An intervertebral expandable implant with first and second vertebral body engagement surfaces includes first and second implant structures defining first and second angled wedge portions. The first angled wedge portion has first and second inwardly-facing rails and first and second inwardly-facing slots. The second angled wedge portion has first and second outwardly-facing rails and first and second outwardly facing slots. The first implant structure is slidably-engaged with the second implant structure with the first inwardly-facing rail positioned in the first outwardly-facing slot, the second inwardly-facing rail positioned in the second outwardly facing slot, the first outwardly-facing rail positioned in the first inwardly-facing slot, and the second outwardly-facing rail positioned in the second inwardly-facing slot.