A computer assisted surgery system with is enhanced graphics features is described
for assisting a surgeon in orthopaedic procedures. A system is described for use
in inserting multiple guide pins in hip fracture surgery using a single bore drill
guide that has a graphical representation comprising its real trajectory and one
or more virtual trajectories, the virtual trajectories representing potential positions
of other guide pins to be placed during the procedure. Additionally, representations
of inserted guide pins and virtual trajectories may be retained on the display
at their inserted positions for use in aligning subsequent guide pins. A system
is also described for orientation of an acetabular cup in a total hip replacement
surgery. During cup insertion, the surgeon is provided with information regarding
the orientation of the cup with respect to a pelvic reference frame that is based
on accepted pelvic landmarks. The positions of each landmark is calculated by the
system when a probe with a virtual tip, separate from its physical tip, is overlaid
on the landmark in roughly orthogonal images of the pelvis.
