Biometry of the normal stapes using stapes axial plane, high-resolution computed tomography

The stapes is difficult to analyse on computed tomography because of the small size of its components and its oblique orientation. The stapes axial plane, parallel to the superstructure, seems optimal for this purpose. The present study assessed the position of the stapes axial plane with respect to the usual axial plane including the lateral semicircular canal, and sought to measure the main dimensions of the stapes.

This retrospective study comprised 208 computed tomography scans of normal ears. Stapes length and width, footplate thickness and incudostapedial joint width were measured.

The stapes axial plane was directed upward, outward (44°) and forward (12°) with respect to the lateral semicircular canal plane. Mean head-to-footplate distance was 3.7 mm and mean superstructure width was 2.7 mm. Mean footplate thickness was 0.27 mm on stapes axial plane versus 0.48 mm on lateral semicircular canal plane. Incudostapedial joint width was systematically less than 0.7 mm.

Stapes dimensions on stapes axial plane were close to anatomical data, particularly for footplate thickness.