Table 1.

Clinical and demographic data of patients.

	Group A (n = 117)	Group B (n = 89)
Age
Mean (year)	67.9 ± 10.6	67.6 ± 11.7
Range (year)	36~86	23~71
Gender
Male	62 (53.0%)	37 (41.6%)
Female	55 (47.0%)	52 (58.4%)
Operate level
L2~L3	2 (1.7%)	2 (2.2%)
L3~L4	13 (11.1%)	15 (16.9%)
L4~L5	96 (82.1%)	67 (75.3%)
L5~S1	6 (5.1%)	5 (5.6%)