Abstract: Objective　To improve the safety and effectiveness of ultrasound-guided paravertebral block through observing the relationship between the spinal nerve and the transverse process or the lateral costotransverse ligament in adult cadavers.     Methods    Eighteen cadavers with normal thoracic spines were collected in this study. The cross point between the lateral edge of the lamina and the thoracic spinal nerve root was taken as the starting point for measurement. The distances between the starting point and the midpoint of the posterior inferior border of transverse process and the midpoint of the inferior border of the lateral costotransverse ligament were measured. According to Mitchell FL's "Three Groups" principle, the adjacent three thoracic segments were divided into 1 group and 12 segments were divided into 4 groups, which were named as T1~3 group, T4~6 group, T7~9 group and T10~12 group, respectively. The one-way ANOVA were performed between the intervals of spinal nerve-transverse process and the intervals of spinal nerve- lateral costotransverse ligament in different groups.    Results    （1）Intervals of spinal nerve-transverse process：average distance was (16.13±5.59) mm. It showed a trend of increasing first and then decreasing from the segment T1 (16.62±3.67) mm to the segment T12（9.76±3.75) mm. The T5 segment was the largest, which was(18.88±5.78) mm. The upwards or downwards from T5 segment gradually decreased. The distance of spinal nerve-transverse process of T1~3 group, T4~6 group, T7~9 group and T10~12 group were (17.50±4.67) mm、(18.19±5.62) mm、(16.92±5.28) mm、(12.00±4.42) mm respectively. There were significant differences among T10~12 and T1~3 (P<0.01), T4~6 (P<0.01), T7~9 group (P<0.01). (2) Intervals of spinal nerve-lateral costotransverse ligament: average distance was (17.67±3.76) mm. The distances of spinal nerve-lateral costotransverse ligament of T1~3 , T4~6 , T7~9 and T10~12 group were (16.95±3.82) mm、(17.55±3.89) mm、(17.81±3.83) mm、(18.30±3.43) mm, respectively. There was no significant difference between each two groups (P>0.05).     Conclusions　It is important to pre-estimate the puncture depth before and during ultrasound-guided thoracic paravertebral nerve block to avoid spinal nerve injury and even spinal anesthesia.

Key words: Thoracic paravertebral block；　Ultrasound-guided；　Puncture depth；　Applied anatomy