Review Question - QID 218140

A 42-year-old female presents to your clinic with 1 year of hip pain. Upon chart review, you find that she had a total hip arthroplasty for hip dysplasia 5 years ago by an outside surgeon. The operative report states that a modular neck hip stem was used. On exam, she has a limb-length discrepancy but otherwise normal gait. On serum labs, erythrocyte sedimentation rate is 1.1 mm/h, C-Reactive Protein is 0.9 mg/L, Cobalt level is 6.1 ng/mL (normal <0.9 ng/mL), Chromium level is 2.3 ng/mL (normal <0.3 ng/mL). Radiographs show a stable modular neck hip stem implant without subsidence or surrounding lucency. MRI with metal-artifact reduction sequence (MARS) is performed and shows capsular thickening with intracapsular fluid.

What is the most likely etiology of her symptoms?