CARTEL

1. 1 23
European Journal of Orthopaedic
Surgery & Traumatology
ISSN 1633-8065
Volume 27
Number 7
Eur J Orthop Surg Traumatol (2017)
27:983-987
DOI 10.1007/s00590-017-1952-6
Risk factors for amputation in
periprosthetic knee infection
Alan Giovanni Polanco-Armenta,
Adrián Miguel-Pérez, Adrián
Huetzemani Rivera-Villa, Manuel
Ignacio Barrera-García, et al.

2. 1 23
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3. ORIGINAL ARTICLE • KNEE - ARTHROPLASTY
Risk factors for amputation in periprosthetic knee infection
Alan Giovanni Polanco-Armenta1 • Adria´n Miguel-Pe´rez1 •
Adria´n Huetzemani Rivera-Villa1 • Manuel Ignacio Barrera-Garcı´a1 •
Marı´a Guadalupe Sa´nchez-Prado1 • Alberto Va´zquez-Noya1 •
Fernando Vidal-Cervantes1 • Jose´ de Jesu´s Guerra-Jasso1 • Jose´ Manuel Pe´rez-Atanasio1
Received: 29 December 2016 / Accepted: 23 March 2017 / Published online: 7 April 2017
Ó Springer-Verlag France 2017
Abstract Treatment for prosthetic knee replacement is
becoming more common. Infection is an arthroplasty-re-
lated complication leading to prolonged hospitalization,
multiple surgical procedures, permanent loss of the
implant, impaired function, impaired quality of life and
even amputation of the limb. Previous studies have eval-
uated the risk factors associated with periprosthetic knee
infection, but scarce information related to risk factors
associated with amputation in this group of patients is
available. The purpose of this study was to identify risk
factors for amputation in periprosthetic infected knee
through a case–control study, analyzing patients treated
from January 2012 to November 2016 in a hospital with a
high incidence of this diagnosis. We included 183 patients
with periprosthetic knee infection; 23 required amputation
as definitive management (cases). We found that patients
with surgical time [120 min (p = 0.01), surgical risk
higher than two points according to the American Society
of Anesthesiology score (p = 0.00), smokers (p = 0.04),
obesity and diabetes mellitus (p = 0.00) had an increased
risk of amputation.
Keywords Risk factors Á Amputation Á Periprosthetic knee
infection
Introduction
Periprosthetic infection after total knee arthroplasty occurs
in approximately 2% of patients and is associated with
medical complications and high socioeconomic cost [1].
Eradication of periprosthetic infection and prevention of
recurrence are the main objectives in the treatment of these
cases [1–3].
Risk factors for infection following total knee arthro-
plasty have been extensively described in the literature
[4–6].
For chronic periprosthetic infection, two-stage pros-
thetic exchange is considered the gold standard for treat-
ment and includes prosthetic removal, extensive
debridement of all infected tissue and insertion of an
antibiotic spacer [6].
After the parenteral treatment with antibiotics and a
negative aspiration of the joint, the second stage includes
the reimplantation of a new prosthesis. The recurrence of
periprosthetic infection after surgical treatment ranges
from 9 to 33% and entails significant morbidity and addi-
tional cost for patients [7, 8].
Factors for failure after two stages of treatment include
medical comorbidity, pathogenic virulence and resistance
to antibiotics in addition to bone condition and adequate
skin coverage of soft tissues [9–11]. However, risk factors
for amputation after this treatment failure have not been
extensively studied.
Patients receiving amputation at the knee level for
treatment of recurrent periprosthetic infection after total
knee arthroplasty have a better function and ambulatory
status compared to patients receiving amputation above the
knee. Amputation at the knee level should be recom-
mended as the treatment of choice for patients who have
& Jose´ Manuel Pe´rez-Atanasio
drmanuelperezata@gmail.com
1
High Specialty Medical Unit ‘‘Dr. Victorio de la Fuente
Narva´ez’’, Mexican Institute of Social Security, Colector 15
s/n (Av. Fortuna) Esq. Av. Polite´cnico nacional. Col.
