A polyaxial interspinous fusion device is described. The polyaxial interspinous fusion device has a fixed anchor, a polyaxial anchor, and a bone spacer. The fixed anchor has a center ring, one or more fixed anchor arms projecting laterally from the center ring, and a barrel projecting transversely from the center ring. The polyaxial anchor has a socket ring and one or more polyaxial anchor arms projecting laterally from the socket ring, wherein the socket ring has a concave engagement surface. The bone spacer has a spacer head having a convex socket engagement surface that matches the concave engagement surface of the socket ring. The bone spacer also has one or more zip lock flanges extending transversely from the spacer head and one or more bone abutments extending transversely from the spacer head. The zip lock flanges and bone abutments of the bone spacer fit through the socket ring and the barrel of the fixed anchor fits through the socket ring. The zip lock flanges engage with the barrel when the zip lock flanges and bone abutments are inserted through the socket ring. When the polyaxial anchor engages with the spacer head, the polyaxial anchor has a polyaxial freedom of movement relative to the spacer head as a result of a ball and socket engagement between the concave engagement surface of the socket ring and convex socket engagement surface of the spacer head.
