Metallosis and pseudotumor following total hip arthroplasty: a case report of two patients

Metallosis is a metal-induced synovitis and inflammatory reaction that arises secondary to friction at implant interfaces and debris release, causing pseudotumor formation. The presentation is often nonspecific but can manifest with severe symptoms and complications that interfere with long-term functionality and quality of life.

Patient A is a 58-year-old female who underwent total hip replacement 16 years ago and presented with deep vein thrombosis. Imaging showed a huge multilobulated complex intrapelvic pseudotumor communicating with the hip joint and causing a mass effect on the surrounding vasculature, along with failure of modular components. She underwent two-stage revision arthroplasty and was ambulatory. Patient B is an 81-year-old female with a history of left hip nailing and subsequent revision to total hip arthroplasty. She experienced failure of the acetabular component with discontinuity of the medial acetabular wall. Intraoperatively, she was found to have severe metallosis and pseudotumor formation. Surgery involved extensive debulking and removal of hardware without the possibility of reconstruction or prosthetic reimplantation due to soft tissue damage, recurrent collections, and infection, requiring the application of a vacuum-assisted closure device and a prolonged course of antibiotics.

There are several risk factors, including female sex, high body mass index, elevated activity levels, and component malposition. Symptoms can be nonspecific but may present as compressive symptoms and more severe complications. Diagnosis requires a thorough history and physical examination, imaging, and adjunctive laboratory tests. A biopsy is required to distinguish pseudotumors from malignancy and infections. Revision arthroplasty involves removing the failed implant and debriding necrotic or inflamed tissue. It is important to revise to a non-metal-on-metal bearing surface. The choice between one-stage versus two-stage revision depends on pseudotumor size, soft tissue destruction, and stability.

Pseudotumor diagnosis requires a combination of clinical, radiographic, and histologic evaluation. Management remains complex, with no universally accepted algorithm. Revision surgery is typically reserved for symptomatic patients, but the prognosis is variable, with notable recurrence and complication rates.