The aim of this study was to evaluate changes in the bearing surface of an alumina head and cup insert after difficult intraoperative reduction of the head.

In two consecutive cases, where the force required for reduction caused scratching on the edge of the acetabular metal shell and marginal cracking of the adjacent portion of the alumina insert, the reduced alumina head was dislocated and retrieved with the alumina cup insert. The changes of the bearing surface were evaluated by gross inspection and by scanning electron microscopy(SEM) and energy dispersive x-ray spectrometry (EDAX).

In both cases, the scratched area of the alumina head was found to have discolored. SEM and EDXA showed the discoloration to be the result of metallic debris from the titanium alloy shell. The metallic debris that was transferred from the head also stained the bearing surface of the alumina insert.

Metallic debris might increase bearing surface wear. If the cracked ceramic fragments from the cup insert are neglected, it is also possible that they could be trapped between bearing surfaces and increase wear.