AJR 2001; 176:1227-1231
© American Roentgen Ray Society
MR Imaging of Sports-Related Pseudotumor in Children
Mid Femoral Diaphyseal Periostitis at Insertion Site of Adductor Musculature
S. E. Anderson1,
J. O. Johnston2,
R. O'Donnell2 and
L. S. Steinbach3
1
Department of Diagnostic Radiology, University Hospital of Bern, Inselspital,
3010 Bern, Switzerland.
2
Department of Orthopedic Surgery, University of California, San Francisco, CA
94143.
3
Department of Radiology, University of California, San Francisco, CA
94143.
Received August 7, 2000;
accepted after revision October 9, 2000.
Address correspondence to S. E. Anderson.
Abstract
OBJECTIVE. The objective of this study was to review the imaging
appearance of the femurs of five patients who had been referred from outside
institutions after presenting with thigh pain and being given a preliminary
diagnosis of primary malignant bone tumor. Typically, when making a diagnosis,
physicians place emphasis on the characteristic appearances of diseases on MR
imaging, but such appearances may be misleading. An awareness of the specific
MR imaging pattern of stress-related partial muscle avulsion can lead to the
correct diagnosis.
CONCLUSION. Femoral diaphyseal periostitis after a sports injury to
the adductor musculature in children has a characteristic imaging appearance.
This condition can initially appear to be misleadingly aggressive. Knowledge
of the findings—particularly of the findings on MR imaging—in the
proper clinical setting can help physicians make the correct diagnosis and
eliminate unnecessary biopsy or inappropriate treatment.
Introduction
With the increasing participation of children and adolescents in sports
[1] and the increased
availability and use of MR imaging, chronic and acute sports-related injuries
in children are more often imaged. The appearance of these images can be
misleading, prompting a more sinister diagnosis. By reviewing the imaging
studies of five patients with stress-related partial adductor strain-avulsion,
we have defined a characteristic set of findings that could help physicians to
make the correct diagnosis of partial avulsion of adductor muscles from
femoral diaphysis and exclude a diagnosis of tumor. Awareness of this imaging
pattern is helpful in diagnosing a young child when clinical findings may be
nonspecific or a history is not attainable.
Materials and Methods
The images and clinical notes for five patients were retrospectively
reviewed. The ages of the five patients (four boys and one girl) ranged from 3
to 15 years. They had been referred from outside institutions for tumor
staging after being given a preliminary diagnosis of sarcoma of bone. Imaging
studies were reviewed by two subspecialized musculoskeletal radiologists:
conventional radiography (n = 4 patients), CT (n = 1),
conventional tomography (n = 1), bone scanning (n = 3), and
MR imaging (n = 3, no contrast agent administered). The MR images
were obtained with a 1.5-T unit (Signa; General Electric Medical Systems,
Milwaukee, WI). T1-weighted (TR range/TE range, 502-550/10-18) and T2-weighted
(2000-4000/102-120), spin-echo, and fat-suppressed T2-weighted fast-spin echo
images were obtained in the axial and coronal or sagittal planes.
We describe three representative patients.
Patient 1
A 15-year-old male marathon runner who was training for wrestling increased
his daily run from 3 to 5 miles (4.8-9.6 km). Over a period of 1 month, he
experienced pain in his right femur that became localized and intermittent
with some stabbing exacerbations in intensity. The pain was not responsive to
antiinflammatories. Imaging was performed to exclude the presence of a tumor.
Conventional radiography (Fig.
1A) showed a posteromedial periosteal reaction at the junction of
the mid and distal thirds of the femur, and bone scintigraphy
(Fig. 1B) showed early focal
uptake at the same location. MR imaging revealed extensive mid to distal
diaphyseal intramedullary edema (Figs.
1C and
1D) on coronal images and a
specific posteromedial periosteal reaction with muscle—bone interface
soft-tissue edema at the junction of the insertion of the vastus intermedius
and the vastus medialis muscles on the femoral cortex
(Fig. 1E). The patient was
advised to put no weight on the femur for 1 week; after this rest period, the
patient's pain was greatly decreased. Evidence of mature periosteal reaction
was seen 2 months later on conventional radiographs.
