Table 1.

Characteristics and evaluation of included studies*

	Year	Country of origin	PLIF/TLIF				Evaluation
			Patients, n	Mean age, y	Male, %	Mean follow up, months
Humphreys et al. [19]	2001	USA	34/40	40.00/41.00	64.71/50.00	13.0/13.0	10
Jae-Sung Park et al. [22]	2005	Korea	99/29	54.00/57.00	43.43/34.48	20.0/10.4	12
Yan et al. [25]	2008	China	60/60	63.60/64.50	55.00/53.33	23.0/23.0	14
Zhuo et al. [27]	2009	China	22/18	41.00/43.00	63.64/72.22	20.0/20.0	13
Mehta et al. [21]	2011	USA	76/43	48.56/48.12	44.74/37.21	24.0/24.0	11
Audat et al. [20]	2012	Jordan	27/37	50.60/45.80	22.22/37.84	36.0/36.0	13
Sakeb et al. [26]	2013	Bangladesh	52/50	46.73/49.04	21.15/28.00	9.0/9.0	14

*All studies were retrospective and comparative.