Surgical instrument and method of positioning same

A surgical instrument for use in an orthopaedic surgical procedure on a distal portion of a femur, the instrument comprising:

• a base member including an anchoring member having a first portion securable to the femur and a base body adjustably repositionable relative to the anchoring member;
• a guide member mountable to the base member to establish a datum for guiding a subsequent surgical component;
• and
• a reference member mountable to the base member and trackable by a surgical navigation system to determine the position of the guide member relative to the femur.

A method of positioning a surgical instrument with respect to an anatomical structure, the method comprising:

• providing an instrument having a base member comprising an anchoring member and a base body adjustably repositionable relative to the anchoring member;
• positioning the anchoring member relative to the anatomical structure with the aid of a computer implemented surgical navigation system;
• securing the anchoring member to the anatomical structure in a selected position;
• and
• selectively adjusting the position of the base member relative to the anchoring member with the aid of a computer implemented surgical navigation system after securing the anchoring member to the anatomical structure.