Aseptic stem loosening in primary THA: migration analysis of cemented and cementless fixation.

Early migration has reportedly been predictive for later implant failure. Using four different migration patterns, this study aimed to analyse migration behaviour of the two types of implant fixation--cemented and cementless--throughout the process of loosening. Migrational behaviour of 69 revised stems (49 cemented, 20 uncemented) was analysed retrospectively with EBRA-FCA (Einzel-Bild-Röntgen-Analyse, Femoral Component Analysis). Uncemented stems failed after early and late onset migration alike, while late migration was the predominant pattern in cemented stems. Mean prosthetic failure after early migration occurred 5.8 (+/-4.4) years postoperatively due to insufficient primary stability. Initially stable stems with late onset migration were revised after 12.4 (+/-4.5) years. Measurement of early migration was found to be a valuable tool to screen short-term and mid-term failure. In the long run the method's sensitivity decreased. Late onset migration, however, preceded long-term failure by a mean of three years.