1-Which of the following is associated with malignant degeneration of Paget disease?
A. Osteoporosis circumscripta
B. Mosaic pattern
C. Osteosarcoma
D. Ivory vertebral body
Rationale:
A: Osteoporosis circumscripta refers to the well defined geographic lytic region seen at the skull secondary to the intense
osteoclastic activity of the lytic phase of Paget disease.
B: The mosaic pattern describes the histology of Pagetoid bone, namely the arrangement of coarsened and enlarged osseous
trabeculae.
C: Malignant degeneration of Paget disease is typically a focal process resulting in bone destruction that appears lytic and
aggressive on conventional radiographs and CT. Osteosarcoma is the most common of these secondary sarcomas. They lack the
new bone formation with sclerosis and periosteal reaction more typical of primary osteosarcoma seen in children.
D: Not all involved vertebral bodies enlarge in Paget’s disease. Occasionally, diffuse osteosclerosis of a vertebral body may
mimic metastasis and lymphoma. The more characteristic pattern, however, is the “picture-frame” vertebral body with
enlargement due to cortical thickening. Pagetic involvement of both the anterior and posterior elements is often helpful with
differential diagnosis, blastic metastasis and lymphoma tending to more focally involve the vertebral body. Malignant
degeneration involves osteolysis not sclerosis.
2- Concerning hyperextension injuries of the cervical spine, which of the following is CORRECT?
A. Cervical spine CT is indicated in cases of posterior arch C1 fracture.
B. Hyperextension dislocation injury is readily appreciated on lateral radiographs.
C. Hangman's fracture involves displacement of the odontoid process.
D. Paravertebral ossification decreases the risk of hyperextension injury.
Rationale:
A: Posterior arch C1 fracture may be isolated or associated with other injuries. Prevertebral soft-tissue swelling is a clue to the
latter. Because of the frequent association of posterior arch fractures with more severe injuries, CT is indicated in the evaluation
of all patients with these fractures.
B: Radiographs often underestimate hyperextension dislocation injuries, showing no malalignment because of immediate
realignment following trauma. The presence of diffuse prevertebral soft-tissue swelling may be the only finding. An avulsion
fracture is seen in two-thirds of cases at the anteroinferior endplate of the vertebral body. Widening of the disk space anteriorly
and the presence of a vacuum disk are less frequently present. The transverse dimension of the anteroinferior avulsion fracture
fragment is typically greater than its vertical height, distinguishing it from hyperextension teardrop fracture, its triangular
fragment has a greater vertical than transverse dimension. With hyperextension dislocation, the anterior longitudinal ligament,
disk, and ligamentum flavum are all disrupted. Stripping of the posterior longitudinal ligament and tears of the paraspinal
musculature may also be present. Neurologic impairment with acute central cord syndrome is almost always present ranging from
upper extremity paresthesias to complete quadriplegia.
C: Hangman's fracture or traumatic spondylolisthesis of C2 is the second most common C2 fracture and involves the pars
interarticularis, not the odontoid. The usual mechanism of injury involves direct impact to the face (rather than judicial hanging)
with hyperextension and pathologic loading of the posterior aspect of the axis, producing bilateral vertically oriented fractures of
the pars interarticularis. Subsequent separation of the body and posterior arch of C2 results in decompression of the spinal canal.
An atypical variant of traumatic spondylolisthesis has been described, with either unilateral or bilateral fractures in the coronal
plane through the posterior body of C2. The identification of atypical traumatic spondylolisthesis is clinically relevant due to the
greater degree of mechanical and potential neurologic deficit associated with this variant. The most common C2 fracture involves
the odontoid process and may also result from hyperextension. There is, however, no association with the Hangman's injury.
D: Diffuse idiopathic skeletal hyperostosis predisposes to significant injury from cervical hyperextension. Patients with
ankylosing spondylitis are also at increased risk for fractures of the cervical spine, which commonly result from hyperextension.
The cervicothoracic junction is most frequently involved, with the fracture extending horizontally through the intervertebral
disk to involve the entire spine at this level. Neurologic deficit may be present in over 50% of patients, with a high mortality
rate.
3-Which of the following may be associated with posterior ankle impingement?
A. Os trigonum
B. Os tibiale externum
C. Os peroneum
D. Os calcaneus secondarius
Rationale:
A: The talus has two posterior tubercles between which is the fibro-osseous tunnel for the flexor hallucis longus tendon. An os
trigonum is an ununited posterior lateral tubercle of the talus (normal fusion occurs by about 13 years of age). It occurs in 10% of
the population and is bilateral 50% of the time. Impingement of the flexor hallucis longus tendon (posterior ankle impingement)
is usually associated with activities that involve weight-bearing with ankle plantar flexion such as ballet dancing. An os trigonum
may (os trigonum syndrome) or may not be associated with posterior impingement. Most individuals with an os trigonum are
asymptomatic. Many with posterior impingement have no os trigonum.
