Pelvis registration instrument and method

A system for use in implanting a prosthesis, the system comprising:

• a pelvis registration apparatus comprising:
• a body having a distal end and a proximal end, the body extending along a longitudinal axis;
• and
• an engagement assembly coupled to the distal end of the body and comprising three or more contact points, wherein the contact points are:
• selectively movable radially with respect to the longitudinal axis to position the contact points at a desired distance relative to a centerline of the body;
• and
• selectively movable about the body to position the contact points at desired circumferential locations relative to one another;
• a controller;
• and
• first and second position sensors capable of reporting position and orientation data to the controller, the first position sensor being removably coupled to the pelvis registration apparatus and the second position sensor disposed in a fixed, spaced relation relative to the first electronic position sensor;
• wherein the controller is configured to:
• receive the position and orientation data from the first and second position sensors;
• and
• calculate angular relationships derived from the position and orientation data.

A method comprising:

• analyzing acetabulum data of a patient to:
• determine a geometry of an acetabular rim;
• and
• identify three or more unique locations along the acetabular rim;
• manipulate an engagement assembly of a pelvis registration apparatus to:
• position three or more contact points of the engagement assembly at a distance relative to a centerline of a body of the pelvis registration apparatus corresponding to the geometry of the acetabular rim;
• and
• position the three or more contact points at circumferential locations of the body of the pelvis registration apparatus corresponding to the three or more unique locations.