Table 1 Results of the stepwise logistic regression analysis, where all potential risk factors are included during the first step and subsequently removed if not significant (p > 0.05). *Please note that p-values at removal of the parameter must not necessarily have the same order than the step at which the factor was removed, since the logistic model recalculates at each step.

Sex (female vs. male gender)

2

0.89

0.88

Age (per decade)

12

0.84

0.34

Body mass index (per unit kg·m^-2)

15

0.95

0.57

ASA-status III and IV versus I and II

18

1.48

0.22

Diabetes mellitus

7

3.72

0.99

Cancerous disease

19

0.48

0.18

Chronic systemic corticosteroid medication

20

1.89

0.13

"immune suppression" (any of the three afore mentioned diseases)

5

1.35

0.99

Skin abscess in the past

3

0.74

0.87

Infection with other catheter material in the past

16

0.17

0.26

Easy perspiration¹

11

2.33

0.32

Any of the three afore mentioned factors

14

1.64

0.43

Localization of the catheter ("clean" vs. "dirty")²

8

0.38

0.37

Puncture site in the groin

Not removed

3.39

0.004

Epidural catheter vs. peripheral nerve catheter

17

1.24

0.11

Disinfection technique (wiping versus spraying)

9

1.88

0.50

Number of attempts during catheter placement

10

1.49

0.38

Fixation technique (tunneling versus suturing)

1

0.97

0.97

Intraoperative corticosteroid medication

4

1.40

0.75

Intraoperative single shot antibiotic administration

6

2.34

0.47

Postoperative antibiotic therapy (at least 3 days or until removal of the catheter)

Not removed

0.41

0.05

Perioperative antibiotic therapy (intra- & postoperative)

23

0.43

0.09

Duration of catheter use (per day)

21

1.17

0.16

Accidental disconnection of the catheter

22

0.78

0.19

Accidental removal of the catheter dressing (n =)

15

0.50

0.37

Intentioned replacements of the catheter dressing (n =)

13

0.83

0.31

Removal of the catheter dressing (intentionally or unintentionally; n =)

Not removed

2.12

0.001