Diameter of Long Process of Incus in Choosing Stapes Prosthesis

Aim To study the diameter of long process of incus in stapes surgery and its utility in determining stapes prosthesis. Materials and Methods Long process of incus diameter was measured in 25 patients undergoing stapes surgery in a tertiary care hospital. Specially designed instruments (both straight and curved) were used to measure the long process of incus diameter 1.5 mm from the tip of long process. According to the diameter measured at surgery the prosthesis was selected and crimped on the long process of incus. Results The crimping procedure is a decisive step during stapes surgery because loose connection between prosthesis and incus will lead to absorption of sound energy leading to conductive hearing loss and microtrauma of the long process causing necrosis of long process of incus. Optimum fitting depends on the diameter and form of long process of incus. Conclusion The purpose of this study is to provide new anatomic information on the long process of incus with special regard to the area of crimping in cases of stapes prosthesis. The long process of incus had a maximum diameter of 1.15 mm and a minimum diameter of 0.52 mm at a level 1.5 mm from the long process. Another possibility to prevent compression of the feeding blood vessels is to develop a new instrument allowing best possible crimping of a prosthesis and keeping the anteromedial quarter of the long process of incus free.