Incidence of low-grade infection in aseptic loosening of total hip arthroplasty

Figures & data

Table 1. Patient demographics, surgical history, and diagnostics

Age, mean (range)	70 (28–92)
Males/females	49/127 (28%/72%)
Indication for THA
osteoarthritis	115 (65%)
childhood disease	21 (12%)
fracture	10 (6%)
inflammatory arthritis	10 (6%)
osteonecrosis	9 (5%)
unknown	9 (5%)
other	2 (1%)
Revision number
1st	130 (74%)
2nd	34 (19%)
3rd	8 (5%)
4th	3 (2%)
5th	1 (1%)
Years in situ of arthroplasty, mean (range)	11 (0.5–35)
Method of fixation
cemented	83 (47%)
hybrid	19 (11%)
uncemented	74 (42%)
Systemic antibiotics at previous surgery
yes	71 (40%)
no	8 (5%)
unknown	97 (55%)
Anamnesis
Pain	161 (91%)
Functional impairment	90 (51%)
Radiography
Normal	21 (12%)
Loosening of cup	74 (42%)
Loosening of stem	47 (27%)
Loosening of both components	34 (19%)
Blood analysis
ESR, mean (range)	17 (1–90)
CRP, mean (range)	5.1 (< 1–45)
Additional diagnostics
No	49 (28%)
Aspiration and arthrography	53 (30%)
Scintigraphy	96 (55%)

Table 2. Results of diagnostic tests on samples from 176 patients

	All samples negative		One or more samples positive		True positives
	n	%	n	%	n	%
Microbiology	127	72	49	28	3	2
PCR-RLB	141	80	35	20	7	4
Pathology	157	89	19	11	5	3
Combined	98	56	78	44	7	4

Table 3. Results of diagnostic tests on samples from patients who were considered to be infected

Patient	ESR	CRP	Aspiration	Culture	Pathology	PCR-RLB ^a
1	55	18	not done	Gram+ cocci (2 of 5)	negative	Staphylococcus sp./CNS (1 of 6)
2	35	10	not done	negative	positive	Salmonella sp. (3 of 4)
3	17	< 5	not done	negative	negative	E. agglomerans (3 of 5)
4	34	< 5	not done	negative	positive	P. acnes (4 of 4)
5	20	4	not done	S. epidermidis (3 of 5)	positive	Staphylococcus sp./CNS (4 of 4)
6	12	11	negative	Skin flora (5 of 7)	positive	Staphylococcus sp./CNS (5 of 6)
7	31	21	not done	negative	positive	Streptococcus sp. (3 of 7)

^a CNS: coagulase-negative staphylococci

Table 4. Results of diagnostic tests on samples from patients who were suspected of being infected

Patient	ESR	CRP	Aspiration	Culture	Pathology	PCR-RLB ^a
8	11	1	not done	negative	negative	Staphylococcus sp./CNS (2 of 7)
9	11	5	not done	Micrococcus sp. (2 of 6)	negative	negative
10	5	2	not done	S. aureus (2 of 7)	negative	negative
11	10	6	not done	Str. kominis (2 of 5)	negative	negative
12	13	2	not done	P. acnes (2 of 4)	negative	negative
13	25	2	not done	P. acnes (2 of 5)	negative	negative
14	9	9	negative	Difteroid rod (2 of 5)	negative	negative
15	14	< 5	not done	P. acnes (2 of 5)	negative	negative
16	3	< 5	not done	CNS (2 of 7)	negative	Staphylococcus sp./CNS (2 of 7)
17	13	13	negative	negative	negative	P. acnes (2 of 6)
18	8	< 7	negative	Negative	positive	negative
19	10	< 7	negative	Streptococcus sp. and Corynebacterium sp. (both 2 of 4)	negative	negative
20	7	6	not done	negative	positive	negative
21	7	10	not done	negative	positive	negative
22	23	4	not done	negative	positive	negative

^a CNS: coagulase-negative staphylococci