Two-year radiologic assessment of the Trident Peripheral Self-Locking cup using EBRA

Abstract

We performed a radiologic assessment of the Trident Peripheral Self-Locking cup 2 years after implantation to assess early migration behaviour and to establish if incomplete postoperative seating correlated with early instability. A retrospective analysis of 30 cases was performed using EBRA. No cups had acetabular screws. Average total migration was 1.5 mm (range 0.1 to 5.9 mm). Seventeen showed total migration >1 mm and 7 of these showed further migration >2 mm (range 2.3 to 5.9 mm). Twenty cups demonstrated incomplete seating on initial post-operative radiographs (mean 1.4 mm, range 0.3 to 3.0). No relationship between incomplete seating and migration was identified (p = 0.86). The majority of gaps consolidated at differing times within the 2 year period. Oxford Hip scores showed significant improvement after surgery (p = 0.001) and this was independent of migration (p = 0.76). At 5 years there were no revisions for aseptic loosening. Conclusion: The majority of the cups demonstrated early radiographic instability, and this was not related to incomplete seating. Five year functional outcome appears good and independent of migration and initial seating