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*Stephen Murphy - New England Baptist Hospital - Boston, USA*Email: stephenbmurphymd@gmail.comImproving Cup Positioning Using a Mechanical Navigation InstrumentSimon D. Steppacher MD 2 , Jens H. Kowal PhD 2 , Stephen B. Murphy MD 11 Center for Computer Assisted and Reconstructive Surgery, New England Baptist Hospital,Boston, University of Bern, Bern Switzerland 2Acetabular component malpositioning is the most common reason for instability and wearresulting in revision total hip arthroplasty (THA). The current study aimed to assess a novelmechanical navigation device which was designed to simply and efficiently indicate appropriatecup orientation during surgery. The accuracy was compared to a series of hip arthroplastiesperformed using CT-based computer-assisted cup placement.The study group consisted of 70 THAs performed using the mechanical device. The controlgroup consisted of 146 THAs performed using CT-based computer navigation. Postoperativecup positioning was measured using a validated 2D/3D-matching method. An outlier wasdefined outside a range of ± 10 degrees from the planned inclination or anteversion.In the study group the mean accuracy for inclination was 1.3 ± 3.4 (-6.6 – 8.2) and 1.0 ± 4.1 (-8.8 – 9.5) for anteversion with no outliers for either parameter. In the control group the accuracyfor anteversion (3.0 ± 5.8 [-11.8 - 19.6]; p=0.6%) and the percentage of outliers (6.8%; p=3.3%)differed significantly. The accuracy for inclination (3.5 ± 4.1 [-12.7 - 9.5]; p=21.4%) and thepercentage of ouliers (4.8%; p=9.9%) did not differ significantly.The use of this mechanical navigation device can result in similar accuracy of acetabular cuporientation compared with CT-based surgical navigation. All cups were placed within a zone of± 10 degree range of inclination and anteversion. This mechanical navigation device allowsaccurate cup navigation with minimal additional time and equipment.Friday, October 8, 2010, 16:30-17:30Session B15: MIS Techniques in TKAProspective Comparison of Total Hip Arthoplasty Performed UsingConventional and Tissue-Preserving Techniques: A Minimum 2-YearOutcome StudySimon Steppacher - New England Baptist Hospital - Boston, USAMoritz Tannast - ctr for computer assisted and reconstructive surgery - boston, usafile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]