FIFTEEN TO TWENTY YEARS RESULTS OF A CEMENTLESS TOTAL HIP ARTHROPLASTY USING A THREADED CUP AND A RECTANGULAR TAPERED STEM

Abstract

Aims: The aim of this study is to present long-term results of the cementless Alloclassic total hip arthroplasty system of up to 21 years.

Matarial and Methods: 152 consecutive primary hip arthroplasties using a threaded conical titanium cup (Alloclassic CSF) and a rectangular titanium press-fit stem (Alloclassic SL) were implanted between September 1987 and December 1988. In all cases a 32 mm alumina ceramic head and a UHMW polyethylene inlay were used. Clinical and radiological results were available for 55 patients (36,2%) with a minimum of 15 years (15.0 to 20.9 years). Clinical results were evaluated according to the Harris Hip Score, the SF-36 and WOMAC score. Radiographic results were analysed on anteroposterior x-rays according to the method of DeLee and Charnley for the cup and of Gruen for the stem.

Results: The average Harris Hip Score at the last follow-up was 87.3. The mean pain score was 41.5, the mean functional score 47.3. Radiographic results showed osteolytic lesions around the cup in one case. Radiolucent lines around the stem were observed only in the proximal zones in 2/3 of the cases, cortical hyperthrophy occurred in the distal zones in ¾ of the evaluated hips.

23 hips (15.1%) needed revision surgery. The majority (17 hips – 73.9% of all reoperations) were revised due to progressive Polyethylene wear, all after a minimum of ten years. Exchange of the polyethylene inlay and the ceramic head was performed in 14 hips. In two cases the acetabular component and in one case the femoral component were found to be loose intraoperatively because of the wear debris and had to be exchanged. 4 hips had to be revised due to aseptic cup loosening without signs of increased polyethylene wear. There was one revision due to a late deep infection and one because of a periprothetic femoral fracture.

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 loosening and the use of modern wear couples such as ceramic-on-ceramic, metal-on-metal or crosslinked polyethylene.