Is It the Trunnion or Is It the Liner? Investigating Bilateral Dual-Mobility Constructs With Different Inner Femoral Head Compositions.

Dual-mobility designs aim to reduce dislocation with a dual head, creating a larger effective head size. However, concerns exist regarding corrosion from dissimilar metal interfaces. An 80-year-old female patient exhibited elevated cobalt (2.6 μg/L) and titanium (7.8 μg/L) but normal chromium (1.2 μg/L) levels after 5 years. She had staged bilateral total hip arthroplasty with identical modular liners, a 22 mm cobalt-chrome and a 28 mm ceramic head in the left and right hips, respectively. Magnetic resonance imaging showed left-sided ALTR. At revision, the trunnion and head showed gross corrosion. Biomechanical analysis confirmed trunnionosis of the 22-mm cobalt-chrome head without liner corrosion, suggesting dual mobility may increase the risk for trunnionosis at this size. This case highlights cobalt-chrome head risks and identifies trunnion corrosion as a cause of metallosis.