MAJOR ARTICLE
Gram-Negative Prosthetic Joint Infections:
Risk Factors and Outcome of Treatment
Pang-Hsin Hsieh,1,2 Mel S. Lee,1,2 Kuo-Yao Hsu,1,2 Yu-Han Chang,1,2 Hsin-Nung Shih,1,2 and Steve W. Ueng1, 2
1
Department of Orthopedic Surgery, Chang Gung Memorial Hospital, and 2College of Medicine, Chang Gung University, Taoyuan, Taiwan
Background. Little information is available regarding the demographic characteristics and outcomes of patients
with prosthetic joint infection (PJI) resulting from gram-negative (GN) organisms, compared with patients with
PJI resulting from gram-positive (GP) organisms.
Methods. We performed a retrospective cohort analysis of all cases of PJI that were treated at our institution
during the period from 2000 through 2006.
Results. GN microorganisms were involved in 53 (15%) of 346 first-time episodes of PJI, and Pseudomonas
aeruginosa was the most commonly isolated pathogen (21 [40%] of the 53 episodes). Patients with GN PJI were
older (median age, 68 vs. 59 years; P ! .001 ) and developed infection earlier (median joint age, 74 vs. 109 days;
P ! .001) than those with GP PJI. Of the 53 episodes of GN PJI, 27 (51%) were treated with debridement, 16
(30%) with 2-stage exchange arthroplasty, and 10 (19%) with resection arthroplasty. Treating GN PJI with debridement was associated with a lower 2-year cumulative probability of success than treating GP PJI with debridement (27% vs. 47% of episodes were successfully treated; P p .002 ); no difference was found when a PJI was
treated with 2-stage exchange or resection arthroplasty. A longer duration of symptoms before treatment with
debridement was associated with treatment failure for GN PJI, compared with for GP PJI (median duration of
symptoms, 11 vs. 5 days; P p .02).
Conclusions. GN PJI represents a substantial proportion of all occurrences of PJI. Debridement alone has a
high failure rate and should not be attempted when the duration of symptoms is long. Resection of the prosthesis,
with or without subsequent reimplantation, as a result of GN PJI is associated with a favorable outcome rate that
is comparable to that associated with PJI due to GP pathogens.
Infection, one of the most devastating complications
after total joint arthroplasty, is often associated with
significant morbidity and increased medical costs [1].
Improvements in operative techniques, aseptic procedures, and the use of perioperative antibiotic prophylaxis have reduced the risk of prosthetic joint infection
(PJI) to 1%–2% of patients at most medical centers
[2]. However, despite these developments, the increasing number of joint replacement surgical procedures
being performed has led to an increase in the number
of cases of infection that need to be treated.
Treatment for PJI can be divided into 1 main groups:
Received 9 March 2009; accepted 26 May 2009; electronically published 19
August 2009.
Reprints or correspondence: Dr. Pang-Hsin Hsieh, Dept. of Orthopedic Surgery,
Chang Gung Memorial Hospital, No. 5, Fu-Hsing St., 333 Kweishian, Taoyuan,
Taiwan ([email protected] or [email protected]).
Clinical Infectious Diseases 2009; 49:1036–43
2009 by the Infectious Diseases Society of America. All rights reserved.
1058-4838/2009/4907-0008$15.00
DOI: 10.1086/605593
1036 • CID 2009:49 (1 October) • Hsieh et al
(1) prosthesis removal with or without subsequent
reimplantation and (2) debridement and implant retention using long-term antibiotics. Removal of all
prosthesis components (ie, resection arthroplasty) has
a higher chance of eradicating infection but requires
extensive surgery and often prolonged immobilization
[3]. Debridement and retention of the prosthesis is an
attractive alternative, which may be attempted for selected patients to salvage the joint prosthesis [4]. This
less-extensive surgery is thought to be associated with
a lower probability of procedure-related morbidity, less
immobilization, and, consequently, less need for rehabilitation. The main problem with debridement and
retention, however, is that a substantial number of patients will ultimately experience a relapse of infection
after this less-aggressive procedure, necessitating exchange or resection arthroplasty [3, 4]. The risk of failure for this type of treatment depends on a number of
factors, including the causative organism(s) [5–8].
