Preoperative semi-automatic segmentation in incus defects

Long-term success rate of partial ossicular replacement prosthesis (PORP) is low. Three-dimensional (3D) imaging technology to identify and model ossicular chain defects may improve this rate. This study aims to evaluate the diagnostic accuracy of a 3D modelling method to identify incus defects.

This retrospective study comprised high-resolution computered tomography (HRCT) and intraopeative images of patients who underwent endoscopic tympanoplasty in a 6-years period. Ears with an incus defect were included in the study, while those with an intact ossicular chain served as controls. HRCT images were processed using 3D Slicer software for automatic segmentation and 3D model construction. Intraoperative findings were then compared with 3D imaging results. Cohen's kappa agreement, sensitivity, specificity, predictive values, and accuracy were reported.

A total of 129 ears (52.7% right) from 106 patients (69 males, 60 females) were analysed, with a mean age of 40.28 ± 13.11 years. Intraoperative images showed incus defects in 46 ears (35.7%); whereas 3D model identified incus defect in 44 ears (34.1%). The agreement between intraoperative view and 3D model in detecting incus defects was excellent (Cohen's kappa = 0.83). 3D model showed incus defect in 40 out of 46 patients with actual defect with a sensitivity of 86.96%, specificity of 95.18%, positive predictive value of 90.91%, negative predictive value of 92.94%, and accuracy of 92.24%.

3D imaging has been shown to provide high diagnostic accuracy for incus defects in well-aerated ears without opacification, which may facilitate surgical planning and the design of personalised prostheses.