DIFFERENTIATING
A SEPTIC ARTHRITIS SECONDARY TO SURGICAL INTERVENTION FROM AN ASEPTIC FLARE OF
JUVENILE
IDIOPATHIC ARTHRITIS
N.M. Wulffraat1, R.J.B. Sakkers2, M.T. van Reisen2
and W. Kuis1
Department
of Pediatric Rheumatology (1) and Pediatric Orthopedic Surgery (2),
Key words:
Baker’s
cyst, Juvenile idiopathic arthritis, Septic arthritis.
Correspondence
to: Dr. N.M. Wulffraat
Dept. Pediatric Rheumatology
Wilhelmina
Children’s Hospital
University
Medical Center
PO box 85090
3508 AB
Utrecht
The
Netherlands
Phone
0031-30-2505350, fax 0031-30-2505350
Email: n.wulffraat@wkz.azu.nl
Abstract
A 10 year old
girl with a 4 years history of oligoarticular Juvenile Idiopathic Arthritis is
described. She developed a swollen and
painful knee joint two weeks after extirpation of a Baker’s cyst. This case
illustrates that differentiation between JIA and septic arthritis can be
difficult. Diagnostic and therapeutic decisions must be guided by the initial
clinical presentation. In case of doubt between septic arthritis and JIA, the
first rather than the latter should be the focus of treatment to avoid the
severe joint damage that may occur after septic arthritis. This treatment
should include intravenous antibiotics and arthroscopic joint irrigation.
Meanwhile. synovial cultures and sensitivities as well as synovial biopsy are
important in adjusting antibiotic treatment.
In
conclusion, the differentiation between juvenile idiopathic arthritis and
septic arthritis following an invasive procedure may be difficult due to
similarities in symptoms and signs of the initial clinical presentation. If the
diagnosis is in doubt, antibiotics should be started and arthroscopy should be
performed.
Introduction
Juvenile Idiopathic Arthritis (JIA) is characterised by idiopathic
synovitis that results in swelling and diminishing of joint function. Based on
the classification developed by the International League Against Rheumatism
(ILAR-1997), several types of JIA can be distinguished (1-3). JIA (previously
called juvenile chronic arthritis or juvenile rheumatoid arthritis) is an
important cause of chronic disability in children. The aim of early and
adequate treatment is to prevent future functional damage. At times, diagnostic
and therapeutic decisions may be complicated by a difficult differentiation
between septic arthritis and the reactivation
of JIA. Patients with JIA have a higher risk of developing septic arthritis
(2). In these cases, a general pediatrician should use strict guidelines for
therapeutic decision making, assisted by the expertise of a pediatric
rheumatologist and a pediatric orthopedic surgeon. In this paper, we present a
case report that illustrates these difficulties within a patient recently
operated on for Baker’s cyst. A Baker’s cyst, also known as popliteal
cyst, is a synovial pouch filled with fluid, located posteromedial from the
knee cavity. More specifically, it is a distension of the communicating bursa
gastrocnemius and bursa semimembranosus caused by excessive fluid production by
the synovia in reaction to damage in the joint capsules (4,5).
Case report
A 10 year old girl, with a 4 years history of JIA involving the left
knee and right wrist, was followed at our outpatient clinic on a regular basis.
She never had symptoms of systemic disease and tested negative for rheumatoid
factor and antinuclear antibodies.
The arthritis was well controlled by a non-steroidal anti-inflammatory drug
(NSAID). During the preceding 2 years she gradually developed a painless
swelling localised posteromedial of her left knee cavity. Based on this
clinical picture, the 10 year old was diagnosed with a Bakers’ cyst. The patient
did not report any complaints at the first presentation. At follow up, however,
the cyst had increased in size, and was accompanied by more complaints of pain
and functional impairment of the left knee (she was a regular soccer player).
The pain and impairment of function led the parents repeatedly to ask for
surgical removal of the cyst. The clinical diagnosis was confirmed by MRI (Figures
1a and 1b).
