O3003 HA COATED THA CUPS – TIGHT INTERFACE BUT INCREASED WEAR

Abstract

Aims: To investigate the cup interface with different means of þxation. Methods: 83 patients (89 hips) (median age of 56 years) were operated with a uncemented hemispherical porous-coated cup made of titanium alloy (Reßection, Smith & Nephew¨) with pressþt technique. The patients were randomised to pressþt-only (PF), PF + Hydroxyapatite (PF+HA), PF + 3 screws (PF+S) and PF + 3 pegs (PF+P). The development of radiolucent lines in percentage of circumference was evaluated on x-ray þlms postoperative and at two years. Radiostereometry was used for migration and wear measurement. Results: All cups were stable after 2 years. The groups showed no signiþcant difference in migration. Radiolucencies were found in a mean of 20% of interface in PF+S, 14% in PF+P, 11% in PF and 0% in PF+HA (P = 0.005, Kruskall Wallis test). 5 focal osteolysis were found in PF+S, 1 in PF+HA and PF and none in PF+P (ns). 35 cups had a gap between the central part of the cup and acetabulum postoperatively (no differences between groups). After 2 years the gaps in the HA group had disappeared. Cup wear was highest for HA coated cups. Conclusions: Further studies are necessary to reveal whether the better implant bone interface will outweigh the risk for increased wear.