B: The os tibiale externum is a Type II accessory navicular bone, located in the midfoot at the medial aspect of the navicular, at
the posterior tibial tendon insertion. Unlike the Type I smaller sesamoid of the posterior tibial tendon, this is an accessory
ossification center, usually 1 cm in size. When the latter is fused, there is a medial posterior prominence of the navicular which is
often referred to as a cornuate navicular. Pain has been associated with the os tibiale externum. Both bone scan and MRI may be
abnormal with focal radionuclide uptake or bone marrow edema respectively.
C: The os peroneum is an anterior structure, embedded in the peroneus longus tendon at the level of the cuboid. It may fracture.
D: The os calcaneus secondarius is an unfused ossification center of the anterior process of the calcaneus. It is well corticated
and should not be confused with an avulsion fracture of the anterior process of the calcaneus at the bifurcate ligament
insertion.
4- Concerning multiple myeloma, which of the following statements is CORRECT?
A. MR is the recommended method for initial diagnostic imaging evaluation.
B. Bone scintigraphy may overestimate bone marrow involvement.
C. Extraskeletal myeloma is found in most patients.
D. Bone lesions may be either lytic or blastic.
Rationale:
A: The radiographic skeletal survey is still the recommended method for initial diagnostic imaging evaluation. However, wholebody magnetic resonance (MR) imaging has higher sensitivity, and it is recommended in patients with solitary plasmacytoma or
monoclonal gammopathy and a normal radiographic bone survey or few (< 5) lytic lesions. Radiographic surveys of the skeleton
continue to be recommended for initial, baseline evaluation. Bone scintigraphy is not useful because the disease process in
multiple myeloma inhibits osteoblastic activity. Recently published guidelines recommend whole-body MR imaging for patients
who have monoclonol gammopathy of undetermined significance or a solitary plasmacytoma and a normal skeletal survey. In
addition, MR imaging is recommended for the evaluation of any patient with multiple myeloma and neurologic dysfunction,
which may be indicative of epidural disease compressing the spinal cord. Advanced imaging techniques also are recommended
for better visualization of extramedullary disease, sites of pain, or focal lesions for the purposes of biopsy or radiation treatment.
Although the most recent treatment guidelines do not require advanced imaging of all patients with multiple myeloma, findings at
multidetector CT, MR imaging, and FDG PET have led to alterations of staging in 15%-25% of patients, and recently, there are
those who advocate the use of MR imaging for routine staging, prognosis, and assessment of response to treatment.
B: Several studies have shown that 99-m Tc bone scans significantly underestimate the extent of bone involvement with
myeloma, and the radiographic bone survey is still most commonly used.
C: Extraskeletal myeloma is extremely unusual, found in less that 5% of patients with the disease.
D: While most skeletal lesions are lytic, a blastic form of the disease is associated with POEMS syndrome (polyneuropathy,
organomegaly, endocrinopathy, M protein, skin changes).
5- Concerning musculoskeletal tuberculosis, which of the following is CORRECT?
A. The knee is most commonly involved.
B. Early, uniform destruction of articular cartilage is characteristic.
C. Intra-articular rice bodies may be seen with MR imaging.
D. Involvement of the hands and feet typically occurs in the elderly.
Rationale:
A: Less than 5% of patients with tuberculosis have involvement of the musculoskeletal system. About half of these have septic
spondylitis and the other half have septic arthritis/bursitis most commonly involving the knee, shoulder and hip.
B: Uniform destruction of the articular cartilage typically is a slow process with preservation of the joint space for several
months, unlike more common bacterial arthritides.
C: Rice bodies are bits of sloughed, infarcted synovium, a sequela of end-stage inflammatory processes, most commonly
rheumatoid and tuberculous arthritis. MR may demonstrate numerous small bodies of similar size within the joint or bursa.
D: Tuberculous dactylitis involves the short tubular bones of the hands and feet in children. At radiography, these lesions
demonstrate soft-tissue swelling and periostitis. These findings are followed by gradual bone destruction and sequestrum
formation. Expansion of the bone with cystic changes is known as spina ventosa. The radiologic differential diagnosis includes
pyogenic or fungal infections, syphilitic dactylitis, sarcoidosis, hemoglobinopathies, hyperparathyroidism, and leukemia.