The Zweymüller threaded cup: a choice in revision? Migration analysis and follow-up after 6 years.

Excellent long-term results are reported for threaded cups with an osteointegrable surface in primary interventions. So far, little data are available on the use of such implants in revision cases. We investigated 30 loosened Aesculap PM threaded cups (Tuttlingen, Germany) with a smooth surface, revised with a conical, corundum-blasted Zweymüller threaded cup (Zweymüller Alloclassic CSF cup, Zimmer, Warsaw, Ind). Aseptic radiological loosening was seen in 8% of cases, and a survival rate of 95% was achieved after 6.1 years. Average migration was 1.4 mm cranially and 0.7 mm medially. The Harris hip score improved from 42 points preoperatively to 75 points at follow-up. Good medium-term results are possible after revision using a threaded cup with an osteointegrable surface, but not if segmental acetabular margin defects are present.