An expandable cage supports adjacent vertebra in spine surgery. The expandable cage includes a first supporting member configured to engage tissue and a second supporting member operatively associated with the first supporting member. The first and second supporting members are movable relative to each other. The expandable cage further includes a cam lock mechanism configured to maintain the first and second supporting members in a fixed relative position. In another embodiment, the expandable cage includes a ring plate lock mechanism in lieu of the cam lock mechanism. The ring plate lock mechanism is adapted to maintain the first and second supporting members in a fixed relative position.