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Updated: Feb 14 2022

TKA Metal Hypersensitivity

  • summary
    • TKA Metal Hypersensitivity is a complication of TKA that may lead to persistent knee pain and stiffness as a result of an allergic reaction to the metallic components.
    • Diagnosis involves careful patient history, and ruling out infection or aseptic loosening. Patch testing may be helpful in diagnosis.
    • Treatment generally involves component exchange to a hypoallergenic femoral component with all-polyethylene tibial component.
  • Epidemiology
    • Incidence
      • rare
  • Etiology
    • Pathophysiology
      • Type IV - delayed-type cell mediated hypersensitivity
        • mediated by T cells
      • reaction to
        • nickel found in cobalt-chromium alloys
        • metal ions deposit in local tissue, must react with proteins to initiate hypersensitivity
        • biggest link may be metal ions/hypersensitivity as a causative initiator of early implant loosening
  • Presentation
    • History
      • may have history of dermatitis, eczema, other signs of atopic hypersensitivity
    • Symptoms
      • vague persistent pain
      • persistent, unremitting effusion/swelling
      • stiffness
    • Physical exam
      • document range of motion
  • Studies
    • Evaluation
      • patch testing (limited evidence for direct link to diagnose hypersensitivity)
      • lymphocyte transformation test (LST)
      • T-lymphyocyte rich immunohistopathology
      • negative work-up for chronic/acute infection (must be ruled out)
    • Diagnosis
      • exact definition is controversial
        • some argue combination of a positive patch test, positive immunohistopathology, and relief of symptoms upon implant exchange is only way to confirm diagnosis
        • others argue that metal hypersensitivity is a diagnosis of exclusion, only arrived upon when infection and aseptic loosening is ruled out
  • Treatment
    • Operative
      • implant exchange
        • indications
          • persistent symptoms affecting quality of life
        • technique
          • hypoallergenic femoral component with all-polyethylene tibial component if possible
          • at time of surgery, chronic inflammatory synovitis typically present
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