Utricle, saccule, and cochlear duct in relation to stapedotomy. A histologic human temporal bone study.

This study was performed to determine the area in which and the circumstances under which stapedotomy can be relatively safely performed. Measurements were made from central areas of the medial surface of the stapedial footplate to the utricle, the saccule, and the cochlear duct in 10 normal and 11 otosclerotic temporal bones. The mean distances to the utricle ranged from 1.9 to 2.4 mm, and those to the saccule from 1.7 to 2.1 mm. The minimal distance to the utricle was measured from the posterior (0.58 mm) and superior (0.62 mm) borders of the stapedial footplate. The minimal distances to the saccule were from the anterior (0.76, 0.86, and 1.00 mm) border of the stapedial footplate. All other measurements were of more than 1 mm. The shortest distance between the cochlear duct and the inferior border of the footplate was 0.2 mm. Statistical analysis has shown no significant differences for the mean values obtained in normal and otosclerotic temporal bones. Fathoming of the vestibule below the central and inferior thirds of the footplate surface has shown that there is no likely danger to the vestibular end organs or cochlear duct if manipulations are carried out no deeper than 1 mm below the surface. The safest place for a stapedotomy opening is in the central and inferior-central thirds of the footplate. A stapedotomy piston of 0.4 mm in diameter can be introduced relatively safely to a depth of 0.5 mm in the vestibule over the entire surface of the stapedial footplate.