Aim: We assessed prospectively clinical and radiographic results of two different polyethylenes (PE) associated with the same prosthetic design (Zimmer-Centerpulse).

Material and Methods: We assessed 56 Allofit cups with Sulene-PE liner (sterilized in nitrogen) and 45 with Durasul-PE liner (highly cross-linked) associated with an Alloclassic stem (28-mm femoral head) implanted between 1999–2002. The mean follow-up was 29.4 months for the Sulene-PE and 25.3 for Durasul-PE. The radiologic study according to Johnston et al. and the PE wear estimated according to a software package (AutoCAD R14), were analysed at 6 weeks (zero position), at 6 and 12 months and annually thereafter.

Results: There were 3 dislocations which were excluded from the follow-up study. There were no infections. All assessed hips had good clinical and radiographic results. There was no loosening of any prosthetic component. There were no radiolucent lines, osteolysis, cortical hypertrophy, or femoral osteopenia. The distances between the acetabular shell and the femoral head centres taken in the early postoperative radiographs (zero position or bedding-in) were 0.30+0.094 mm for the Sulene-PE group and 0.20+0.074 for the Durasul-PE (p=0.029). The mean wear related with the zero position was 0.1035+0.0686 and 0.0819+0.078 (p=0.108) respectively.

Conclusions: Despite the measurement error of PE wear being higher in the Allofit cup, a higher zero position (bedding-in) was found in the Sulene-PE group than in the Durasul-PE. Although the mean wear was higher in the Sulene-PE than in the Durasul-PE, with the number of hips available, differences were not significant after 3 years