Chapter 45: Metabolic Bone Diseases *complete*

Front 1

What's the difference between osteoporosis and osteomalacia?
Can you tell the difference on plain films?

Back 1

-Osteoporosis is defined as diminished bone quantity in which the bone is otherwise normal.
-This contrasts to osteomalacia, in which the bone quantity is normal but the quality of the bone is abnormal in that it is not normally mineralized.
-Osteomalacia results in excess nonmineralized osteoid.
-It is not possible in most cases to distinguish between osteoporosis and osteomalacia on plain films; hence, many prefer the term “osteopenia” for the plain film finding of diminished mineralization.

Front 2

What are the different types of osteoporosis?

Back 2

-There are myriad causes of osteoporosis, the most common of which is primary osteoporosis (so-called senile osteoporosis or osteoporosis of aging).
-This is seen most commonly in postmenopausal women and is a major health concern because of the increase in vertebral body and hip fractures in this patient population.
-Secondary osteoporosis implies that an underlying disorder, such as thyrotoxicosis or renal disease, has caused the osteoporosis.
-Only about 5% of osteoporosis cases are of the secondary type.
-A type of osteoporosis that can be seen in a patient of any age is disuse osteoporosis.
-It results from immobilization from any cause, most commonly following treatment of a fracture.
-The radiographic appearance of disuse osteoporosis differs from that of primary osteoporosis in that it occurs somewhat more rapidly and gives the bone a patchy appearance
-This is from osteoclastic resorption in the cortex, which causes intracortical holes. If the disuse were to continue, the bone would resemble any bone with marked osteoporosis, that is, severe cortical thinning.

Front 3

What are the radiographic findings in osteopenia? Where should you look for osteopenia?

Back 3

-The main radiographic finding in osteoporosis is thinning of the cortex.
-Although this can be seen in any bone, it is most reliably demonstrated in the second metacarpal at the middiaphysis.
-Normal metacarpal cortical thickening should be approximately one fourth to one third the thickness of the metacarpal.
-In osteoporosis, this cortical thickness is decreased

Front 4

What does "aggressive osteoporosis" mean?
How can you tell the difference between a permeative lesion and a pseudopermeative lesion?
Name some causes of pseudopermeative lesions:

Back 4

-Occasionally, aggressive osteoporosis from disuse can mimic a permeative lesion, such as a Ewing sarcoma or multiple myeloma, because of the multiple cortical holes that project over the medullary space, thus resembling a medullary permeative process
-The way to differentiate a true intramedullary permeative process from an intracortical process such as osteoporosis is to observe the cortex and see whether it is solid or riddled with holes
-If the cortex is solid, one can assume the permeative process is emanating from the medullary space
-If the cortex has multiple small holes, the clinician can assume the permeative pattern is from the cortical process.
-I call a permeative appearance that is secondary to cortical holes a “pseudopermeative” process to distinguish it from a true permeative process.
-Other causes for a pseudopermeative process include hemangioma and radiation.

Front 5

Explain how hemangiomas can cause the appearance of a permeative lesion:

Back 5

A hemangioma can cause cortical holes in two ways: from focal hyperemia causing
focal osteoporosis, or by the blood vessels themselves tunneling through the cortex

Front 6

Explain how radiation therapy can cause the appearance of a permeative lesion in bone:

Back 6

-Radiation can cause cortical holes in bone and mimic a permeative pattern because of the death of cortical osteocytes, which can result in large lacunae in the cortex.
-The cortical holes from radiation can be large, in which case they would not be confused with a true permeative process, but they can also be small and resemble an aggressive lesion.

Front 7

What's your differential for a permeative bone lesion in a young patient (<30 years)? What about an older patient?
What's your differential for a pseudopermeative lesion?

Back 7

-If a permeative lesion is found, the differential diagnosis is usually an aggressive process such as Ewing sarcoma, infection, or eosinophilic granuloma in a young person (<30 years of age) or multiple myeloma, metastatic carcinomatosis, or primary lymphoma of bone in an older patient.
-If, however, the permeative pattern is a result of cortical holes—that is, a pseudopermeative pattern—the differential diagnosis is considerably less sinister: aggressive osteoporosis, hemangioma, or radiation changes.

This differential diagnosis does not arise often but is very useful when it does

Front 8

What is the most common cause of osteomalacia?
What are the radiographic findings of osteomalacia?

Back 8

-The most common cause is renal osteodystrophy.

-The plain radiographic findings are almost identical to those of osteoporosis (cortical thinning), and, for the most part, the two disorders are indistinguishable.
-The only finding that is pathognomonic for osteomalacia is a Looser fracture, which is a fracture through large osteoid seams
-They are extremely uncommon but tend to occur in the femur, pelvis, and scapula.

Front 9

What is osteomalacia in children called?
What does it look like on radiographs?
What are the most common causes?

Back 9

-In children, osteomalacia is called rickets.
-It causes the epiphyses to become flared and irregular and the long bones to undergo bending from the bone softening
-As in adults, the most common cause is renal disease, although other causes such as biliary disease and dietary insufficiencies are occasionally seen.

