A spine fixation system (10； 210； 310) comprises a first rod (16； 216) that connects a first vertebra (V2) to a second vertebra (V) but not to a third vertebra (V4), and a second rod (14； 214) that connects the second vertebra (V3) to the third vertebra (V4) but not to the first vertebra. The spine fixation system is configured such that first vertebra (V2), but not the third vertebra (V4), is allowed to move relative to the second (V3) vertebra after the spine fixation system has been completely implanted.
