Preoperative waiting time increased the risk of periprosthetic infection in patients with femoral neck fracture

Figures & data

Table 1. Demographic characteristics of patients according to infection

Variable	No infection (n = 167)	Infection (n = 17)
Mean (SD) age at fracture, years	81 (10)	79 (9)
Female sex, n (%)	115 (69%)	11 (65%)
ASA group I or II, n (%)	71 (43%)	5 (29%)
Mean (SD) BMI ^a	23 (4)	25 (4.4)
Previously recognized cognitive failure	38 (23%)	3 (18%)
Mean (SD) duration of surgery, min ^b	77 (20)	78 (14)
Cemented stem	163 (98%)	17 (100%)
30-day mortality, n (%)	10 (5%)	1 (6%)
1-year mortality, n (%)	35 (21%)	8 (47%)

^a n = 145.

^b n = 161 due to missing data.

Flow chart of treatment and final outcome including 1-year mortality.

Table 2. The risk of postoperative infection in patients with or without known risk factors

Risk factor	Infection with risk factor, n/N (%)	Infection without risk factor, n/N (%)	Relative risk (95% CI)	p-value
ASA group III or IV	12/108 (11%)	5/76 (7%)	2 (0.6–4.6)	0.3
Cognitive failure	3/41 (7%)	14/143 (10%)	1 (0.4–4.3)	0.6
Diabetes	4/25 (16%)	13/159 (8%)	0.5 (2.2–1.4)	0.2
Obesity (BMI > 30)	3/14 (21%)	8/131 (6%)	3.5 (1–11.7)	0.04
Malignancy	2/9 (22%)	15/175 (9%)	3 (0.7–9.7)	0.2
Previous infection in contralateral hip	1/1 (100%)	16/183 (9%)	NA	0.09
Renal failure	1/3 (33%)	16/181 (9%)	4 (0.7–20)	0.2
Urinary tract infection	2/12 (17%)	15/172 (9%)	2 (0.5–7.4)	0.4
Alcohol abuse	2/10 (20%)	15/174 (9%)	2 (0.6–8.8)	0.2
Chronic lower leg ulcer	0/2	17/182 (9%)	NA	0.7
Use of steroids and other immunosuppressants	3/14 (21%)	14/170 (8%)	3 (0.8–8)	0.1
1 or more of the risk factors above	13/86 (15%)	4/98 (4%)	4 (1.3–11)	0.01
2 or more of the risk factors above	5/22 (23%)	12/162 (7%)	3 (1–8)	0.02

Data were missing for some patients.

Table 3. Relation between risk of prosthetic joint infection and time between admission and surgery

Waiting time cut point	Infection rate longer time, n/N (%)	Infection rate shorter time n/N (%)	RR (95% CI)	p-value
12 h	16/157 (10%)	1/26 (4%)	3 (0.4–19)	0.3
24 h	13/101 (13%)	4/82 (5%)	3 (0.9–8)	0.06
36 h	9/62 (15%)	8/121 (7%)	2 (0.9–5)	0.08
48 h	5/33 (15%)	12/150 (8%)	2 (0.7–5)	0.2
72 h	4/14 (29%)	13/169 (8%)	4 (1.4–10)	0.01
96 h	2/6 (33%)	15/177 (9%)	4 (1.1–13)	0.04

n = 183 because data for 1 patient were missing.

Table 4. Results of culture in 17 hips with PJI

Type of organism	No. of hips
Coagulase-negative staphylococci (MRSE)	7 (4)
Staphylococcus aureus (MRSA)	7 (0)
Enterococcus species	5
Corynebacterium species	3
Other	3
Culture-negative infection	2
Polymicrobial infection	5
Culture not obtained	1

MRSE: methicillin-resistant Staphylococcus epidermidis

MRSA: methicillin-resistant Staphylococcus aureus