Front 10

Explain the difference between primary and secondary hyperparathyroidism:
What's the most common cause of hyperparathyroidism?

Back 10

-Primary HPT is caused by parathyroid adenomas and hyperplasia.
-Up to 40% of patients with primary HPT will demonstrate skeletal abnormalities radiographically.
-The most common cause of HPT is from renal disease, which leads to secondary HPT.
-Secondary HPT is the result of the parathyroids secreting excess PTH in response to the hypocalcemia that occurs from chronic renal failure

Front 11

Describe the radiographic findings in hyperparathyroidism:
Where is the best place to look for these findings?

Back 11

-The radiographic sign that is pathognomonic for HPT is subperiosteal bone resorption.
-It is seen most commonly on the radial aspect of the middle phalanges of the hand, but it can be seen in any long bone in the body.
-It is commonly seen on the medial aspect of the proximal tibia, at the sacroiliac joints and in the distal clavicle.
-Other radiographic findings include osteosclerosis, which is usually diffuse but often involves the spine in a manner resembling the stripes on rugby jerseys, hence the name “rugger jersey spine”
-Brown tumors are cystic lesions that are often expansile and aggressive in appearance
-A brown tumor can have a variety of appearances, so its only unique characteristic is its association with subperiosteal bone resorption.

Front 12

Describe imaging findings in hypoparathyroidism:

Back 12

-Few skeletal changes occur in hypoparathyroidism.
-The calvaria on occasion will show thickening, and calcification in the basal ganglia of the brain has been described.

Front 13

What is pseudohypoparathyroidism?

Back 13

-Pseudohypoparathyroidism is caused by a congenital failure of tissues to respond to PTH.
-The parathyroid glands are normal in these cases.
-Treatment of these patients with PTH is of no help because the problem lies in the end organs, not in the parathyroid glands.
-A characteristic appearance is seen in these patients: obesity, round facies, short stature, and brachydactyly.
-The tubular bones of the hands and feet are often all short.
-Shortened fourth and fifth metacarpals are a frequent finding in this entity (knuckle knuckle dimple dimple--Turner's syndrome has blunting only of the 4th metascarpal "knuckle knuckle dimple knuckle")

Front 14

What is pseudopseudohypoparathyroidism?

Back 14

-In pseudopseudohypoparathyroidism, there is no parathyroid abnormality and no end-organ problem; these patients merely resemble patients with pseudohypoparathyroidism.

Front 15

What causes gigantism/acromegaly?

Back 15

A secreting adenoma or hyperplasia of the anterior lobe of the pituitary gland will result in accelerated bone growth. If it occurs before the epiphyses close, it causes giantism. If it occurs after the epiphyses are closed, the result is acromegaly.

Front 16

Describe radiographic manifestations of acromegaly:

Back 16

-Acromegaly has several characteristic radiographic features in the skeletal system.
-The skull film invariably shows calvarial thickening, enlarged sinuses, and an enlarged sella turcica.
-The jaw is prognathic.
-The terminal tufts of the distal phalanges become hypertrophied and have a so-called spade appearance (an appearance not unlike a spade or shovel)
-The joint spaces are occasionally minimally enlarged because of hypertrophy of the hyaline articular cartilage.
-Early DJD ensues because the cartilage itself is abnormal.
-The soft tissues also hypertrophy, with various measurements of soft tissue thickening used by some as an indicator for acromegaly.
-For instance, thickening of the heel pad adjacent to the calcaneus has been used as a sign of acromegaly.

Front 17

Describe radiographic manifestations of hyperthyroidism:

Back 17

-A rare manifestation of hyperthyroidism in adults is thyroid acropachy.
-This occurs only after prior thyroidectomy, and the cause is unknown.
-A characteristic-appearing periostitis occurs in the metacarpals and phalanges of the hands and feet
-It invariably involves the ulnar aspect of the fifth metacarpal, a useful differential point that can be used to tell thyroid acropachy from other causes of diffuse periostitis, such as hypertrophic pulmonary osteoarthropathy and pachydermoperiostitis, a rare form of idiopathic periostitis and skin thickening.

Front 18

Describe radiographic manifestations of congenital hypothyroidism (cretinism):

Back 18

-Decreased thyroid secretion, or cretinism, results in delayed skeletal maturation in children.
-Delay in ossification of epiphyseal centers with occasional appearance of “stippled” epiphyses is seen.
-A delay in epiphyseal closure also occurs, in some instances with failure of epiphyseal closure noted in the third and fourth decade.

Front 19

What's your differential for diffusely dense bones (osteosclerosis)?

Back 19

“Regular Sex Makes Occasional Perversions Much More Pleasurable And Fantastic.”

Renal osteodystrophy
Sickle cell disease
Myelofibrosis
Osteopetrosis
Pyknodysostosis
Metastatic carcinoma
Mastocytosis
Paget disease
Athletes
Fluorosis

Front 20

When should you consider renal osteodystrophy as a cause of osteosclerosis?