Most PJIs are caused by gram-positive (GP) pathogens. Staphylococci (including Staphylococcus aureus
and coagulase-negative staphylococci) and streptococci are
among the most common organisms, constituting 65%–85%
of all isolates. Gram-negative (GN) bacteria, which are less
commonly associated with PJI, constitute 6%–23% of all episodes [9–12]. Although GN infections constitute a relatively
minor proportion of all PJIs, they are of significant clinical
importance, because treatment of such infections is considered
more complicated as a result of the virulence of the organisms,
their growing resistance to antimicrobial agents, and the comorbid conditions of patients [6–8].
Although there have been numerous reports regarding treatment of PJI, the comparison between GN and GP PJIs has not,
to our knowledge, been reported in the English-language literature. The purposes of our retrospective comparative study
were, therefore, to evaluate the demographic characteristics and
outcomes of patients treated for GN PJI and to identify prognostic factors that would lead to treatment failure.
on examination of periprosthetic tissues, (3) development of a
sinus tract, or (4) death related to PJI.
We summarized the collected data (which included patient
demographics, history of orthopedic surgery, comorbidities, presenting signs of PJI, duration of symptoms, laboratory findings,
surgical and medical treatments, and bacteriologic results) at the
time of study enrollment. GN and GP PJI data were analyzed
and compared to determine risk factors and prognostic factors
predicting outcomes.
Statistical analysis. As appropriate, a x2 analysis or a Fisher
exact test was used for analyzing categorical data. For numerical
data, an independent t test or the nonparametric Mann-Whitney U test was used for between-group comparisons. The survival rate free of treatment failure was estimated using the
Kaplan-Meier survival method and the log rank test. A P value
of !.05 was considered to be statistically significant. All statistics
were 2-sided and were performed using SAS software, version
9.1.3 (SAS).
PATIENTS AND METHODS
Study design. This was a retrospective case cohort study in
which the surgical and medical treatment modalities of the
patients were not randomized. Decisions of management were
made by the treating physicians. The patients were observed
from the date of diagnosis of PJI until treatment failure, final
clinic visit, death, or loss to follow-up.
Study population. Our study included all patients with a
diagnosis of PJI of the hip or knee who were treated at our
institution during the period from January 2000 through December 2006. After approval was obtained from the institutional review board, patients were identified using the electronic
database of the hospital, by matching them to the International
Classification of Diseases, Ninth Revision, Clinical Modification,
specific for PJI (code 996.66). Two independent researchers reviewed and confirmed the medical records. Only cases in which
the first episode of PJI was treated at our institution were included in the analysis.
Definitions. A PJI was diagnosed if the same microorganism was recovered from at least 2 joint aspirate or intraoperative tissue specimens for culture or if at least one intraoperative
culture was positive for the microorganism, plus if there was
evidence of infection at the site of hip or knee prosthesis (ie,
presence of a discharging sinus communicating with the joint,
operative findings of purulence, or positive laboratory and histopathological test results) [13]. A GN PJI was defined as the
presence of at least 1 GN pathogen at the site of infection,
regardless of the total number of different strains. Treatment
failure was defined as the occurrence of the following conditions
at any time after the initial surgical procedure: (1) the presence
of a PJI due to the original microorganism (relapse of infection)
or a different strain (reinfection), (2) surgical findings of purulence around the joint or acute inflammatory histopathology
RESULTS
Study population. Fifty-three first-time episodes of GN PJI
occurring among 50 patients from January 1, 2000, through
December 31, 2006, were treated at our institution. This accounted for 53 (15%) of 346 first-time episodes of culturepositive PJI encountered during the study period (table 1).
Patients with GN PJI were older (median age, 68 vs. 59 years;
P ! .001) and developed infection earlier after the index joint
replacement surgery (median joint age, 74 vs. 109 days; P !
.001) than did patients with GP PJI. Other risk factors for GN
PJI that approached statistical significance included fever
(P p .09) and the presence of a sinus tract (P p .12). Patients with GN PJI did not considerably differ from patients
with GP PJI with regard to sex, joint location, multiple operations, polymicrobial infection, laboratory findings, underlying comorbidity, presence of pus in the joint, bacteremia, or
type of surgical treatment modality.
