Table 1 Summary statistics of the baseline characteristics

<  1 year

1 ~ 5 years

> 5 years

(N = 110)

(N = 110)

(N = 110)

Age, yr (mean ± SD)

54.48 ± 9.94

55.06 ± 10.30

56.36 ± 8.68

0.320

Female (%)

67 (60.91)

64 (58.18)

69 (62.73)

0.482

BMI (mean ± SD)

24.48 ± 3.11

24.12 ± 3.77

24.03 ± 3.67

0.619

Operation history (%)

0.788

 0

30 (27.27)

33 (30.00)

31 (28.18)

 1

47 (42.73)

41 (37.27)

46 (41.82)

  ≥ 2

33 (30.00)

36 (32.73)

33 (30.00)

Smoking (%)

40 (36.36)

43 (39.09)

39 (35.45)

0.359

Level of preoperative pain (VAS) (mean ± SD)

1.71 ± 0.65

1.88 ± 0.69

2.07 ± 0.71

< 0.05*

SAS (mean ± SD)

36.91 ± 6.72

40.03 ± 6.59

43.25 ± 6.36

< 0.05*

SDS (mean ± SD)

39.31 ± 7.21

42.35 ± 6.83

46.25 ± 7.28

< 0.05*

FRAIL (mean ± SD)

1.71 ± 0.70

1.66 ± 0.76

1.74 ± 0.75

0.760

Duration of surgery, min (mean ± SD)

121.01 ± 8.69

122.99 ± 9.40

123.75 ± 10.69

0.088

Etiology of back pain(%)

0.817

 spinal stenosis

57 (51.82)

51 (46.36)

49 (44.55)

 spondylolisthesis

34 (30.91)

37 (33.67)

41 (37.27)

 disc herniation

19 (17.27)

22 (19.97)

20 (18.18)