Abstract: For performing an osteotomy operation at a selected location on a patient's bone, a cutting apparatus comprising a screw device having a tubular shell with at least one longitudinal slot through said shell. A knife holder is slidable longitudinally in the bore to pivotally support at least one knife for displacement between a closed position and an opened position. In its closed position the knife is contained within the bore, and is pivotable to said opened position to project outwardly through the slot to perform the cutting operation, The knife is displaced longitudinally in the bore by an applicator operable to be telescopically displaced in the bore and operable upon its longitudinal displacement to contact an extended end of said knife and pivot the knife into its opened position through the slot, and thereafter to displace said knife holder toward the opposite end of said tubular shell.