Predictable prosthesis length on a high-resolution CT scan before a stapedotomy

(1) To assess the correlation between preoperative high-resolution CT (HRCT) imaging measurement from the long process of the incus to the footplate and the length of intraoperative selected prosthesis. (2) To determine if HRCT has a predictive value of prolapsed facial nerve during stapedotomy.

We evaluated in our tertiary care center, in a retrospective case series, 94 patients undergoing primary stapedotomy. Preoperative temporal bone HRCT scans were reformatted in the plane of the stapes to measure on the same section the distance between the long process of the incus and the footplate. Measurement was performed by otolaryngology resident and neurotologist. We analyze the interobserver correlation and the mean length measured on the HRCT to the selected prosthesis size intraoperatively.

Mean HRCT measurement of the incus long process/footplate distance assessed by the otolaryngology resident and neurotologist was 4.34 and 4.38 mm, respectively. Interobserver correlation was statistically significant [intraclass correlation coefficient (ICC) of 0.679 (p < 0.001)]. Mean selected prosthesis length intraoperatively was 4.36 mm. Correlation between the mean selected length prosthesis and the mean HRCT measurement was also statistically significant [ICC of 0.791 (p < 0.001)]. Postoperatively, a statistical improvement was shown in air conduction (p < 0.001), bone conduction (p < 0.001) and air–bone gap reduction (p < 0.001). 2 cases of facial nerve covering one-half of the oval window were identified by HRCT and confirmed intraoperatively.

HRCT is a valuable tool to predict preoperatively the length of the stapedotomy prosthesis. Moreover, it might be helpful to identify a potential prolapsed facial nerve, to confirm the diagnosis of otosclerosis and to rule out other abnormalities. Ultimately, it may optimize the stapedotomy procedure planning.