Results with a cementless alumina-coated cup with dual mobility. A twelve-year follow-up study.

Between April 1980 and December 1981, 135 alumina-coated hemispherical cups were inserted without cement in patients with degenerative lesions. The cups were anchored by press fit and secured with a tripod attachment. The follow up was for over ten years. A bipolar polyethylene insert was used. Only one patient was lost to follow up in less than 2 years. Forty-four implants worked perfectly up to the time of death of the patients. Four cups were replaced, two after the patients sustained violent trauma, and there was an isolated instance of replacement of the insert only. The cumulative survival rate was 95.4% at 10 and 12 years follow up. The 78 surviving patients (85 cups) were examined, and radiographs were taken in 62 of them. Three patients showed clinical signs of deterioration and radiological signs of loosening, 2 others showed radiological signs of cup displacement without clinical symptoms. There was no evidence of osteolysis at the bone-cup interface in well functioning implants. These results confirm that cementless hemispherical cups survive well and demonstrate the value of a cup without holes for screws which can allow migration of polyethylene particles which might induce osteolysis of the adjacent ilum.