Metabolic bone disease: Radiology

Question 1

What are the common imaging modalities used for bone density?

Answer 1

X-ray
CT
Bone densitometry

Question 2

What are MRI scans of bones used to determine?

Answer 2

Biochemical composition

Question 3

What scan do you use for bone turnover?

Answer 3

Radionuclide bone scans

Question 4

Difference between radiological sign and pathology?

Answer 4

Radiological signs are a change in imaging apperance that may help point towards a pathology

Question 5

How do you diagnose osteoporosis?

Answer 5

Bone densitometry - DEXA scan
Measures Bone Mineral Density (BMD)
Compare BMD to normal reference data
T-score -1.5 to -2.5 = osteopenia
T-score LESS THAN -2.5 = osteoporosis

Question 6

Radiology of osteoporosis?

Answer 6

Very thin cortex (white line on x-ray)
Loss of trabeculae
Insufficiency fractures (normal stress on ABNORMAL bones)

Question 7

Where are the common sites of insufficiency fractures?

Answer 7

Sacrum
Underside of femoral neck
Vertebral bodies
Pubic rami

Question 8

What would Imaging of insufficiency fractures look like?

Answer 8

X-ray/CT - Increased density around fracture (show as white)
MRI - increased bone density (T1 MRI bone is darker)
Bone scan - increased osteoblast activity

Question 9

How do you interpret bones on a T1 MRI?

Answer 9

Fat = bright white

Inside of bones should normally be white because bone marrow contains fat

Question 10

What happens to bones in osteomalacia

Answer 10

Reduce mineralisation of bone

Looser’s zone (too much unmineralised bone)

Question 11

Radiology of osteomalacia?

Answer 11

Osteopenia
Looser’s zones
Bending deformities
Codfish vertebrae

Question 12

What are Looser’s zones?

Answer 12

Similar to insufficiency fractures

Short lucent lines with irregular sclerotic margins

Question 13

What are codfish vertebrae

Answer 13

Fish shaped (biconcave) vertebrae
Occurs in both osteoporosis and osteomalacia

Question 14

Radiological signs of rickets?

Answer 14

Fraying + Cupping of metaphysis
Enlargement of anterior ribs
Osteopenia
Bent bones

Question 15

Main difference between primary and secondary hyperparathyroidism

Answer 15

Primary = Bone resorption
Secondary = Bone resorption AND increased density

Question 16

Radiology of hyperparathyroidism?

Answer 16

Cortex not a sharp, crisp line (indicates subperiosteal bone resorption)
Can also get brown tumours, but difficult to diagnose with just radiology so you need clinical history

Question 17

Radiology of renal osteodystrophy?

Answer 17

Same signs as osteomalacia/osteoporosis
PLUS signs of secondary hyperparathyroidism:
- Subperiosteal erosions
- Brown tumours
- Rugger jersey spine (increased density at endplates of vertebrae while decreased density in the middle)
- Soft tissue calcification at vessels/cartilages in joints

Question 18

Radiology of Paget’s?

Answer 18

Thickening of cortex
Bone gets bigger
Coarsening of trabeculae (denser)
Osteolytic, mixed and osteosclerotic lesions
Osteoporosis circumscripta cranii (focal lytic lesions of skull bone)

Question 19

Key feature of Paget’s?

Answer 19

Only affects ONE BONE, doesn’t affect adjacent bone

If adjacent bone is affected it probably isn’t Paget’s