Biomechanical evaluation of anterior screw fixation for type II fractures of the odontoid process: The influence of different lengths of the screws
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    Abstract:

    Objectives To determine the influence of different lengths of the anterior odontoid screws on the fixation stability. Methods Twenty cadaveric C2 vertebrae were harvested and an osteotomy was performed to simulate a Type II fracture pattern in each vertebra. The angle of type II fracture line was 0°in 6 specimens, 17°in 8, and 25°in 6. In this way, Different lengths of fractured odontoid processes were created and then divided into 2 groups (<10mm vs >10mm). The fractures were then treated by anterior screw fixation. And insertional torque, and pull-out force and stiffness of the bone-screw was tested. Results The lengths of the screws bedded in fractured odontoid process were 8.3mm-12.3mm. The relationship between the pull-out strength (Y) and the length of the screw (X) was determined by the regression equation (Y=156.69+67.97X, r=0.28). However, No significant differences of the insertional torque, and pull-out force and stiffness of the bone-screw were found between the <10mm and >10mm groups. Conclusions Bone-screw stability is not closely related to the distal part of the fractured odontoid process. Anterior screw fixation could be used even when distal fractured part of the odontoid process less than 10mm.

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FANG Hong-wei, WANG Xiang-yang, SHI Da, CHEN Zhuo, ZHAO Yun-zhen, WANG Xiao-cheng, HUANG Xiao-dong, OUYANG Jun, WU Zheng-hui. Biomechanical evaluation of anterior screw fixation for type II fractures of the odontoid process: The influence of different lengths of the screws[J]. Journal of medical biomechanics,2009,24(3):189-192

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  • Received:August 04,2008
  • Revised:November 21,2008
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