Table 1.

Measured anatomical distances and their clinical relevance

Anatomical measurements	Indication for measured distance:
Length of malleus (manubrium + head)	Universal measurement, easy to compare, no direct surgical relevance
Distance from body of incus to mastoid cortex	The estimate for drilling depth, e.g. in mastoidectomy
Horizontal diameter of bony ear canal (external meatus)	Estimation of drilling work during canaloplasty
Vertical diameter of bony ear canal (internal meatus)	Estimation of tympanic membrane diameter, universal anatomic measurement
Size of facial recess	Space for posterior tympanotomy
Distance from facial recess to mastoid cortex	The estimate for drilling depth regarding the facial nerve
Distance from facial nerve (mastoid part) to recess of bony ear canal	Limit of posterior drilling in canaloplasty
Diameter of oval window	Stapedotomy, stapedectomy. Identification of the oval window area and surgical access to stapes footplate
Diameter of round window	Cochlear implantation and active middle ear implantation. Identification of round window area and evaluation of surgical approach
Length of styloid process	Universal anatomical measurement, stylalgia
Distance from sigmoid sinus to back wall of bony ear canal	The space available for drilling in e.g. mastoidectomy