WEAR OF RETRIEVED CEMENTED POLYETHYLENE ACETABULA WITH ALUMINA FEMORAL HEADS

Four yttrium-stabilized alumina ceramic-on-polyethylene articulations obtained from patients who were undergoing revision surgery for sepsis (3) or recurrent dislocation (1) between 34 and 73 months were evalua ted to assess their in vivo wear performance. The annual volumetric we ar of the acetabular components determined directly by a fluid displac ement method ranged from 58 to 140 mm(3)/y. Scanning electron microsco pe examination of these four ceramic heads revealed similar surface da mage in all cases from a variety of causes. These included differentia l granular wear (alumina grains and yttrium-stabilized alumina grains at different depths), multidirectional scratches with heaped up bounda ries, and incompletely sintered grains, as well as the formation of cr aters and separation of grain boundaries. The femoral heads in this sm all series of revision cases show that yttrium-stabilized alumina cera mic heads may develop surface irregularities from either manufacturing processes or in vivo use. The wear rates of this type of alumina-on-p olyethylene articulation up to the time of revision were not substanti ally different from those found in other metal-on-polyethylene articul ations retrieved at revision surgery.