Magdalena de las Salinas, Delegacio´n Gustavo A. Madero,
07760 Mexico City, Mexico
123
Eur J Orthop Surg Traumatol (2017) 27:983–987
DOI 10.1007/s00590-017-1952-6
Author's personal copy

4. persistent prosthetic knee infection after failure of the two-
stage reimplantation procedure [12].
Female gender, heart disease and psychiatric disorders
increase the risk of hip and knee periprosthetic infection
recurrence. Patients with periprosthetic infection of the hip
and with heart disease are at higher risk of infection per-
sistence [13]
Therefore, the purpose of this study was to identify risk
factors for amputation in periprosthetic knee infected,
focusing on medical comorbidity, perioperative and sur-
gical factors.
Materials and methods
A case–control study was carried out in a joint replacements
concentration hospital. In this hospital, more than 1400 knee
arthroplasties are performed annually, and 28 high-grade
orthopedic surgeons participated in the surgeries.
The study population consisted of 183 patients who had
a diagnosis of periprosthetic knee infection and who were
surgically treated from January 2012 to November 2016
systematically registered in a standardized database that
includes demographic data, comorbidity, medications,
clinical evolution and postoperative complications
obtained from the clinical file. Authorization was obtained
from the local research and ethics committee with regis-
tration number: R-2016-3401-36.
Patients who presented amputation as a definitive treat-
ment for periprosthetic knee infection were considered as
cases. Control group was matched by age and sex in a ratio of
7:1 with cases, which were selected from patients with
periprosthetic knee infection who were not undergoing
amputation. Risk factors were identified in the literature and
by biological plausibility based on clinical experience.
There was no verbal, physical or telephone communi-
cation with cases or controls for the purposes of this study.
Demographics of cases and controls were compared
using summary statistics. The descriptive analyses for
the variables were based on percentages and frequen-
cies, and for continuous variables on the mean and
standard deviation (SD) or medians and the interquartile
range.
The SPSSÒ
version 22 program was used to perform
linear regression analysis to obtain odds ratios (OR) with
95% confidence intervals (CI) for the association between
each risk factor and the presence of amputation considering
as significant a p 0.05.
Results
Of the 183 patients studied, 107 were treated with knee
arthrodesis and 53 with two-stage revision surgery con-
sisting of surgical debridement, removal of prosthetic
components and knee revision arthroplasty. In 23 patients
who were considered as cases, supracondylar amputation
was performed after treatment failure with knee arthrodesis
and multiple joint debridements.
The demographic characteristics of the study popula-
tion are shown in Table 1. It shows that within the
population studied, the right knee was the most affected,
mean age was 68.7 for amputees, men were more likely
to have incidence of amputation (60.8%) and the main
reason for total primary knee arthroplasty was
osteoarthritis (91.30%).
Table 1 Demographic
characteristics of the study
population
Characteristics Amputated (n = 23) Nonamputated (n = 160) p value
Affected knee
Right 12 (52.17%) 84 (52.5%) 0.97
Left 11 (47.82%) 76 (47.5%)
Age (years)
Mean 68.7 (SD 9.7) 69.2 (SD 8.9) 0.7
Sex
Male 14 (60.8%) 67 (41.8%) 0.09
Female 9 (39.1%) 93 (58.1%)
Reason for joint replacement
OA 21 (91.30%) 139 (86.87%) 0.55
RA 2 (8.69%) 16 (10%) 0.84
Sequelae of hip development dysplasia 0 3 (1.87%) 0.97
Osteonecrosis 0 2 (1.25%) 0.84
Septic arthritis 0 1 (0.62%) 0.62
OA osteoarthritis, RA rheumatoid arthritis, SD standard deviation
984 Eur J Orthop Surg Traumatol (2017) 27:983–987
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5. The mean time between arthroplasty and the diagnosis
of prosthetic joint infection was 74 days (range
10–264 days). The pathogens involved in prosthetic joint
infections identified by deep intraoperative tissue samples
are shown in Table 2. Staphylococcus aureus was the most
frequently identified pathogen, of which 58% were resis-
tant to methicillin. Secondly, polymicrobial infections that
included mainly gram-negative bacilli, enterococci and
staphylococci were found. All bacteria identified in
polymicrobial infections were isolated from specimens
deposited on solid media.
