When the airplanes exploded into the World Trade Center and Pentagon seven years ago tomorrow, Andrew Hillstrom was studying 10th-grade geometry back in Kenosha, Wis. Now he lies in a rumpled bed at the Walter Reed Army Medical Center, in Washington, D.C., and awaits surgery on the remains of his right elbow.

Shrapnel shattered it into tiny pieces when Army Sgt. Hillstrom, 21, was hit last Sept. 21 in Iraq. Since then, he’s been in and out of operating rooms. He arrived here for surgery five months ago, and came back the other day for more cutting.