An expandable spinal implant is disclosed. The implant includes a plurality of ribs which are deformable between first and second states. In the first state, the ribs present a generally cylindrical implant. In the expanded second state, the ribs are arced outwardly to define a generally spherical implant. A tie mechanism is provided for urging the ribs between the first and second states and for holding the ribs in the expanded state. A novel surgical method is disclosed for stabilizing the spine by inserting the implant in the first state between opposing vertebrae and expanding the implant to the second state.