목적: The human cochlea varies in shape and size depending on the individual, influencing the extent to which a cochlear implant electrode is inserted. This study aimed to investigate the relationship between cochlea size and the insertion characteristics of straight electrodes. 방법:Fresh-frozen temporal bones extracted within 72 hours postmortem were used for this study. A total of 10 AL20 electrodes and 6 AL23 electrodes were inserted. The AL20 electrode featured an active length of 20 mm and a pitch of 0.625 mm, and the AL23 electrode had an active length of 24 mm and a pitch of 0.75 mm. Both electrodes included 32 contacts, with a tip size of 0.45 mm in width and 0.35 mm in height, and a base size of 0.8 mm in width and 0.6 mm in height. The electrodes were constructed using platinum-iridium alloy and silicone elastomer, consistent with commercially available electrodes. A highly experienced surgeon performed cochlear implant procedures on the temporal bones, exposing the round window of the cochlea. Electrodes were inserted slowly, stopping upon encountering resistance, and then secured with glue. Micro-CT images were acquired to assess cochlea size and angular insertion depth (AID). Key measurements included distance A (the maximum distance from the round window to the opposite cochlea wall), distance B (perpendicular to distance A), and cochlea height (H). These measurements were analyzed in relation to the insertion characteristics. 결과:The cochlea size measurements for A, B, and H were 9.4 ± 0.44 mm(mean ± standard deviation), 7.1 ± 0.31 mm, and 4.3 ± 0.40 mm, respectively. The angular insertion depth of the AL23 electrode was 395.5 ± 62.3°, and that of the AL20 electrode was 388.4 ± 47.9°. Positive correlations were observed between A and B (correlation coefficient, CC = 0.51), A and A/B (CC = 0.43), A and H (CC = 0.23), and B and H (CC = 0.30). A negative correlation was observed between B and A/B (CC = -0.46). For the AL23 electrode, AID showed a positive correlation with B (CC = 0.27) and a negative correlation with H (CC = -0.60). For the AL20 electrode, AID showed a positive correlation with A/B (CC = 0.23) and a negative correlation with A (CC = -0.28) and B (CC = -0.39). 결론:The cochlea size parameters (distance A, B, and H) exhibited positive correlations with each other. The insertion angle of the AL23 electrode showed a positive correlation with the cochlea distance B and a negative correlation with the cochlea height. In contrast, the AL20 electrode demonstrated a negative correlation with A and B, and a positive correlation with A/B. These findings highlight that even for straight electrodes, the relationship between cochlea size and insertion characteristics varies depending on electrode length.