The exoscalpel is a precision surgical instrument, and the medical version of a laser scalpel. It employs laser beams make an incision in skin or other tissue. After completion of surgery, a dermal regenerator can be used to repair the cut tissue.
An exoscalpel was used during the surgery to replace Lieutenant Worf's spinal column in 2368. (TNG: "Ethics")
The exoscalpel was a standard medical tool aboard the USS Prometheus (NX-59650) in 2374. (VOY: "Message in a Bottle")