Enlargement of the external auditory canal by drilling all around the walls of the bony canal (360°). At the end of the procedure, the external auditory canal resembles a cut cone in shape.

The main indication is tympanic membrane perforation in which the anterior edge of the perforation cannot be observed sufficiently. It is also used as an intermediate stage to widen the exposure in cases such as primary cholesteatoma limited to the middle ear.

The soft tissues have been elevated from the lateral surface of the temporal bone, exposing the external auditory canal and the mastoid. The critical structures are indicated in the figure.

EAC: External auditory canal

HS: Henle spine

TB: Tympanic bone

TMS: Tympanomastoid suture

TSS: Tympanosquamous suture

Using a medium-sized cutting burr, the lateral part of the external auditory canal is drilled circumferentially. All the overhanging areas of bone, including the tympanomastoid and tympanosquamous sutures, are removed.

II: 3–4mm cutting burr

MIL: Temporomandibular joint reflection

IEAC: Isthmus of external auditory canal