Microbiologic findings. The microbiologic findings of the
53 episodes of GN PJI are outlined in table 2. A single microorganism was isolated in 51 episodes (96%), and multiple microorganisms were isolated in 2 episodes (4%). For patients
with GN PJI, Pseudomonas aeruginosa was the most commonly
isolated pathogen, involved in 21 episodes (19 monomicrobial
and 2 polymicrobial episodes), followed next by Escherichia coli
in 10 (19%) episodes and then by Klebsiella pneumoniae in 8
(15%) episodes.
Surgical and medical treatment. The most common initial
surgical intervention for the treatment of GN PJI was debridement and retention of prosthesis, used in 27 (51%) episodes,
followed by 2-stage exchange in 16 (30%) episodes and resection arthroplasty in 10 (19%) episodes. Debridement typically
included complete surgical exposure of the joint, removal of
Gram-Negative Prosthetic Joint Infections • CID 2009:49 (1 October) • 1037
Table 1. Characteristics of 343 Patients with 346 Episodes of Gram-Negative (GN) or Gram-Positive
(GP) Prosthetic Joint Infection (PJI)
GN PJI
(n p 53 episodes)
Characteristic
a
Age, median years (range)
Male sex
Osteoarthritis
Total hip arthroplasty
68
33
29
36
a
Prosthesis age, median days (range)
Multiple operations (⭓2 times) before PJI
Polymicrobial PJI
Laboratory data, median (range)
C-reactive protein level,b mg/L
White blood cell count, 109 cells/L
Underlying comorbidity
Diabetes mellitus
Rheumatoid arthritis
Malignancy
Liver cirrhosis
Use of steroid
Presentation of infection
Discharging sinus
Purulent fluid or pus in the joint
Fever (temperature, ⭓38.3C)
Bacteremia
Type of surgery
Debridement
2-stage exchange
Resection arthroplasty
(35–85)
(62)
(55)
(68)
74 (8–296)
20 (38)
2 (4)
GP PJI
(n p 293 episodes)
59
200
177
206
P
(32–79)
(68)
(60)
(70)
!.001
109 (6–976)
94 (32)
!.001
16 (5)
.48
.43
.75
.42
.75
39 (9–312)
34 (7–320)
.32
1.2 (0.3–2.2)
1.1 (0.4–2.1)
.27
21 (40)
107 (37)
6
3
6
8
(11)
(6)
(11)
(15)
39
12
36
36
(13)
(4)
(12)
(12)
.67
.69
.71
.84
.57
23 (43)
95 (32)
.12
17 (32)
10 (19)
108 (37)
31 (11)
.50
.09
5 (9)
14 (5)
0.19
27 (51)
16 (30)
127 (43)
118 (40)
.31
.17
10 (19)
48 (16)
.66
NOTE. Data are no. (%) of episodes, unless otherwise indicated. There were 53 episodes of GN PJI that occurred
among 50 patients, and there were 293 episodes of GP PJI that occurred among 293 patients.
a
b
A P value of !.05 was considered to be statistically significant.
There were 9 episodes with missing data.
the inflamed soft tissues and bone, and debridement of prosthetic-bone interfaces. Implantation of antibiotic-loaded cement beads within the joint was performed at the time of
removal of the prosthesis and in 6 (22%) of the 27 episodes
treated with debridement and retention.
All patients with GN PJI received appropriate intravenous
antimicrobial therapy that was based on the antimicrobial susceptibility pattern of the bacteria isolated from the intraoperative cultures (table 3). The median duration of effective parenteral antibiotic therapy was 38 days (range, 24–52 days) for
GN PJI episodes treated with debridement and retention of the
components, 23 days (range, 6–36 days) for 2-stage exchange,
and 17 days (range, 10–39 days) for episodes treated with resection arthroplasty. Patients with GN PJI who received debridement and retention were given additional oral antibiotic
suppression for a median of 49 days (range, 28–92 days). Various regimens of oral antibiotic treatment were prescribed, including ciprofloxacin for 15 patients, clindamycin for 2 patients, a combination of both for 7 patients, and a combined
1038 • CID 2009:49 (1 October) • Hsieh et al
therapy of ciprofloxacin, sulfamethoxazole, and trimethoprim
for 3 patients.
