An interspinous fusion device for holding adjacent spinous processes of a spine of a patient in a fixed configuration, including: a first plate configured to engage one side of the adjacent spinous processes; a second plate configured to engage another side of the adjacent spinous processes opposite the one side of the adjacent spinous processes; and a spacer disposed between and coupling the first plate to the second plate, wherein the spacer allows one or more of the first plate and the second plate to pivot relative to the other plate in a first unlocked configuration and prevents one or more of the first plate and the second plate from pivoting relative to the other plate in a second locked configuration. Each of the first plate and the second plate includes a pair of opposed wing members protruding from a central bore.