Anatomic Parameters of the Long Process of Incus for Stapes Surgery

Hypothesis: The purpose of this study is to offer new anatomic data about the long process of incus (LPI) for stapes surgery. Background: Anatomic study of 50 human macerated incudes to measure different parameters of cross sections of the LPI. Methods: Step-by-step cutting of the LPI perpendicular to its axis starting from its free end next to the lenticular process. The layer thickness was 0.5 mm. The cutting surfaces were documented with Canon EOS 20D camera, and a standard software tool (MATLAB) was used for automated statistical analysis. Results: The LPI had a maximum diameter of 1.15 mm and a minimum diameter of 0.52 mm at the level of 1.5 mm far from the tip of the long process, which is the most common site for stapes prosthesis attachment. Concerning each cross section, having a long and a short diameter, the average long diameter is 0.9011 mm, and the short diameter is 0.6507 mm. Conclusion: Our anatomic study revealed wide variations of diameters and shape of the LPI. Best possible crimping of stapes prosthesis depends not only on the shape and diameters of the LPI but also on the vertical surface of the LPI as well. To prevent incus necrosis due to compression of the feeding blood vessels, the maximum contact surface of the loop of stapes prosthesis should be about 1.9 mm inlength.