Patent ID: 7996061

Claim:
A method for creating a receiving cavity to receive an acetabulum in a navigated pelvic bone with the aid of a navigated tool, comprising: determining position data of two anterior superior iliac spines of the pelvic bone and of a pubic symphysis by means of a navigated scanning instrument, determining a plane of a pelvic inlet from the position data of the two anterior superior iliac spines of the pelvic bone and the pubic symphysis, locating a tear-drop point on the pelvic bone by means of the navigated scanning instrument, determining position data of the located tear-drop point; determining a tear-drop plane from the position data of the tear-drop point and the plane of the pelvic inlet of said pelvic bone, which tear-drop plane lies perpendicular to said plane of the pelvic inlet and extends parallel to a line connecting the two anterior superior iliac spines and running through the located tear-drop point, determining a position of a secondary acetabulum by means of the navigated scanning instrument, the secondary acetabulum comprising an actual position of an acetabulum of a patient which is displaced in a cranial direction relative to a primary acetabulum comprising a correct positioning of the acetabulum, determining a reference point at a defined height above the tear-drop plane and in a defined position in an anterior-posterior direction and at a defined spacing from an outer surface of the pelvic bone in a lateral-medial direction, the height of the reference point above the tear-drop plane being selected such that a maximum value of a spacing between the height of the reference point and the position of the secondary acetabulum is not exceeded, and working the tool into the pelvic bone in a desired direction relative to the reference point until a predetermined disposition of the tool relative to the reference point is reached.