RHEUMATOLOGY
Diagnosis and management
of prosthetic joint infections
in rheumatoid arthritis
This article reviews the epidemiology, pathogenesis, investigation and management
of prosthetic joint infections in patients with rheumatoid arthritis
Georgina Beckley
MBBS MRCP FRCPath
Elizabeth Darley
MBChB MRCP
FRCPath MD
North Bristol NHS Trust,
Bristol, UK
Infection following prosthetic joint infection (PJI)
is a recognised surgical complication. However, it
has serious consequences requiring both surgical
and antimicrobial management. Patients with
rheumatoid arthritis (RA) are both more likely to
have joint replacement due to abnormal anatomy
and be immunosuppressed due to the underlying
disease and immunomodulatory therapies. These
factors make them more at risk as a population
for post- operative infection.
Epidemiology
Due to progressive joint destruction, patients
with RA commonly have to undergo joint
replacement. It is estimated that 24% of patients
with RA will eventually require their first major
joint replacement at 16–20 years after diagnosis. 1
Of those who have a total hip or knee
replacement 5–7% have RA compared to 1% in the
general population. 2 There is an increased risk of
PJI due to the underlying RA which can be
2.5-times that of a person with osteoarthritis. 2
Pathogenesis
In the general population, infection in PJI can
occur from direct seeding peri- or post-operatively
or haematogenous spread or recurrence of
existing infection from previous prosthesis. The
prosthetic material allows the bacteria to form a
protective glycocalyx layer or biofilm. This means
the bacterial colonies deep within this are
protected from host defences and antimicrobials.
There may also be poor wound healing and poor
host defences due to the underlying inflammatory
arthritis in patients with RA. This, coupled with
immunomodulatory therapy, makes a favourable
environment for infection.
Investigation
According to the International consensus meeting
in 2013 on peri-prosthetic joint infections, the
diagnostic criteria for PJI is as follows. 3
Major
• Two positive peri-prosthetic cultures with
phenotypically identical organisms
• Sinus tract communicating with the joint.
Minor
• Raised C-reactive protein (CRP) and erythrocyte
sedimentation rate (ESR)
• Raised synovial fluid white blood count on
leucocyte esterase test strip
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HHE 2019 | hospitalhealthcare.com
• Raised synovial fluid polymorphonuclear
neutrophil percentage
• Positive histological analysis of peri-prosthetic
tissue
• A single positive culture.
A patient is required to have one major or
three minors to be diagnosed. However, in a
patient with RA, there are limitations to these
criteria.
Initial investigation of prosthetic joint
infection in patients with RA is similar to other
patients. A careful history and examination
should be taken to ellicit:
A) Local features of infection joint swelling, pain,
wound breakdown and sinus tract
B) Past medical and surgical history, including
previous revisions, microbiology and previous
antimicrobial treatment, previous limb cellulitis
and other prosthetic material
C) Medication and drug allergy.
There should also be clear documentation on
the use of immunosuppressants, acute
prescriptions of corticosteroids and infusion
therapy that may not be listed on patients’
regular medications as this can affect the immune
system up to 12 months after administration.
Full blood count, urea and electrolytes, CRP,
ESR and liver function tests should also be part of
the standard work up. However, in patients who
have RA it might be difficult to differentiate
between raised inflammatory markers due to
infection or underlying inflammatory arthritis
flare. CRP may also be falsely low due to use of
immunomodulatory therapies. White blood cells
can be elevated due to corticosteroid use.
Other biomarkers specific for bacterial
infection, for example, procalcitonin,
interleukin-6 (IL-6) and tumour necrosis factor,
are in development. A prospective study looking
at the sensitivity and specificity of these in
prosthetic joint infection identified a combination
of IL-6 and CRP as the most useful and that
procalcitonin was the most specific. 4
There has also been increasing interest in
using joint fluid biomarkers to aid in the
diagnosis of PJI (for example, CRP, adenosine
deaminase (ADA), alpha-2-macroglobulin) which
show some promise increasing the positive
predictive value in diagnosing PJI vs aseptic
loosening. 5 Leucoesterase dip stix are easy to use
and commercially available but again could also
be positive due to underlying RA rather than
infection. However none of these biomarkers