Table 3 shows the risk factors for amputation in the
patients studied. It was found that patients with prolonged
surgical time greater than 120 min had a higher incidence
of amputation (p = 0.01), as well as those assigned a
surgical risk greater than 2 points on the American Society
of Anesthesiology scale (p = 0.00). Smokers with a
smoking rate greater than 21 had a higher risk of
amputation than nonsmokers (p = 0.04). Those with obe-
sity with a body mass index over 30 were also more likely
to suffer amputation (p = 0.00), and patients with diabetes
mellitus more than 5 years of age (p = 0.00) had an
increased risk of amputation compared to patients with
persistent periprosthetic knee infection who did not require
amputation as a definitive management.
Discussion
Different studies have addressed the major complications
that may occur after total knee arthroplasty [12–14].
However, there are few data on the incidence of amputa-
tions due to failure or complications of knee prostheses.
From the more than 9000 knee prostheses evaluated, Rand
et al. described two cases (0.02%) of infrapatellar ampu-
tation related to vascular insufficiency [15, 16].
Table 2 Agent causing
prosthetic infection
Organism Amputated (n = 23) Nonamputated (n = 160) Total (n = 183)
S. aureus 10 (43.47%) 83 (51.87%) 93 (50.81%)
Coagulase-negative
Staphylococcus
3 (6.97%) 27 (14.75%) 27 (14.75%)
Streptococcus sp. 1 (4.34%) 6 (3.75%) 7 (3.8%)
Enterococcus sp. 1 (4.34%) 0 1 (0.54%)
Corynebacterium sp. 1 (4.34%) 6 (3.75%) 7 (3.82%)
Propionibacterium sp. 1 (4.34%) 0 1 (0.54%)
Gram-negative bacilli 2 (8.69%) 0 2 (1.09%)
Polymicrobial 4 (17.39%) 31 (19.37%) 35 (19.12%)
No organism cultured 0 7 (4.37%) 7 (3.82%)
Table 3 Risk factors for amputation
Risk factors Amputated (n = 23) Nonamputated (n = 160) OR(95% CI) p value
ASA score ([II) 22 (95.7%) 107 (66.8%) 10.89 (4.1–236.9) 0.000
BMI ([30) 23 (100%) 82 (51.2%) 44.72 (2.67–748.9) 0.008
Skin–skin time ([120 min) 20 (86.9%) 95 (59.3%) 4.56 (1.3–15.9) 0.017
Blood transfusion 22 (95.7%) 120 (75%) 7.33 (0.95–56.1) 0.055
Drainage tube 21 (91.3%) 155 (96.8%) 0.33 (0.06–1.8) 0.212
Length of stay ([30 days) 23 (100%) 132 (82.5%) 10.10 (0.59–171.3) 0.109
SAH 17 (73.3%) 129 (80.6%) 0.45 (0.18–1.1) 0.084
DM 20 (86.9%) 87 (54.3%) 5.59 (1.59–19.5) 0.007
Dyslipidemia 8 (33.3%) 78 (51.6%) 0.86 (0.22–1.3) 0.213
Cardiac arrhythmia 2 (8.6%) 16 (10%) 0.21 (0.18–3.9) 0.844
RA 3 (13.0%) 25 (15.6%) 0.81 (0.22–2.9) 0.748
PVD 16 (69.5%) 116 (72.5%) 0.75 (0.30–1.8) 0.554
Renal failure 1 (4.3%) 12 (7.5%) 0.56 (0.06–4.5) 0.587
Smoking 14 (60.8%) 61 (38.1%) 2.52 (1.03–6.1) 0.042
ASA American Society of Anesthesiology, BMI body mass index, CI confidence interval, DM diabetes mellitus, SAH systemic arterial hyper-
tension, RA rheumatoid arthritis, PVD peripheral vascular disease
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6. After performing 12,118 total knee arthroplasties,
Bengston and Knutson studied 357 patients who evolved
with a deep infection of which 23 were treated with
transfemoral amputation; therefore, the incidence was
0.18% of all cases and 6% when only cases of infected
arthroplasty were considered [17]. Isiklar et al. Reported an
incidence of 0.18%, 9 amputees of the 5045 arthroplasty
procedures performed [18]. In the study of Sierra et al. in
25 patients, the cause of the amputation was related to the
knee replacement prosthesis, corresponding to a prevalence
of 0.14% [19].
