Design-Dependent Calculation of the Prosthesis Length in Malleostapedotomy

OBJECTIVE: The results of a recently published micro-CT study suggested a correlation of the distance between long incus process and stapes footplate and the required prosthesis length in malleostapedotomy. The goal of this study was to test the reliability of that assumption. METHODS: Rectangular and bent prostheses were tested in 11 cadaveric human temporal bone specimens; 1 of them showed a stapedial artery. Prosthesis length was calculated based on the distance between long incus process and stapes footplate. The rate of acceptable prosthesis insertion into the vestibule was investigated. RESULTS: In both prostheses designs, the insertion depth into the vestibule did not exceed 1.0 mm. Two prostheses did not pass the footplate level in bent prostheses (18%) and 1 in rectangular prostheses (9%). CONCLUSION: A rough estimation of the required prosthesis length in malleostapedotomy seems possible if the distance between long incus process and stapes footplate is known and a design-dependent equation exists.