rod which is suitable for use in the sacro-iliac region of the spine.
SUMMARY
• The bone anchoring element of the disclosed bone anchoring device is compact with few parts and provides a reliable fixation.
• The bottom of the receiver part and the surface of the pressure element which contacts the head of the bone anchoring element preferably have a spherical surface which correspond to the spherical section of the surface of the head. This provides for a balanced clamping stress to clamp the head. As a result, the clamping stress onto the head can be reduced.
• The bone anchoring device has a further advantage in that it allows to orient the screw relative to the receiving part at an angle which is greater than 90°.
• Further features and advantages of the invention will become apparent and will be best understood by reference to the following detailed description of embodiments taken in conjunction with the accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 shows an exploded perspective view of a first embodiment of the bone anchoring device.
• FIG. 2 shows a sectional view of the bone anchoring device ofFIG. 1 in an assembled state.
• FIG. 3 shows a side view of the bone anchoring device ofFIG. 1 in an assembled state.
• FIG. 4 shows a top view of a spinal stabilization system which includes the bone anchoring device according to the invention.
• FIG. 5 shows an exploded cross-sectional view of the bone anchoring device according to a second embodiment.
• FIGS. 6ato6cshow cross-sectional views of different steps of assembly of the bone anchoring device according toFIG. 5.
• FIG. 7 shows a side view of the bone anchoring device according toFIG. 5 in an assembled state.
• FIG. 8 shows a side view rotated by 180° of the bone anchoring device according toFIG. 5 in an assemble state.
• FIG. 9 is a sectional view of a bone anchoring device according to a third embodiment.
• FIG. 10 is a rear side view showing the bone anchoring device of the third embodiment.
• FIG. 11 is a perspective view of the bone anchoring element of the third embodiment.
DETAILED DESCRIPTION
• Thebone anchoring device1 according to a first embodiment shown inFIGS. 1 to 3 comprises ascrew member2 having a threadedshaft3 and ahead4 which is preferably shaped as a spherical segment, and a receivingpart5 for receiving arod100 to be connected with thescrew member2. Thehead4 has arecess4′ at its free end for engagement with a screwing-in tool. Thereceiving part5 has afirst end6 and an oppositesecond end7 andfirst bore8 being open to thefirst end6 and defining afirst bore axis9. The receivingpart5 further has a substantially U-shaped recess10 defining two free legs for receiving therod100 in-between. Aninternal thread11 is provided at the legs.
• Thereceiving part5 further comprises asecond bore12 having asecond bore axis13, thesecond bore12 being in communication with thefirst bore8 and being open to a lateral side of thereceiving part5 between thefirst end6 and thesecond end7. Thesecond bore axis13 intersects thefirst bore axis9 at an angle α of approximately 90°±12°, preferably slightly less than 90°, for example, 85°. The angle α is measured from the bottom of thereceiving part5. The diameter of thesecond bore12 is smaller than the largest diameter of thehead4 but larger than the diameter of the threadedshaft3 of thescrew member2. Adjacent to the outer wall of the receivingpart5 thesecond bore12 comprises asection14 with an increasing diameter in the direction of the outer wall. The diameter may increase, for example, in the shape of a conical section widening towards the outer wall. At the bottom of the receivingpart5 at the second end7 aseat15 is provided in which a part of thehead4 can rest. Preferably, theseat15 has a spherical shape which is adapted to the spherical outer surface of thehead4.
• Furthermore, thereceiving part5 comprises athird bore16 having athird bore axis17, thethird bore16 being in communication with thefirst bore8 and being open to the lateral side of thereceiving part5 between thefirst end6 and thesecond end7 which is opposite to thesecond bore12. Preferably, thethird bore axis17 is coaxial with thesecond bore axis13 of thesecond bore12. The diameter of thethird bore17 is larger than the largest diameter of thehead4 and thus larger than the diameter of the threadedshaft3. Since thethird bore16 is in communication with thefirst bore8 it is also in communication with thesecond bore12.
