Methods and apparatus for intervertebral disc prosthesis insertion
A method for inserting an intervertebral disc prosthesis into a space between two vertebrae involves inserting the prosthesis partway into the space under constraint to prevent endplates of the prosthesis from articulating, releasing the prosthesis from constraint, and inserting the unconstrained prosthesis farther into the space. In some embodiments, the method involves grasping the prosthesis with a grasping device to insert the prosthesis partway under constraint, loosing the grasping device to release the prosthesis from constraint, and pushing the prosthesis farther into the disc space using the grasping device and/or one or more separate pusher devices. A system includes a grasping device, at least one separate pushing device, and optionally a vertebral spreading device and/or a vertebral midline indicator device.
1. A method of inserting an intervertebral prosthesis into a space between two adjacent vertebrae, the method comprising:
providing an intervertebral prosthesis having first and second endplates which articulate with respect to one another;
inserting the prosthesis partway into the space with the first and second endplates attached to an insertion tool; and
pushing the prosthesis farther into the space by individually pushing upper and lower endplates of the prosthesis in a stepwise manner.
2. A method as in claim 1 , wherein the prosthesis comprises a core disposed between the first and second endplates and the endplates of the prosthesis are prevented from articulating about the core of the prosthesis when attached to the insertion tool, and wherein the endplates of the prosthesis are free to articulate about the core to help the prosthesis conform to the space between the two vertebrae once detached from the insertion tool.
3. A method as in claim 1 , wherein inserting the prosthesis partway into the space comprises: grasping the endplates with the insertion tool such that they cannot move relative to one another; and pushing the prosthesis partway into the space using the insertion tool.
4. A method as in claim 1 , wherein the prosthesis is released from the insertion tool by loosening the insertion tool prior to pushing the prosthesis farther into the space.
5. A method as in claim 4 , wherein pushing the prosthesis farther into the space is performed using the loosened insertion tool.
6. A method as in claim 4 , wherein inserting the prosthesis farther into the space is performed using a separate pusher tool.
7. A method as in claim 1 , wherein inserting the prosthesis partway comprises inserting the prosthesis less than halfway into the space.
8. A method as in claim 1 , wherein the prosthesis is inserted in approximately an anterior-to-posterior direction.
9. A method as in claim 1 , wherein the prosthesis is inserted in approximately a lateral-to-lateral direction.
10. A method as in claim 1 , wherein the prosthesis is inserted in an anterolateral-to-posterior direction.
11. A method as in claim 1 , wherein pushing the prosthesis farther into the space comprises positioning a center of rotation of the prosthesis closer to posterior edges of the two vertebrae than to anterior edges of the vertebrae.
12. A method as in claim 1 wherein inserting the prosthesis farther into the space comprises sliding at least one fin on the endplate(s) into at least one corresponding slot formed in one of the vertebrae.
13. A method as in claim 1 , wherein the endplates of the prosthesis are unconnected parts.
14. A method as in claim 1 , wherein insertion tool is detached from the prosthesis prior to pushing the prosthesis farther into the space.
15. A method as in claim 1 , wherein the prosthesis is attached to the insertion tool by grasping the first and second endplates with movable opposing jaws.
16. A method as in claim 1 , wherein the prosthesis is inserted partway into the space while the prosthesis is constrained.