Review Question - QID 218116

A 72-year-old male presents to the clinic with worsening left hip and groin pain that no longer responds to NSAIDs. He denies any traumatic events, but recently completed ten sessions of physical therapy for a side-bending gait pattern without any improvement. The patient states he had received a total hip replacement approximately 10 years ago by another surgeon and that he felt good for the first couple of years. The operative report indicates a cobalt-chromium head implant. His presenting radiographs are shown in Figure A. Metal artifact reduction sequencing (MARS)-MRI shows an appreciable fluid collection around his hip implant as shown in Figure B. Review of his recent labs shows a cobalt level of 15.2 µg/L (average: 0.7-3.4 µg/L) and a chromium level of 3.1 µg/L (average: 0.5-2.5 µg/L). Which of the following is the root cause of this patient's underlying condition?