An illustration explains the bilateral arm transplant

An illustration explains the bilateral arm transplant surgery performed on U.S. Army. Sgt. Brendan Marrocco by doctors at Johns Hopkins Hospital in Baltimore, Dec. 18, 2012. Marrocco, 26, lost all four limbs to an explosively formed projectile in Iraq in 2009. The Armed Forces Institute of Regenerative Medicine funded research to advance the techniques that made the surgery possible. (U.S. Army photo courtesy of Johns Hopkins Hospital/Released)