Outcomes and prognostic factors. The 2-year survival rate
free of treatment failure for patients with GN PJI was 27%
(95% confidence interval [CI], 16%–34%) for debridement and
retention, 87% (95% CI, 80%–99%) for 2-stage exchange, and
69% (95% CI, 59%–84%) for resection arthroplasty (figure 1).
Patients with GN PJI who underwent debridement alone were
significantly more likely to experience treatment failure than
those who underwent 2-stage exchange (P ! .001) and resection
arthroplasty (P p .008).
The outcomes of patients treated for GN PJI with 2-stage
exchange and resection arthroplasty were similar to those of
patients treated for GP PJI with similar surgical modalities: the
2-year estimates of the survival rate free of treatment failure
for patients with GP PJI were 94% (95% CI, 86%–100%;
P p .39) for 2-stage exchange and 78% (95% CI, 70%–91%;
P p .30) for resection arthroplasty. However, treating GN PJI
with debridement and retention of components was associat-
Table 2. Microbiologic Findings of 53 Episodes of Gram-Negative (GN) Prosthetic Joint Infection (PJI) Occurring among Patients Treated during 2000–2006
patients), underlying malignancy (6 patients), myocardial infarction (2 patients), and a traffic accident (1 patient).
DISCUSSION
Infecting microorganism(s)
GN PJI
(n p 53 episodes)
Monomicrobial
Pseudomonas aeruginosa
Escherichia coli
Klebsiella pneumoniae
19 (36)
10 (19)
8 (15)
Enterobacter cloacae
Acinetobacter baumannii
3 (6)
2 (4)
Salmonella enterica
Hemophilus influenzae
Proteus mirabilis
Bacteroides fragilis
2
2
1
1
Unidentified
Polymicrobial
P. aeruginosa, methicillin-resistant S.
aureus
P. aeruginosa, coagulase-negative Staphylococcus species
(4)
(4)
(2)
(2)
3 (6)
1 (2)
1 (2)
NOTE. Data are no. (%) of episodes. Because of rounding, percentages
may not add up to 100%.
ed with a lower 2-year cumulative survival rate free of treatment
failure than treating GP PJI with debridement and retention of
components (27% vs. 47% of episodes were successfully treated;
P p .002).
The potential risk factors leading to the differences between
the subgroups of patients receiving debridement and retention
are outlined in table 4. No risk factor was identified in terms
of age, sex, joint location, duration of symptoms prior to surgery, multiple operations before PJI, polymicrobial infection,
laboratory findings, durations of intravenous and oral antibiotic therapies, single antimicrobial medication, use of local antibiotic beads, underlying comorbidity, or presentation of PJI.
Of the 27 episodes of GN PJI occurring among 27 patients
treated with debridement and retention, treatment failure was
observed in 20 (74%) episodes. A total of 21 (78%) patients had
their serum C-reactive protein levels decrease to half their pretreatment levels during antimicrobial therapy. However, of these
21 episodes, only 7 (33%) showed no evidence of recurrent infection, and 14 (67%) ultimately involved treatment failure during follow-up. A shorter duration of symptoms before treatment
was associated with successful debridement in episodes of GN
PJI (median duration of symptoms, 11 vs. 5 days; P p .02) (table
5). No other risk factor for treatment failure was identified.
Mortality. Twenty-six patients had died during the course
of writing this paper. Seven (5 patients with GP PJI and 2 with
GN PJI) deaths were related to the infection. Other causes of
death included complications secondary to liver cirrhosis (10
The number of total joint replacement surgical procedures is
increasing rapidly. It is estimated that, from 2005 to 2030, the
number of primary total hip arthroplasties in the United States
will increase by 174%, to 572,000 procedures per year, and new
cases of total knee replacement will increase by 673%, to 3.48
million procedures per year [14]. Although the rate of infection
after prosthetic joint replacement remains relatively constant,
these large projected increases in demand for hip and knee
replacements imply that the demand for treating patients with
PJI is likely to increase. Although many authors have reported
on the treatment of PJI of the hip or knee [4, 6, 9, 11, 12],
most of them dealt with infections resulting from a mixed group
of microorganisms, with GP bacteria being the most common
pathogens involved in these studies.
