US Patent 8486115 Spinal plate assemblies with backout protection cap and methods

A bone plate assembly includes a plate, at least one bone screw, and at least one cap member. The screw extends into a through hole of the plate and a head of the screw seats in the through hole. The plate includes an undercut slot adjacent to the through hole. The cap includes at least one tab member that extends radially outward. The cap is mounted in the through hole with the tab member positioned in the undercut slot to inhibit the screw from backing out of the plate. In some arrangements, the tab member is rotatable within the undercut slot from an unlocked position to a locked position.