IMPINGEMENT OF METAL NECK ON CERAMIC LINER IN CERAMIC-ON-CERAMIC THA

We evaluated 3 cases of ceramic-on-ceramic THA in that the evidence of the impingement between the metal neck and the ceramic liner was found. Between July 2007 and January 2008, impingement between the metal and the ceramic liner was found in 3 cases of ceramic-on-ceramic THA during re-operation. The re-operation was performed 3–6 years after the primary surgery because of ceramic head fracture, deep infection and cup loosening. All patients frequently sat on the floor in tailor fashion but did not have any sound in the hip after THA. In all cases, V-shaped indented wear scar was found on the postero-superior aspect of the metal neck. Two ceramic liners could be retrieved. Both showed black staining in the postero-superior portion of the rim. The outer edge of the bearing surface of the retrieved acetabular liners was evaluated with SEM. The black stained area of the acetabular liner rim was found to be roughened. A micro-crack propagating into the deep portion of the ceramic liner was observed in one liner. Our observations suggest that impingement between the ceramic liner and the metal neck can cause crack formation leading to ceramic liner failure in vivo.