Download Piriformis pyomyositis: a report of three cases

Journal of Orthopaedic Surgery 2008;16(3):389-91
Piriformis pyomyositis: a report of three cases
CH Wong, SH Choi, KY Wong
Department of Orthopaedics and Traumatology, Princess Margaret Hospital, Hong Kong
ABSTRACT
Pyomyositis is a subacute infection of skeletal muscles.
It can be life-threatening if diagnosis and treatment
are delayed. Only 5 cases of isolated piriformis
pyomyositis have been reported. We report signs
and symptoms of piriformis pyomyositis in 3 women
who were treated mainly with antibiotics. Computed
tomography is useful in making the diagnosis. Early
diagnosis and treatment may avoid surgical treatment
and reduce mortality.
Key words: infection; pyomyositis; sciatica
INTRODUCTION
Pyomyositis is a subacute infection of skeletal
muscles, most commonly involving the quadriceps,
followed by the gluteal muscles and iliopsoas,1,2
with a mortality rate of up to 3.6% of cases.3 It can
be primary or secondary and more commonly occurs
in patients in tropical and subtropical areas aged 2
to 5 years and 35 to 40 years because of kwashiorkor
and marasmus.4,5 It is also known as tropical myositis,
myositis tropicans, purulenta tropica, and tropical
pyomyositis.
The incidence of pyomyositis has been rising in
temperate areas, predominantly in men; half of the
cases in North America have been in intravenous
drug abusers or immunosuppressed patients with
rheumatoid diseases, malignancies, diabetes mellitus,
chronic liver diseases, or acquired immune deficiency
syndrome.3,6–11 Only 5 cases of isolated piriformis
pyomyositis have been reported.6,12–15 We report signs
and symptoms of piriformis pyomyositis in 3 women
who were treated mainly with antibiotics. One of
whom had drainage.
CASE REPORTS
Case 1
In July 2006, a 45-year old woman presented with
lower back pain radiating to the left leg. She was
afebrile and initially diagnosed with sciatica and
observed for 3 days. The pain progressively increased
and she developed a high fever (39ºC) and could not
walk or sleep. Her left buttock was tender and the
pain was increased by internal rotation of the left
hip, limiting the straight leg raise. There was no
neurological deficit of the leg. Inflammatory markers
were elevated (white cell count [WCC], 14.5 x109/l;
erythrocyte sedimentation rate [ESR], 49 mm/h; Creactive protein [CRP], 241 mg/l). Radiographs of
the lumbrosacral spine were normal. Computed
tomography (CT) showed abscess formation in the left
pelvis, with extension to the iliacus and piriformis. She
was empirically treated with intravenous cefazolin
1 g every 8 hours for one week. Blood culture grew
Address correspondence and reprint requests to: Dr Chong-hing Wong, Resident Medical Officer, Department of Orthopaedics
and Traumatology, Princess Margaret Hospital, Lai Chi Kok, Hong Kong. E-mail: nelsonwchi@yahoo.com.hk
Journal of Orthopaedic Surgery
390 CH Wong et al.
Staphylococcus aureus and antibiotics were changed to
intravenous cloxacillin 1 g every 8 hours for 5 days
and oral cloxacillin 1 g 4 times daily for 6 weeks. The
pain gradually subsided and inflammatory markers
returned to normal as the abscess resolved.
(a)
Case 2
In January 2007, a 58-year-old woman presented with
tachycardia and high fever after a 2-week history of
progressive lower back and buttock pain and a oneweek history of fever, chills, and rigours. Inflammatory
markers were elevated (WCC, 22 x109/l; ESR, 71 mm/h;
CRP, 302 mg/l). Radiographs of the lumbrosacral
spine were unremarkable. She was empirically treated
with intravenous augmentin 1.2 g every 8 hours, but
remained febrile and hypotensive, requiring inotrope
support. Blood culture was negative. Antibiotics were
changed to intravenous meropenem 500 mg every 8
hours and flagyl 500 mg every 8 hours because of the
persistent fever. A CT scan showed an abscess in the
right piriformis and a small pre-forming abscess in the
left piriformis. Following CT-guided drainage of the
right piriformis abscess, the fever and pain subsided.
The aspirate yielded negative culture but showed
numerous neutrophils, compatible with an acute
inflammatory exudate. The abscesses resolved after 2
weeks of intravenous augmentin 1.2 g every 8 hours
and 3 weeks of oral augmentin 375 mg 3 times daily.
(b)
Figure
Transverse and coronal computed tomographic
images showing the piriformis abscess (arrows).