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Fig. 1C. —Patient 1: 15-year-old male marathon runner and wrestler.
Coronal T1-weighted MR image (C) (TR/TE, 533/18) and coronal
T2-weighted fat-saturated MR image (D) (4000/120) reveal marked diffuse
bone marrow edema (arrows, D) and absence of bone or
soft-tissue mass.
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Fig. 1D. —Patient 1: 15-year-old male marathon runner and wrestler.
Coronal T1-weighted MR image (C) (TR/TE, 533/18) and coronal
T2-weighted fat-saturated MR image (D) (4000/120) reveal marked diffuse
bone marrow edema (arrows, D) and absence of bone or
soft-tissue mass.
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Fig. 1E. —Patient 1: 15-year-old male marathon runner and wrestler.
Axial T2-weighted fat-saturated MR image (fast spin-echo; 2000/120) shows
posteromedial periosteal reaction and muscle—bone interface edema at
junction of vastus intermedius and vastus medialis insertion
(asterisk).
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Patient 2
A 3-year-old girl who had been doing monkey-bar splits developed sudden
pain and a limp. She underwent MR imaging and was diagnosed at an outside
institution as having a sarcoma because of the appearance of the injured area
on MR images. Parasagittal MR images (Figs.
2A and
2B) revealed focal fluid at the
muscle—bone interface of the vastus medialis and adductor musculature
with the medial femur and extensive bone marrow edema. An axial MR image
(Fig. 2C) showed
muscle—bone interface edema and periosteal reaction at the site of
partial avulsion of the vastus medialis, the vastus intermedius, and the
adductor muscles. After 1 week of non—weight-bearing rest of the
affected femur, the patient was free of pain.
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Fig. 2B. —Patient 2: 3-year-old girl injured doing monkey-bar splits.
More anteriorly located oblique sagittal T2-weighted fat-saturated MR image
reveals focal fluid (arrows) at anteromedial aspect of proximal femur
at site of partial avulsion of adductor muscle group.
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Fig. 2C. —Patient 2: 3-year-old girl injured doing monkey-bar splits.
Axial T2-weighted fat-saturated MR image (fast spin-echo; TR/TE, 4000/102)
reveals edema at muscle—bone interface (arrows).
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Patient 3
A 15-year-old male gymnast who had been doing splits (abruptly exercising
the adductor muscles) developed ill-defined thigh pain. Conventional
radiography revealed a mid femoral medial periosteal reaction
(Fig. 3A), and a delayed bone
scan (Fig. 3B) showed focal
medial cortical uptake at the site of the periosteal reaction. After
non—weight-bearing rest and no training for 2 months, the patient was
free of pain.
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Fig. 3A. —Patient 3: 15-year-old male gymnast who had been exercising
adductor muscles several weeks before images were obtained. Conventional
radiograph shows subtle periosteal new bone formation (arrow).
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Fig. 3B. —Patient 3: 15-year-old male gymnast who had been exercising
adductor muscles several weeks before images were obtained. Corresponding
delayed phase of bone scan reveals focal uptake at site of periosteal
reaction.
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Results
Conventional radiographs of the patients revealed smooth posteromedial
periosteal reaction along the femoral cortex at the junction of the proximal
and mid thirds (n = 2) and mid and distal thirds of the femur
(n = 2). Bone scans showed focal femoral cortically based uptake in
three patients, and CT showed medial cortical periosteal new bone in one
patient.
MR images revealed periosteal reaction on the posteromedial aspect of the
femur centered at the muscle—bone interface of the vastus medialis and
intermedius, adductor longus, adductor brevis, and adductor magnus insertions
on the femoral shaft (n = 3) with diffuse widespread intramedullary
edema (n = 3) and absence of a bone or a soft-tissue mass (n
= 3). No stress fracture lines were identified. Results for all patients are
summarized in Table 1.
A history of sports-related injuries was elicited from all patients after
clinical review. Sporting activities included marathon running and wrestling
(n = 1), basketball (n = 1), and gymnastics (n =
3). Two gymnasts and the basketball player had an acute single event,
including one acute event experienced by a patient that was exacerbated by his
continuing regular athletic training. Two patients had lowgrade pain for 2
weeks to 1 month that increased when training continued or increased. All
patients denied any history of direct trauma to the thigh region. The average
clinical follow-up period for the patients was 2 years.
