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Insufficiency fractures of the distal tibia misdiagnosed as cellulitis in three patients with rheumatoid arthritis.

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BRIEF REPORT
INSUFFICIENCY FRACTURES OF THE DISTAL TIBIA MISDIAGNOSED
AS CELLULITIS IN THREE PATIENTS WITH
RHEUMATOID ARTHRITIS
KARIN V. STRAATON, ADA L6PEZ-MENDEZ, and GRACIELA S. ALARC6N
We describe 3 patients with rheumatoid arthritis
who presented with diffuse pain, swelling, and erythema
of the distal aspect of the lower extremity, suggestive of
either cellulitis or thrombophlebitis, but were found to
have insufficiency fractures of the distal tibia. The value
of technetium-99m diphosphonate bone scintigraphy in
the early recognition of these fractures and a possible
explanation for the associated inflammatory symptoms
are discussed.
Insufficiency (or nondisplaced) fractures, with
or without a history of trauma, are not uncommon in
elderly patients with osteoporosis. Such fractures
have been reported to occur in the ribs, sacrum,
pelvis, proximal femur, and proximal and distal tibia
and fibula (1-5). Insufficiency fractures occurring near
a joint in the proximal tibia have been reported in
patients with rheumatoid arthritis (RA). These are
generally mistaken as worsening knee synovitis or
infectious arthritis (5-10) and may go undiagnosed for
weeks or even months. We describe here 3 patients
with RA and nondisplaced fractures of the distal tibia,
who presented with swelling, tenderness, and pain of
the distal aspect of the lower extremity, mimicking
cellulitis.
From the Division of Clinical Immunology and Rheumatology, The University of Alabama at Birmingham.
Supported in part by NIH grant AR-20614.
Karin V. Straaton, MD: Assistant Professor; Ada LopezMkndez, MD: Instructor; Graciela S. Alarcon, MD, MPH: Profes-
sor.
Address reprint requests to Graciela S. Alarcbn, MD,
MPH, 615 MEB, The University of Alabama at Birmingham, UAB
Station, Birmingham, AL 35294.
Submitted for publication September 5, 1990; accepted in
revised form February 7, 1991.
Arthritis and Rheumatism, Vol. 34, No. 7 (July 1991)
Case reports. Patient 1 , a 47-year-old white
woman, had overlap RNsystemic lupus erythematosus (symmetric polyarthritis, leukopenia, pleural effusion, interstitial lung disease, positive antinuclear antibodies, and positive rheumatoid factor of 12 years
duration), requiring as much as 60 mg of prednisone
per day to control the disease manifestations. Most
recently, she had been taking 5 mg of prednisone per
day, parenteral chrysotherapy (50 mg every 2 weeks),
and analgesics. During recent months, her level of
ambulation had remained the same (mild to moderate),
and her white blood cell (WBC) count had fluctuated
between 3,2001mm3 and 4,500/mm3.
Two weeks before presenting to our outpatient
department, the patient noticed a gradual onset of
pain, swelling, warmth, and erythema of the distal
aspect of the left lower extremity. On examination, the
patient was afebrile and exhibited diffuse swelling of
the distal aspect of the left lower extremity from the
ankle to the knee. The ankle was aspirated and lavaged, and the lavaged fluid was sent for cultures, the
results of which were negative. A complete blood cell
(CBC) count demonstrated a WBC count of 3,8001
mm3, with a normal differential cell count. The differential diagnosis included cellulitis and thrombophlebitis. Results of Doppler studies of the distal aspect of
the patient’s left lower extremity were normal. Intravenous (IV) antibiotic therapy with nafcillin was
started.
A radiograph of the patient’s left leg demonstrated a nondisplaced fracture of the distal tibia. The
leg was immobilized in a short cast and IV nafcillin
therapy was discontinued on the second hospital day.
The cast was removed after 4 weeks, and the patient
BRIEF REPORTS
gradually resumed her previous level of ambulation
without further problems.
Patient 2, a 73-year-old white woman with
advanced, seropositive RA of 21 years duration, presented with a flare of her arthritis of approximately 4
weeks in duration. Her medications included 5 mg of
prednisone per day and analgesics. She was admitted
to the hospital and was given intraarticular corticosteroid injections in both knees. While in the hospital, she
experienced worsening of the left ankle pain. A radiograph was obtained and was interpreted as “changes
compatible with arthritis and a healing fracture of the
lateral malleolus. ” The left ankle was aspirated dry
and then injected with corticosteroids.
Three weeks later, the patient presented with
worsening pain in the ankle and the distal aspect of the
left lower extremity, with no apparent inciting event
and no increased physical activity. The patient was
afebrile, and the distal aspect of the left lower extremity was swollen, warm, erythematous, and diffusely
tender. The ankle was painful on motion. A CBC
count demonstrated a WBC count of 4,200/mm3, with
80% polymorphonuclear leukocytes. Diagnoses of cellulitis and infectious arthritis were considered. The left
ankle was again aspirated dry and lavaged, and IV
therapy with antibiotics (ciprofloxacin) was started.
Cultures of the lavage fluid gave negative results.
A radiograph demonstrated a nondisplaced
fracture of the distal tibia and a healed impacted
fracture of the lateral malleolus. The leg was immobilized in a short cast, and the 1V antibiotics were
discontinued. The cast was removed after approximately 4 weeks, and the patient gradually became
ambulatory.
