FIXATION DEVICE FOR BONES

• US 20090030520A1
• Filed: 07/25/2008
• Published: 01/29/2009
• Est. Priority Date: 07/26/2007
• Status: Active Grant

• Current Assignee: Biedermann Technologies GmbH & Co. KG
• Original Assignee: Biedermann Technologies GmbH & Co. KG
• Inventors: Schwarzenbach, Othmar, Matthis, Wilfried, Biedermann, Lutz, Pabst, Martin
• Granted Patent: US 8,790,405 B2
• Time in Patent Office: Days
• US Class Current: 623/17.160
• CPC Class Codes: A61B 17/8033 having indirect contact with screw heads, or having contact with screw heads maintained with the aid of additional components, e.g. nuts, wedges or head covers
• CPC Class Codes: A61B 17/8042 the additional component being a cover over the screw head
• CPC Class Codes: A61B 17/8052 immobilised relative to screws by interlocking form of the heads and plate holes, e.g. conical or threaded
• CPC Class Codes: A61B 17/8605 Heads, i.e. proximal ends projecting from bone
• CPC Class Codes: A61F 2/4455 for the fusion of spinal bodies, e.g. intervertebral fusion of adjacent spinal bodies, e.g. fusion cages intervertebral discs A61F2/442
• CPC Class Codes: A61F 2/447 substantially parallelepipedal, e.g. having a rectangular or trapezoidal cross-section
• CPC Class Codes: A61F 2/4611 of spinal prostheses
• CPC Class Codes: A61F 2002/30593 hollow
• CPC Class Codes: A61F 2002/30774 internally-threaded
• CPC Class Codes: A61F 2002/30784 Plurality of holes
• CPC Class Codes: A61F 2002/30787 inclined obliquely with respect to each other
• CPC Class Codes: A61F 2002/3079 Stepped or enlarged apertures, e.g. having discrete diameter changes
• CPC Class Codes: A61F 2002/3082 Grooves
• CPC Class Codes: A61F 2002/30841 Sharp anchoring protrusions for impaction into the bone, e.g. sharp pins, spikes
• CPC Class Codes: A61F 2310/00023 Titanium or titanium-based alloys, e.g. Ti-Ni alloys

Abstract

A fixation device for bones includes a member which is to be fixed to one or more bones and has at least one bore for receiving a bone screw, wherein the at least one bore comprises a first internal thread portion. The bone screw has a first shaft section provided with a first external thread portion arranged to cooperate with the internal thread portion of the at least one bore, and a head section having a diameter larger than that of the shaft section to provide a catch arranged to engage with a stop formed in the bore. The bone screw further has a second shaft section which includes a clearance groove extending between the catch of the head section and the external thread of the first shaft section. The clearance groove allows disengagement of the two thread portions, such that the bone screw is prevented from being unscrewed off the bore when it is loosened within the adjacent bone. The member can also include a side wall of a cage used in an intervertebral implant device, or can represent a plate of a bone plate assembly.

Claims

1. A fixation device for bones, comprising:

a member configured to be fixed to one or more bones and has at least one bore for receiving a bone screw for insertion through the at least one bore into the bone, wherein the at least one bore comprises a first internal thread portion;

the bone screw having;

a first shaft section provided with a first external thread portion configured to cooperate with the internal thread portion of the at least one bore;

a head section having a diameter larger than that of the shaft section to provide a catch configured to engage with a stop formed in the at least one bore; and

a second shaft section comprising a clearance groove extending between the catch of the head section and the external thread of the first shaft section

wherein the member is an intervertebral implant comprising a device body having an upper face and a lower face for engaging with end plates of an upper vertebral body and a lower vertebral body, respectively, and a side wall including the at least one bore.

2. The fixation device according to claim 1, wherein the second shaft section of the bone screw has an outer diameter smaller than the inner diameter of the first internal thread portion of the at least one bore.

3. The fixation device according to claim 1, wherein the second shaft section comprising the clearance groove has a length substantially equal to a length of the first internal thread portion of the at least one bore.

4. The fixation device according to claim 1, wherein:

the external thread portion of the first shaft section comprises a helical projection;

a thread runout is provided at a transition between the external thread portion of the first shaft section and the clearance groove of the second shaft section; and

the helical projection provided at the thread runout is configured to abut on an end face of the device body surrounding an opening of the at least one bore, when the catch of the head section abuts on the stop formed within the at least one bore.

5. The fixation device according to claim 1, wherein the second shaft section comprising the clearance groove has an outer diameter smaller than an outer diameter of the first shaft section.

6. The fixation device according to claim 5, wherein the clearance groove of the second shaft section has an outer diameter equal to or larger than a diameter of a core portion of the first shaft section.

7. The fixation device according to claim 1, wherein the clearance groove of the second shaft section is non-threaded and has a substantially cylindrical shape.

8. The fixation device according to claim 1, wherein the at least one bore further has a cylindrical guiding portion extending adjacent to the stop and has a larger diameter than a diameter of the internal thread portion of the at least one bore in order to receive the head section of the bone screw.

