Table 4 Risk factors of S. aureus surgical site infections (SSI)

Age in years, median (Q1-Q3)

64.5 (54 – 70)

68 (60 – 76)

0.98 (0.96 – 1.01)

0.119

Gender, n (%)

Male

20 (0.9)

2303 (99.1)

ref.

0.012

Female

10 (0.3)

2945 (99.7)

0.39 (0.183 – 0.84)

BMI in kg/m2, median (Q1-Q3)

n= 30

n= 2614

1.05

0.010

1.05 (1.0 – 1.1)

0.049

30.7 (28.1-41.8)

27.5 (23.2 – 32.5)

(1.01 – 1.10)

CCI, median (Q1-Q3)

1 (0 – 2)

0 (0 – 1)

1.36 (1.11 – 1.67)

0.003

0.034

ASA score, n (%)

n= 4539

0.273

1

4 (0.45)

878 (99.5)

ref.

2

15 (0.56)

2658 (99.4)

1.24 (0.41 - 3.74)

3 and 4

11 (1.1)

1003 (98.9)

2.41 (0.78 – 7.82)

Altemeier classification, n (%)

1

29 (0.5)

5209 (99.5)

ref.

0.205

2

1 (2.5)

39 (97.5)

4.61 (0.61 – 34.73)

Hospitalisation duration before the surgery in hours, median (Q1-Q3)

18 (17 – 21)

17 (16 – 19)

0.99 (0.99 – 1.02)

0.132

Duration of surgery in minutes, median

n= 5275

(Q1-Q3)

81 (67 – 118)

68 (52 – 88)

1.01 (1.01 – 1.02)

0.001

1.01 (1.00 – 1.02)

0.006

Type of surgery, n (%)

Hip (primary arthroplasty and revision)

8 (0.4)

2245 (99.6)

ref.

0.009

OS (of the UEF and others)

7 (1.7)

396 (98.3)

4.9 (1.79 – 13.76)

Knee (primary arthroplasty and revision)

15 (0.6)

2607 (99.4)

1.61 (0.68 – 3.82)

Site, n (%)

North

14 (1.3)

1063 (98.7)

ref.

<

South

16 (0.4)

4185 (99.6)

0.29 (0.14 – 0.60)

0.001

Period of surgery,

Period before

19 (0.8)

2427 (99.2)

2.01 (0.95 - 4.32)

0.061

n (%)

Period after

11 (0.4)

2821 (99.6)

ref.

Presence of preoperative screening, n (%)

n= 29

n= 5159

0.112

0.24 (0.08 – 0.73)

0.012

Yes

No

4 (0.29)

25 (0.66)

1387 (99.71)

3772 (99.34)

0.44 (0.15 – 1.25)

ref.

Result of preoperative screening, n (%)

n= 4

n= 1387

1.000

Positive

1 (0.28)

354 (99.7)

0.97 (0.10 - 9.40)

Negative

3 (0.29)

1033 (99.7)

ref.

Result of perioperative screening^a, n (%)

n= 1

n= 106

1.000

Positive

1 (10.0)

9 (90.0)

Negative

0

97 (100)