EARLY INDUCIBLE DISPLACEMENT OF TIBIAL COMPONENTS IN TOTAL KNEE PROSTHESES INSERTED WITH AND WITHOUT CEMENT - A RANDOMIZED STUDY WITH ROENTGEN STEREOPHOTOGRAMMETRIC ANALYSIS

The fixation of tibial components randomized to insertion with or with out cement in twenty-six knees was examined for inducible displacement at six weeks and one year postoperatively with use of roentgen stereo photogrammetric analysis. Furthermore, migration was studied during th e first two postoperative years. Inducible displacement was found in a ll knees at both the six-week and the one-year follow-up examination, but no differences were detected with respect to the type of fixation (p > 0.05). All tibial components migrated for as long as one year pos toperatively, after which most stabilized. No difference was found bet ween the groups with respect to migration during the first two years p ostoperatively (p > 0.05), with the exception of subsidence of the com ponent, which was found to be 0.0 +/- 0.1 millimeter (mean and standar d error of the mean) for the components inserted with cement and 0.5 /- 0.1 millimeter for the components inserted without cement (p < 0.01 ). Migration after one year was the same for both groups. We found a r elationship between inducible displacement at six weeks and at one yea r as well as one between inducible displacement and migration at one y ear. To our knowledge, the present study is the first in which the mic romotion of an interference-fit prosthesis was found to be similar to that of a device inserted with cement. The results of the present stud y emphasize the importance of the initial prosthetic fixation.