Revision of failed acetabular components utilizing a cementless oblong cup: an average 9-year follow-up study

Failure of acetabular components often leads to bone loss with extensive elongated defects in the surrounding bone. In these cases, reconstruction is challenging and stable fixation of the revision implant difficult. The use of an oblong cup has been described as an option for acetabular reconstruction in such revisions. We report the first long-term results obtained with this implant to date. Fifty-six longitudinal oblong revision cups (LOR (TM)) were evaluated clinically and radiologically after a follow-up of 8-12 years (average 9 years). The defects treated with the LOR (TM) cup ranged from Paprosky type 1-3. Allogenic cancellous bone chips were additionally used in 31 reconstructions to fill cavitary defects. Based on radiological criteria, 50 acetabular implants underwent osseointegration without any definitive signs of loosening; 2 consistently exhibited zonal radiolucent lines that were always smaller than 2 mm, 1 migrated by around 3 mm. None of these cases exhibited any clinical symptoms. In 11 cases where acetabular defects manifested postoperatively, 8 were remodeled completely and 3 partially at final follow-up. Three revision implants migrated farther than 5 mm and had to be revised before 32-month follow-up. In addition, 1 septic implant failure occurred. After an average follow-up of 9 years, 93% of the investigated implants remained in situ without further revision and 95% without aseptic implant failure. This 12-year clinical study demonstrates that the LOR (TM) cup offers a successful concept for the revision of failed acetabular components that also promotes the biological reconstruction of bony defects. Compared with other methods with similarly long follow-ups, our long-term results prove this procedure has a very low rate of revision and aseptic implant failure.