목적: Narrow and curved EACs obstruct the view for examining the tympanic membrane and may hinder the drainage and ventilation of fluid from the middle ear cavity, resulting in fluid residue and an exacerbated condition of otitis externa or otitis media. The purpose of this study is to measure the actual length of the tympanic bone and EAC and explore the ensuing middle and outer ear complications. 방법:EAC length is measured using reconstructed temporal bone CT image, which is obtained via DICOM viewer program (Radiant DICOM viewer). CT scans of 50 chronic otitis media (COM) patients (20 males, 30 females) and those of their age and sex matched control group with no history of COM are analyzed. The reconstructed axial image shows the anterior, posterior wall length and posterior wall protrusion of bony EAC, while the reconstructed coronal image displays the inferior wall length and the inferior wall protrusion of bony EAC. 결과:Comparison of the male and female patients of the control group show that the anterior, posterior and inferior wall length of bony EAC are significantly longer and the inferior wall protrusion of bony EAC is larger in males. In the COM group, the inferior wall length of bony EAC is longer and the posterior wall protrusion of bony EAC is larger in males than their female counterparts. However, between COM and control groups, there is no difference in the bony EAC length and protrusion in ears with and without history of COM. 결론:Tympanic bone of the EAC is inevitably manipulated during various otologic surgeries. Thorough understanding of its anatomical characteristics can affect the physician’s management of chronic otitis externa or otitis media. This study demonstrates that there is no association between EAC protrusion and COM. Future research on the structure of the bony EAC may aid the surgeon in implementing appropriate treatment and surgical procedure in otology.