MSK: Osteoporosis, Osteopenia, and AVN

Question 1

Osteomalacia

Answer 1

Soft bone due to excessive unmineralized osteoid, usually related to vitamin D issues (e.g. renal failure, liver disease, etc.)

Question 2

Imaging findings of osteomalacia

Answer 2

• Ill-defined trabeculae
• Ill-definted corticomedullary junction
• Bowing of the bones
• Looser zones (a subtype of insufficiency fracture)

Question 3

Answer 3

Looser zones (lucent bands that run perpendicular to the cortex with surrounding sclerosis)

Note: These are a type of insufficiency fracture commonly seen at the femoral neck and pubic rami.

Question 4

Answer 4

Looser zones (a type of insufficiency fracture)

Question 5

Differential for looser zones

Answer 5

• Osteomalacea
• Rickets
• Osteogenesis imperfecta (rare)

Question 6

Imaging findings of osteoporosis

Answer 6

• Thin sharp cortex
• Prominent trabecular bars
• Lucent metaphyseal bands
• Spotty lucencies

Question 7

What are the most common fractures in the setting of osteoporosis?

Answer 7

• Spine (most common)
• Hip (2nd)
• Wrist (3rd)

Question 8

What is the DEXA T score relative to?

Answer 8

A young adult

Question 9

What is the T score that defines osteoporosis?

Answer 9

T score less than -2.5

Note: T score of -1.0 to -2.5 is osteopenia.

Question 10

What should a normal DEXA T score be?

Answer 10

Above -1.0

Question 11

What is the DEXA Z score relative to?

Answer 11

An age-matched database

Question 12

Common cause of a false positive DEXA

Answer 12

Absence of normal structures (e.g. laminectomies)

Question 13

Common causes of false negatives on DEXA

Answer 13

• Including high density things that shouldn’t be included (e.g. Sclerosis, osteophytes, dermal calcifications, metal objects, etc.)
• Including too much of the femoral shaft while measuring the hip

Question 14

What does the FRAX tool estimate?

Answer 14

10-year probability of a major fracture

Note: Pts with an elevated FRAX might benefit from therapy even if they are only osteopenic.

Question 15

What is considered an elevated FRAX score (meaning treatment should be considered even though they aren’t osteoporotic)?

Answer 15

> 3% risk of hip fracture

Or

> 20% risk of major fracture

Question 16

What are the most common sites involved in reflex sympathetic dystrophy (AKA complex regional pain syndrome)?

Answer 16

Hands and shoulders

Question 17

Chronic right hand pain following a remote fracture…

Answer 17

Reflex sympathetic dystrophy (AKA complex regional pain syndrome)

Note: Periarticular osteopenia distal to a right radial fracture.

Question 18

Chronic left wrist pain

Answer 18

Reflex sympathetic dystrophy (AKA complex regional pain syndrome)

Question 19

Imaging findings of reflex sympathetic dystrophy (AKA chronic regional pain syndrome)

Answer 19

• Regional severe osteopenia with preserved joint spaces
• 3 phase hot region on bone scan (intraarticular uptake is classic due to increased vascularity of the synovial membrane)

Question 20

What are the two major types of transient osteoporosis?

Answer 20

• Transient osteoporosis of the hip
• Regional migratory osteoporosis

Question 21

30 y/o F with third trimester pregnancy

Answer 21

Transient osteoporosis of the hip

Note: This will resolve in a few months.

Question 22

Third trimester pregnancy

Answer 22

Transient osteoporosis of the hip

Note: This will resolve in a few months.

Question 23

Third trimester pregnancy

Answer 23

Transient osteoporosis of the hip

Note: This will resolve in a few months.

Question 24

50 y/o M with joint pain associated with focal osteoporosis that gets better, but then shows up again in a different joint…

Answer 24

Regional migratory osteoporosis

Note: This is self-limiting and more common in males than females.

Question 25

Answer 25

Avascular necrosis of the right femoral head

Question 26

Answer 26

Avascular necrosis of the left femoral head

Question 27

Answer 27

Subchondral insufficiency fracture Note: Avascular necrosis should have a more serpiginous dark line that doesn't parallel the subchondral bone.

