AIM To study the pullout force of pedicle screws with different forms of thread and to supply the experimentdata for the clinical application of transpedicular internal fixators.

• 目的了解不同形状螺纹的椎弓根螺钉在椎弓根内的拔出力的大小,给临床应用不同类型的经椎弓根内固定器提供实验依据。