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| |  AAOS: Computer-Assisted Navigation Better Than Freehand Methods When Positioning Acetabular Components in Hip Arthroplasty By Jill Stein SAN FRANCISCO, CA -- March 15, 2004 -- Computer-assisted acetabular-component insertion is more effective than conventional freehand methods in total hip arthroplasty (THA), researchers announced on March 10th here at the 2004 Annual Meeting of the American Academy of Orthopedic Surgeons. The findings were reported by James B. Stiehl, MD, Columbia St. Mary's Hospital, Milwaukee, Wisconsin, United States. Dr. Stiehl's group compared the efficacy of computer-aided surgery to the efficacy of standard techniques for the placement of acetabular component orientation in the optimised radiographic position of acetabular-cup inclination of 45 degrees and anteversion of 20 degrees in THA. Standard techniques include extramedullary guides, anatomical landmarks, and body positioning. "Acetabular component placement in total hip arthroplasty can be difficult, with optimal placement required to prevent chronic instability, exaggerated wear, and implant migration," Dr. Stiehl observed. The trial included 69 patients who had undergone THA with freehand cup insertion and 98 patients who had undergone THA using a computed tomography-based computer-navigation technique. In the study, a postoperative CT scan determined cup position with a validated computer algorithm, where the frontal plane of the pelvis was defined by a reference that connected the anterior superior iliac spines and the pubic tubercles. An analysis of the postoperative computed tomography scans showed that the average acetabular inclination for computer navigation was 43.03 degrees; for acetabular anteversion, the average was 22.22 degrees. For the freehand group, the average acetabular inclination was 45.74 degrees; the average acetabular anteversion was 28.51 degrees. "The importance of our study is that we have compared our early experience using computer-assisted navigation with freehand conventional methods of acetabular-component positioning using a validated methodology which required a postoperative computed-tomography study of all patients," Dr. Stiehl observed. "Acquisition of data from computed tomography is highly reproducible, and our computer resolution permitted unimpaired determination of cup position, despite the presence of some metal image distortion." In addition, Dr. Stiehl said the group was able to demonstrate a significant improvement in the desired surgical result through the use of computer-assisted navigation in THA. Dr. Stiehl added that he expects the new technology to allow surgeons to more accurately relate implant alignment to dislocation rates, prosthetic wear, implant loosening, and patient outcomes.
[Study Title: Comparison of Conventional versus Computer Assisted Acetabular Component Insertion. Abstract 31]
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