The incidence of amputation as a treatment for a com-
plication of total knee arthroplasty ranges from 0.02 to
0.41% [20]. In our study, the incidence was higher
(12.52%), probably because the osteoarticular rescue ser-
vice concentrates the most complicated cases of skeletal
muscle disease in our country.
In a retrospective study evaluating 462 cases of
periprosthetic knee infection, the main risk factors for
complications were prolonged duration of surgery, high
body mass index (BMI), postoperative bleeding, hematoma
formation, advanced age, diabetes mellitus, Rheumatoid
arthritis or other immunocompromised conditions [21]
The presence of diabetes mellitus in our group of
amputees was 86.95% (20 patients) with an average evo-
lution time of 10.5 years, in agreement with the national
epidemiology report and with Word Health Organization
that said Mexico occupies the 10th world place in preva-
lence of diabetes mellitus [22]. As a risk factor, diabetes
showed an OR of 5.59 with a 95% CI (1.59–19.5).
Obesity has a negative effect on outcomes after total
knee replacement. In a meta-analysis of 2012, patients who
were obese (BMI C 30) showed an increase in infection
rates OR 1.90, 95% CI (1.47–2.47) [23]. The association
between amputation and obesity has previously been
associated with increased complications; in our study, all
patients had a BMI greater than 30 with an OR for
amputation of 44.72 with a 95% CI (2.6–748.9).
Surgery time greater than 120 min was presented as a
risk factor for amputation with an incidence of 22%, an OR
of 10.89 and 95% CI (4.1–236.9), which is similar to that
reported in the literature. Prolonged surgical time had been
associated with periprosthetic infection, although the rele-
vance of our study is association as a risk factor for
amputation [2, 7, 24].
The surgical risk assessment of ASA greater than II in
our study was observed as a risk factor associated with
amputation in 95.65% with an OR 10.89 and 95% CI
(4.1–236.9) which differs from the worldwide literature
[5, 8]. This finding may be due to our patients being treated
for a complication and not a primary surgical procedure.
Bongartz et al. [11] reported in their prospective study
44 patients with joint prosthesis and staphylococcal
bacteremia, periprosthetic infection occurred in 34% of
patients. In a study with 50 cases of periprosthetic infec-
tion, the majority of hematogenous infections were due to
Staphylococcus aureus, beta-hemolytic streptococci or
gram-negative bacilli [2, 25]. In our study, the main bac-
teria found associated with amputation were Staphylococ-
cus aureus (43.47%).
The presence of smoking in association with amputation
in patients with periprosthetic knee infection was present in
9 of the 23 cases (39.13%) with an OR of 1.04, with 95%
CI (0.42–2.55), being higher than reported by Pulido et al.
[5] and Mortazavi et al. [8].
Our study reflects the practice of multiple orthopedic
surgeons and specialists in orthopedic infectious diseases,
and despite the implementation of standardized protocols,
individualization of treatment was inevitable.
The strengths of our study are consistent follow-up of all
cases of periprosthetic knee infections, the systematic
recording of all medical, surgical and perioperative com-
plications that may be associated with the incidence of
supracondylar amputation.
In conclusion, our study found that the incidence of
amputation in periprosthetic knee infection is high. To
confirm the risk factors for the present analysis and to
investigate whether there are additional risk factors, further
studies with larger sample sizes are warranted. This
information could help us provide better advice to our
patients regarding prognosis, and eventually redefine our
treatment strategies for the management of total knee
arthroplasties. On the other hand, the value of methicillin-
resistant Staphylococcus aureus transmission should be
redefined for testing surveillance, patient screening and
decolonization using topical and/or systemic agents, as
well as emphasizing the importance of the prevention,
diagnosis and treatment of obesity as a predisposing factor
of complication in total primary knee arthroplasty through
timely detection, nutrition programs and individualized
physical conditioning and exercise routines for each
patient.
Compliance with ethical standards
Conflict of interest None.
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