Abstract

Femoral stem centralizers were originally designed for double tapered, straight stems. In a slightly modified configuration, the PMMA centralizer is plugged in a hole in the tip of the ABG II femoral prosthesis®. The purpose of this study was to determine the effect of the centralizer on the position of the anatomical ABG II stem®. Thirty-nine cemented ABG II stems® with a centralizer were compared with thirty-nine stems without a centralizer. We evaluated positioning of the tip of the stem according to a standard selection of criteria, using conventional AP and lateral X-ray imaging. The centralizer supplied with the ABG II® was found to have no additional value in guaranteeing optimal varus-valgus positioning. If a stem was not placed neutral, generally it was placed in a slight valgus position. The number of deficient cement mantles was not influenced by the three-fin centralizer. Furthermore, the distal centralizer of the ABG II prosthesis® adds a length of 27 mm to the stem, and the distal cement plug found in stems with centralizer was almost twice as long on average. The ABG II centralizer® was found in this study to provide insufficient guiding of this anatomical stem and to add excessive length to the distal cement plug.