Table 1 Baseline demographics and surgical data between the IS and S2AI groups

No. of patients

111

31

Age, (yrs)

67.9 ± 16.7

65.2 ± 15.8

0.422

Female sex, n (%)

92 (82.8)

25 (80.6)

0.772

BMI, (kg/m²)

28.5 ± 8.7

27.6 ± 8.2

0.607

Follow-up, (mos)

32.8 ± 8.0

30.7 ± 6.2

0.179

Smoking, n (%)

12 (10.8)

5 (16.1)

0.530

Diabetes, n (%)

32 (28.8)

9 (29.0)

0.982

Osteoporosis, n (%)

53 (47.7)

13 (41.9)

0.566

Hypertension, n (%)

11 (9.9)

5 (16.1)

0.518

Primary diagnosis, n (%)

0.891

 Degenerative

72 (64.95)

19 (61.3)

 Idiopathic

14 (12.6)

4 (12.9)

 Congenital

7 (6.3)

3 (9.7)

 Post-traumatic

18 (16.2)

5 (16.1)

ASA class, n (%)

0.379

 I

14 (12.6)

7 (22.6)

 II

79 (71.2)

19 (61.3)

 III

18 (16.2)

5 (16.1)

No. of levels fused

8.82 ± 3.7

8.65 ± 7.6

0.084

UIV level, n (%)

0.802

 Above T10

9 (8.1)

2 (6.5)

 T10

89 (80.2)

24 (77.4)

 Below T10

13 (11.7)

5 (16.1)

 L1/2

11 (9.9)

2 (6.5)

0.734

 L2/3

101 (90.9)

27 (87.1)

0.506

 L3/4

109 (98.2)

29 (93.5)

0.208

 L4/5

110 (99.1)

30 (96.8)

0.390

 L5/S1

109 (98.2)

30 (96.8)

0.525

 L2

5 (4.5)

2 (6.5)

0.647

 L3

8 (7.2)

3 (9.7)

0.705

 L4

2 (1.8)

1 (3.2)

0.525

Surgical duration (mins)

388.2 ± 99.1

377.6 ± 102.1

0.602

Blood loss (ml)

2421.2 ± 255.1

2368.3 ± 354.1

0.353

Length of stay (days)

20.6 ± 5.7

19.1 ± 6.8

0.217