Abstract: A computer-assisted surgery system for guiding an operator in altering a pelvis. A sensing apparatus is provided for tracking a reference tool and a bone altering tool. A position calculator calculates a position and orientation of a pelvic frame of reference as a function of the tracking of the reference tool, and for calculating a position and orientation of the bone altering tool with respect to the frame of reference. A source of posture data and a posture data correction calculator are provided and are operative to provide a display of information allowing an operator to take into consideration the posture data from the source of posture data when altering the pelvis. A display unit is connected to the position calculator and to the posture data correction calculator for displaying the display of information and the bone altering tool with respect to the pelvic frame of reference.

Abstract: An interface apparatus (20) for tracking by a tracking system (40) of an object(s) in space for position and orientation and for interacting with the tracking system (40). The interface apparatus (30) comprises passive detectable devices (12,14,16,22) trackable for position by the tracking system (40). A mounting device (10,24) receives the passive detectable devices (12,14,16,22) in a known geometry, and is secured to the object(s) such that a position and orientation of the object(s) is calculable by the tracking system (40) as a function of a tracking of the known geometry of the passive detectable devices (12,14,16,22). One of the passive detectable devices (22) is displaceable with respect to the object(s). A displacement of the passive detectable device (22) with respect to the object(s) is detectable to initiate an interaction with the tracking system (40) while maintaining the tracking of the object(s).

Abstract: There is described a method for determining a mechanical axis of a femur using a computer aided surgery system having an output device for displaying said mechanical axis, the method comprising: providing a position sensing system having a tracking device capable of registering instantaneous position readings and attaching the tracking device to the femur; locating a center of a femoral head of the femur by moving a proximal end of the femur to a first static position, acquiring a fixed reading of the first static position, repeating the moving and the acquiring for a plurality of static positions; and locating the centre by determining a central point of a pattern formed by the plurality of static positions; digitizing an entrance point of the mechanical axis at a substantially central position of the proximal end of the femur; and joining a line between the entrance point and the center of rotation to form the mechanical axis.

Abstract: A method of calibrating a circular portion of an object, such as to determine the center point of the object, is provided. The method includes determining spatial coordinates of at least two points on a circumferential edge of the circular portion of the object, and calculating the center point of the circular portion using the spatial coordinates of the two points and a geometric parameter representative of the diameter of the circular portion. A calibration device and system are also provided for use with a computer tracking system in order to calibrate such an object having a circular portion.

Abstract: A system for automatic calibration of instruments (S) having varying cross-sectional dimensions within a predetermined range and having detectable elements (110, 112, 113, 114) thereon for computer-aided surgery, comprising a calibration base (C) having detectable elements (43, 44, 46, 48) secured thereto for detecting a position and an orientation thereof in space by sensors (204) connected to a position calculator (202). The calibration base is adapted to receive and to releasably secure a working shaft (100) of any of the instruments (S) and provides an abutting surface (14) for a tip (102) thereof in such a way that a position and orientation of the tip (102) of the instrument (S) secured therein is calculable when working shaft cross-section dimensions thereof are known. The position calculator (202) receives instrument data (214) and calibration data (218) from an operator through a user interface (206) and stores the instrument data (214) and calibration data (218) for subsequent calibrations.