Chapter 47: Miscellaneous Bone Lesions *complete*

Front 1

What is the most common cause of dwarfism?

Back 1

Achondroplasia

Front 2

What causes achondroplasia?

Back 2

It’s a hereditary failure of endochondral bone formation

Front 3

Long bone findings in achondroplasia on imaging?

Back 3

Femurs and humeri are more profoundly affected than the other long bones, although the entire skeleton is abnormal

The long bones are short but have normal width, giving them a thick appearance

Front 4

Spine findings in achondroplasia on imaging?

Back 4

The spine typically has narrowing of the interpedicular distances in a caudal direction, the opposite of normal, in which the interpedicular distances get progressively wider as one proceeds down the spine.

Front 5

Define avascular necrosis:

Back 5

Lack of blood supply with subsequent bone death and ensuing bony collapse in an articular surface

Front 6

Name some causes of AVN:

Back 6

-Trauma
-Steroids
-Collagen vascular diseases
-Alcoholism
-Idiopathic
-Infection

Front 7

What does AVN look like on imaging?

Back 7

It ranges from patchy sclerosis to articular surface collapse and fragmentation

Just before collapse, a subchondral lucency is occassionally seen (this is inconsistent)

Front 8

What is the best modality to evaluate AVN?

Back 8

MR

Front 9

What is the long name for clubbing of the fingers?

Back 9

Hypertrophic pulmonary osteoarthorpathy

Front 10

Who gets clubbing?

Back 10

Most commonly, lung cancer, but also seen in bronchiectasis, GI disorders, and liver disease.

Front 11

What is the mechanism of clubbing?

Back 11

Unknown

Front 12

Differential for periostitis in a long bone without underlying bony abnormality:

Back 12

-Hypertrophic pulmonary osteoarthropathy
-Venous stasis
-Thyroid acropachy
-Pachydermoperiostosis
-Trauma

Front 13

What is melorheostosis?

Back 13

Rare, idiopathic disorder characterized by thickened cortical new bone that accumulates near the ends of long bones, usually only on one side of the bone

Appearance has been term “dripping candle wax”

Front 14

What is Morquio syndrome?

Back 14

Abnormal storage and excretion of keratan sulfate

Front 15

What is Hurler syndrome?

Back 15

Abnormal storage and excretion of heparan sulfate

Front 16

What does Morquio syndrome look like on imaging?

Back 16

-Shortened spines
-Platyspondyly (generalized flattening of the vertebral bodies)
-Central anterior projection or “beak” off the vertebral body on lateral films
-Wide, flared iliac wing and broad femoral necks

Front 17

What do Hunter and Hurler syndrome look like on imaging?

Back 17

-Shortened spines
-Platyspondyly (generalized flattening o the vertebral bodies)
-Anteroinferiorly positioned beak off the vertebral body on lateral films
-Wide, flared iliac wing and broad femoral necks
-The hands have a pointed proximal fifth metacarpal base that has a notched appearance to the ulnar aspect.

Front 18

What is multiple hereditary exostosis also known as?

Back 18

Diaphyseal aclasia

Front 19

What are the findings in multiple hereditary exostosis?

Back 19

Multiple osteochondromas or exostoses

Front 20

What is an osteochondroma?

Back 20

Cartilage-capped bone outgrowth that may be pedunculated or sessile

Undertubulation (a widened diameter of the bone) is invariably present at the site of the exostosis

Front 21

Which areas are typically involved in multiple hereditary exostosis?

Back 21

The knees are virtually always involved

The proximal femurs are frequently involved

Front 22

What is the rate of malignant degeneration in multiple hereditary exostosis?

Back 22

It’s extremely rare

Front 23

Which lesions in multiple hereditary exostosis undergo malignant degeneration?

Back 23

The more axially situated the lesions, the more they are prone to undergo malignant degeneration

Front 24

How does osteoid osteoma present?

Back 24

Painful bone lesion in patients younger than 30.

Front 25

What do osteoid osteomas look like?

Back 25

-Cortically based sclerotic lesion in a long bone that has a small lucency within it called the nidus
-If the nidus is located in the medullary rather than the cortical portion of a bone, or if it is located in a joint, there is much less reactive sclerosis present
-Rarely, it will be in the periosteum, causing exuberant periostitis.
-the nidus is often lucent, but can develop calcification within it. If it calcifies completely, it blends into the surrounding sclerosis.
-Therefore, diagnosis should not depend on visualization of a nidus.

Front 26

How is osteoid osteoma treated?

Back 26

-Surgical excision or thermal ablation
-It is the nidus that cuases the pain and surrounding reactive sclerosis
-If the nidus is removed or ablated, the pain stops.
-The natural history of this disease is eventual spontaneous regression

Front 27

What is the imaging of choice for osteoid osteoma?

Back 27

CT is often helpful in demonstrating the exact location of the nidus

Front 28

What is osteoid osteoma often confused with? Why?

Back 28

Osteomyelitis

The nidus is usually lucent, but often develops some calcification within it. IT then has the appearance of a sequestrum

Front 29

How can you tell the difference between an osteoid osteoma and osteomyelitis?

Back 29

Nuclear bone scans—the nidus avidly accumulates radiotracer relative to the uptake of the surrounding reactive sclerosis. This is called the “double-density sign”

In contrast, osteomyelitis has a photopenic area corresponding to the avascular focus of purulent material

Front 30

Define osteopathia striata:

Back 30

-Also known as Voorhoeve disease
-Multiple 2-3 mm thick linear bands of sclerotic bone aligned parallel to the long axis of a bone
-It usually affects multiple long bones and is asymptomatic, so it’s usually just an incidental finding

Front 31

Define osteopoikilosis:

Back 31

Hereditary asymptomatic multiple small (3-10mm) sclerotic bony densities affecting primarily the ends of long bones and the pelvis

Front 32

What is the clinical significance of osteopoikilosis?

Back 32

There is none, except that it can be confused for diffuse osteoblastic metastases.

Front 33

Define pachydermoperiostosis

Back 33

-Rare familial disease
-Thickening of the skin of the extremities and face, clubbing of the fingers, and widespread periostitis.
-More common in black patients.
-The periosteal reaction looks like hypertrophic pulmonary osteoarthropathy, but it is only occassionally painful

Front 34

What does sarcoid look like in the bones?

Back 34

-The hands are the most often affected
-It causes a characteristic lacelike pattern of body destruction in the hands
-Multiple phalanges are typically affected in either one or both hands

Front 35

What is the differential diagnosis for sarcoid-like changes of the hands?

Back 35

There is none; it is very characteristic

Front 36

Describe transient osteoporosis of the hip:

Back 36

-Findings of osteoporosis limited to a single, painful, hip
-Some think that this is early AVN, but this has not been proven
-Invariably self-limited with full resolution
-Tends to occur more in men

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