Assessment of the ability of the radiological incudo-stapedial angle to predict the stapedotomy technique type; a prospective case-series study

Background: Reversal-steps stapedotomy (RSS) has become a standard technique that entails perforation of the footplate when the ossicular chain is still intact, followed by immediate placement and stabilization of the prosthesis and, lastly, removal of the stapes superstructure. It can prevent incus dislocation and footplate luxation, helping to improve surgical outcomes. Objectives: This study aimed to propose a radiological classification of the incudo-stapedial angle on preoperative high-resolution computed tomography (HRCT) images. We also assessed the proposed radiological classification's ability to predict feasibility of RSS. Methods: This prospective case-series observational study was conducted at a tertiary referral institute between January 2021 and August 2022, and included 83 candidates for stapedotomy operation because of otosclerosis. Two physicians reviewed the preoperative HRCT images, focusing on the coronal cut on the incudo-stapedial (IS) joint, and measured its radiological angle. According to this measurement, the radiological incudo-stapedial joint could be divided into three types; obtuse, right, and acute angle. This radiological classification was correlated with the intraoperative use of RSS technique. Results: The RSS technique was used in forty-two (97.7%) patients with an obtuse IS angle and twenty-six (89.7%) patients with a right angle. At the same time, the classical, non-reversal technique was used in all patients with an acute angle. The three groups differed significantly regarding the method used for stapedotomy (P-value<0.001). Moreover, Spearman′s correlation coefficient revealed a significant correlation between the used technique and the radiological type of the IS angle (P-value <0.001). Conclusions: Our prospective study proposes a preoperative radiological classification of the IS angle at the HRCT. This classification was significantly correlated with stapedotomy technique used. The reversal stapedotomy technique was feasible in most cases with obtuse or right radiological IS angles. Conversely, the non-reversal method was used in all patients with an acute radiological IS angle. This radiological classification could help for predict the feasibility of the RSS technique with an accuracy of 95.18%, a sensitivity of 73.33%, and a specificity of 100%.