. 2013 Sep 23;8(9):e74827. doi: 10.1371/journal.pone.0074827

Table 2. Results in axial pullout tests in three groups (n = 8, means ± SD).

Study periods	Parameters	CPS group	PMMA-PS group	EPS group
6-week	F_max (N)	827.88±139.22	1426.38±235.75^*	1252.13±203.51^*#
	E (J)	1.66±0.30	2.84±0.55^*	2.48±0.45^*#
12-week	F_max (N)	906.63±152.50 &	1472.75±248.65^*&	1518.88±256.81^*#Δ
	E (J)	1.80±0.35 &	2.95±0.60^*&	3.09±0.59^*#Δ

CPS, PMMA-PS and EPS indicate conventional pedicle screw, polymethylmethacrylate-augmented pedicle screw and expansive pedicle screw, respectively. F_max and E indicate the maximum pullout strength and energy-to-failure, respectively.

Compared with CPS group at the same study period, p<0.05; # Compared with PMMA-PS group at the same study period, p>0.05; & Compared with 6-week in the same group, p>0.05; Δ Compared with 6-week in the same group, p<0.05.