Back 20

-Although the most common presentation of renal osteodystrophy is osteopenia, about 10% to 20% of patients with renal osteodystrophy will exhibit osteosclerosis, and the reasons for it are unknown.
-The sine qua non of renal osteodystrophy is subperiosteal bone resorption, seen earliest and most reliably at the radial aspect of the middle phalanges of the hands.
-Without this finding, osteosclerosis caused by renal disease should not be entertained.

Front 21

What are radiographic manifestations of sickle cell disease?

Back 21

-As in renal osteodystrophy, the underlying cause of dense bones in sickle cell disease is unknown.
-It occurs in a small percentage of patients.
-Additional signs to look for are bone infarcts and step-off deformities of the vertebral body endplates.
-These are also called “fish” vertebrae because they resemble the vertebrae found in fish.
-Avascular necrosis of the hip and humerus is frequently an accompanying finding.

Front 22

What findings should make you suspicious for myelofibrosis?

Back 22

Whenever osteosclerosis is seen in a patient older than 50 years of age, a search should be made for a large spleen and extramedullary hematopoiesis characteristic of myelofibrosis

Front 23

Describe radiographic manifestations of osteopetrosis:

Back 23

-Osteopetrosis is a hereditary abnormality that results in extremely dense bones throughout the skeleton
-A characteristic finding is the so-called bone-in-bone appearance often seen in the vertebral bodies, in which the vertebrae have a small replica of the vertebral body inside the normal one.
-Also characteristic are “sandwich vertebrae,” in which the endplates are densely sclerotic, giving the appearance of a sandwich
-The sandwich vertebrae appearance resembles a rugger jersey spine but the pattern is much denser and more sharply defined.

Front 24

What's the difference between a rugger jersey spine and sandwich spine?
Which disorders are associated with each?

Back 24

-Rugger jersey spines are manifestations of the osteosclerosis related to hyperparathyroidism, most commonly seen with chronic renal disease.
-The upper and lower endplates of the verterbal bodies are dense, appearing like stripes on a rugby jersey.

-Sandwich vertebrae occur with osteopetrosis
-The sandwich vertebrae appearance resembles a rugger jersey spine but the pattern is much denser and more sharply defined.

Front 25

What is pyknodysostosis?
What are the radiographic manifestations?

Back 25

-These patients are typically short and have hypoplastic mandibles.
-The distinguishing radiographic finding that is essentially pathognomonic is acroosteolysis with sclerosis.
-The distal phalanges often have the appearance of chalk that has been put into a pencil sharpener: they are pointed and dense, without distal tufts.
-No other disease process has this appearance.
-Another name for this disorder is Toulouse-Lautrec syndrome, named for the famous artist who was afflicted with pyknodysostosis.

Front 26

What is mastocytosis?

Back 26

-Mastocytosis is another rare disorder that can cause uniformly increased bone density.
-Unfortunately, there are no other plain film findings that might help with the diagnosis.
-Patients with this disease have thickened small bowel folds with nodules, but, of course, to see these, an upper GI contrast study must be performed
-Urticaria pigmentosa is a characteristic skin lesion found in these patients (hives break out wherever the skin is scraped)

Front 27

Describe radiographic manifestations of Paget's dsiease:

Back 27

-Paget disease classically causes bony enlargement and thickening
-It occurs most commonly in the pelvis where it has been said that the iliopectineal line on the pelvic brim is almost always thickened
-Paget disease can occur in any bone in the body, including the smaller bones of the hands and feet.
-Paget disease has three distinct phases that are visible radiographically: a lytic phase, a sclerotic phase, and
a mixed lytic-sclerotic phase.
-The lytic phase often has a sharp leading edge, called a flame-shaped or blade-of-grass leading edge
-In a long bone, with the sole exception being the tibia, Paget disease always starts at the end of the bone; therefore, if a lesion is present in the middle of a long bone and does not extend to either end, one can safely exclude Paget disease.

Front 28

Describe radiographic manifestations of fluorosis:

Back 28

-A radiographic finding that patients with fluorosis often have is ligamentous calcification.
-Calcification of the sacrotuberous ligament is said to be characteristic for fluorosis.

Front 29

Back 29

1

Front 30

Back 30

2

Front 31

Back 31

3

Front 32

Back 32

4

Front 33

Back 33

5

Front 34

Back 34

6

Front 35

Back 35

7

Front 36

Back 36

8

Front 37

Back 37

9

Front 38

Back 38

10

Front 39

Back 39

11

Front 40

Back 40

12

Front 41

Back 41

13

Front 42

Back 42

14

Front 43

Back 43

15

Front 44

Back 44

16

Front 45

Back 45

17

Front 46

Back 46

18

Front 47

Back 47

19

Front 48

Back 48

20

Front 49

Back 49

21

Front 50

Back 50

22

Front 51

Back 51

23

Front 52

Back 52

24

Front 53

Back 53

25

Front 54

Back 54

26