trephine

A trephine is a surgical instrument used to cut a circular section of bone, most commonly a disk from the skull, but also for bone biopsy or dental procedures. It can be driven manually or powered, and is typically a hollow cylindrical blade with a sharpened rim or teeth along the edge. Many designs include a depth stop or gauge to limit penetration and a handle or chuck for rotation.

Design and variants include manual hand-held trephines, powered rotary trephines, and smaller dental or alveolar trephines. Some models are designed to extract a bone cylinder, while others are intended to create access holes without removing a segment of bone. In medical practice, the instrument may be used in craniostomy, orthopedic applications, or for harvesting bone grafts; in dentistry, trephines are used for procedures involving the jawbone or for preparing sites for implants.

History and usage context: Trephination is an ancient procedure that involved removing a circular piece of bone to relieve pressure or treat injuries. Modern medicine has largely replaced crude trepanation with controlled burr holes and craniotomies performed with specialized drill systems, but the trephine remains a recognized tool in certain diagnostic and surgical contexts, including bone marrow biopsy and maxillofacial procedures.

Safety and considerations: Procedures require sterile technique, imaging guidance when appropriate, and careful depth control to minimize risk of brain or tissue injury, bleeding, and infection. Alternative methods may be used when a circular bone sample is not needed.

See also: craniotomy, burr hole, bone marrow biopsy, dental implant procedures.