Patent ID: 7594933

Claim:
A method of using a surgical navigation system for positioning in a femur a femoral prosthetic component of a hip joint replacement prosthesis, said method comprising the steps of: acquiring a pelvic frame of reference; acquiring a center of rotation of said hip joint in said pelvic frame of reference; acquiring a first femoral point substantially fixed with respect to said femur in said pelvic frame of reference while said hip joint is intact; calculating a length of a first line between said first acquired femoral point and said center of rotation of said hip joint; implanting a prosthetic cup component of said hip joint replacement prosthesis in said pelvis; acquiring a position of a center of rotation of said implanted prosthetic cup component in said pelvic frame of reference; calculating a first difference in position between said center of rotation of said hip joint and said center of rotation of said implanted prosthetic cup component in said pelvic frame of reference; forming a hole in said femur for accepting said femoral prosthetic component; rigidly mounting a marker in said hole, said marker having a known position relative to a position of a center of rotation of a prosthetic femoral head of a femoral prosthetic component if implanted in said hole; calculating a position of a center of rotation of said prosthetic femoral head if implanted in said hole as a function of said position of said marker mounted in said hole; while said marker is mounted in said hole, re-acquiring said first femoral point relative to said position of said marker mounted in said hole; calculating a length of a second line between said re-acquired first femoral point and said center of rotation of said prosthetic femoral head; calculating a second difference in length of said first line and said second line; and displaying leg length data as a function of said first and second differences.