Table 1.

Basic characteristics of included studies

Studies	Study type	Country	Group	Sample size	Mean age (years)	Gender (Male)	Follow up (month)
Alvin et al. [20]	Retrospective	USA	ACDF	45	49.3 ± 9.6	28 (62.2%)	12
			open PCF	25	46.5 ± 11.2	15 (60.0%)	12
Cho et al. [9]	Retrospective	Korea	ACDF	30	49.7 ± 10.4	17 (56.7%)	61.2 ± 20.2
			open PCF	31	52.4 ± 9.6	22 (71.0%)	62.6 ± 19.9
Dunn et al. [26]	Retrospective	USA	ACDF	210	46.6 ± 6.6	95 (45.2%)	44.9 ± 10.3
			MI-PCF	49	46.9 ± 10.3	38 (77.6%)	42.9 ± 6.6
Forster et al. [18]	Retrospective	UK	ACDF	634	49 ± 12	313 (49.4%)	24
			open PCF	54	50 ± 11	17 (31.5%)	24
Herkowitz et al. [25]	RCT	USA	ACDF	17	43 (26–52)	NA	60.4 (19.2–98.4)
			open PCF	16	39 (21–50)	NA
Korinth et al. [23]	Retrospective	Germany	ACDF	124	45.9 ± 8.2	73 (58.9%)	72.1 ± 25.9
			open PCF	168	46.9 ± 10.4	98 (58.3%)
Lin et al. [10]	Retrospective	Korea	ACDF	55	52.5 ± 10.7	31 (56.4%)	39.5 ± 13.5
			MI-PCF	21	53.1 ± 11.9	14 (66.7%)	35.9 ± 16.6
Mansfield et al. [27]	Retrospective	USA	ACDF	79	49 (24–75)	35 (46.1%)	NA
			MI-PCF	22	49 (31–69)	12 (57.1%)	NA
Mok et al. [17]	Retrospective	USA	ACDF	816	51.2 ± 11	400 (49.0%)	NA
			open PCF	145	53.8 ± 9.3	82 (58.2%)	NA
Ruetten et al. [28]	RCT	Germany	ACDF	86	NA	NA	24
			MI-PCF	89	NA	NA	24
Scholz et al. [19]	Retrospective	Germany	ACDF	40	50 ± 10.1	20 (50.0%)	33 ± 18.4
			open PCF	67	51 ± 10.7	38 (56.7%)	47 ± 16.4
Selvanathan 2015 [21]	Retrospective	UK	ACDF	150	48	61 (40.7%)	24 ± 1.4
			open PCF	51	50	34 (66.7%)	25 ± 1.2
Tumialan et al. [22]	Retrospective	USA	ACDF	19	39.3 (24–52)	19 (100%)	18.1 (6–34)
			open PCF	19	41.4 (27–56)	17 (89.5%)	11.2 (5–24)
Wirth et al. [24]	RCT	USA	ACDF	25	41.7	14 (56.0%)	2
			open PCF	22	43.8	9 (40.9%)	2
Witiw et al. [16]	Retrospective	USA	ACDF	46147	48.5 ± 9.6	21141 (45.8%)	1
			open PCF	4851	49.7 ± 9.7	2821 (58.2%)	1

RCT randomized controlled trial, ACDF anterior cervical discectomy and fusion, PCF posterior cervical foraminotomy, MI minimally invasive, NA not available