Table 1 Comparison of general conditions and surgical categories of the three groups

Age (years, \(\bar x \pm s\))

45 ± 10

47 ± 11

48 ± 12

1.044

0.354

Male/female (n)

43/18

41/21

42/22

0.403

0.818

BMI (kg/m², \(\bar x \pm s\))

24.2 ± 2.9

24.1 ± 3.0

25.0 ± 3.1

1.543

0.216

ASA grade I/II (n)

23/28

26/36

24/40

0.328

0.849

Surgical categories (n)

1.599

0.999

 Lumbar disc herniation

15

17

17

 Cervical spondylosis

17

13

15

 Spinal stenosis

12

12

13

Lumbar spondylolisthesis

11

13

12

 Spinal tuberculosis

3

4

5

 Spinal tumor

3

3

2