Expandable anterior lumbar implants
Expandable fusion devices, systems, and methods thereof. The expandable fusion implant may include upper and lower endplates configured to engage adjacent vertebrae and an actuator assembly for expanding the upper and lower endplates to independently control anterior and posterior heights of the implant. The actuator assembly may be operated in two modes: (1) to force the upper and lower endplates apart resulting in parallel expansion; and (2) to increase the anterior height of the implant resulting in an increase in lordotic angle.
1. An expandable implant comprising:
an upper endplate and a lower endplate configured to engage adjacent vertebrae; and
an actuator assembly extending along a longitudinal axis of the implant and positioned between the upper and lower endplates for expanding the upper and lower endplates to independently control anterior and posterior heights of the implant, the actuator assembly including a moveable anterior actuator, a moveable posterior actuator, a stationary posterior actuator, an actuator screw threaded into an anterior actuator nut located in the moveable anterior actuator, and a posterior actuator nut located in the stationary posterior actuator, wherein the actuator screw threads through the moveable posterior actuator to translate the moveable posterior actuator,
wherein the upper and lower endplates each define a plurality of ramps configured to mate with corresponding male protrusions on the moveable anterior actuator and the moveable and stationary posterior actuators, wherein the male protrusions on the moveable anterior actuator and the moveable and stationary posterior actuators include point contact pivoting ramps defined thereon which act as a pivot point, facilitating pivoting or rotational movement for a lordotic angle adjustment between the upper and lower endplates,
wherein when the actuator screw and the anterior actuator nut are turned together, the moveable posterior actuator moves toward the stationary posterior actuator, forcing the upper and lower endplates apart resulting in parallel expansion, and when only the anterior actuator nut is turned, the moveable anterior actuator moves alone to increase the anterior height, resulting in an increase in a lordotic angle of the implant.
2. The expandable implant of claim 1 , wherein the ramps on the upper and lower endplates include female T-slots.
3. The expandable implant of claim 1 , wherein the moveable anterior actuator includes a laterally extending body with an enlarged central portion defining a non-threaded bore and opposing free ends defining an irregular cross-sectional shape.
4. The expandable implant of claim 1 , wherein the moveable posterior actuator includes a laterally extending body defining a threaded bore with a flat anterior face and an opposite posterior face.
5. The expandable implant of claim 1 , wherein the stationary posterior actuator includes a laterally extending body defining a non-threaded bore with an anterior face.
6. The expandable implant of claim 1 , wherein the actuator screw includes a shaft having a single type of thread profile along its length and a reduced diameter at its distal end for threading into the posterior actuator nut, wherein the single type of thread profile is used to achieves both parallel and lordotic expansion.
7. An expandable implant comprising:
an upper endplate and a lower endplate configured to engage adjacent vertebrae; and
an actuator assembly extending along a longitudinal axis of the implant and positioned between the upper and lower endplates for expanding the upper and lower endplates to independently control anterior and posterior heights of the implant, the actuator assembly including a moveable anterior actuator receiving and securing a plurality of anterior pivot ramps, a moveable posterior actuator, a stationary posterior actuator engaged with upper and lower posterior pivot ramps, and an actuator screw threaded into an anterior actuator nut located in the moveable anterior actuator, and a posterior actuator nut located in the stationary posterior actuator, wherein the actuator screw threads through the moveable posterior actuator to translate the moveable posterior actuator,
wherein each anterior pivot ramp has a smooth inner surface to allow each anterior pivot ramp to rotate on the moveable anterior actuator,
wherein the upper and lower endplates each define a plurality of ramps configured to mate with corresponding ramped surfaces on the anterior pivot ramps and the upper and lower posterior pivot ramps,
wherein when the actuator screw and the anterior actuator nut are turned together, the moveable posterior actuator moves toward the stationary posterior actuator, forcing the upper and lower posterior pivot ramps outward resulting in parallel expansion of the upper and lower endplates, and when only the anterior actuator nut is turned, the moveable anterior actuator moves alone to increase the anterior height, resulting in an increase in a lordotic angle of the implant.
8. The expandable implant of claim 7 , wherein each anterior pivot ramp has a ring received on the moveable anterior actuator and a foot comprising the ramped surface configured to mate with the respective ramps on the upper and lower endplates.
9. The expandable implant of claim 8 , wherein each foot is a male projection extending from one side of the ring, and each ramp on the upper and lower endplates is female recess configured to receive the respective male projection of the foot.
10. The expandable implant of claim 8 , wherein the moveable anterior actuator includes a laterally extending body with an enlarged central portion defining a non-threaded bore and opposing free ends defining cylindrical ends.
11. The expandable implant of claim 10 , wherein each anterior pivot ramp is configured to rotate on the cylindrical ends of the moveable anterior actuator.
12. The expandable implant of claim 7 , wherein the upper and lower posterior pivot ramps each include left and right sections positioned on opposite sides of the actuator screw.
13. The expandable implant of claim 7 , wherein the upper and lower posterior pivot ramps each include a laterally extending body with a bell-shaped cross section having a tapered end and a flared end.
14. The expandable implant of claim 13 , wherein the flared end of the upper and lower posterior pivot ramps includes a lateral rib having a circular cross section configured to pivot in a corresponding channel in the upper and lower endplates.
15. A method of spinal fixation comprising:
inserting an expandable intervertebral implant into a disc space between adjacent vertebrae, the expandable implant comprising upper and lower endplates each configured to engage one of the adjacent vertebrae and an actuator assembly extending along a longitudinal axis of the implant and positioned between the upper and lower endplates for expanding the upper and lower endplates to independently control anterior and posterior heights of the implant, the actuator assembly including a moveable anterior actuator, a moveable posterior actuator, a stationary posterior actuator, an actuator screw threaded into an anterior actuator nut located in the moveable anterior actuator, and a posterior actuator nut located in the stationary posterior actuator,
wherein the actuator screw threads through the moveable posterior actuator to translate the moveable posterior actuator,
wherein the upper and lower endplates each define a plurality of ramps configured to mate with corresponding male protrusions on the moveable anterior actuator and the moveable and stationary posterior actuators, wherein the male protrusions on the moveable anterior actuator and the moveable and stationary posterior actuators include point contact pivoting ramps defined thereon which act as a pivot point, facilitating pivoting or rotational movement for a lordotic angle adjustment between the upper and lower endplates;
and
expanding the implant in height by:
(1) rotating the actuator screw and the anterior actuator nut together to move the moveable posterior actuator toward the stationary posterior actuator, thereby forcing the upper and lower endplates apart resulting in parallel expansion; or
(2) rotating only the anterior actuator nut to move the moveable anterior actuator alone to increase the anterior height, resulting in an increase in a lordotic angle of the implant.
16. The method of claim 15 , further comprising inserting bone anchors through sockets in the upper and lower endplates and into the adjacent vertebrae.
17. The method of claim 16 , further comprising inserting blocking screws through holes in the upper and lower endplates and rotating the blocking screws in the upper and lower endplates to cover the bone anchors and prevent the bone anchors from backing out.