9. The fixation device according to claim 1, wherein the member comprises three of said at least one bores associated with three of said bone screws.

10. The fixation device according to claim 9, wherein said three bores are arranged in a front wall forming part of the sidewall of the device body.

11. The fixation device according to claim 10, wherein the front wall is further connected to a back wall via two first arc-shaped vertical inner walls.

12. The fixation device according to claim 11, wherein a left side wall and a right side wall forming part of the sidewall are each connected with the back wall via two second arc-shaped inner walls.

13. The fixation device according to claim 12, wherein each one of the three bores opens toward a separate inner space of the device body, the inner spaces being open towards the end plates of the adjacent vertebral bodies and defined by one of:

(a) a space between the two first arc-shaped inner walls;

(b) a space between one of the two first arc-shaped inner walls and a left one of the two second arc-shaped inner walls; and

(c) a space between the other of the two first arc-shaped inner walls and a right one of the two second arc-shaped inner walls.

14. The fixation device according to claim 1, wherein the upper and lower faces of the device body are provided with small teeth configured to penetrate into the end plates of the adjacent vertebral bodies upon compression by to the bone screw being screwed into the adjacent vertebral bodies.

15. The fixation device according to claim 1, wherein the member is configured as an anterior lumbar interbody fusion device.

16. The fixation device according to claim 1, wherein the member is a plate.

17. A fixation device for bones, comprising:

a member configured to be fixed to one or more bones and comprising at least one bore for receiving a bone screw for insertion through the bore into the bone, wherein the at least one bore comprises a first internal thread portion and a cylindrical guiding portion adjacent to the internal thread portion;

the bone screw having;

a shaft section provided with a first external thread portion configured to cooperate with the internal thread portion of the at least one bore; and

a head section having a larger diameter than a diameter of the shaft section to provide a catch configured to engage with a stop formed in the at least one bore, and comprising a second external thread portion configured to cooperate with the first internal thread portion and, after screwing-in of the bone screw into the at least one bore, to be received by the cylindrical guiding portion when the catch engages with the stop.

18. A Method of implanting an intervertebral implant device between two adjacent vertebral bodies, comprising:

inserting a device body between the two adjacent vertebral bodies, the device body having an upper face and a lower face for engaging with an end plate of an upper and a lower vertebral body, respectively, a side wall, and at least one bore formed in the side wall for receiving a bone screw and the at least one bore further comprising a first internal thread portion;

attaching the bone screw to the at least one bore, the bone screw having a first shaft section comprising a first external thread portion configured to cooperate with the internal thread portion of the at least one bore, a head section having a diameter larger than that of the shaft section to provide a catch configured to engage with a stop formed in the bore, and a second shaft section comprising a clearance groove extending between the catch of the head section and the external thread portion of the first shaft section;

screwing the bone screw such that the external thread portion is screwed through the internal thread portion until (a) the catch abuts the stop, and (b) the external thread portion and the internal thread portion disengage from each other due to the clearance groove, in order to compress the device body towards the adjacent vertical bodies; and

applying a further screwing movement of the bone screw to protect the bone screw against loosening.

19. A method of attaching a fixation device to a bone, the fixation device comprising a member configured to be fixed to one or more bones and has at least one bore for receiving a bone screw for insertion through the at least one bore into the bone, wherein the at least one bore comprises a first internal thread portion, the bone screw having a first shaft section provided with a first external thread portion configured to cooperate with the internal thread portion of the at least one bore, a head section having a diameter larger than that of the shaft section to provide a catch configured to engage with a stop formed in the at least one bore, and a second shaft section comprising a clearance groove extending between the catch of the head section and the external thread of the first shaft section, wherein the member is an intervertebral implant comprising a device body having an upper face and a lower face for engaging with end plates of an upper and lower vertebral bodies, respectively, and a side wall including the at least one bore, the method comprising:

inserting the bone screw through the at least one bore by screwing the external thread portion of the first shaft in the first internal thread portion of the at least one bore;

screwing the bone screw into a vertebrae to a first position until the catch abuts the stop, wherein the first external thread portion disengages from the first internal thread portion;

screwing the bone screw further into the vertebrae to a second position;

wherein engagement of the first external thread portion with the first internal thread portion is prevented when unscrewing the bone screw from the second position toward the first position.

20. The method according to claim 19, further comprising:

inserting a second bone screw through a second bore of the member by screwing an external thread portion of a first shaft of the second bone screw in a first internal thread portion of the second bore;

screwing the second bone screw into an adjacent vertebrae to a first position until a catch of the second bone screw abuts a stop of the second bore, wherein the first external thread portion of the second bone screw disengages from the first internal thread portion of the second bore;

screwing the second bone screw further into the adjacent vertebrae to a second position;

wherein engagement of the first external thread portion of the second bone screw with the first internal thread portion of the second bore is prevented when unscrewing the second bone screw from the second position toward the first position.