An expandable intervertebral fusion cage that includes an inferior baseplate and a superior baseplate, an insert rotatbly received between the inferior and superior baseplates, and a guide pin coupled to the inferior and superior baseplates for facilitating the rotation of the insert. The insert includes a pair of protuberances, each of which are releasably engageable with a corresponding lock groove formed within the inferior and superior baseplates. When said insert is rotated relative to the guide pin, the protuberances engage the lock grooves, and the inferior and superior baseplates expand from a collapsed position, in which said inferior and superior baseplates are juxtaposed with one another, and an expanded position, in which said inferior and superior baseplates are diverged away from one another. As a result, the cage distracts in parallel. Tabs formed on the superior baseplate continuously engage slots formed within the inferior baseplate when the baseplates expand from their collapsed position to their expanded position.