Fiducial marker devices, tools, and methods

An apparatus comprising:

• a fiducial marker including:
• a substantially spherical imagable fiducial locator head that is locatable by an imaging system, the imagable fiducial locator head including at least one slot for driving the fiducial marker to secure it to a bone;
• a receptacle that is sized and shaped for engaging a locator instrument of a positioning system, the receptacle integrated with the imagable fiducial locator head to permit access to a center of the imagable fiducial locator head;
• and
• a shaft that extends outward from the imagable fiducial locator, the shaft integrated with the imagable fiducial locator head, at least a portion of the bone screw shaft being configured for being directly secured to the bone.

A method comprising:

• driving directly into a bone of a patient a fiducial marker device including both an imagable locator head and an integral male or female receptacle sized and shaped for mating to an instrument detectable by a positioning system;
• obtaining, using an imaging system, an image of the patient, the image including the imagable locator head;
• and
• mating the instrument to the receptacle to register an actual position of the patient to the image of the patient.