The patients' focal thigh pain resolved after 1 week to 2 months of
non—weight-bearing rest, and laboratory results, such as erythrocyte
sedimentation rate, remained normal.
Discussion
We believe that our report is the first in which MR imaging of children is
used to reveal partial adductor muscle avulsion from the femoral diaphysis
with new periosteal bone formation. Such appearances can mimic primary bone
tumors in children. However, femoral diaphyseal periostitis after a sports
injury to the adductor musculature in children has a characteristic imaging
appearance. Knowledge of these imaging findings—particularly those seen
on MR images—may lead to the correct diagnosis and eliminate unnecessary
biopsy or inappropriate treatment. This condition has been studied using bone
scans in adults in army training and termed "adductor insertion avulsion
syndrome" or "thigh splits"
[2]. The cause is thought to be
related to excessive adductor contraction with stripping of the femoral
periosteum anteromedially [2].
A chronic avulsion injury of the deltoid insertion of the upper limb in
adolescents has been described
[3].
Proximal adductor avulsion injuries near the symphysis pubis
[4] and intramuscular strains
[5] have been described in
adults. Bone reactions to stress vary depending on the severity of overload.
Bone reactions may include stress periosteal reaction, and if the overload
continues, a stress fracture may develop
[6,7,8,9].
Stress fractures of the femoral diaphysis are rare. They are usually seen in
athletes and military personnel
[6,
9]. Stress reactions of the
femur may mimic a tumor [10,
11] or progress to become an
overt fracture. Stress reactions and stress fractures of the femoral diaphysis
in adults revealed on MR imaging, CT, and conventional radiography are well
documented, with a fracture line being evident on MR images to fulfill the
diagnostic criterion of stress fracture
[6,7,8,9].
Chronic muscle avulsive injuries in a variety of lower limb sites in children
are described in the literature
[12]; however, partial muscle
avulsion from the medial femoral diaphysis in children after a sports injury
has not, to our knowledge, been described.
The MR imaging appearances represent an early periostitis after the partial
muscle avulsion. Often after the physician conducts a close clinical review,
the patient may recall a specific movement or single acute event. The patient
often has focal muscle tenderness during palpation and finds that using the
adductor muscles precipitates pain. Such an injury differs from a more chronic
repetitive injury—overuse syndrome associated with stress fracture in a
patient with a history that usually involves weeks to months of increasing
pain. Specific MR imaging features in the proper clinical setting can allow
the physician to make an adductor-strain diagnosis with anteromedial or
posteromedial femoral cortical diaphyseal periosteal reaction,
muscle—bone interface edema centered on the junction of the vastus
medialis and the vastus intermedius, and presence of diffuse marrow edema and
absence of soft-tissue mass or bone destruction. If findings are more within
the proximal third of the femur, the adductor brevis is more involved. If
these changes are seen in the mid third of the femur, the adductor longus is
more involved. If there is extensive involvement in the region of the
posterior femur, then the adductor magnus is implicated. In all five patients,
clinical review elicited a history of a sports injury that could appropriately
be associated with adductor muscle strain.
Differential diagnosis for the imaging appearances includes primary tumors
such as Ewing's sarcoma and osteogenic sarcoma, monostotic Langerhans' cell
histiocytosis, and lymphoma. These were all provisional diagnoses given to
these patients who presented from outside institutions for consultation. These
diseases usually can be excluded on the basis of the lack of dramatic uptake
on the early vascular phase of the bone scan, an absence of bone destruction,
or an absence of discrete bone or soft-tissue mass. Osteoid osteoma and
osteomyelitis can be excluded by laboratory results, specific clinical
history, and a combination of imaging findings. Stress fracture is also a
differential diagnosis; however, there is an absence of a horizontal or
vertical fracture line, and the clinical findings are different from those
found in partial adductor muscle avulsion.
Acknowledgments
We thank Elisabeth Lühi for manuscript
preparation and support.
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Abstract
Introduction
