Trunnionosis refers to corrosion and wear at which junction, and how is it detected clinically?

• A. It is wear at the cup-edge interface causing osteolysis; detected by fever and redness
• B. It describes corrosion and wear at the head–neck junction producing metal debris; detected by pain, squeaking, elevated metal ions, and imaging signs of metallosis
• C. It is wear at the polyethylene liner interface with no symptoms
• D. It is a fracture at the stem-bone interface

Answer: (B)

Trunnionosis is corrosion and wear at the head–neck taper (the trunnion) of a modular total hip implant. The micromotion at this junction causes metal debris and ion release, leading to a local metallosis-type reaction in surrounding tissues. Clinically this shows up as hip pain, and many patients notice squeaking or grinding with movement, sometimes with reduced range of motion. Serum metal ions (such as cobalt and chromium) are often elevated, and imaging—especially MRI with metal-artifact reduction or CT—can reveal signs of metallosis, including periprosthetic soft-tissue changes or pseudotumors. Fever or redness is more typical of infection, not the trunnion wear process. Worn wear at the cup-edge or liner interfaces tends to present differently (often with osteolysis or different symptoms), and a stem-bone fracture is a separate mechanical failure.