Metallosis Following Primary Total Knee Arthroplasty

Aim and background: Characterized by pain and swelling, metallosis following primary total knee arthroplasty (TKA) is a rare but known complication.Polyethylene wear due to biomechanical stress and debris deposition in periprosthetic tissue often leads to osteolysis, chronic inflammation and implant loosening, necessitating careful planning, adequate debridement, and competent revision surgery execution.Case description: A 78-year-old hypertensive healthy female with a body mass index (BMI) of 25.5, underwent primary bilateral TKA 19 and 15 years ago on the right and left side, respectively.She presented with deep grinding pain of insidious onset for 6 months, chronic swelling for 3 months, restricted range of motion (20-80°), and recurrent instability of the right knee.Plain radiography revealed "bubble sign" and "cloud sign" with osteolysis suggesting implant loosening, polyethylene liner dissociation and loss of joint congruity.Blood investigations returned unaltered.She underwent single-stage surgery for debridement, synovectomy, implant removal, and revision arthroplasty using a hinged prosthesis.Intraoperative findings included synovial thickening with black deposits, a severely worn off polyethylene insert, and metal surface attrition with erosion.Specimen biopsy and histopathology showed pigmentation, histiocyte infiltrates and multinucleated giant cells.Postoperatively, she was pain-free and achieved an improved range of motion (10-120°) with adequate joint stability.Conclusion: Although rare after primary knee arthroplasty, metallosis results in chronic debilitating pain and loss of joint function due to osteolysis and implant loosening.Accurate diagnosis, intricate planning, and a well-performed synovectomy with revision arthroplasty followed by postoperative rehabilitation are essential to relieve symptoms, restore joint function, and allow a return to routine daily activity.Clinical significance: Metallosis is a rare but known complication following primary TKA, often due to various causes.With an exponential rise in the number of TKA in India, it is imperative that rare complications form part of clinical literature and add to the knowledge of fellow surgeons, aiding them in the prevention, diagnosis, and management of such complications.