Bones and Arthritis

Question 1

Normal bone in plain radiography

Answer 1

When viewed in tangent, the cortex is seen as a smooth, white line, varying in thickness in different parts of the bone ( white arrows ).

The medullary cavity lies within the cortical shell and contains an interlacing network of trabeculae ( white circle).

The corticomedullary junction is the interface between the inner margin of the cortex and the medullary cavity ( solid black arrow ) .

Question 2

Diagram, x-ray, and CT of the knee joint

Answer 2

Question 3

Avascular necrosis of the femoral head

Answer 3

Question 4

Avascular necrosis of the humeral head

Answer 4

Question 5

What is going on in this patient’s femur?

Answer 5

This patient had an old medullary infarct

These appear as dense, amorphous deposits of bone within the medullary cavities of long bones, frequently marginated by a thin, sclerotic membrane

Question 6

What is going on in this patient’s pelvic radiograph?

Answer 6

This is Paget’s disease of bone

Note the accentuation and coarsening of the trabeculae and the thickening of the cortex

Question 7

Pattern of bone loss in hyperparathyroidism

Answer 7

Predominately subperiosteal and asymmetric in distribution, as shown in this image, with relative sparing of the interior bone.

This is in contrast to osteoporosis, which is diffuse and symmetric.

Question 8

Signs of hyperparathyroidism on radiography

Answer 8

• Subperiosteal bone erosion
• Distal clavicular resorption (shown)
• Brown tumors (aka osteoclastomas, well circumscribed lytic lesions within bone)

Question 9

What is happening with this bone?

Answer 9

This is a geographic lytic bone lesion, suggestive of malignancy

Question 10

What is happening with this bone?

Answer 10

This appearance is described as “moth-eaten”, and is suggestive of numerous tiny lytic lesions within bone, suggestive of aggressive malignancy

Question 11

What is happening with this bone?

Answer 11

This pattern of erosion is described as “permeative”

Sometimes called “Round cell” lesions for the shape of cells that produce them

Often due to: Ewing’s sarcoma, myeloma, leukemia

Question 12

What is happening with this bone?

Answer 12

This is multiple myeloma

Note the “punched out” appearance to the skull with very well marginated lytic lesions, as well as the diffuse distribution (not focal like scant metastasis)

Question 13

What is happening with this bone?

Answer 13

This is osteomyelitis

Note the focal cortical destruction of bone .

Often accompanied by new periosteal bone formation and inflammatory changes (swelling, focal osteoporosis, hyperemia)

Question 14

Joint space narrowing in osteoarthritis vs rheumatoid arthritis

Answer 14

Rheumatoid: uniform

Osteo: Patchy/nonuniform

Question 15

In RA, you see subchondral __.

In osteoarthritis, you see subchondral __.

Answer 15

In RA, you see subchondral erosion.

In osteoarthritis, you see subchondral cysts.

Question 16

Common indications for bone density scans

Answer 16

• Female over age 65
• Male over age 75
• Younger individuals with risk factors:
  
  • Hx of osteoporosis-associated fracture with minor trauma
  • Low BMI (<23)
  • Premature menopause
  • Testosterone deficiency in men
  • Chronic glucocorticoid therapy

Question 17

Causes of osteopenia

Answer 17

Osteoporosis vs osteomalacia (vitamin D related)

Question 18

DEXA scan t scores

Answer 18

Question 19

Z score

Answer 19

Takes into account patient demographics

NOT used for DEXA grading (we use the t score, which is basically compared against healthy 20 somethings)

Question 20

Imaging in osteomyelitis

Answer 20

Start with a plain radiograph

If this is negative but there is still clinical suspicion, or if more information is required, MRI is indicated

Question 21

Timing of findings in osteomyelitis plain radiography

Answer 21

• After 3-5 days, early signs become visible:
  
  • Focal loss of the white cortical line
  • Subchondral lucency
  • Periosteal retraction (fluffy calcification next to cortex)
• After 2-3 weeks, late signs become visible:
  
  • Periosteal elevation
  • Cortical/medullary lucency

Question 22

Differentiating osteomyelitis from Charcot joint

Answer 22

Done via nuclear medicine by comparing a 3-phase bone scan plus a WBC scan

3-phase bone scan should be positive in both, but WBV scan will be positive in osteomyelitis but negative in Charcot joint.

Question 23

When is vertebroplasty indicated?

Answer 23

• Spinal fracture with poor alignment
• Spinal fracture with neural impingement
• Failure of conservative management
• Uncontrolled pain leading to hospitalization or inability to tolerate pain medications
• Inability to tolerate bed rest (high risk for DVT, decubitus ulcer, permanent incapacitation)
• Respiratory compromise due to thoracic back pain (in case of thoracic vertebra)

Question 24

Posterior shoulder dislocation

Answer 24

Note the “lightbulb sign”

Question 25

CT in MSK imaging

Answer 25

Best at looking at the cortex and for calcifications

Allows you to localize in 3d, unlike x-ray

Also excellent for detecting air in soft tissue

Question 26

What is the difference in how coronal, saggittal, and axial images are acquired on CT and MRI?

Answer 26

In CT, if you take an axial you can reconstruct saggittal and coronal

On MRI, you need to do all views individually, so it takes 3x as long!

Question 27

Utility of bone scintigraphy

Answer 27

Tells you where bone mets are

Question 28

Infective osteitis vs osteomyelitis

Answer 28

Infetive osteitis is infection of just the bone cortex

If the marrow is involved, it is osteomyelitis

Question 29

Loss of cortical white line

Answer 29

Suggestive of bone destructive process, potentially osteomyelitis

May have a mottled appearance if there is air produced by the infection

Question 30

Managing suspected septic arthritis

Answer 30

1. Arthrotcentesis with gram stain/culture for dx
2. Surgical debridement and drainage of the joint to clear infection and prevent sepsis/joint destruction

Question 31

Calcific tendinitis

Answer 31

Deposition of hydroxyapatite in tendons/bursae

Question 32

If you see an osteophyte, . . .

Answer 32

. . . there is 100% osteoarthritis

There may be more going on, but the patient also has osteoarthritis

Question 33

Osteoarthritis joint space narrowing is ___

Rheumatoid arthritis joint space narrowing is ___

Answer 33

Osteoarthritis joint space narrowing is asymmetric

Rheumatoid arthritis joint space narrowing is symmetric

Question 34

Rheumatoid arthritis leading to osteoarthritis

Answer 34

RA can destroy the cartilage, leading to formation of osteophytes and development of osteoarthritis!

Question 35

Types of osteonecrosis

Answer 35

Just involving bone marrow: Bone infarct

Involving cortical bone and extending to joint space: Avascular necrosis

Question 36

Most common primary bone tumor

Answer 36

Multiple myeloma