INCREASED VARUS-VALGUS TILTING OF SCREW-FIXATED KNEE PROSTHESES - STEREORADIOGRAPHIC STUDY OF UNCEMENTED VERSUS CEMENTED TIBIAL COMPONENTS

Twenty-six women and three men (34 knees) with osteoarthrosis were ope rated with the Miller-Galante I (Zimmer, Warsaw, IN) knee prosthesis. The patients were randomized to either cemented or uncemented fixation of the tibial component. All patients received a TiVaAl alloy tibial plate with four pegs and titanium fiber-mesh undersurface. in the unce mented knees four screws were added. The fixation of the tibial compon ent was determined by roentgen stereophotogrammetric analysis during t he first 2 postoperative years. Rotations of the entire tibial compone nt were recorded, as well as proximal or distal translation of various parts of the prosthetic edge corresponding to subsidence and lift-off . The uncemented components displayed almost all rotation and translat ion during the first 6 weeks, whereas the cemented ones displayed a mo re gradually increasing migration during the 2 years. Tibial component rotation about the sagittal axis was significantly increased in the u ncemented knees throughout the investigation period. This corresponded to increased subsidence medially or laterally in the uncemented knees , whereas lift-off was equal in the two groups. Thin (8.5 mm) uncement ed tibial components displayed more subsidence than the thicker ones a t the medial or lateral edge 3 months after surgery.