Musculoskeletal 2 - The radiology of Metabolic Bone Disease

Question 1

Name 3 imaging methods used to measure bone density

Answer 1

1. X rays
2. CT
3. Bone densitometry

Question 2

What does MRI determine

Answer 2

Biochemical composition of bones

Question 3

What do radionuclide bone scans determine

Answer 3

Bone turnover

Question 4

Very dense things (e.g. bone) are what colour on X rays / CT?

Answer 4

White

Things like fat etc are darker

Question 5

In MRI, what colour does fat show up as?

Answer 5

White

Question 6

What 2 things does imaging enable us to do?

Answer 6

1. Reveal structural failures

2. Serves as proxy to metabolic dysfunction

Question 7

How is osteoporosis diagnosed?

Answer 7

Use a DEXA scan

T score from -1.5 to -2.5 is osteopenia

Less than -2.5 = osteoporosis

Question 8

Before DEXA, check radiological signs of osteoporosis, which include?

Answer 8

1. Loss of cortical bone (outer white line)
2. Loss of trabeculae
3. Insufficiency fractures - stress fracture due to normal stress on abnormal bones

Question 9

Name 4 areas prone to getting insufficiency fractures

Answer 9

1. Sacrum
2. Underside of femoral neck
3. Vertebral bodies
4. Pubic rami

Question 10

How may insufficiency fractures show on different imaging modalities?

Answer 10

XR/CT : periosteal reaction and callus (rare), increased sclerosis around fracture lines (common)

MRI: bone oedema

Bone scan: increased osteoblastic activity

Question 11

Osteomalacia = osteopenic, soft bones, caused by decreased bone mineralisation. What is also common in osteomalacia

Answer 11

Loosers zone - caused by too much unmineralised osteoid

Question 12

What may osteomalacia result in if calcium stays low?

Answer 12

Secondary hyperparathyroidism

Question 13

Radiologically, how may osteomalacia signs differ in adults and children

Answer 13

In adults - codfish vertebrae, bending deformities etc

In children (rickets) - occurs before growth plate closure - radiological signs are centred mainly to growth plates

Question 14

Where are common areas for Loosers zones?

Answer 14

1. Medial proximal femur
2. Lateral scapula
3. Pubic rami
4. Posterior proximal ulna
5. Ribs

Loosers zone = irregular sclerotic margins

Question 15

What are codfish vertebrae

Answer 15

Biconcave appearance of vertebrae - seen in osteoporosis and osteomalacia

Question 16

What is a giveaway sign of rickets?

Answer 16

Cupping of metaphysis - in femur, ulna, etc

Anterior rib may also be enlarged

Question 17

What are the differences in primary and secondary hyperparathyroidism in terms of bone

Answer 17

Primary hyperparathyroidism = bone resorpton

Secondary hyperparathyroidism = bone resorption and increased density

Question 18

What are causes of primary and secondary hyperparathyroidism

Answer 18

primary - due to parathyroid adenoma. High PTH, low Ca and PO3

secondary - CKD, rickets/osteomalacia. High PTH, low CA, low/normal PO3

Question 19

Where are common sites of bone resorption - sign of primary/secondary hyperparathyroidism

Answer 19

1. Subperiosteal
2. Subchondral
3. Intracortical
4. Brown tumours

Question 20

What are the features of renal osteodystrophy

Answer 20

1. Osteomalacia and osteoporosis

2. Secondary hyperparathyroidism - superiosteal erosions, brown tumours, sclerosis, soft tissue calcification

Question 21

Rubber jersey spine, what is it a feature of?

Answer 21

Renal osteodystrophy.

The end plates have increased density but the middle has reduced density

It is a sign of sclerosis, which is a feature of renal osteodystrophy

Question 22

What is Paget’s disease and what are the stages?

Answer 22

It is a disease of bone remodelling.

3 stages:

1. Lytic phase
2. Mixed lytic/sclerotic phase
3. Sclerotic phase

Question 23

What are the symptoms of Pagets

Answer 23

Bone pain, deformity, spontaneous fractures.

Nerve entrapment, spinal stenosis and deafness

Osteogenic sarcoma

Raised serum alkaline phosphate, urinary hydroxyproline, pyridinoline cross links

Question 24

What are the radiological features of Pagets

Answer 24

1. Cortical thickening
2. Bone expansion
3. Trabeculae coarsening
4. Osteolytic, osteosclerotic and mixed lesions
5. Osteoporosis circumscripta