Two weeks after surgical excision, the patient complained of a slightly
painful swelling of her left knee joint and a temperature of 38 degrees
Celsius. General physical examination revealed an obvious hydrops of the left
knee, without a decreased range of motion. The knee was only slightly painful
in passive movement. Laboratory results showed leucocytes of 10.1·109
/L (reference 4-10 x 109 /L), a differential count of 74 % segmented
neutrophils, 16% lymphocytes, 1% eosinophils and 9 % monocytes, hemoglobin of
7.4 mmol/L, thrombocytes of 235·109 /L (normal values 150 – 400 x 109/L),
C- reactive protein of 104 mg/L (normal values less than 10 mg/L) and an
erythrocyte sedimentation rate (ESR) of 40 mm/hour.
This presentation prompted us to perform a diagnostic synovial fluid
aspiration. The gram stain of the synovial fluid was negative. We decided to
wait 2 days for the results of the synovial fluid culture. A negative gram
stain and presence of only minimal pain on joint movement made a reactivation
of JIA the most obvious diagnosis at that time.
Over the course of the next two days, the clinical presentation
worsened. The patient reported a more painful left knee joint and her
temperature had increased to 39°C. Physical examination then showed a fixed
flexion of the left knee that was very painful on passive motion. Her
laboratory tests revealed a peripheral leucocyte count of 6.1 x 109/L,
with a differential count of 66% neutrophils, 25% lymphocytes, 1% eosinophils,
9% monocytes. Her C-reactive protein had further increased to 148 mg/L. The
synovial fluid culture was still negative. Given this evolution of clinical
symptoms of increased temperature and pain, a septic arthritis now was suspected, even in the absence of positive
synovial fluid cultures. An arthroscopy was performed that same day. At
arthroscopy, hyperaemic synovia without pus were seen. The bursa
suprapatellaris and the cartilago seemed to be unaffected. Before joint irrigation, cultures and biopsies were
taken for culture and pathology. The gram stain of the joint fluid was again
negative.
Because of
the obvious clinical symptoms of septic arthritis, intravenous antibiotic
therapy with amoxicillin/clavullic acid (®Augmentin) and gentamycin
(®Garamycin) was started. After two days, a group B hemolytic streptococcus was
cultured from the wound (from the previous arthroscopy), the synovia, and the
synovial fluid that was sensitive to amoxicillin. After one week the clinical
picture improved to such an extent that parenteral antibiotic therapy could be
changed to oral antibiotics for an additional 2 weeks. The patient soon started with passive motion therapy to prevent
contractures. Intensive physiotherapy during two months resulted in complete
recovery of her knee function.
This case report describes a patient with a history of juvenile
idiopathic arthritis and a Baker’s cyst at her left knee. Medical decisions had
to be made in three different phases of the disease on the basis of three
different diagnoses. The first was the decision whether or not to remove the
Baker’s cyst. Because most cysts in children disappear or decrease in size in
five or ten years time, our general policy is not to remove such a cyst but to
wait and check the knee on a regular base (4,5). At follow up however,
progressive impairment of knee function caused us to reconsider a possible
surgical removal. Impairment of movement and progressive increase in size, are
accepted indications for surgical intervention. The parents and the patient
herself repeatedly asked for surgical removal. Usually, MRI is not needed for
the diagnosis. In this case it was performed as a preoperative screening to
confirm beyond any doubt the presence of the cyst.
The second phase was characterised by a mildly painful and swollen knee
with the absence of a definite diagnosis. Reactivation of JIA was initially
suspected because of remitting minimal complaints of pain without much
functional impairment and a negative synovial fluid gram stain. However, this
diagnosis had to be changed to septic arthritis due to further impairment of
the knee function, as well as more pain and fever and an increase of C-reactive
protein after two days.
