Unidirectional dynamic interbody fusion device and method of use

1. A method of using an interbody fusion device, comprising:

preparing a space between two adjacent vertebral bodies;

obtaining an interbody fusion device, wherein the interbody fusion device comprises:

a top member having a first bone-engaging surface and a threaded opening;

a base member received by the top member, the base member having a second bone-engaging surface and an open cavity aligned with the threaded opening of the top member;

an expansion member disposed within the open cavity for rotation about an axis, the expansion member having a threaded portion configured to threadably engage with the threaded opening and a central bore to maintain an opening through the threaded opening in the first bone-engaging surface through the open cavity in the second bone-engaging surface; and

a support ring coupled to the base member within the open cavity, the support ring configured to retain the expansion member within the base member in a fixed position along the axis relative to the second bone-engaging surface;

wherein the expansion member further comprises a gear portion and a radially extending portion disposed between the gear portion and the threaded portion, the radially extending portion disposed adjacent the support ring; and

using an expansion tool to move the top member in a direction relative to the base member, wherein the support ring is positioned in a notch inset into the base member to secure the top member within the base member.

2. The method of claim 1 , wherein the gear portion includes a first side and a second side with the first side having a plurality of gear teeth and the second side being in contact with the base member.

3. The method of claim 1 , wherein the gear portion includes a plurality of axially extending gear teeth.

4. The method of claim 3 , wherein the base member includes a tool insertion opening in communication with the open cavity.

5. The method of claim 4 , wherein the method further comprises:

obtaining the expansion tool, the expansion tool comprising a handle, a shaft having a first end and a second end, wherein the first end is connected to the handle and the second end is configured for engagement with the expansion member.

6. The method of claim 5 , wherein the method further comprises:

inserting the expansion tool into the tool insertion opening and engaging the second end of the expansion tool with the expansion member.

7. The method of claim 6 , wherein using the expansion tool to move the top member in a direction relative to the base member comprises:

rotating the expansion tool to move at least one of the first bone-engaging surface or second bone-engaging surface.

8. The method of claim 7 , wherein the first bone-engaging surface includes at least one first through hole, and the second bone-engaging surface includes at least one second through hole aligned with the at least one first through hole.

9. The method of claim 7 , wherein using the expansion tool to move the top member in a direction relative to the base member comprises:

rotating the expansion member about a first axis extending transverse to the first bone-engaging surface and the second bone-engaging surface;

threadably engaging the expansion member with the threaded opening of the top member; and

translating the first bone-engaging surface away from the second bone-engaging surface along the first axis to contact the two adjacent vertebral bodies.

10. The method of claim 9 , wherein the expansion tool is rotated about a second axis that is transverse to the first axis to rotate the expansion member.

11. The method of claim 1 , wherein the method further comprises:

inserting the interbody fusion device into the space.

12. The method of claim 1 , wherein the support ring is non-threaded.

13. A surgical method for maintaining a space between two vertebral bodies in a spine, the method comprising:

obtaining a movable interbody implant, the implant comprising:

a top member having a superior bone-engaging side and a threaded opening;

a base member configured to be received by the top member, the base member having an expansion tool opening, an inferior bone-engaging side and an open cavity in communication with the threaded opening of the top member and expansion tool opening;

an expansion member positioned within the open cavity for rotation about an axis extending transverse to the superior and inferior bone-engaging sides, the expansion member having a threaded portion threadably engaged with the threaded opening and a central bore to maintain an opening through the threaded opening in the superior bone-engaging side through the open cavity in the inferior bone-engaging side, and

a support ring coupled to a notch inset into the base member within the open cavity, the support ring configured to retain the expansion member within the base member in a fixed position along the axis relative to the inferior bone-engaging side,

wherein rotation of the expansion member moves the top member relative to the base member along the axis, while the support ring maintains the fixed position of the expansion member relative to the inferior bone-engaging side along the axis;

inserting the movable interbody implant into a space between two vertebral bodies.

14. The surgical method of claim 13 , wherein the method further comprises:

expanding the movable interbody implant by rotating the expansion member about the axis until the superior bone-engaging side and inferior bone-engaging side pressingly contact the two vertebral bodies.

15. A surgical method for maintaining a space between two bones, the method comprising:

obtaining a movable surgical implant, the implant comprising:

a top member having a first bone-engaging side and a threaded opening;

a base member received by the top member, the base member having a second bone-engaging side and an open cavity in communication with the threaded opening of the top member;

an expansion member secured within the open cavity for rotation about an axis extending transverse to the first and second bone-engaging sides, the expansion member having a threaded portion threadably engaged with the threaded opening and a central bore to maintain an opening through the threaded opening in the first bone-engaging side through the open cavity in the second bone-engaging side, and

a support ring fixed to the base member within the open cavity, the support ring configured to secure the expansion member within the base member in a fixed position along the axis relative to the second bone-engaging side,

wherein rotation of the expansion member translates the top member relative to the base member along the axis;

wherein the support ring is configured to be snapped into a notch in the base member within the open cavity to retain the expansion member within the base member; and

wherein the expansion member further comprises a first end opposite the threaded portion, and a radially extending portion disposed between the first end and the threaded portion, the radially extending portion disposed adjacent the support ring; and

using an expansion tool to move the top member in a direction relative to the base member.

16. The surgical method of claim 15 , wherein using an expansion tool to move the top member in a direction relative to the base member comprises:

inserting the movable surgical implant into a space between two bones; and

enlarging the movable surgical implant by rotating the expansion member about the axis until the first bone-engaging side and second bone-engaging side pressingly contact the two bones.

17. The method of claim 15 , wherein the support ring is non-threaded.