Cementless total hip arthroplasty with a threaded acetabular cup.

Eighty cementless total hip arthroplasties, using smooth threaded cups (Lord universal model), were carried out between 1985 and 1988. Sixty of these patients were available for clinical and radiological study with a mean follow up of 6 years. Five cups were revised for aseptic loosening and another 6 are awaiting revision, so 18% of the cups have failed. Fixation was classified as stable, fibrous-stable and unstable on radiographs. Twenty-six (43%) had fibrous-stable fixation and most were satisfactory clinically. This type of fixation must be carefully watched for signs of osteolysis, especially around the threads, as this precedes failure. Smooth threaded cups have good short term results, but deteriorate because of deficient osteointegration and later from wear debris. This type of cup does is not a good alternative to cemented cups.