Which of the following describes trunnionosis and its contributing factors?

• A. Trunnionosis is corrosion and wear at the head–neck junction producing metal debris; factors include micromotion, head size, material combination, taper design, and assembly
• B. Trunnionosis is infection around the implant
• C. Trunnionosis is bone loss due to osteoporosis
• D. Trunnionosis is a postoperative soft tissue swelling

Answer: (A)

Trunnionosis is corrosion and wear at the head–neck taper of a modular hip prosthesis that produces metal debris, which can provoke adverse tissue reactions. The contributing factors come from how the junction moves and how the components interact: micromotion at the head–trunnion interface causes fretting and corrosion; using larger femoral heads increases the lever arm and forces at the taper, promoting wear; the material pairing and electrochemical properties of the head and trunnion influence corrosion potential; the taper design and surface finish affect how well the head seats and distributes load; and the assembly process (cleanliness, proper seating, and sufficient impaction) determines how securely the components fit and resist micromotion. This description matches trunnionosis, whereas infection, osteoporosis-related bone loss, or postoperative soft tissue swelling describe other problems unrelated to the head–neck junction wear and metal debris.