Table 5.

Plasma VEGF concentration at different time in NEC group and PRE group (ng/ml), mean ± SD

Time points	NEC group	PRE group	t	P
Baseline	73.73 ± 15.54	76.72 ± 16.37	–0.476	0.638
1 week	128.82 ± 12.73	110.51 ± 18.06	2.295	0.039
2 weeks	155.00 ± 14.23	134.13 ± 26.23	2.522	0.021
4 weeks	118.70 ± 7.89	101.97 ± 9.86	3.056	0.014
12 weeks	83.92 ± 20.08	70.67 ± 11.78	1.367	0.205

NEC group: Osteonecrosis group; PRE group: Prevention group; VEGF: Vascular endothelial growth factor; SD: Standard deviation.