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.