US Patent 7011658 Devices and methods for spinal compression and distraction

A device for applying a corrective force to a spinal column segment is provided that includes a mechanism with opposite first and second engagement ends and driving means for moving the opposite engagement ends in extension and retraction directions. A locking mechanism has a first position in engagement with the mechanism to prevent the opposite engagement ends from being moved in one of the extension and retraction directions while allowing movement in the other of the extension and retraction directions. The locking mechanism has a second position that allows the opposite engagement ends to be moved in both of the extension and retraction directions. The locking mechanism can also be configured to prevent the opposite engagement ends from being moved in either of the extension and retraction directions when in the first position.