The present invention provides an expandable intervertebral implant, including: 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 separation of the superior member from the inferior member; wherein the expansion mechanism includes 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 aligned and/or staggered (i.e. nested) track structures and rail structures.