Ceramic on Ceramic Bearings for Dysplastic Hips: Analysis of Uncemented 2,861 THAs

We analyzed 2,861 uncemented primary total hip arthroplasties (THAs) with ceramic on ceramic bearing couple (C on C) for dysplastic hips followed up at least one year. The age at THA was 58 and the follow-up period was 6.8 (maximum of 21.4) years. Those belonged to Crowe's classification I were 76.4%, II were 14.6%, III were 7.0%, and IV were 2.0%. Two types of C on C were used: alumina on alumina (A on A) for 1979 hips and zirconia toughened alumina on zirconia toughened alumina (ZTA on ZTA) for 882 hips. Osteolysis was not detected. Dislocation occurred in six (0.2%) hips and the prevalence did not differ between A on A and ZTA on ZTA. Two liner fractures occurred only in A on A. Joint noise was detected in 79 (2.8%) hips. The prevalence of the noise was lower in ZTA on ZTA than in A on A. The revision rate was 0.5% and had no difference between A on A and ZTA on ZTA. All revisions in ZTA on ZTA were performed early after the initial surgery, while there was only one early revision in A on A. Taking endpoint as revision for any reason, the final survival rate was 97.2% for all C on C. At nine years after THA, the survival rate was higher in A on A than in ZTA on ZTA. Preventing the early failure by careful surgical procedure is essential to expect the same long-term durability of ZTA on ZTA as that of A on A.