[Results of the GECO series]

301 hip prostheses were implanted in patients under the age of 50 years. All patients were followed for a minimal period of 3 years or until revision. The young age is due to the etiologies: femoral head necrosis, congenital hip dislocation, post-traumatic arthrosis. The implanted prostheses were of different types: both components were usually cementless; most bearing surfaces were alumina-polyethylene, with a head diameter of 32 or 28 mm. Patients were followed for 3 to 18 years after implantation (mean: 7 years). At the last follow-up, 59 prostheses (20%) had been exchanged; 232 cases had a good functional result according to Merle d'Aubigné (77% of the whole series and 96% of the surviving prostheses). The non revised patients mostly had an excellent result with regard to pain, range of motion and gait, and 85% returned to work.The final X-ray examinations of surviving prostheses showed 22% acetabular and 25% femoral radiolucent lines without loosening, 7% severe acetabular polyethylene wear. 3% of acetabular and 9% of femoral prostheses had migrated, mostly during the first months after cementless implantation with subsequent stabilisation.Revisions were performed after 6 months to 16 years. Main reasons were primary instability of a cementless implant (14 cases), secondary instability of a cementless implant (18 cases) and loosening of a cemented implant (18 cases). The global survival rate is 67% after 10 years, and 47% after 14 years. The survival rate of cemented cups was higher than screwed uncemented cups after 12 years (73% vs 59% - p<0,05), and there was no difference with uncemented press-fit cups after 7 years (95% vs 90%). The survival rate of cemented cups was higher than uncoated uncemented cups after 13 years(67% vs 53% -p<0,05), and there was no difference with hydroxyapatite-coated uncemented cups after 5 years (97% vs 93%). There was no difference between survival rates of cemented or cementless femoral prosthesis after 12 years (63% vs 54%) with respect to the presence or absence of hydroxyapatite. There was no difference between the survival rates of all bearing surfaces after 5 and 11 years, but none of the zirconia-polyethylene bearings had been revised after 5 years. There was no difference between survival rates of 28 mm and 32 mm heads after 8 years (86% vs 78%).Cemented prostheses are clearly indicated for patients under 50. Screwed uncemented cups are no longer indicated. Uncemented prostheses showed no better survival than cemented ones. Zirconia-polyethylene bearings could lead to a better survival rate than alumina-polyethylene or steel-polyethylene bearings.