We report a case of excessive wear of a polyethylene insert after the incomplete seating of the acetabular metal wire retaining ring in the Omnifit modular noncemented acetabular component (Osteonics Corporation, Allendale, NJ, U.S.A.). Seventy-five months after a primary total hip arthroplasty, metal fragments generated by metal wire breakage in the incompletely seated ring induced excessive abrasive third-body wear at the inner articulating surface and the liner-backing interface. Marked periprosthetic osteolytic lesions, which necessitated revision surgery, were observed. This case suggests that when this type of locking mechanism is used, an intraoperative radiograph should be taken to confirm the proper seating of the retaining ring. When incomplete seating is noticed postoperatively, the patient should be followed up carefully, particularly when the wire is broken.