Pseudotumor Caused by Titanium Particles From a Total Hip Prosthesis

摘要

A 77-year-old woman underwent metal-on-polyethylene total hip arthroplasty for osteoarthritis of the right hip at another institution. During surgery, the greater trochanter was broken and internal fixation was performed with a trochanteric cable grip reattachment. Although postoperative recovery was uneventful, approximately 6 years later, the patient had severe right hip pain with apparent swelling, and she was referred to the authors' institution. Plain radiographs showed evidence of severe osteolysis in the proximal femur and cable breakage; however, preoperative aspiration culture findings were negative for bacterial growth. Magnetic resonance imaging showed a well-circumscribed mass, presumed to be a pseudotumor. Serum cobalt and chromium levels were within normal limits, and the serum titanium level was high. During surgery, the mass was excised and removal of the cable system revealed a sharp deficit in the bare femoral stem. Gross surgical findings showed no obvious evidence of infection and no corrosion at the head-neck junction; therefore, all components were retained besides the cable system, which resulted in clinical recovery. All of the cultures from specimens were negative for bacterial growth, and histologic findings were compatible with a pseudotumor, such as histiocytes containing metal particles, abundant plasma cells, and CD8-positive cells. Quantitative analysis by inductively coupled plasma atomic emission spectrometry showed that the main source of metal debris in the pseudotumor was the femoral stem, which was made of titanium alloy, not the broken cable, which was made of cobalt-chromium alloy. The findings suggest that titanium particles can form symptomatic solid pseudotumors.