Question 28

Post contrast

Answer 28

Malignant vertebral compression fracture Note: Avid enhancement that extends beyond the deformed bone with an expanded posterior convex border. Osteoporotic compression fractures typically result in a more band-like appearance.

Question 29

Answer 29

Benign vertebral compression fracture Note: There is a linear, horizontal fracture line. If there were nonlinear abnormal marrow signal with involvement of the posterior margin, then you should think about malignancy.

Question 30

Answer 30

Think malignant replacement of bone marrow Note: Normally the vertebral body bone marrow should be brighter than adjacent intervertebral discs on TI.

Question 31

Next step:

Answer 31

Image the entire spine (looking for other metastases)

Question 32

Osteochondritis dissscans

Answer 32

Aseptic separation of an osteochondral fragment from the underlying bone that can lead to gradual fragmentation of the articular surface and secondary osteoarthritis Note: Most of the time this is secondary to trauma or avascular necrosis.

Question 33

Osteochondritis dissecans is most common in what pt population?

Answer 33

Males under age 18

Question 34

What is the most classic location for osteochondritis dissecans?

Answer 34

- Femoral condyle - Patella - Talus - Capitellum

Question 35

What is the staging system for osteochondritis dissecans?

Answer 35

Stage 1: Stable (covered by intact cartilage, continuous with host bone) Stage 2: Stable on probing, partial discontinuity with host bone Stage 3: Unstable on probing, complete discontinuity of lesion Stage 4: Dislocated fragment

Question 36

What imaging feature should you look for to suggest that an osteochondral lesion is unstable?

Answer 36

High T2 signal between the osteochondral fragment and underlying bone Note: Edema can cause a false positive.

Question 37

What is a common location for osteochondritis dissecans in pitchers?

Answer 37

The capitellum of the dominant arm (specifically the anterior convex margin) Note: Image shows osteochondral dissecans (yellow arrow) and loose body formation (red arrow).

Question 38

Answer 38

Pseudo-defect of the posterior capitellum Note: The posterior capitellum can appear to have an osteochrondral defect on coronal images when you are actually just seeing the non-articular portion of the capitellum (look at sagittal images to confirm).

Question 39

Panner disease

Answer 39

Osteochondrosis of the capitellum (developmental disorder of the growing capitellum epiphysis) Note: This occurs in younger males (7-12 y/o) compared to osteochondritis dissecans, which usually occurs in males age 12-16.

Question 40

9 y/o male pitcher with lateral elbow pain

Answer 40

Panner's disease (developmental disorder of the growing capitellum epiphysis) Note: This involves the entire capitellum and occurs in younger males (7-12 y/o) compared to osteochondritis dissecans, which usually occurs in males age 12-16.

Question 41

Osteochondroses

Answer 41

Developmental disorders of a growing epiphysis/apophysis with findings of collapse, sclerosis, and fragmentation (suggesting avascular necrosis) Note: These are seen in childhood.

Question 42

Male 4-6 y/o

Answer 42

Kohl's disease (osteochondrosis of the taller navicular) Note: Treatment is not surgical.

Question 43

Adolescent female

Answer 43

Freiberg infraction (osteochondrosis of the second metatarsal head) Note: This can lead to secondary osteoarthritis.

Question 44

Answer 44

Sever's disease (AKA calcaneal apophysitis) Note: This represents osteochondrosis of the calcaneal apophysis. Some people think this is a normal finding.

Question 45

Pediatric pt age 4-8

Answer 45

Legg-Calve-Perthes disease (osteochondrosis os the femoral head)

Question 46

Adults age 20-40

Answer 46

Kienbock disease (osteochondrosis of the lunate) Note: This is associated with negative ulnar variance.

Question 47

Answer 47

Scheuermann disease (osteochondrosis of the thoracic spine leading to wedging of 3 adjacent levels and exaggerated thoracic kyphosis)

Question 48

Pediatric pt age 10-15

Answer 48

Osgood-Schlatter disease (osteochondrosis of the tibial tubercle) Note: This is commonly seen in kids who jump and kick a lot.

Question 49

Pediatric pt age 10-15

Answer 49

Sinding-Larsen-Johansson disease (osteochondrosis of the inferior patella) Note: This is commonly seen in kids who jump a lot.