Table 2.

Radiographic parameters (±SD)

Group	Intervertebral mobility at L2–3		Intervertebral mobility at L3–4		General adjacent segment mobility (GASM)
	Before surgery	3 years after surgery	Before surgery	3 years after surgery	3 years after surgery
Topping-off	4.11 ± 1.52a	4.30 ± 1.71a	4.42 ± 1.91b	3.03 ± 1.33b	7.19 ± 2.31
PLIF	4.29 ± 1.81b	7.03 ± 2.14b	–	–	7.03 ± 2.14*
t	1.364	31.782	–	–	0.721
P	> 0.05	< 0.01	–	–	> 0.05

^aP>0.05, ^bP<0.05, comparison before surgery and at 3 years after surgery

*It is the intervertebral mobility at L2–L3