Expandable intervertebral implant and associated surgical method

1. An expandable intervertebral implant, comprising:

a superior member configured to engage a superior intervertebral body;

an inferior member configured to engage an inferior intervertebral body; and

an expansion mechanism disposed between the superior member and the inferior member configured to selectively adjust a vertical separation of the superior member from the inferior member;

wherein the expansion mechanism comprises a proximal wedge structure and a distal wedge structure that are relatively translated between the superior member and the inferior member, wherein the proximal wedge structure and the distal wedge structure are each coupled to the superior member and the inferior member by track structures and rail structures;

wherein a load-bearing portion of a bottom surface of the superior member is configured to mate vertically with a load-bearing portion of a top surface of the inferior member when the expansion mechanism is undeployed via conformal protruding and recessed features; and

wherein the superior member and the inferior member each comprise a pair of rails, wherein the rails of the superior member are horizontally offset in the same direction from the rails of the inferior member such that each rail of the superior member is disposed substantially side-by-side horizontally adjacent to a respective one of the rails of the inferior member when the expandable vertebral implant is in an unexpanded configuration, and wherein one rail of the superior member is disposed between an associated rail of the inferior member and a central axis of the implant and another rail of the inferior member is disposed between the associated rail of the superior member and the central axis of the implant in the unexpanded configuration.

2. The expandable intervertebral implant of claim 1 , wherein one or more track structures and rail structures associated with a top surface of the distal wedge structure are offset horizontally with respect to one or more track structures and rail structures associated with a bottom surface of the distal wedge structure.

3. The expandable intervertebral implant of claim 1 , wherein one or more track structures and rail structures associated with a top surface of the proximal wedge structure are offset horizontally with respect to one or more track structures and rail structures associated with a bottom surface of the proximal wedge structure.

4. The expandable intervertebral implant of claim 1 , wherein the expansion mechanism further comprises an actuation bolt that passes through the proximal wedge structure and is coupled to the distal wedge structure and causes the wedge structures to relatively translate when rotated.

5. The expandable intervertebral implant of claim 4 , further comprising a ratcheting structure disposed between a head portion of the actuation bolt and the proximal wedge structure of the expansion mechanism, wherein the ratcheting structure is configured to resist rotation of the actuation bolt with respect to the proximal wedge structure of the expansion mechanism.

6. The expandable intervertebral implant of claim 1 , wherein the superior member and the inferior member each comprise a plurality of ramp structures.

7. The expandable intervertebral implant of claim 6 , wherein the superior member comprises a ramp structure that engages the proximal wedge structure and a ramp structure that engages the distal wedge structure.

8. The expandable intervertebral implant of claim 6 , wherein the inferior member comprises a ramp structure that engages the proximal wedge structure and a ramp structure that engages the distal wedge structure.

9. The expandable intervertebral implant of claim 1 , further comprising an elongate arm structure protruding from the superior member engaging a corresponding recess of the inferior member and an elongate arm structure protruding from the inferior member and engaging a corresponding recess of the superior member.

10. The surgical method of claim 5 , wherein the expandable intervertebral implant further comprises an elongate arm structure protruding from the superior member engaging a corresponding recess of the inferior member and an elongate arm structure protruding from the inferior member and engaging a corresponding recess of the superior member.

11. A surgical method, comprising:

providing an expandable intervertebral implant, comprising:

a superior member configured to engage a superior intervertebral body;

an inferior member configured to engage an inferior intervertebral body; and

an expansion mechanism disposed between the superior member and the inferior member configured to selectively adjust a vertical separation of the superior member from the inferior member;

wherein the expansion mechanism comprises a proximal wedge structure and a distal wedge structure that are relatively translated between the superior member and the inferior member, wherein the proximal wedge structure and the distal wedge structure are each coupled to the superior member and the inferior member by a plurality of track structures and rail structures;

wherein a load-bearing portion of a bottom surface of the superior member is configured to mate vertically with a load-bearing portion of a top surface of the inferior member when the expansion mechanism is undeployed via conformal protruding and recessed features; and

wherein the superior member and the inferior member each comprise a pair of rails, wherein the rails of the superior member are horizontally offset in the same direction from the rails of the inferior member such that each rail of the superior member is disposed substantially side-by-side horizontally adjacent to a respective one of the rails of the inferior member when the expandable vertebral implant is in an unexpanded configuration, and wherein one rail of the superior member is disposed between an associated rail of the inferior member and a central axis of the implant and another rail of the inferior member is disposed between the associated rail of the superior member and the central axis of the implant in the unexpanded configuration;

disposing the expandable intervertebral implant between the superior intervertebral body and the inferior intervertebral body; and

selectively adjusting the separation of the superior member and the inferior member, thereby selectively adjusting a distraction of the superior intervertebral body from the inferior intervertebral body.

12. The surgical method of claim 11 , wherein one or more track structures and rail structures associated with a top surface of the distal wedge structure are offset horizontally with respect to one or more track structures and rail structures associated with a bottom surface of the distal wedge structure.

13. The surgical method of claim 11 , wherein one or more track structures and rail structures associated with a top surface of the proximal wedge structure are offset horizontally with respect to one or more track structures and rail structures associated with a bottom surface of the proximal wedge structure.

14. The surgical method of claim 11 , wherein the expansion mechanism further comprises an actuation bolt that passes through the proximal wedge structure and is coupled to the distal wedge structure and causes the wedge structures to relatively translate when rotated.

15. The surgical method of claim 14 , wherein the expandable intervertebral implant further comprises a ratcheting structure disposed between a head portion of the actuation bolt and the proximal wedge structure of the expansion mechanism, wherein the ratcheting structure is configured to resist rotation of the actuation bolt with respect to the proximal wedge structure of the expansion mechanism.

16. The surgical method of claim 11 , wherein the superior member and the inferior member each comprise a plurality of ramp structures.

17. The surgical method of claim 16 , wherein the superior member comprises a ramp structure that engages the proximal wedge structure and a ramp structure that engages the distal wedge structure.

18. The surgical method of claim 16 , wherein the inferior member comprises a ramp structure that engages the proximal wedge structure and a ramp structure that engages the distal wedge structure.