Trunnion fracture of femoral prosthesis following a large metal-on-metal uncemented total hip arthroplasty: a case report.

The primary reason for the trunnion fracture in our case was the faulty stem design of the AML [with a small (9/10) taper, and a large head], causing excessive bending moment at the trunnion, worsening the cantilever effect and leading to subsequent cyclic fatigue failure. Whilst gross trunnion failure (GTF) with dissociation of the head from the taper is commonly reported, trunnion fracture per se is a rare and devastating complication. The AML-A stem has since been recalled by the company and there is a need to constantly monitor these patients for potential trunnion-related complications.