Body armor is useful, too. The shard strikes the Kevler-enforced abdomen of his suit, which yanks its wearer back to the here and now. That was close. A vice-like grip reaches for Nightwing's wrist in the aftermath of that strike as Batman snaps commandingly, "Stop this for two seconds and think." He wants to twist that arm, hear it snap, and the degree to which he desires that violent breaking one bones is enough to stop him in his tracks.