Effect of microseparation and corner radius on contact mechanics and failure of dual mobility implants under regular and physically demanding gait loads

Dual mobility implants plays a vital role in reducing revision rate of implants. The contact mechanics of ceramic-on-polyethylene with ceramic liner and head lateral displacement accompanied by corner radius for acetabular shell inner diameter for regular and physically demanding gait loads in dual mobility implants are investigated in the current study. Three corner radii of 2, 4 and 6 mm with head lateral displacements of 0.25, 0.5 and 0.75 mm are investigated along with zero head lateral displacement with sharp corner for better comparison of results. Gait activities of four groups named as A, B, C and D consisting of 19 gait loads are applied to the finite element model. The contact pressure at primary and secondary interface of dual mobility implants is predicted for UHMWPE (ultra high molecular weight polyethylene) acetabular shell and silicon nitride ceramic material for head and liner. The von Mises stress plot is obtained for each case to predict the failure of implants under adverse head displacements as well as during physically demanding gait loads. The von Mises stress of round corner of 4 mm radius is found to be effective for head lateral displacement up to 0.25 mm. The primary and secondary contact pressure is also low for the above conditions. Though round corner 4 mm is found to be effective for all head lateral displacements, von Mises stress plot obtained for head lateral displacement beyond 0.25 mm are found to be higher than yield stress of UHMWPE. The sharp corner geometry fails for high load gait activities even under no head lateral displacement.