Objective.To determine if a hollow screw would be more resistant to loosening than a solid pedicle screw when placed into the pedicles of S1 and tested under stair-cased cyclic loading.

• 目的：植入S1椎弓根并分级循环加载下测试，确定空心螺钉是否比实心椎弓根螺钉有更强的反抗松动能力。