Arash Anavim, MD
, from Martin Luther King Hospital, Los Angeles, CA; and
Jamshid Tehranzadeh, MD,
from the Section of Musculoskeletal Radiology, Department of
Radiological Science, University of California, Irvine Medical
Center, Orange, CA.
A 34-year-old white man presented with right hip pain of 1-year
duration. He is a mechanic and has been an avid footbag player for
several years. He denies any specific trauma. On physical
examination, pain was present with any range of motion but was more
severe with external and internal rotation and straight-leg raise.
He was treated with non-weight-bearing, non-steroidal
anti-inflammatory drugs, and analgesics for 1 year, but the pain
was refractory. Plain radiograph (Figure 1), radionuclide bone scan
(Figure 2), and MRI of the right hip (Figure 3) were obtained.
Intertrochanteric occult stress fracture in an avid Hacky Sack
(WHAM-O, Inc., Emeryville, CA) player.
A plain radiograph of the right hip was unremarkable except for
bilateral degenerative joint disease and the presence of os
acetabulum at the right hip (Figure 1). A bone scan revealed
augmented radionuclide uptake at the right hip, prominently at the
intertrochanteric region (Figure 2). This area showed low signal
intensity on Tl-weighted imaging (T1WI) (Figure 3A) and a band of
bright signal on T2-weighted imaging (T2WI) (Figure 3B), consistent
with a bone contusion or occult stress fracture. A CT-guided bone
biopsy was performed, which revealed no tumor, infection, or other
pathologic lesion. He underwent open reduction and internal
fixation of the right hip with a Synthes dynamic screw (Synthes,
Paoli, PA). The intertrochanteric region was scraped by curette and
the bone specimen was sent to pathology. On microscopic
examination, numerous small fragments of bone with empty lacunae,
possibly due to necrosis or crush artifact, were noted. No evidence
of tumor or osteomyelitis was noted.
Footbag is a growing sport. Although played as leisure for many
years, it has existed as a competitive sport in several forms since
the late 1970s and has a growing number of events each year. It is
played mainly in the United States and Canada, but there are many
footbag clubs and players around the world. During play, the bag,
which is a small, hard or soft ball, may not contact the body
except below the knee. Several forms of footbag sport include
freestyle, footbag net, team freestyle, and footbag golf.
Bone contusions, so-called occult fractures, are microfractures
of the cancellous bony trabeculae with edema and hemorrhage.
These contusions were originally described by magnetic resonance
(MR) as speckled or reticulated areas within cancellous bone
revealing low signal intensity on T1WI and high signal intensity on
T2WI. Occasionally, they would have band-like low-signal areas
simulating stress fractures. They have been known by a variety of
terms, such as bone bruises, occult fractures, osteochondral
fractures, and occult osseous lesions. Accordingly, they may
represent a spectrum of radiographically occult bone injury,
ranging from simple trabecular hemorrhage, infarction, and edema;
to microscopic compression fractures of cancellous bone; to
osteochondral fractures that can be seen arthroscopically.
Bone contusions are best imaged on fat-saturated or STIR MR
imaging. When different MR techniques were examined, fast-spin-echo
with fat saturation and fast-spin-echo short tau inversion recovery
(STIR) sequences proved to be superior to conventional STIR
sequences for the diagnosis of bone contusion.
Femoral neck stress fracture (FNSF) is uncommon and accounts for
3% to 4% of stress fractures. It is generally seen in young, active
endurance athletes and military recruits, or in the elderly with
Stress fractures are more common in the lower extremities, with
7.2% occurring in the femur, the fourth most common site in
athletes after tibia (49%), tarsals (25.3%), and metatarsals
However, the actual incidence of femoral stress fracture is
difficult to assess. Stress fracture at the trochanteric region is
very rare. Stress fractures are mostly transcervical at the femoral
neck. Femoral neck stress fractures in younger individuals are
often the result of athletic activities--such as long-distance
running and ballet dancing--and are also seen in military recruits.
They are especially associated with initiation of a new athletic
activity or an increase in the frequency or intensity of a current
There are two primary types of FNSF: tension and compression
stress fractures. The tension type is usually directed
perpendicular to the line of force transmission in the femoral
neck. It originates at the superior surface of the neck, is at
increased risk for displacement, and is treated surgically. The
compression type has radiologic changes (callus formation) on the
inferior femoral neck without apparent cortical disruption and is
usually managed nonsurgically.
Stress fractures of the femoral neck are often (67%) not visible on
plain radiographs. Unlike fractures in the cortical bone, which
show radiolucent lines on X-ray, cancellous bone fractures are not
visible on initial radiographic examination. They usually appear as
a sclerotic line on follow-up study, with or without periosteal new
Rarely, a radiolucent line called "dreaded black line" may be the
only subtle finding on the plain radiograph.
Bone scan, although sensitive, is nonspecific for stress fractures.
Magnetic resonance is considered the modality of choice for occult
femoral neck fractures.
Limited MRI with coronal TlWI spin-echo sequence is adequate for
fast and inexpensive diagnosis of femoral neck fractures.
Bone contusions in the distal femur are treated conservatively.
Bone contusions or occult fractures in the femoral neck deserve
careful consideration. Treatment is based upon the type of FNSF.
Tension fractures are unstable and require operative stabilization
with multiple screws or a sliding hip screw. The area of fracture
can be curetted or reamed at surgery to induce biologic reaction
and decrease the chance of nonunion.
The compression type can be managed nonsurgically with several days
of rest and protected weight bearing. Frequent radiographs may be
needed to detect any changes or displacement. A displaced FNSF in a
young adult is an orthopaedic emergency and requires open reduction
and internal fixation.
This case reports the clinical and imaging findings of
intertrochanteric fracture in an avid footbag player and discusses
stress fractures of the femoral neck.