A number of difficulties occur during the treatment of bone
and joint infections caused by GN bacteria. These difficulties
occur primarily affect immunocompromised patients and are
associated with treatment failure [6–8]; only a limited number
of experimental models have been described [15], and randomized, controlled clinical trials are hampered by the fact that
most institutions do not have a sufficient number of patients
for such studies. We sought to report the demographic charTable 3. Intravenous Antimicrobial Therapy Used for 53 Episodes of Gram-Negative (GN) Prosthetic Joint Infection (PJI) Occurring among Patients Treated during 2000–2006
Type of antimicrobial therapy, drug(s)
Monotherapy
Ciprofloxacin
GN PJI
(n p 53 episodes)
4 (8)
Clindamycin
Imipenem
3 (6)
3 (6)
Metronidazole
2 (4)
Ceftriaxone
Aztreonam
2 (4)
1 (2)
Amikacin
1 (2)
Gentamicin
Piperacillin
1 (2)
1 (2)
Combination therapy
Ceftazidime and ciprofloxacin
Cefepime and gentamicin
Ceftazidime and amikacin
10 (19)
9 (17)
6 (11)
Ceftriaxone and clindamycin
Ceftriaxone and metronidazole
Vancomycin and aztreonam
5 (9)
3 (16)
1 (2)
Vancomycin and ciprofloxacin
1 (2)
NOTE. Data are no. (%) of episodes. Because of rounding, percentages
may not add to 100%.
Gram-Negative Prosthetic Joint Infections • CID 2009:49 (1 October) • 1039
Figure 1. Survival rate free of treatment failure in 346 episodes of prosthetic joint infection (PJI) treated with debridement, 2-stage exchange, or
resection arthroplasty during the period from 2000 through 2006. GN, gram-negative; GP, gram-positive.
acteristics and treatment outcomes of patients with GN PJI and
the prognostic factors associated with GN PJI. Data provided
by the present study may help treating physicians identify patients at risk of acquiring GN infection and then make informed
decisions (eg, regarding the selection of a broader empiric antimicrobial coverage after the surgery). These data might serve
as a guide for predicting the outcome of such infections.
Our data suggest that GN PJIs represent a substantial pro-
Table 4. Comparison of Episodes of Gram-Negative (GN) and Gram-Positive (GP) Prosthetic Joint
Infection (PJI) Occurring among Patients Who Underwent Debridement and Retention of the Prosthesis
GN PJI
(n p 27 episodes)
GP PJI
(n p 127 episodes)
P
Age, median years (range)
Male sex
63 (36–80)
16 (59)
59 (35–73)
84 (66)
.17
.50
Total hip arthroplasty
Duration of symptoms, median days (range)
Multiple operations (⭓2 times) before PJI
Polymicrobial PJI
17
8
11
0
84
10
36
4
.75
.34
.20
.35
Laboratory data, median (range)
C-reactive protein level,a mg/L
White blood cell count, 109 cells/L
34 (9–134)
1.1 (0.5–1.6)
39 (11–216)
1.1 (0.6–1.4)
.44
.38
Intravenous antibiotic therapy, median days
(range)
38 (24–52)
37 (12–54)
.12
Oral antibiotic suppression, median days
(range)
Local antibiotic therapy
49 (28–92)
6 (22)
58 (21–112)
37 (29)
.22
.47
Underlying comorbidity
Diabetes mellitus
Rheumatoid arthritis
11 (41)
4 (15)
48 (38)
17 (13)
.77
.77
Malignancy
2 (7)
4 (3)
.28
Liver cirrhosis
Use of steroid
3 (11)
5 (19)
6 (5)
16 (13)
.19
.54
Presentation of infection
Discharging sinus
Purulent fluid or pus in the joint
6 (22)
8 (30)
35 (28)
39 (31)
.57
.91
Fever (temperature, ⭓38.3C)
3 (11)
16 (13)
.83
Bacteremia
2 (7)
8 (6)
.63
Variable
(63)
(2–19)
(41)
(0)
NOTE. Data are no. (%) of episodes, unless otherwise indicated.
a
There were 2 episodes with missing data.
