Kirschner wires, or K-wires, are commonly used in hand surgery to fix fractures. They are named after Martin Kirschner, a German surgeon who introduced them in 1909. They are made of stainless steel and have a sharp tip.
Sometimes the end of the wire is left sticking out of the skin; other times, they are cut so that they are beneath the skin. This is a photo of a different patient with two K-wires in her finger.