The correlation between immediate radiolucent lines and early implant migration in cemented acetabular components

Periacetabular radiolucent lines (RLLs) on postoperative radiographs have been associated with early loosening of the acetabular component. It has also been shown that excessive migration of an implant corresponds to an increased incidence of later clinical failure. This study relates RLLs on anterior-posterior hip radiographs taken 10 days and 6 months postoperatively to implant migration detected by roentgen stereophotogrammetric analysis. We have shown that RLLs in DeLee and Charnley zone III in the first week postoperatively as well as at 6 months are positively and significantly (P < .05) associated with migration detected by roentgen stereophotogrammetric analysis. No significant association was found for zone I or II at either 10 days or at 6 months. Considering the limitations in observing RLLs, their presence in zone III appears to reflect on the mechanical stability of the acetabular cup from the beginning. This indicates that zone III, which represents the inferomedial aspect of the acetabulum, might have to receive special attention when preparing the acetabulum and implanting the acetabular cup.