Patent ID: 7643867

Claim:
An apparatus comprising: a fiducial marker including: an imagable fiducial locator head that is locatable by an imaging system, the head being at least semispherical; a conical receptacle that is sized and shaped for engaging a locator instrument of a positioning system, the receptacle is threaded and defined within the imagable fiducial locator head and wherein the conical receptacle has a base at an edge defined by a surface of the locator head and an apex at a center of the locator head to permit access to a center of the imagable fiducial locator head; and a bone screw shaft that extends directly outward from the imagable fiducial locator head, at least a portion of the bone screw shaft is configured for being secured to a bone; and a protective cap sized and shaped for protecting the fiducial marker, wherein the protective cap has a disk-like portion with a threaded portion extending from the disk-like portion that is threadable into the receptacle and a cylindrical circumferential skirt extending from the disk-like portion in the same direction as the threaded portion.