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

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

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

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.

ISSN: 1471-2474