Copyright © 2014 Lippincott Williams & Wilkins. Unauthorized commercial reproduction of this slide is prohibited Supplemental PowerPoint Slides Positioning thoracic pedicle screw entry point using a new landmark: A study based on three-dimensional CT scan Deng-bin Qi, Ph.D, Jing-ming Wang, M.D, Yong-gang Zhang, Ph.D, Guo-quan Zheng, Ph.D, Xue-song Zhang, Ph.D, Yan Wang, M.D. 1: Department of Orthopaedics, Chinese People’s Liberation Army General Hospital (301 Hospital) 28 Fuxing Rd., Beijing , PR China

Key points: ● We found a new landmark in vertebral plate to locate the entry point in thoracic spine. ● We found the landmark was stable after analyzing the anatomy of the thoracic vertebrae. ● We measured the distance between the landmark and the entry point in thoracic spine in 110 adolescents, and provided a new method to provide a quantitative location of the entry point in each thoracic vertebra. ● The new method can not only be used in normal spine, but also used in the AIS patients. ● No significant was found between the concavity and the convexity in the comparison of the location of the entry point by using the new method. ● Performing the new method in 21 patients, the accuracy was 92.2%, which is higher than that of entry point selection using traditional Kim’s method (77.5%, p<0.001).

ABC A, was the 3 dimensional CT reconstruction of T5, the new landmark was at the junction of the base of the superior articular process (green line), transverse process ridge (red line) and ridge of the vertebral plate (blue line); B, was the landmark after the exposure, the invagination was easy to be found after the exposure; C, First step, moved laterally along the transverse process from the landmark according to the value of entry point in transverse plane. Second step, the location was adjusted as a reference of the ridge of the transverse process in sagittal plane. At last, the location was identified after its values in transverse plane and sagittal plane were identified.

Positions of TPSs Parameter No.of TPSs(%) Our Conventional technique (Group 1) Kota Watanabe` Conventional technique (Group 2) Our New technique (Group 3) Intrapedicular214 (77.5%) *171(67.1%) *282 (92.2 %) * Pedicle breach of≤2.0mm 25 (9.1%) *20(7.8%) *13 (4.2%) * Pedicle breach of ＞ 2.0mm 15(5.4%)*32(12.5%) *5 (1.6%) * Intracostovertebral jont 22(8.0%)*32(12.5%) *6 (2.0%) * total276(100%) *255(100%) *306 (100%) * The significant difference was found between Group 1 and Group 3, Group 2 and Group 3, respectively. P value was in the Rank sum test using the Kruskal-Wallis method. The significant difference existed between Group 1 and Group 3, Group 2 and Group 3 in the total and 4 subgroups.