A Case Report of Metallosis-Related Aseptic Loosening of Primary Total Knee Arthroplasty Implant Managed with Revision Total Knee Arthroplasty

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Abstract

Metallosis is a rare but serious long-term complication following total knee arthroplasty (TKA), most commonly resulting from polyethylene insert wear that leads to unintended metal-on-metal articulation and subsequent metallic debris deposition. We present the case of a 70-year-old female who developed progressive pain, stiffness, and instability in her right knee, 19 years after undergoing primary TKA. Radiographic evaluation revealed loosening of both femoral and tibial components, while laboratory investigations ruled out infection. Intraoperatively, extensive metallosis was identified with diffuse, black-stained synovium, metallic debris accumulation, and complete wear of the medial polyethylene insert exposing the tibial tray. Both prosthetic components were found to be loose, accompanied by collateral ligament laxity. Thorough synovectomy and debridement were performed, followed by revision TKA using a constrained condylar knee prosthesis (Zimmer Rotating Hinge Knee [RHK]). Metallosis-associated inflammatory reaction can result in osteolysis, soft tissue destruction, and eventual implant failure, making early diagnosis and timely intervention essential despite the non-specific clinical presentation. Revision arthroplasty with appropriately constrained implants can achieve satisfactory outcomes in cases associated with instability and severe component loosening.