A new constrained total hip arthroplasty (THA) is currently in use. We report on one patient with 2 failed Trilogy constrained acetabular liners in the same hip (Zimmer, Warsaw, IN). We are not aware of any other published reports concerning failure of this implant. Both times, the constrained THA seems to have been properly assembled. Impingement of the modular femoral head skirt on the polyethylene liner appears to have caused the reinforcing ring to disengage and the THA to dislocate. Skirted modular femoral heads should probably not be used with this implant.