Case 3
In May 2007, a 71-year-old woman presented with a
one-day history of fever and pain in the left buttock
and lower abdomen. Inflammatory markers were
elevated (WCC, 15.1 x109/l; ESR, 96 mm/h; CRP, 186
mg/l). Radiographs of the lumbrosacral spine showed
degenerative changes only. Ultrasonography of the
abdomen showed bilateral hydronephrosis. A Foley
catheter was inserted but the right hydronephrosis
persisted. Cystoscopy was performed and bilateral
ureteric catheters were inserted. She was empirically
treated with intravenous cefuroxime 750 mg every 8
hours. Urine and blood culture grew S aureus and the
antibiotics were changed to intravenous cloxacillin 1
g every 8 hours. A CT scan showed myositis along the
left piriformis (Fig.). The pain and fever subsided and
the myositis resolved after 2 weeks of intravenous
cloxacillin 1 g every 8 hours and 4 weeks of oral
cloxacillin 1 g 4 times daily. A retrograde pyelogram
showed that the right hydronephrosis was likely
due to right pelviureteric junction obstruction and
left duplex kidney—the predisposing factor for the
urinary tract infection.
DISCUSSION
Muscle is intrinsically resistant to infection unless
traumatised. Animal studies have shown that
intravenous injection of sublethal doses of S aureus
failed to initiate infection unless muscles were
traumatised by electric shock, pincing, or ischaemia.16
In a case of piriformis pyomyositis involving a
swimmer, repeated backstrokes were considered
the cause of the damage and subsequent infection of
the piriformis.15 Other predisposing factors include
vitamin C deficiency, beriberi, and parasite, virus
or spirochaete infection. Human immunodeficiency
virus (HIV) myositis and the mitochondrial toxicity
of antiretroviral medications also increase the risk of
infection.3,17
The most common causative organism is S aureus,
accounting for 95% and 70% of the cases in tropical
and temperate areas, respectively. Other organisms
include streptococcal species, Gram-negative bacilli,
and anaerobes. Gram-negative organisms are more
common among immunosuppressed patients, who
Vol. 16 No. 3, December 2008
usually present with a normal WCC and are more
susceptible to multifocal involvement, with a higher
mortality rate.3
The progress of infection and presentation can be
divided into 3 stages.5 Stage 1 is the invasive stage,
with minimal inflammation and no pus collection. The
muscle is wooden or ‘hard-rubber’ stiff on palpation.
Stage 2 is the suppurative stage, occurring 10 to 21 days
after symptom onset, with most patients presenting
at this stage. In stage 3, patients present with systemic
upset, with high fever and septicaemia.
A diagnosis of pyomyositis is made when the
patient has any 3 of the following: (1) a recent visit
to the tropics or subtropics, (2) eosinophilia of >10%
with muscle tenderness, (3) tenderness and oedema
in the susceptible skeletal muscle, and (4) needle
aspiration of muscle yielding pus and exclusion of
parasite infection.5 These criteria are less valid in
developed countries because of acquired immune
deficiency syndrome and other immunosuppressive
diseases. Besides, 80% of cases in tropical areas have
eosinophilia, probably secondary to parasite infection,
but this is not the situation in temperate areas.5
Swelling of the piriformis secondary to injury
or inflammation may compress the nerve and
cause sciatica. The endopelvis fascia overlies the
psoas, iliacus, piriformis, and obturator muscles
and provides a route for infection from the spine
or pelvis to the piriformis.12 Two cases of piriformis
Piriformis pyomyositis 391
pyomyositis were reported in patients who had had
obstetrical intervention.
Only 5 cases of isolated piriformis pyomyositis
have been reported6,12–15; all presented with sciatica
and were likely to be positive to Pace’s test (pain and
lower weakness with resisted hip external rotation
and abduction) and Freiberg’s sign (pain with passive
internal rotation of the hip). A tender, sausageshaped swelling, palpable on pre-rectal examination
was reported in a case of piriformis syndrome.16
Inflammatory markers are usually elevated but
muscle enzyme levels are generally normal. Only
13% and 19% of HIV-infected and HIV-negative
patients, respectively, had elevated muscle enzyme
levels.3 Contrast CT and magnetic resonance imaging
are useful for diagnosis.9
Antibiotics and drainage are the mainstay
of treatment, which may be combined with
decompression of the sciatic nerve by tenotomy of the
piriformis tendon at its musculo-tendinous junction
near the greater trochanter.14 Three to 4 weeks of
antibiotic use (with initial intravenous treatment) has
been suggested,3 with immune status and the number
of abscesses taken into account.3,18
In our series, the mean time to diagnosis was 5
days. A high index of suspicion is the key to making
the diagnosis. The disease can be life-threatening if
treatment is delayed. Early diagnosis and treatment
may avoid surgical treatment and reduce mortality.
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