Table 4.

Detailed results of the meta-analysis

Item	Time point	Number of study	Early group			Late group			Heterogeneity (I2, P)	Heterogeneity between groups P
			n	WMD (95% CI)	Heterogeneity (I2, P)	n	WMD (95% CI)	Heterogeneity (I2, P)
ΔVAS scores for back pain	Within postoperative 3 days	5	42	2.90 (1.96–3.84)	NAa	201	2.36 (1.64–3.07)	89.8%–<0.001	86.5%, <0.001	0.368
	3 months	7	72	3.26 (2.72–3.80)	0.0%, 0.758	270	2.98 (2.29–3.67)	94.1%, <0.001	91.3%, <0.001	0.529
	6 months	4	42	3.57 (2.65–4.49)	NAa	104	3.27 (2.29–4.25)	93.7%, <0.001	90.7%, <0.001	0.663
	12 months	5	72	3.49 (2.95–4.03)	0.0%, 0.654	205	3.01 (2.16–3.85)	87.6%, <0.001	79.1%, <0.001	0.345
ΔVAS scores for leg pain	Within postoperative 3 days	10	146	6.87 (6.26–7.48)	84.8%, 0.001	341	4.47 (3.56–5.37)	96.9%, <0.001	98.0%, <0.001	<0.001
	3 months	10	72	6.45 (4.64–8.26)	94.2%, <0.001	510	5.34 (4.46–6.21)	98.3%, <0.001	98.1%, <0.001	0.279
	6 months	8	74	7.59 (7.20–7.98)	32.3%, 0.224	290	5.67 (4.93–6.41)	98.4%, <0.001	96.8%, <0.001	<0.001
	12 months	8	72	6.58 (4.31–8.84)	96.5%, <0.001	205	5.68 (4.76–6.59)	96.6%, <0.001	97.2%, <0.001	0.47
ΔODI values	Within postoperative 3 days	7	114	26.68 (13.07–40.30)	97.6%, <0.001	188	32.87 (25.24–40.50)	95.9%, <0.001	96.2%, <0.001	0.437
	3 months	8	72	45.09 (32.54–57.65)	90.6%, <0.001	321	44.92 (40.31–49.54)	94.1%, <0.001	92.8%, <0.001	0.98
	6 months	9	74	42.51 (13.74–71.28)	99.3%, <0.001	244	43.67 (37.77–49.57)	97.3%, <0.001	98.0%, <0.001	0.938
	12 months	8	72	54.56 (41.44–67.68)	92.5%, <0.001	324	48.84 (46.50–51.17)	43.6%, 0.131	83.9%, <0.001	0.4
Complication rate	NA	13	176	0.03 (0.01–0.06)	0.00%, 0.44	439	0.07 (0.02–0.12)	71.3%, <0.001	64.3%, <0.001	0.164
MacNab criteria		12	134	0.91 (0.85–0.95)	NAb	438	0.90 (0.87–0.93)	NAb	NA	0.884

NA, not available; ΔVAS scores, the reduction in VAS score from preoperative to postoperative periods; ΔODI values, the reduction in ODI values from preoperative to postoperative periods.

^aOnly one study was included.

^bI² = 0.