Patient 3, a 46-year-old white woman, had
advanced, seropositive RA of 19 years duration. She
had undergone right total knee arthroplasty 4 years
before, but the prosthesis subsequently became infected, requiring its removal and an arthrodesis. The
patient had regained her relatively limited level of
ambulation when she noticed the onset of pain in the
distal aspect of the right lower extremity. Her medications at that time included methotrexate (12.5 mg/
week) and prednisone (7.5 mg/day).
The patient presented with pain and swelling of
the distal aspect of her right lower extremity of approximately 2 weeks duration, and a 2-day history of
chills and mild elevation of body temperature. On
examination, the patient was afebrile, but she had
swelling and redness of the lower two-thirds of the
distal aspect of her right lower extremity and tender-
913
ness over the distal aspect of the tibia. The differential
diagnosis included cellulitis and osteomyelitis. A CBC
count demonstrated a WBC count of 6,700/mm3, with
a normal differential cell count.
A radiograph of the patient’s right leg demonstrated a nondisplaced fracture of the distal tibia
(Figure 1A). A technetium-99m diphosphonate bone
scintigram demonstrated uptake of the radiotracer at
the fracture site (Figure 2). A short cast was applied to
her leg. The cast was removed after approximately 4
weeks, and the patient gradually regained her previous
level of ambulation. A radiograph taken 8 weeks after
the first demonstrated callus formation (Figure 18).
Discussion. We have described 3 patients with
RA who experienced the gradual onset of pain and
swelling in one lower extremity, suggestive of either
cellulitis, thrombophlebitis, or osteomyelitis. One patient was premenopausal and the others were perimenopausal; none of them had increased their physical
activity or participated in any unusual physical activity
preceding the onset of symptoms in the distal aspects
of the lower extremities. Likewise, there was no preceding trauma. Two patients had clinical evidence of osteoporosis. In patient 1, the fracture was clearly evident
in the first radiograph taken (not shown), whereas in
patient 3, the fracture was barely discernible (Figure
lA), but correlated very well with the bone scan findings
(Figure 2). In patient 2, the first radiograph was misread,
and a bone scan was not done.
A correct diagnosis could have been made
earlier in all patients, if a technetium-99m diphosphonate bone scintigram had been performed (11). The
scintigram will show increased uptake of the radiotracer at the fracture site as early as 48 hours after
its occurrence. Computed tomography scanning has
been reported to be very useful for the diagnosis of
pelvic insufficiency fractures in elderly women with
normal or inconclusive findings on radiographs (12),
but is of little or no value in the diagnosis of fractures
of the long bones.
Patients with RA, especially women in high-risk
groups (Caucasians, Asians, postmenopausal, or receiving corticosteroids), may experience accelerated
osteoporosis (13-15). The presence of knee deformity
has been reported to be an additional risk factor for the
occurrence of proximal, but not distal, tibia1 fractures
in patients with RA (10). In these RA patients, fracture
may present as the insidious, rather than abrupt, onset
of pain and may be misdiagnosed as worsening knee
synovitis, infectious arthritis, or osteonecrosis. The
BRIEF REPORTS
914
A
B
Figure 1. Radiographs of the distal aspect of the right lower extremity of patient 3. A, Two weeks after the onset of pain, there was a
nondisplaced transverse fracture of the distal tibia. B, Eight weeks later, callus formation is clearly evident.
diagnosis may thus evade clinicians for days or even
weeks and delay initiation of proper treatment.
Our 3 RA patients presented with rather similar
features of diffuse swelling and tenderness from the
ankle to the knee, which started insidiously. The
swelling and erythema resolved with immobilization,
rather than with the use of antibiotics, which suggests
that these manifestations were related to the fracture.
These features distinguish our patients from patients
with insufficiency fractures of the long bones of the
lower extremities which have been described in the
literature (5-10).
The precise mechanism of this noninfectious
reactive inflammatory process is unclear. The possibility that it is a neurovascular phenomenon, similar to
the reflex sympathetic dystrophy syndrome, must be
considered, although resolution of these manifestations after immobilization would be unusual if this
were the
(16)'
patients were taking a low
dose of prednisone each day in addition to nonsteroidal antiinflammatory drugs and analgesics, and 2 of
Figure 2. Technetium-99m diphosphonate bone scintigram of patient 3, taken at the same time as the radiograph shown in Figure IA,
demonstrating linear uptake of the radiotracer in the right distal tibia.
BRIEF REPORTS
them were taking a disease-modifying antirheumatic
drug. It is conceivable that these medications attenuated the patients’ symptoms and contributed to their
delay in seeking medical treatment. Patients 1 and 2
were clinically osteoporotic, were frail, and had dystrophic skin changes, whereas patient 3 had had 1
episode of mononeuritis multiplex, which was likely
related to vasculitis, with residual right foot drop, but
no evidence of current active vasculitis. The possible
contribution of both the dystrophic skin changes and
the previous vasculitis to the inflammatory response
observed can only be surmised.
Insufficiency fractures should be considered in
the differential diagnosis of persistent pain in the distal
aspect of the lower extremity in patients with RA. If
the radiographs appear normal, a bone scan may be
helpful in the diagnostic evaluation of such patients. A
later radiograph will demonstrate the fracture as it
heals and callus forms, but by that time, the patient
may have been subjected to unnecessary and costly
treatments and may have endured considerable pain.
Acknowledgments. We are grateful to Drs. William J.
Koopman, William W. Daniel, Stuart X. Stephenson, and
Eva Dubowski for their most helpful comments, and to Ella
Henderson for her most expert secretarial assistance.
915
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cellulite, patients, misdiagnosed, insufficiency, arthritis, tibial, three, fractured, distal, rheumatoid
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