The differential diagnosis of monoarthritis with a low grade fever is
extensive (see Table 1). Given the history of JIA and the recent surgery, we
assumed either reactivation of JIA or a wound infection. This diagnosis
was confirmed at that time by positive cultures of a haemolytic
streptococcus group B from the synovial biopsy, synovial fluid culture and
subcutaneous tissue. Interestingly, the macroscopic impression was compatible
with relapsing JIA. However, given the
increase in pain and fever she was treated as a having septic arthritis. Thus
there had been a doctor’s delay of 2 days. This was justified by the absence of
definite criteria at that time. It is important to emphasize that a negative
gram stain of the synovial fluid does not exclude the diagnosis of septic
arthritis. Studies have shown that only 65% of synovial fluid gram stains of septic
arthritis are positive (6).
This clinical presentation of low grade fever, swelling and pain of the
joint is clearly indicative of a possible septic arthritis and should be
treated as such without delay. Furthermore, opaque synovial fluid obtained by
arthroscopy, with no pus and an unaffected bursa and cartilage, can be
misleading because it may contain many bacteria. In addition, cloudy synovial
fluid does not always indicate bacterial infection since it can also be caused
non-infectious inflammation (7).
Thus, in case of fever and increased joint complaints within one month
after an orthopaedic procedure, it is crucial to consider a septic arthritis.
Occasionally, the interval between such a procedure and the onset of symptoms
may be as long as 3 months (8). A bacterial joint infection can develop by
direct inoculation from a wound, after joint aspiration, arthroscopy or
surgery, local spread from an adjacent site, or by hematogeneous spread from a
distant infection such as a furuncle or upper airway infection (8). As a joint
infection may not be detected even as late as four weeks or more following an
invasive procedure (9), we recommend aggressive evaluation and treatment for
septic arthritis in case of symptoms within four weeks of the procedure. Early
arthroscopy may be prudent. Moreover, obtaining cultures and biopsies and
performing joint irrigation to decrease the risk of joint damage is also
important (10).
For fully vaccinated children, the main causative microorganisms of
septic arthritis are Staphylococcus aureus, haemolytic Streptococcus group B,
Streptococcus pneumonia and Neisseria gonorrhoeae (7,11). In one third of
patients with septic arthritis no causative micro-organism will be cultured
(7,12). The initial antibiotic treatment has to be directed against the most
likely pathogen and should be changed based on the culture results and
sensitivities of cultures. There is little consensus in the literature about
the duration of the intravenous antibiotic treatment. Over the past years, courses
of intravenous therapy tend to become shorter. Some studies report intravenous
treatment for a week, followed by oral antibiotic therapy for two additional
weeks in case of a good initial clinical response (9,13,14).
In conclusion, the case presented here
is an example of the difficult differentiation between reactivated JIA and
septic arthritis in a ten-year-old girl. The diagnosis should be primarily based on the clinical presentation
with repeated physical examinations as well as the synovial fluid culture. If
there is any doubt, it is better to treat for septic arthritis since septic
arthritis can cause destruction of cartilage in a short time. The synovial
fluid gram stain and culture as well as the synovial tissue culture are
important in decision-making concerning antibiotic treatment but should not be
used as primary diagnostic indicators.
Acknowledgements:
We thank Dr.
R.A.J. Nievelstein, paediatric radiologist, Wilhelmina Children’s Hospital, for
evaluation of figure 1.
References
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et al. A Shortened Course of
Parenteral Antibiotic Therapy in the Management of Acute Septic Arthritis of
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Figure
1. T2- weighted magnetic resonance image of the left knee. The
circumscribed mass with increased signal intensity posterior in the left knee
represents a Baker’s cyst. Figure 1a: Sagittal section; Figure 1b: Transversal
section.
Table: Differential diagnosis of mono-arthritis with and without fever
Mono-arthritis
with fever
|
|
Septic arthritis (local surgery, hematogeneous) |
|
Reactive Arthritis |
|
Arthritis causes by viruses, borrelia, mycobacteria |
|
Osteomyelitis |
|
Malignancy |
|
Oligoarticular JIA (occasionally) |
|
Familial Mediterranean fever |
|
Systemic connective tissue diseases |
|
Mono-arthritis without fever |
|
Oligoarticular JIA |
|
Trauma, Lesions of the meniscus |
|
Hemophilia |
|
Sickle cell disease |
|
Gout |
|
Malignancy |