A retention system for maintaining a screw to a vertebral plate. One or more screws extend through apertures within the vertebral plate. A cavity is positioned adjacent to and overlaps into the aperture. A ring is positioned within the cavity and held in position by a cap. The cap attaches to the plate to prevent removal of the ring. The ring is deflectable between a first shape to allow the screw to be inserted and removed from the aperture, and a second shape to prevent screw back-out from the aperture. A method of using the system is also included and comprises positioning the ring within a cavity in the plate, maintaining the position of the ring to the plate by attaching a cap, inserting a screw through the aperture and attaching the plate to a vertebral member, and positioning the ring over the screw head and preventing the screw from backing-out.