Table 6

Analysis of effect size, heterogeneity, and ANOVA testing of difference by surgery type.

	Type of Surgery	Number of Studies Included in This Analysis	Effect Size	Lower Limit	Upper Limit	Higgins I ² Statistic of Heterogeneity	Variance	Standard Error	Number of Patients
Oswestry Disability Index	Endoscopic-assisted MIS fusion	4	0.9496	0.9087	0.9905	0.0000	0.0004	0.0209	166
	Open laminectomy	5	0.9294	0.8793	0.9795	0.0000	0.0007	0.0255	1188
	Endoscopy	81	0.9178	0.9013	0.9343	0.0000	0.0001	0.0084	12,710
	Tubular microdiscectomy	16	0.8968	0.8543	0.9394	0.0000	0.0005	0.0217	2895
	Standalone endo fusion	1	0.8337	0.7336	0.8984	0.0000	0.0017	0.0410	36
	ANOVA Q test random effects with separate estimates of T ²				Sig = 0.049		Total patient samples		16,995
VAS back	Endoscopic-assisted MIS fusion	2	0.9325	0.8087	1.0563	0.0000	0.0040	0.0632	28
	Tubular microdiscectomy	11	0.8186	0.6960	0.9413	0.0000	0.0039	0.0626	1962
	Open laminectomy	4	0.7918	0.6583	0.9253	0.0000	0.0046	0.0681	726
	Endoscopy	34	0.7732	0.7122	0.8342	0.0000	0.0010	0.0311	5028
	Standalone endo fusion	1	0.7320	0.5740	0.8374	0.0000	0.0044	0.0662	36
	ANOVA Q test random effects with separate estimates of T ²				Sig = 0.607		Total patient samples		7780
VAS LEG	Endoscopic-assisted MIS fusion	4	0.9313	0.8945	0.9682	0.0000	0.0004	0.0188	166
	Tubular microdiscectomy	15	0.9172	0.8770	0.9574	0.0000	0.0004	0.0205	2348
	Endoscopy	80	0.9158	0.9002	0.9315	0.0000	0.0001	0.0080	12,631
	Open laminectomy	5	0.8929	0.7910	0.9949	0.0000	0.0027	0.0520	1188
	Standalone endo fusion	1	0.8796	0.8070	0.9261	0.0000	0.0009	0.0295	36
	ANOVA Q test random effects with separate estimates of T ²				Sig = 0.592		Total patient samples		16,369

ANOVA, analysis of variance; MIS, minimally invasive surgery; Sig, significance level of 95% CI; VAS, visual analog scale.