A method and system are provided for installing a spinal fusion cage. The spinal fusion cage includes an outer cage having a proximal outer cage endwall and a distal outer cage endwall. An inner cage has a proximal inner cage endwall and a distal inner cage endwall. The proximal and distal inner cage endwalls each are in slidable contact with a corresponding one of the proximal and distal outer cage endwalls. The inner and outer cages collectively define a fusion cage cavity space having a volume which varies responsive to relative sliding of the inner cage with respect to the outer cage. An actuation tool includes a shaft and an operative portion. The operative portion of the actuation tool has an asymmetrically tapered portion which includes a longitudinally aligned face extending substantially parallel to the longitudinal axis and an angled face extending at an acute angle to the longitudinal axis.
