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Thursday, October 7, 2010, 14:00-14:40Session A5: Hip MechanicsEffect of Cup Abduction and Head Lateral Microseparation on ContactStress in Ceramic-on-Ceramic THA*Sari-Ali El-Hadi - Hopital Pitie Salpetriere - Paris, FranceTodd Stewart - University of Leeds - Leeds, UKZonhgmin Jin - university of Leeds - Leeds, UKJohn Fisher - university of Leeds - Leeds, UK*Email: hedisari@yahoo.frBackground: High cup abduction angles generate increased contact stresses, higher wear ratesand increased revision rates. However, there is no reported study about the influence of cupabduction on stresses under head lateralisation conditions for ceramic-on-Ceramic THA.Material and method: A finite elements model of a ceramic-on-ceramic THA was developed inorder to predict the contact area and the contact pressure, first under an ideal regime and thenunder lateralised conditions. A 32 mm head diameter with a 30 microns radial clearance wasused. The cup was positioned with a 0°anteversion angle and the abduction angle was variedfrom 45° to 90°. The medial-lateral lateralisation was varied from 0 to 500 microns. A load of2500 N was applied through the head center.Results: For 45° abduction angle, edge loading appeared above a medial-lateral separation of 30μm. Complete edge loading was obtained above 60 μm medial-lateral separation. For 45degrees inclination angle, as the lateralisation increased, the maximal contact pressure increasedfrom 66 MPa and converged to an asymptotic value of 205 MPa. A higher inclination angleresulted in a higher maximum contact pressure. However, this increase in contact pressureinduced by higher inclination angle, became negligible as the lateral separation increasedDiscussion Both inclination angle and lateral displacement induced a large increase in thestresses in Ceramic-on-Ceramic THA. Edge loading appeared for a small lateralisation. Theinfluence of acetabular inclination angle became negligible for a lateral displacement above 240μm, as the stresses reached an asymptotic value.FiguresFigure 1 Figure 2file:///E|/ISTA2010-Abstracts.htm[12/7/2011 3:15:47 PM]