1040 • CID 2009:49 (1 October) • Hsieh et al
(66)
(3–35)
(28)
(3)
Table 5. Data on 27 Episodes of Gram-Negative Prosthetic Joint Infection Occurring among Patients
Who Underwent Debridement and Retention of the Prosthesis
Successful
debridement
(n p 7 episodes)
Persistent infection
(n p 20 episodes)
P
Age, median years (range)
Male sex
62 (47–79)
4 (57)
63.5 (37–80)
12 (60)
.59
.89
Total hip arthroplasty
Prosthesis age, median days (range)
2 (29)
59 (14–123)
8 (40)
73 (8–121)
.68
.53
.02
Variable
a
Duration of symptoms, median days
(range)
5 (3–8)
11 (2–19)
Multiple operations (⭓2 times) before PJI
3 (43)
8 (40)
NS
Polymicrobial PJI
Laboratory data, median (range)
C-reactive protein level, mg/L
White blood cell count, 109 cells/L
0 (0)
0 (0)
NA
Intravenous antibiotic therapy
Duration, median days (range)
Monotherapy
Oral antibiotic suppression
Duration, median days (range)
Monotherapy
Local antibiotic therapy
Underlying comorbidity
31 (9–134)
36 (15–111)
.65
1.1 (0.5–1.6)
1.1 (0.6–1.4)
.38
46 (29–52)
1 (14)
37 (24–44)
6 (30)
.10
.63
45 (28–87)
6 (86)
1 (14)
53 (36–92)
11 (55)
5 (25)
.51
.2
.66
Diabetes mellitus
Rheumatoid arthritis
4 (57)
1 (14)
7 (35)
3 (15)
.39
NS
Malignancy
Liver cirrhosis
Use of steroid
Presentation of infection
0 (0)
2 (29)
2 (29)
2 (10)
1 (5)
3 (15)
.60
.16
.58
Discharging sinus
Purulent fluid or pus in the joint
0 (0)
2 (29)
6 (30)
6 (30)
.15
NS
Fever (temperature, ⭓38.3C)
Bacteremia
1 (14)
1 (14)
2 (10)
1 (5)
NS
.46
NOTE. Data are no. (%) of episodes, unless otherwise indicated. NA, not applicable; NS, not significant.
a
A P value of !.05 was considered to be statistically significant.
portion of all occurrences of PJI. The proportion of episodes
(53 [15%] of 346 episodes of PJI) that occurred in the present study is in conformity with those reported in the literature
[9–12]. We found that GN PJIs tend to occur more frequently among elderly patients and during the early postoperative
period. Although not statistically significant, patients with GN
PJI are more likely to have fever and develop a discharging sinus. We also found that patient with GN PJI who were treated
with 2-stage exchange and resection arthroplasty had a favorable outcome comparable to that of patients with GP PJI who
are treated with similar surgical modalities. However, in our
study, the attempt to retain the prosthesis with debridement
alone was associated with a significantly less favorable outcome
for patients with GN PJI than for patients with GP PJI.
In an attempt to find the reason for the worse outcome of
debridement and retention associated with GN PJI, we have
compared the subgroups of patients with GN and GP PJI who
underwent debridement surgery on the basis of a number of
factors. However, with the numbers of patients available, no
factors could be identified in terms of patients’ demographic
characteristics, surgical and medical treatment history, comorbidity, laboratory data, or presentation of infection. This finding mirrored the fact that the development of PJI as a result
of a GN pathogen, in itself, might be an important factor contributing to the poor outcome of debridement and retention.
In an analysis of 99 episodes of PJI among patients who
underwent debridement and retention, Marculescu et al [4] did
not find GN infection to be associated with treatment failure.
One explanation for this might be that only a small number
of episodes of GN PJI (ie, 6 [6%] of 99 episodes) were included in their study; thus, their study lacked sufficient power to
detect a difference.
