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COM group whereas both components were made of Biolox Delta® in the COC group.Simulation was run to a total of 2.4x10 6 cycles. Wear measurements were performed inintervals of 0.2x10 6 cycles using a gravimetric method (Sartorius Genius ME235S, measuringsolution: 15 µg, Sartorius, Göttingen, Germany).ResultsWear of the COM and COC pairings is shown in Figure 1. During the first 200,000 cycles amean wear rate of 0.16mm 3 /10 6 cycles was found followed by a decreased wear rate of0.04mm 3 /10 6 cycles for the COC bearings. The overall wear ranged from 0.08mm 3 to0.17mm 3 , with a mean of 0.12 mm 3 . There was found a high variability in the wear progressionbetween the four COM implants (Figure 1). A mean wear rate of 0.13mm 3 /10 6 cycles wasdetermined during the first 200,000 cycles followed by a decreased wear rate of 0.05mm 3 /10 6cycles. The overall wear of the COM implants ranged from 0.02mm 3 to 0.21mm 3 , with a meanof 0.13 mm 3 . All ceramic heads from the COM bearings showed metallic material transfer inform of stripes whereas no visible wear traces were found on the COC heads.Discussion and ConclusionThe COM implants showed very low wear levels that were similar to the COC bearings and farbelow wear levels of conventional MOM bearings. However, there was a spreading up to thethirteen fold between lowest and highest wear volume of the COM at the end of the study.Concerning COM implants such high variability was also seen by other investigators. Thesimulator conditions are highly reproducible (as seen for the COC bearings). Considering thehigh variations in patients demand, the influence of patient related activity parameters should befurther investigated in terms of wear. Moreover, this study was performed withoutimplementing subluxation, impingement or malalignment which might also increase wear.These effects together with the influence of third body wear needs to be further considered.Figure 1: Mean wear progression of COM and COC bearings. Standard deviation at eachinterval is labeled by indicators.FiguresFriday, October 8, 2010, 16:30-17:20Session A16: Computer Navigation in THAComparison of Computer Navigated Total Hip Arthroplasty VersusConventional Total Hip Arthroplasty Utilizing the Direct AnteriorApproach*Stefan Kreuzer - Memorial Bone and Joint Research Foundation - Houston, USAfile:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]