Patent ID: 8915944

Claim:
A screw cap for use in an apparatus for aligning and/or stabilizing the spinal column comprising either a rod or a plate, a pedicle screw, and a nut for engaging the pedicle screw to affix the rod or plate thereto, the screw cap comprising: a base having a bore therethrough defining a cavity for receiving a head of a pedicle screw and a threaded riser formed thereon for receiving a threaded nut, the cavity and the head of a pedicle screw providing for cooperative screw cap retaining means that allows the head of the pedicle screw to enter the cavity from a cavity lower end opening and be retained in the cavity such that the base can be positioned in a plurality of positions relative to a longitudinal axis of the pedicle screw during surgical fixation, a longitudinal axis of the riser and a longitudinal axis of the bore in the base being laterally offset each other; a washer having a hole therethrough for receiving the riser formed on the base and a surface adapted for engagement by either a rod or a plate, movement of the rod or plate relative to the base being resisted when the threaded nut is tightened against the washer; and an extension configured to be releasably mounted on the riser being laterally offset from the longitudinal axis of the bore of the base, the riser having an intertnal and external threads, the extension comprising an unthreaded refresher gap and a threaded post located proximate the refresher gap, wherein the refresher gap is dimensioned to be slightly larger than the height of the threaded nut, and wherein the internal thread in the riser is configured to receive the threaded post while the external thread in the riser is configured to receive the the threaded nut.