Tehran University of Medical Sciences Acta Medica Iranica 0044-6025 46 6 2008 12 15 447 450 P Habib-Allah -Zadeh Department of Orthopedic, Sina Hospital, School of Medicine, Tehran University of Medical Sciences, B Mirzashahi Department of Orthopedic, Sina Hospital, School of Medicine, Tehran University of Medical Sciences, M Sadat Department of Orthopedic, Sina Hospital, School of Medicine, Tehran University of Medical Sciences, B Siavashi Department of Orthopedic, Sina Hospital, School of Medicine, Tehran University of Medical Sciences, B Mohammad-Hosseini Mechanic Engineering, Sharif Industrial University of Tehran, Tehran, Iran S Mohammad-Hosseini Mechanic Engineering, Sharif Industrial University of Tehran, Tehran, Iran A Ziaei-Moayyed Department of Material Engineering, Sharif Industrial University of Tehran, Tehran, Iran 2015 09 28 Pedicle screws provide rigid fixation for instabilities in the lumbar and lumbosacral spine. Anatomical consideration and potential risk of neurologic complications are the reasons to hesitate using pedicle screws in the thoracic spine. Twenty moulages similar to human vertebrae were instrumented with Cotrel-Dubousset (CD) system pedicle screw by intratransverse process, extrapedicular and intrapedicular methods and pullout strength was measured. There was statistically significant difference between three techniques. By increasing the length of screw in any method, pullout strength increased. Average pullout strength in extrapedicular technique was less than two other techniques in dynamic state. The strongest technique for screw placement was intratransverse process technique. It seems that intratransverse process technique is safe for posterior fixation of spine. https://acta.tums.ac.ir/index.php/acta/article/view/3517 https://acta.tums.ac.ir/index.php/acta/article/download/3517/3493