1. The osteotome is adjustable hollow gouge, which comprises a gouge handle, a connection rod, and a gouge core.

2. Methods Transcranial drainage and closed tee-junctions irrigation was carried out under local anesthesia in 31 cases of chronic subdural hematoma by using self-made trocar and osteotome .

3. The osteotome (1) is dimensioned such that a first Antinode (5) of the ultrasonic vibrations is located at a proximal end of the waveguide (2), a second Antinode (7) is located at the distal tip of the blade (3) and a node (6) is located where the waveguide (2) and blade (3) meet.