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Updated: Dec 26 2023

THA Trunnionosis

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https://upload.orthobullets.com/topic/422821/images/trunnionosis_example_2.jpg
https://upload.orthobullets.com/topic/422821/images/trunnion_wear.jpg
https://upload.orthobullets.com/topic/422821/images/pseudotumor.jpg
  • summary
    • THA Trunnionosis is a complication of hip arthroplasty caused by metal ion release from corrosion at the femoral head-neck interface morse taper leading to hip pain and adverse local tissue reactions.
    • Diagnosis can be suspected in a patient with elevated serum metal ions with cobalt levels being elevated more substantially than chromium levels. MRI studies can be helpful to assess for pseudotumors. 
    • Treatment is observation for patients without symptoms. Single stage revision THA is indicated for patients with a painful THA in the absence of an infection. 
  • Epidemiology
    • Risk factors
      • modular designs
      • large cobalt chrome femoral heads
        • larger heads may put more torsional forces on the trunnion.
      • taper design
        • shorter taper length may afford less interference fit and more micromotion
        • greater rigidity of the taper may lead to less wear
      • metal on metal
        • serum metal ions may contribute to taper wear
        • no pathognomonic serum metal ion level for trunnionosis
        • serum cobalt >1 ng/ml (ppb) should lead to consideration for mechanically assisted crevice corrosion (MACC)
      • mixed alloy components
  • Etiology
    • Pathophysiology
      • Galvanic corrosion
        • corrosion caused by an electrochemical transfer of electrons between dissimilar metals
          • i.e. cobalt-chromium (CoCr) alloy femoral head on a titanium alloy stem
      • Fretting corrosion
        • corrosion from relative micromotion between two materials causing wear
          • i.e. tolerance between male and female morse taper allows for micromotion and wear
          • contributes to trunniononsis
      • Crevice corrosion
        • physicochemical interaction between a metal and environment leading to altered mehcanical properties
        • stainless steel most prone to crevice corrosion
    • The adverse reaction to metal debris generation may result in an aseptic lymphocyte-dominant vasculitis association lesion (ALVAL; also referred to as pseudotumor) similar to that seen in metal-on-metal hips 
  • Presentation
    • History
      • pain and limp are the most common complaints
    • Physical exam
      • occasionally if ALTR is large enough a palpable pseudocyst can be felt
      • abduction weakness if ALTR has caused soft tissue destruction of abductors
  • Imaging
    • AP and lateral hip views should be obtained
      • imaging studies may be normal in the setting of trunnnionosis
    • Judet views and/or CT scan may be obtained if advanced osteolysis is present
    • MARS MRI
      • findings may include periarticular pseudotumors and/or soft tissue destruction
  • Studies
    • Infection should be ruled out
      • ESR, CRP, WBC
      • Aspiration
        • consider manual cell count as metal debris can cause a false elevation of automated cell count
    • Metal ion levels
      • cobalt and chromium ion levels
        • cobalt levels are elevated substantially more than chromium levels 
          • ratio of at least 2:1 encountered when caused by head-neck junction trunnionosis
          • ratio of 1:1 is suggestive of metal-on-metal implant wear
  • Treatment
    • Operative
      • revision total hip
        • indications
          • painful THA with the above risk factors and elevated serum cobalt level compared to serum chromium level elevation
        • technique
          • frozen-sections and intraoperative cultures
          • extensive synovectomy
          • inspection of the taper and decision for retention of stem versus revision stem
          • to ceramic head with titanium sleeve and new polyethylene liner
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