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Table 2 The measured and predicted pullout strengths of the six pedicle screws.

From: Comparison and prediction of pullout strength of conical and cylindrical pedicle screws within synthetic bone

Group Pullout Strength
(mean value ± one standard deviation)
R 2 Value
   UPS-4 UPS-3 Diapason HCD CCD Moss-Miami  
Experiment 1904 ± 72 1600 ± 53 1568 ± 46 1583 ± 59 1610 ± 33 1570 ± 100 ---
Chapman's Formula 1/4L 1175 1198 1067 1035 1073 1146 0.40
  1/2L 1096 1198 1082 1035 1073 1146 -0.26
  3/4L 1017 1198 1090 1035 1073 1146 -0.71
Integral Formula 1861 1483 1411 1509 1636 1481 0.93
Modified Chapman's Formula 1/4L 1561 1482 1067 1509 1622 1418 0.38
  1/2L 1742 1482 1356 1509 1622 1418 0.83
  3/4L 2079 1482 1725 1509 1622 1418 0.88
  1. There are three types of defining the equivalent outer and inner diameter of the UPS-4 and Diapason screws in the Chapman's and modified Chapman's formulae. Unit: N.