TRANSMEATAL APPROACH AND THE OPTIMAL DEVICE FOR MINIMAL INVASIVE SURGERY
The transmeatal operation is the favorable approach for a small lesion in the mesotympanum, congenital cho-lesteatoma, malformation of the ossicles, perforation of the ear drum, and also otosclerosis. The advantage of the transmeatal operation is that it involves minimal invasive surgery. The disadvantage of this approach is the limitation of the operation field because of the shape and size of the external auditory canal.
The external auditory canal was measured using temporal CT images of 48 ears of 32 adults. Table 1 shows the width of external auditory canal. The width of the canal was 10.4 mm x 12.4 mm at the external orifice, 8.7 mm x 8.8 mm at the osteochondral junction and 9.1 mm x 9.1 mm at the annuls of the drum. The width of the canal was 4.5 mm x 4.8 mm at the isthmus. The superior-inferior length is always greater than the antero-posterior length.
Table 1. Width of the ear canal measured using temporal CT images.
The 3D shape of the external canal was reconstructed and cut in round slices. The cross section of the external auditory canal is oval-shaped, not round (Figs. 1 and 2).
We found that the favorable shape of the ear speculum is oval in the cross section in order to use the space more effectively (Fig. 3).
Fig. 1. 3D reconstruction of the external ear using a human temporal bone specimen. The dotted line shows the cutting direction of the ear canal.
Fig. 2. Cross section of the reconstructed ear canal. The shape is oval, not round.
Fig. 3. Top: ear speculum and speculum holder. Bottom left: oval-shaped ear speculum. Bottom right: round-shaped ear speculum.
Address for correspondence: Taeko Okuno, Kandaizumicho, Chiyodaku, Tokyo, Japan. tokuno@mitsuihosp.or.jp
Cholesteatoma and Ear Surgery – An Update, pp. 361–362
Edited by Haruo Takahashi
2013 © Kugler Publications, Amsterdam, The Netherlands