Anatomical study of position of the rib head for placing anterior vertebral body screws in a chinese population.

In this study, the variability of rib head position in a Chinese population in terms of the spinal canal and vertebral body was analyzed using computed tomography (CT). Images from transverse CT scan of the T4 to T12 vertebral bodies of 30 normal individuals were 3-dimensionally reconstructed, and analyzed for measurement of parameters that define the relative anatomic position of the rib head. We have found that the distance between the anterior border of the rib head and the posterior margin of the vertebral body, posterior safe angle, and the distance between the most inferior border of the rib head and inferior end plate in the sagittal plane gradually decrease. However, the distance between the anterior boarder of the rib head and the anterior margin of the vertebral body, transverse dimension, anterior safe angle, and the distance between the most inferior border of the rib head and superior end plate in the sagittal plane gradually increase from T4 to T12. This indicates that the position of the rib head is oriented from a more anterior position to a more posterior position and from a more superior position to a more inferior position as the number of the vertebra increases, which is different from what has been reported from western populations. Our study has identified useful parameters to define the position of the rib head, and provides a comprehensive reference guide for accurate and safe instrumentation of vertebral body screws in treating related spine diseases.