WEAR IN RETRIEVED ACETABULAR COMPONENTS - EFFECT OF FEMORAL-HEAD RADIUS AND PATIENT PARAMETERS

Forty-seven explanted Porous Coated Anatomic (PCA, Howmedica, Rutherfo rd, NJ) cementless acetabular components were acquired at revision sur gery. All the components articulated against CoCrMo femoral heads of 3 2-mm diameter. The penetration depth and angle were measured using the shadowgraph technique. The wear volume was then calculated using Kabo 's formula. Using weighted linear regression analysis, the mean penetr ation rate and mean volumetric wear rate were calculated to be 0.23 (S E, 0.03) mm(3)/y and 96 (SE, 13) mm(3)/y, respectively. The creep comp onent was not found to be significantly different from zero. The clini cal wear factor, k(clinical), for this cohort was also calculated usin g linear regression analysis but with the assumption that creep was ze ro. The value found, k(clinical) = 1.93 (SE, 0.29) X 10(-6) mm(3)/N-m, was similar to those in previous studies involving cemented joints wi th a 22-mm femoral head diameter. The similar k(clinical) values of th ese substantially different joint types suggest that the high volumetr ic wear rate for the PCA joint can be attributed entirely to its large r head size and the younger, more active, patient profile. Fixation te chnique and metal backing seem not to influence the rate of wear.