ZIRCONIA AND ALUMINA CERAMICS IN COMPARISON WITH STAINLESS-STEEL HEADS: POLYETHYLENE WEAR AFTER 15 YEARS FOLLOW-UP.

We studied hips with these two different ceramics during the same period and with a minimum follow-up of 15 years. Because the sizes of the alumina and zir-conia heads were different, hips with 32 mm alumina heads and those with 28 mm zirconia heads were compared with control hips with stainless-steel heads of the same sizes. The same stem and the same PE cup were implanted with cement at the same period. The femoral head was made of alumina with a diameter of 32 mm in 62 cases, and made of yttrium-oxide-partially-stabilized zirconia with a diameter of 28 mm in 40 cases. These ceramic heads were compared with 32 and 28 mm stainless steel heads (40 hips)There was an increased linear rate of penetration of the femoral heads into the liner between years five and 15 for the zirconia and the stainless-steel groups. This was severe in the zirconia group (0.4 mm/year compared with 0.13 mm/year for the stainless-steel group). During the same 15-year period there was, however, no significant change in the rate of ...