Gram-Negative Prosthetic Joint Infections • CID 2009:49 (1 October) • 1041
In choosing between retention and removal of the prosthesis
for the management of PJI, clinicians and patients are often
forced to face a trade-off between short-term surgical morbidity and mortality and long-term relapse of infection. Patients
sometimes ask to retain the prosthesis, under the misapprehension that a failed attempt at debridement causes little harm.
This is a common clinical scenario. In fact, a failed attempt at
debridement and retention of the prosthesis can result in the
kind of morbidity associated with an orthopedic surgical procedure. It also consumes valuable healthcare resources, because
further surgery is often required. We are not aware of any data
from prospective clinical trials comparing prosthesis retention
and removal for the treatment of PJI. Fisman et al [3], using
a Markov model to compare the cost-effectiveness of debridement and staged exchange in simulated patients, concluded that
debridement and retention would provide greater quality-adjusted life expectancy gains than would 2-stage exchange arthroplasty among patients with infected hip after arthroplasty.
However, this model was based on published studies in which
GP microorganisms were the most common pathogens. The
authors found that their results were most sensitive to the annual rate of relapse after debridement. Thus, their conclusion
might not be applied properly to the episodes of GN PJI reported in our study, which resulted in a significantly higher
rate of treatment failure.
Despite the dismal figure, debridement and retention of
prosthesis was successfully attempted in 7 (26%) of 27 episodes of GN PJI. A short duration of symptoms before surgery was the only identified factor contributing to the success
of treatment. In fact, in all of these episodes, the surgery was
performed within 8 days after the onset of symptoms. These
observations are consistent with outcome data from other cohorts of patients infected mainly by GP pathogens. Brandt et
al [16], in a study of 33 staphylococcal PJIs, reported that
prostheses that were debrided more than 2 days after onset of
symptoms were associated with a higher probability of treatment failure than were those debrided within 2 days of onset.
For 34 patient in a retrospective study by Tattevin et al [12],
there were 13 patients (38%) who had a significantly short
interval (!5 days) from onset of symptoms to debridement and
were successfully treated, and there were 21 (62%) patients who
had a much longer median interval (54 days) and experienced
a failed debridement. Marculescu et al [4] reported that a duration of symptoms of ⭓8 days was associated with a greater
risk of treatment failure, higher by a factor of 2, after debridement and prosthesis retention. On the basis of the results of
previous studies and the present study, we emphasize the importance of expedient debridement when attempting to salvage the prosthesis.
The presence of a sinus tract has been associated with treatment failure in previous reports [4, 17]. In our current study,
1042 • CID 2009:49 (1 October) • Hsieh et al
given the small number of successful debridements for patients with GN PJI, we were unable to determine whether the
presence of a sinus tract was a significantly poor prognostic factor (P p .15). Nevertheless, it is important to note that none
of the GN PJI episodes that were managed successfully involved
patients who had a sinus tract.
Our study has several limitations. First, this is a retrospective
study with all the potential drawbacks implicit in such a study
design. Our institution is a tertiary care referral center with an
established protocol for the treatment of PJI. Furthermore, in
all cases, decisions were made in consultation with the infection
specialists. Nonetheless, there remains the potential for uncontrolled selection bias among treating physicians. In addition,
the number of GN PJIs included during the study period was
relatively small, and thus our study may have lacked enough
power to detect slight differences among subsets of patients.
Finally, the quality of debridement among patients is likely to
affect the outcome. However, it was very difficult to evaluate
the quality of surgery, and thus we did not specifically address
this variable in the present study.
In summary, GN PJI accounts for a substantial percentage
of all PJI episodes. We believe that the choice of antimicrobial
therapy for PJI should take into account the possibility of GN
infection, especially in suspected patients who are older and
who develop PJI early in the postoperative period. In comparison with PJI due to GP pathogens, GN PJI treated with 2stage exchange and resection arthroplasty is associated with a
comparatively favorable outcome. However, debridement and
retention for GN PJI carries a higher rate of treatment failure and should be used sparingly among patients within the
first few days after the onset of symptoms. Further data from
randomized clinical trials are required to substantiate these
findings.
Acknowledgments
We thank Zoe Chen for her assistance with statistical analysis.
Potential conflicts of interest. All authors: no conflicts.
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