A trephine (; from Greek τρύπανον, trypanon '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 meant to be used for. A trephine 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 (e.g., the skull), or cutting out a round piece of the cornea for eye surgery. A cylindrically shaped core of bone (or bone biopsy) obtained with a bone marrow trephine is usually examined in the histopathology department of a hospital under a microscope. It shows the pattern and cellularity of the bone marrow as it lay in the bone and is a useful diagnostic tool in certain circumstances such as bone marrow cancer and leukemia.
See also Trepan Trepanning Trepanation in Mesoamerica Instruments used in general surgery
References
External links "Trepan" . The American Cyclopædia. 1879.


![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]](https://upload.wikimedia.org/wikipedia/commons/thumb/4/4b/Dr_John_Clarke_trepanning_a_skull_operation.jpg/330px-Dr_John_Clarke_trepanning_a_skull_operation.jpg?utm_source=en.wikipedia.org&utm_campaign=parser&utm_content=thumbnail)
