Definition
A trepan is a surgical instrument used to remove a circular section of bone, typically from the skull. It's an ancient tool used in a procedure called trepanation, which is basically drilling a hole in the skull. Think of it as a very old-school drill for the head 💀. Unlike modern surgical drills, the trepan was operated manually. Trepanation was performed for various reasons, from relieving pressure to attempting to cure mental disorders. It's one of the oldest known surgical procedures.