Measurement of the Cement Thicknessaround the Femoral Stemin THRA: CAD Data Analysis Obtained from 3D Scanner

Cho, Myung Rae; Park, Wee Tae; Park, Chang Min; Lee, Sang Wook; Kim, Shin Kun; Kwon, Koing Woo

Abstract

PURPOSE: To measure the cement mantle thickness that developed from a rotation of the femoral stem in virtual space made by the broach.
MATERIALS AND METHODS
The C stem and Versys stem of the subjects enrolled in this study were examined. A C250/400VZ(Steinbichler Co. Germany) and S/W: Geomagic & CATIA V5 was used to examine the three-dimensional configurations. The axial images were acquired after neutral placement of the femoral stem, horizontal rotation, coronal tilting, and a combination of both. The thickness was measured from the distance between the outer surface of the femoral stem and the closest vertex in the outer contour of the broach in cross-sectional images.
RESULTS
The distance was <1 mm at the horizontal rotation of 3 degrees in the C stem, and at 5 degrees in the Versys stem. The distance was <1 mm at varus of 0.25 degrees in the C stem, and touched at 0.8 degrees. In the case of the Versys stem, the femoral stem touched at a varus of 1 degree. A combination of both horizontal and pivot rotation made the distance <1 mm at rotation of all angles.
CONCLUSION
It might be necessary to develop a new instrument for the accurate insertion of the femoral stem along the broached space or to modify the stem design to stand against the change in the femoral stem position in the broached space.