Chinese Journal of Tissue Engineering Research ›› 2011, Vol. 15 ›› Issue (17): 3085-3088.doi: 10.3969/j.issn.1673-8225.2011.17.012

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Biomechanical analysis about the pedicle screw fixation of S2 sacral fractures

Zhao Bao-lin1, Zhang Zhong-jun2, Piao Cheng-dong3, Meng Qing-yang3, Ma Hong-shun4   

  1. 1Department of Orthopedics, Third Hospital of Jilin University, Changchun  130031, Jilin Province, China
    2Department of Basic, Air Force Aviation University, Changchun  130022, Jilin Province, China
    3Department of Orthopedics, Second Hospital of Jilin University, Changchun  130041, Jilin Province, China
    4Department of Engineering Mechanics, Nanling Campus of Jilin University, Changchun  130022, Jilin Province, China
  • Received:2010-10-08 Revised:2010-12-24 Online:2011-04-23 Published:2011-04-23
  • Contact: Ma Hong-shun, Professor, Department of Engineering Mechanics, Nanling Campus of Jilin University, Changchun 130022, Jilin Province, China mahs@jlu.edu.cn
  • About author:Zhao Bao-lin, Professor, Department of Orthopedics, Third Hospital of Jilin University, Changchun 130031, Jilin Province, China mahs@jlu.edu.cn

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Abstract:

BACKGROUND: Studies on surgery for sacral fracture and S2 sacral pedicle screw fixation have been conducted. However, the strain distribution rule of sacrum under maximum pulling-out force of S2 sacral pedicle screw is rarely reported.
OBJECTIVE: To explore the pulling-out force of S2 sacral pedicle screw and the strain distribution of sacrum so as to provide biomechanical parameters for clinical fixation.
METHODS: Fresh sacrum specimens from fresh corpses of normal people, with the method of S2 sacral pedicle screw fixation outside. The small sensors were connected to fixation device of pedicle screw to measure the tightening force of pedicle screw. At the same time, the electric strain on the strain gauge of different parts which was resistance to static and dynamic strain gauge pre-pasted on the four fixed-site edge of pedicle and the different parts of sacrum was measured using the resistance strain gauge. The entry point of screw 1 was the lowest point of the inferior margin of left first posterior sacral foramina; screw 2 was the lowest point of the inferior margin of right first posterior sacral foramina; screw 3 was the intersection point of left first posterior sacral foramina and lateral sacral crest; screw 4 was the intersection point of right first posterior sacral foramina and lateral sacral crest. Maximum pulling-out forces of pedicle screw and strain distribution values of the different points of sacrum were measured.
RESULTS AND CONCLUSION: The screw pulling-out force of screws 1, 2, 3 and 4 were (399±7.2) N, (281.0±5.2) N, (196±   4.3) N, and (201±4.6) N, respectively. The minimum strain was found in the 8th measurement point of screw 2 (13.5±1.1) με, and the maximum strain was found in the 1st measurement point of screw 1 (96.8±6.5) με. These findings indicate that S2 sacral pedicle screw procedure accords with the biomechanical principle.

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