An intervertebral implant system for a human spine including a first body having a first external surface to be disposed adjacent a first vertebrae during use and a first internal surface opposite the first external surface, a second body having a second external surface to be disposed adjacent a second vertebrae during use and a second internal surface opposite the second external surface, an elongated insertion instrument releasable coupleable to the first or second body during use, and a spacer linearly advanced between the first internal surface of the first body and the first internal surface of the second body during use. The elongated insertion instrument guides at least a portion of the linear advancement of the spacer, and wherein the linear advancement of the spacer results in expansion of the intervertebral implant such that the first external surface and the second external surface move away from one another to expand a height of the implant.