Fixation of the tibial component in knee arthroplasty after six weeks

The fixation of cemented and uncemented PCA modular cruciform-stemmed tibial components was examined 6 weeks after operation using roentgenstereophotogrammetric analysis in 26 randomly selected patients. Physiological external forces were applied in external/internal rotation and eccentric posterior loading generated by squatting. All cases showed inducible displacement, but there were no statistically significant differences between the 2 groups in inducible displacement or in the initial migration, except for subsidence between the lying and standing position. In some, the greatest movement was found when changing from resting to standing, or during rotational stress; in others, the greatest movement was found during squatting. There was a statistical difference in subsidence on squatting which was greater in the uncemented group. The design of the cruciform stem and the use of an internally cooled saw may explain this small differences between the 2 groups.