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Table 2 Univariate analysis of risk factors for PJK

From: Risk factors for proximal junctional kyphosis after posterior long-segment internal fixation for chronic symptomatic osteoporotic thoracolumbar fractures with kyphosis

Factors

All patients (n = 95)

PJK Group (n = 30)

Non-PJK Group (n = 65)

χ2 value

P value

Age (%)

 60 ~ 64 years

28 (29.5)

1 (3.3)

27 (41.5)

34.257

0.000

 65 ~ 70 years

40 (42.1)

9 (30.0)

31 (47.7)

 > 70 years

27 (28.4)

20 (66.7)

7 (10.8)

BMI (%)

 < 24.0 kg/m2

27 (28.4)

2 (6.7)

25 (38.5)

33.035

0.000

 24.0 ~ 28.0 kg/m2

39 (41.1)

7 (23.3)

32 (49.2)

 > 28.0 kg/m2

29 (30.5)

21 (70.0)

8 (12.3)

BMD (%)

 − 3.5SD ≤ T value ≤ -2.5SD

58 (61.1)

7 (23.3)

51 (78.5)

26.235

0.000

 T value < − 3.5SD

37 (38.9)

23 (76.7)

14 (21.5)

Smoking (%)

 No

62 (65.3)

20 (66.7)

42 (64.6)

0.038

0.845

 Yes

33 (34.7)

10 (33.3)

23 (35.4)

Combined diseases (%)

 Hypertension

35 (36.8)

10 (33.3)

25 (38.5)

0.232

0.630

 Diabetes

42 (44.2)

14 (46.7)

28 (66.7)

0.107

0.743

 Heart diseases

23 (24.2)

8 (26.7)

15 (23.1)

0.144

0.704

 Strokes

26 (27.4)

9 (30.0)

17 (26.2)

0.153

0.696

ASIA grading (%)

 D

19 (20.0)

8 (26.7)

11 (16.9)

1.218

0.270

 E

76 (80.0)

22 (73.3)

54 (83.1)

PLC injury (%)

 No

57 (60.0)

7 (23.3)

50 (76.9)

24.562

0.000

 Yes

38 (40.0)

23 (76.7)

15 (23.1)

UIV (%)

 T10 or higher

51 (52.6)

9 (30.0)

42 (64.6)

9.892

0.002

 T10-T12

44 (47.4)

21 (70.0)

23 (35.4)

LIV (%)

 L5 or higher

52 (54.7)

11 (36.7)

41 (63.1)

5.779

0.016

 S1

43 (45.3)

19 (63.3)

24 (36.9)

Fixed segments (%)

 ≤ 7

50 (52.6)

11 (36.7)

39 (60.0)

4.483

0.034

 > 7

45 (47.4)

19 (63.3)

26 (40.0)

Pre-PJA (%)

 ≤ 5°

67 (70.5)

17 (56.7)

50 (76.9)

4.052

0.044

 > 5°

28 (29.5)

13 (43.3)

15 (23.1)

Pre-SVA (%)

 ≤ 50 mm

55 (57.9)

12 (40.0)

43 (66.2)

5.760

0.016

 > 50 mm

40 (42.1)

18 (60.0)

22 (33.8)

Pre-PI-LL (%)

 ≤ 20°

57 (60.0)

9 (30.0)

48 (73.8)

16.442

0.000

 > 20°

38 (40.0)

21 (70.0)

17 (26.2)

Pre-PT (%)

 ≤ 30°

26 (27.4)

5 (16.7)

21 (32.3)

2.526

0.112

 > 30°

69 (72.6)

25 (83.3)

44 (67.7)

Pre-SS (%)

 ≤ 25°

38 (40.0)

17 (56.7)

21 (32.3)

5.075

0.024

 > 25°

57 (60.0)

13 (43.3)

44 (67.7)

  1. PJK proximal junctional kyphosis, BMI body mass index, BMD bone mineral density, ASIA American Spinal Injury Association, PLC posterior ligament complex, UIV upper instrumented vertebral, LIV lower instrumented vertebral, Pre preoperative, PJA proximal junctional angle, SVA sagittal vertebral axis, PI pelvic incidence, LL lumbar lordosis, PI-LL pelvic incidence-lumbar lordosis mismatch, PT pelvic tilt, SS sacral slope