Trephine

![Dr. John Clarke trepanning a skull, ca. 1664, in one of the earliest American portraits. Clarke has a trephine in his right hand. The painting is in Harvard Medical School.[1]](/uploads/202502/17/Dr_John_Clarke_trepanning_a_skull_operation2046.jpg)
A trephine (/trᵻˈfaɪn/; from Greek trypanon, meaning an instrument for boring) is a surgical instrument with a cylindrical blade. It can be of one of several dimensions and designs depending on what it is going to be used for. They may be specially designed for obtaining a cylindrically shaped core of bone that can be used for tests and bone studies, cutting holes in bones (i.e., the skull) or for cutting out a round piece of the cornea for eye surgery.