Catastrophic Wear-induced Pseudotumor Formation 20 Years Post-total Hip Arthroplasty: A Rare Complication of Non-Metal-on-Metal (MoM) THR

Abstract

Pseudotumors following adverse reactions to metal debris are most commonly associated with metal-on-metal (MoM) total hip replacements (THRs). However, their occurrence in non-metal-on-metal (non-MoM) THRs, such as metal-on-polyethylene (MoP), is rare. We present a case of pseudotumor formation secondary to catastrophic polyethylene liner wear in a MoP THR two decades after the index procedure. A 68-year-old male presented with progressive pain, stiffness, and swelling around the left hip 20 years after receiving a MoP total hip arthroplasty. Clinical evaluation revealed a firm, non-fluctuant periprosthetic mass. Radiographs demonstrated eccentric femoral head position with a large expansile osteolytic lesion. MRI revealed a heterogeneous soft tissue mass with metal artifact. Serum cobalt and chromium levels were elevated. Aspiration yielded sterile dark fluid, and histopathology showed lymphoplasmacytic infiltrates consistent with an ALVAL-type response. Intraoperatively, complete polyethylene liner wear was noted with metal-on-metal contact between the cobalt-chromium head and titanium shell, generating extensive metallosis and pseudotumor formation. The patient underwent a two-stage revision, including pseudotumor excision and distal femoral replacement. Pseudotumors can develop in non-MoM THRs due to catastrophic polyethylene wear and secondary metallosis. Long-term follow-up is essential for early detection of wear-related complications, even in conventionally inert bearing surfaces. Surgeons should maintain vigilance for late-onset masses in THA patients, regardless of implant type.