MIGRATION MEASUREMENT OF ACETABULAR COMPONENTS IN CEMENTLESS TOTAL HIP-ARTHROPLASTY

Purpose: Migration measurements of acetabular components using a speci al computer aided method (EBRA=abbrevation for the German term ''Ein-B ild-Rontgenanalyse'') were perform ed to evaluate early results of the implants and predict aseptic loosening. Methods: Standard ap-radiogra phs of the pelvis were marked, specific points were digitised. Simulat ing the spatial situation the programme computes longitudinal and Vert ical migration of the cup. 74 acetabular components in 71 patients cou ld be studied by migration measurements. Results: 14 patients showed m igration of more than 1 mm, which is the confidence limit of this meth od. Each of these patients showed diverse reasons for the migration, i .e. osteoporosis of the acetabular bone stock or problems concerning t he surgical technique which means malposition of the cup or insufficie nt reaming of the bone. There were some patients with severe congenita l dysplasia of the hip and in some cases the inclination angle of the cup was too great. Conclusion: The technique applied for measuring mig ration of acetabular components can be useful for evaluating early ins tability of the implant and can be helpful in detecting problems conce rning the surgical technique.