In a total hip arthroplasty, the artificial hip joint is composed of an acetabular cup and a femoral head. To minimize the wear of the joint, the bearing surface should be precisely spherical. There were concerns that the press-fitting of the acetabular cup to the pelvis may cause the deformation of the cup and accelerate the wear of the joint, but its in-vivo measurement was challenging. In this paper, 3 dimensional finite element(FE) models of a pelvis and acetabular cups of Metasul 50mm and Pinnacle 50-60mm cups were used to simulate the deformation of the acetabular cups. For Metasul cups, the change of inner radius with respect to the location and the maximum shrinkage of the inner radius were found. For the Pinnacle cups, maximum change of the outer diameter were found and compared with the literature. FE model showed that the maximum shrinkage of the inner radius of the Metasul cup was 23μm (1.0mm press-fit, Bone stiffness 17GPa case). The shrinkage occurred mainly on the anterior and posterior side of rim of the cup, and the amount was proportional to the press-fit amount. The diametric change of the Pinnacle cup was 0.16mm on average, which was in same range of the clinically reported value. In conclusion, under the normal condition the reduction of the inner radius of the Metasul cup was too small to cause the jamming or the excessive wear.

Deformation monitoring of dams has been widely used for its safety management. In this study, improvement of the deformation monitoring with a total station was suggested by calibrating coordinate of a total station. The position of TS was initially measured through 3∼4 given points and the coordinate of total station was considered as an absolute value. However, when the targeting point was measured by the total station, the coordinate of the total station was changed and it means that deformation of the total station was also occurred. Therefore, the deformation of dams was increased by deformation of the total station. Before the calibrating, the deformation of the target point located at 50m from total station was ±20mm. After the calibrating, the deformation was decreased by ±2mm.