Introduction and purpose: This study analyses the long-term results and the polyethylene wear rate of a first-generation hemispherical porous shell.

Materials and methods: 40 Tri-Lock shells were analyzed associated to an ACS (DePuy) PE insert implanted between 1988 and 1992. The PE had been gamma sterilized in air. The mean follow-up until revision or last control was 9.3 years (range: 3.1–15.0). PE wear was assessed by means of image digitalization with an Auto-CAD 14R software after 6 weeks (position zero), 6 and 12 months and, then, once a year. All cases were associated to a Profile stem.

Results: All shells showed themselves to be radiographically osseointegrated. 7 cases had acetabular osteolysis (Kaplan-Meier survival: 74.1% at 13 years). The appearance of osteolysis was related to a higher average wear rate (p=0.0021) and a higher wear rate at the end of follow-up (p=0.0147). 11 cases showed a breakage of the PE (Kaplan-Meier survival: 61.69+29.9% at 13 years). These breakages appeared on average after 60.1 months. The distance between the axis of the femoral head and that of the shell on the initial radiograph (position zero or initial settling) was 0.6018 in cases with breakage and 0.2338 in cases with no breakage (p=0.009). PE breakage was related to a higher mean wear rate (p< 0.0001) and the verticalization of the shell (p=0.0016).

Conclusions: Although all Tri-Lock cups were osseoin-tegrated, the breakage of the ACS insert was an usual finding, which was related with a higher initial settling of the PE, a higher mean wear rate and the verticalization of the shell.