We report recurrent dislocation with two failed Duofit IPR constrained liners in the same hip. Both times, the cementless cup and stem were well fixed and well positioned, and the constrained liner was found to be well fixed within the cup and undamaged. The locking ring was well positioned with complete seating into the liner, but had a small "scratch" and a plastic deformation of superior and inferior poles, respectively. This finding suggested that impingement between the neck and the rim of the ring had occurred, especially during flexion, so-called failure type IV. It required revision to a large-diameter metal-on-metal modular articulation. The well-fixed and wellpositioned femoral stem was left in place. We are not aware of any other published reports concerning failure of this implant.... [Leer más...]