IMAGE-GUIDED NAVIGATION SYSTEM TO MEASURE INTRAOPERATIVELY ACETABULARIMPLANT ALIGNMENT

There has been little clinical research to examine the effects of pati ent positioning and pelvic motion on the alignment of the acetabular i mplant during total hip replacement surgery. Until now, no tools were capable of accurately measuring these variables during the actual proc edure. As part of a broader program in medical robotics and computer a ssisted surgery, a clinical system has been developed that includes se veral enabling technologies. The hip navigation system (HipNav) contin uously and precisely measures pelvic location and tracks relative impl ant alignment intraoperatively. HipNav technology is used to gauge cur rent clinical practice and provide intraoperative feedback to surgeons with the goal of improving the precision and accuracy of acetabular a lignment during total hip replacement. This system provides surgeons w ith a new class of image guided measurement tools and assist devices. These tools successfully were introduced into the clinical practice of surgery with results showing the following: (1) There exist unpredict able and large variations in the initial position of patients' pelves on the operating room table and significant pelvic movement during sur gery and during intraoperative range of motion testing; (2) current me chanical acetabular alignment guides do not account for these variatio ns, and result in variable and in the majority of cases unacceptable a cetabular alignment; and (3) press fitting oversized acetabular compon ents influences the final cup orientation.