A 65-year-old man presents 14 years after total hip replacement with progressive thigh pain and audible clicking. Radiographs show no loosening. Serum cobalt level is markedly elevated. The most likely diagnosis is:

• A Aseptic loosening of the femoral stem
• B Stress fracture of the greater trochanter
• C Iliopsoas impingement
• D Adverse local metal reaction from trunnionosis ✓

Explanation

Trunnionosis, or mechanically assisted crevice corrosion at the head-neck taper junction, can occur even with well-fixed implants and produce elevated serum metal ions, thigh pain, and pseudotumor formation. It is increasingly recognized as a cause of late failure in metal-on-polyethylene bearings when the metal head corrodes against a metal stem taper. Iliopsoas impingement causes groin pain without metal ion elevation.

Reference: Campbell's Operative Orthopaedics, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.