Reactive Peri-Arthroplasty Pseudotumors: A Rare Cause of Hip Pain and Iatrogenic Sciatica.

Total hip arthroplasty (THA) is the preferred treatment for patients with hip joint disorders refractory to conservative management. While original implants were designed to articulate a metallic femoral head onto a polyethylene liner, the popularity of "metal-on-metal" (MoM) hip implants surged in the early 21st century due to their perceived superior long-term durability and lower revision rates. However, subsequent follow-up studies showed high failure rates due to inflammatory responses to periprosthetic metallic debris leading to lymphocytic proliferation, soft tissue necrosis or fibrosis, systemic metal toxicity, and/or the development of cystic pseudotumors. Although these discoveries resulted in a significant decrease in MoM THA and revision procedures, the majority of MoM hip implants persist in the adult population. In this case report and review, we report the presentation, diagnostic work-up, and management of an 84-year-old status-post MoM THA who presented with unilateral leg tenderness and poor ambulation secondary to pseudotumor-induced sciatica.