• Thebone anchoring device1 further comprises apressure element20 which has a substantially cylindrical outer surface with a largest diameter which is smaller than the inner diameter of thefirst bore8 to such an extent that thepressure element20 can move within thefirst bore8. On its side facing thefirst end7 thepressure element20 comprises aspherical recess21 the shape of which is adapted to the spherical surface of thehead4. On its opposite side thepressure element20 comprises a cylindrical recess shaped and sized to receive a part of therod100 when therod100 is inserted. Further, thepressure element20 comprises, on opposite sides of the cylinder axis of thecylindrical recess22 at the end which has thespherical recess22, cut-outs23 for allowing a pivoting of the threadedshaft3 when thehead4 of thescrew member2 is partly encompassed by thepressure element20. As can be seen inFIG. 3 the cut-outs23 have such a size so as to allow access to therecess4′ of thehead4 of thescrew member2 even if thebone anchoring device1 is in an assembled state.
• Thebone anchoring device1 also comprises a lockingscrew25 with an external thread cooperating with theinternal thread11 of the receivingpart5.
• The dimension of thepressure element20 is such that in an assembled state when thescrew member2 is inserted into the receivingpart5 and therod100 is inserted into thepressure element20 and when the lockingscrew25 is not yet tightened, the bottom of thecylindrical recess22 of thepressure element20 projects above the bottom of the U-shaped recess of the receivingpart5.
• Thebone anchoring device1 is assembled by first introducing the threadedshaft3 through thethird bore16 and thesecond bore12 which is in communication with thethird bore16 until thehead4 rests in theseat15. Then thepressure element20 is moved so as to engage the part of thespherical segment head4 with itsspherical recess21. Thebone anchoring device1 may be preassembled in such a manner before it is used in surgery.
• In use, first, thescrew member2, which is preassembled with the receivingpart5 and thepressure element20, is screwed into the bone by engaging therecess4′ of thehead4 with a screwing-in tool reaching through thethird bore16. Thefirst bore axis9 encloses with the longitudinal axis of thescrew member2 an angle which can be approximately at least α±10° which depends on the size of the diameter of thesecond bore12 and the size of thesection14 having the increasing diameter. Similarly, the longitudinal axis of thescrew member2 can include an angle of ±10° with an axis which is perpendicular to thefirst bore axis9 and perpendicular to the longitudinal axis L of therod100. Hence, thescrew member2 can be pivoted in an angular range of ±10° within a cone around thesecond bore axis13, the angular range depending on the size of thesecond bore12 and of thesection14.
• Once therod100 is inserted and the angular position between thescrew member2 and the receivingpart5 adjusted, the lockingscrew25 is screwed-in which presses onto therod100 to fix therod100 and simultaneously presses onto thepressure member20 via therod100 to lock thehead4 of thescrew2 in its position.
• FIG. 4 shows the application of the bone anchoring device I in a stabilization system in the sacro-iliac region of the spine. A plurality of known anchoringdevices101 are each connected with arod100. Therods100 of the stabilization system extend into the region of thesacrum50.Bone anchoring devices1 according to the invention are used for sacro-iliac fixation. For this purpose, it is necessary that thescrew members2 extend at an angle of approximately 90° from the plane which comprises the longitudinal rod axis L and thefirst bore axis9. Thescrew member2 can pivot with respect to the second bore axis within an angular range of ±10° as described above.
• FIGS. 5 to 8 show a second embodiment of the bone anchoring device. The bone anchoring device of the second embodiment differs from the bone anchoring device of the first embodiment in the construction of the second and third bore of the receiving part. All other parts are identical to the first embodiment and have the same reference numerals as in the first embodiment. A description thereof is not repeated. The receivingpart500 comprises asecond bore120 which is in communication with thefirst bore8 and which defines asecond bore axis130. As in the first embodiment thesecond bore120 is open to the lateral side of the receivingpart500 and thesecond bore axis130 extends at an angle of approximately 90° from the plane defined by the longitudinal axis of therod100 and thefirst bore axis9. The diameter of thesecond bore120 is larger than the largest diameter of thehead4 of thescrew member2 such that thehead4 of thescrew member2 can be introduced into the receivingpart500 through thesecond bore120 until thehead4 rests in theseat15 on the bottom of the receivingpart500. On the side opposite to the second bore120 athird bore160 is provided which is in communication with thefirst bore8 and which defines athird bore axis170. Thethird bore axis170 is preferably coaxial with thesecond bore axis130. Thethird bore160 is open to the lateral side and has a diameter which is at least as large so that a screwing-in tool can be introduced for engagement with therecess4′ of thehead4 but the diameter is smaller than the largest diameter of thehead4 so that thescrew member2 can not escape through thethird bore160. Since thethird bore160 is in communication with thefirst bore8 it is also in communication with thesecond bore120.
