A computer assisted surgery system is described for assisting a surgeon in aligning
a drill with the interlocking holes of an implanted intramedullary (IM) rod used
for fixation of long bone fractures. With the IM rod inserted, a localizing device
measures the pose of a tracked adapter attached to the rod's exposed end. Approximate
AP and lateral fluoroscopic x-ray images are acquired of the end of the rod with
the interlocking holes. Image processing algorithms determine the actual position
of the rod and calculate an adjustment to the pose of the tracked adapter and IM
rod. Using the adjusted pose information, the system displays, in three roughly
orthogonal views, a representation of the drill trajectory relative to the images
of the IM rod and relative to a graphic representation of the IM rod.
