LONG-TERM SURVIVORSHIP OF THE CEMENTLESS ALLOCLASSIC TOTAL HIP ARTHROPLASTY

Abstract

Aims: The aim of this study is to present clinical and radiographic long-term results including a survival analysis of the cementless Alloclassic total hip arthroplasty system.

Matarial and Methods: 103 consecutive primary hip arthroplasties using a threaded conical titanium cup (Alloclassic CSF) and a rectangular titanium pressfit stem (Alloclassic SL) were evaluated clinically and radiographically with an average follow-up period of 14.4 years (range 10.2 to 17.1 years). In all cases a 32 mm alumina ceramic head and a UHMW polyethylene inlay were used. Clinical results were evaluated according to the Harris Hip Score, the SF-36 and WOMAC score. Radiographic results were analysed on antero-posterior x-rays. A statistical survivorship analysis was calculated using Kaplan-Meier curves.

Results: The average Harris Hip Score at the last follow-up was 89.2. The mean pain score was 41.6, the mean functional score 47.6. Radiographic results showed a continuous radiolucency around the cup in three cases. Radiolucent lines around the stem were observed only in the proximal zone 1 in 52 and in zone 7 in 26 cases. Cortical hyperthrophy occurred in the distal zone 3 in 33 cases and in zone 5 in 72 cases. Fifteen hips were revised, eleven of them because of increased polyethylene wear after a minimum follow-up of 10 years. One patient needed revision due to a late deep infection after 7.4 years. There were three cases of aseptic loosening without signs of progressive polyethylene wear that led to a cup exchange. The cumulative survivorship with revision due to aseptic component loosening as endpoint was 95.6 % for the cup and 100 % for the stem after 15 years.

Conclusion: Our data suggest that excellent long-term results can be achieved with the cementless Alloclassic system. The main limiting factor for implant survival was found in increased polyethylene wear. We therefore recommend early exchange of the inlay to avoid component loosening and the use of modern wear couples such as ceramic-on-ceramic, metal-on-metal or crosslinked polyethylene.