Table 3.

Comparison of the prevalence of rASD

		rASD N/(X ± S)	N-rASD N/(X ± S)	rASD Ratio	P
Age (y)		56.6 ± 11.7	49.4 ± 11.7	/	< 0.001*
Follow-up time (moth)		37.2 ± 22.3	29.4 ± 23.2	/	0.011*
Adjacent segment	Total	77	217	26.2%	/
	Cephalic	55	139	28.4%	0.241
	Cauda	22	78	22.0%
Diseases	Disc herniation	54	114	32.1%	0.96
	Spinal stenosis	25	54	36.2%
	Degenerative spondylolisthesis	16	31	34.0%
Fusion levels	1 level	44	168	20.8%	< 0.001*
	2 levels	19	37	33.9%
	≥ 3 levels	14	12	53.8%

^{*, Represents a significant difference among the groups(P<0.05)}