O1131 TEN YEAR FOLLOW-UP OF ACETABULAR COMPONENT WEAR

Abstract

Purpose: The purpose of this research was to evaluate the degree of polyethylene wear in the acetabular component 10 years after cemented total hip arthroplasty. In addition, with the help of the accepted standards the connection between the degree of acetabular wear and acetabular loosening was studied. Materials/Methods: 110 cases, operated with cemented arthroplasty of the hip in 1990–1992, were selected for the study. Antero-posterior (AP) and lateral radiographs were analyzed with regard to migration, radiolucent lines, pelvic osteolysis and two-dimensional linear wear of the polyethylene. The diameter of the component was measured (diameter of the wire markers imbeded in the plastic), and the distance between the central point of the femoral head component and the outer ring (T1 and T2). The ratio calculated from these distances (T1/T2) presents the linear scale of the component wear and the migration of the femoral head component. The polyethylene wear was further studied in contrast of the femoral head component size (26 and 32). In addition, the degree of acetabular loosening was measured by the De Lee and Charnley radiological score. Results: Out of the 110 cases, 23.1% of the T1/T2 ratio equaled 1, measured on the AP roentgenographs, which means that there is no wear in the acetabular component. 30.5% of the cases had a ratio of 0.96–1 (minimal wear), 30.5% of the cases had a ratio of 0.92–0.96 (intermediate wear). Severe wear (less than 0.92) was observed in 15.9% of the cases. These same ratio groups on the lateral view had the following distribution in respected order: 27.3%, 33.4%, 28.7%, 10.6%. Polyethylene wearing was found to be more evident when a 26 size femoral head was used. Advanced acetabular loosening in the radiological findings was only evident in the most deteriorated group. Conclusion: It can be concluded that the degree of the polyethylene wear of the acetabular component can be satisfactorily measured from the migration of the femoral head component on the roentgenographs. The dissimilar distribution of the ratio groups between the AP and lateral roentgenographs indicate asymmetrical wear.