Disclosed is a bone fixation device for retaining vertebra of a spinal column in a desired spatial relationship. In one embodiment, the device comprises a first member connectable to a first vertebra and a second member connectable to a second vertebra and interconnected with the first member. The first and second members are movable relative to one another across a range of motion. An adjustor member transitions between a first state and a second state, wherein the range of motion between the first member and second member spans a first distance when the adjustor member is in the first state, and wherein the range of motion between the first member and second member spans a second distance when the adjustor member is in the second state.