THE STABILITY OF 3 DIFFERENT CEMENTLESS TIBIAL COMPONENTS - A RANDOMIZED RADIOSTEREOMETRIC STUDY IN 45 KNEE ARTHROPLASTY PATIENTS

We conducted a prospective, randomized study of 45 patients to evaluat e 3 different uncemented tibial component designs in total knee arthro plasty. The stability of the components was assessed by radiostereomet ry (RSA), both as migration during 2 years and as inducible displaceme nt at 2 years. The PCA resurfacing, the Tricon stem and the Tricon-M p rosthesis groups showed a similar level of migration at 2 years, about 1.4 mm. In response to externally applied rotatory forces, the Tricon groups rotated more than the PCA group, interpreted as a consequence of the more conforming articular surface in the Tricon design. The ser ies was divided into one group of continuously migrating prostheses wi th a poor prognosis (unstable, one third) and another group of prosthe ses in which migration stopped after 1 year (stable, two thirds). With this classification, no differences between the prostheses design gro ups were revealed. However, the unstable group showed a larger inducib le displacement by provocation, an association hitherto not establishe d.