Table 1. Demographic data of patients who underwent ultrasound-guided facet joint injections for failed back surgery syndrome (n=27).

	n	%	Mean±SD
Age (year)			43.6±11.5
Sex
Female	19	70.3
Male	8	29.7
Body mass index (kg/m2)			32.5±4.6
Duration of pain (month)			6.7±5.7
Low back pain distribution
Bilateral	18	66.6
Unilateral	9	33.4
Mean period between operation and injection (month)			7.8±1.3
Surgery level
One level	23	85.2
Multilevel	4	14.8
			Injection level
Surgical level
L3-4	3	11.1	(L2-3, L3-4, L4-5)
L4-5	8	29.6	(L3-4, L4-5, L5-S1)
L5-S1	12	44.4	(L4-5, L5-S1)
Multilevel (L4-5 and L5-S1)	4	14.8	(L3-4, L4-5, L5-S1)
SD: Standard deviation.