• Thebone anchoring device1 is preassembled as shown inFIGS. 6aand6bin that thescrew member2 is introduced with itshead4 through thesecond bore120 until thehead4 rests in theseat15. Then, in use, thescrew member2 is screwed into the bone by introducing a screwing-in tool which engages therecess4′ of the head through thethird bore160. Thereafter, the angular position of thescrew member2 relative to the receivingpart500 is adjusted, the rod is inserted and the device is locked by screwing-in thescrew25.
• In an alternative use, thescrew member2 can be screwed into the bone and the receivingpart500 can be later on connected to thescrew member2 by introducing the head of the screw member through thesecond bore120 into the receivingpart500.
• FIGS. 9 to 11 show a bone anchoring device according to a third embodiment. The bone anchoring device differs from the bone anchoring device according to the first embodiment only in the design of the bone anchoring element. The receivingpart5 is identical. Thebone anchoring element200 comprises a threadedshaft3 and ahead400. On its side opposite to the threadedshaft3 thehead400 comprises a hexagonally-shapedprojection401 for engagement with a tool which can be introduced through thethird bore16. This has the advantage that thehead400 can be made as a solid sphere or spherical segment without a recess. Theprojection401 can have any shape which is appropriate for engagement with a tool. In a further modification theprojection401 itself has a recess for engagements with a tool.
• Modifications of the invention are possible, for example, in the case of the second embodiment when thescrew member2 is screwed-in into the bone first, and thereafter connected to the receivingpart500, it may be possible to omit thethird bore160. The size of the second bore may vary in order to allow pivoting of the bone screw member relative to the receiving part in an enlarged or in a reduced angular range. Thecut outs23 at the pressure element may be omitted, as long as it is possible to access the screw head with a tool. Alternatively, only one cut out is provided.
• For the purpose of preassembly, it is possible to connect thepressure element20 with the receiving part via crimp bores.
• Theseat15 needs not to have a spherical shape, it can have another shape or be flat. For the closure mechanism other mechanisms than those using a single locking screw are possible. For example, a locking assembly consisting of a rod locking screw and a head locking nut-like element are possible. A pressure element in this case has upstanding legs projecting above the rod so that the pressure element can be pressed down independently of the rod.
• The shaft need not to be threaded but can have any other shape and structure which allows retention in the bone. The pressure element can also be shaped as a flat disc.
• While a particular form of the disclosure has been illustrated and described, it will be apparent that various modifications can be made without departing from the spirit and scope of the disclosure. Accordingly, it is not intended that the disclosure be limited, except as by the appended claims.

Claims (4)

1-17. (canceled)

18. A bone anchoring device comprising:

a bone anchoring element having a shaft and a head;

a rod having a longitudinal axis; and

a receiving part configured to connect to the bone anchoring element, the receiving part comprising:

an open first bore with a first bore axis, the first bore defining a recess configured to receive the rod;

a second bore having a second bore axis, the second bore being in communication with the first bore and configured to receive the head with a part of the shaft extending through the second bore;

wherein the second bore axis lies in a different plane than a plane defined by the first bore axis and the longitudinal axis of the rod.

19. The bone anchoring device according toclaim 18, further comprising a pressure member acting onto the head to lock the position of the head relative to the receiving part.

20-23. (canceled)

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