Metabolic bone disease: Radiology

Question 1

Purpose of bones

Answer 1

mechanical/structural function

Metabolic function as a reservoir/buffer for calcium and phosphates

Question 2

why is imaging useful for bones?

Answer 2

haematopoeisis) Imaging can:

- Reveal structural failures such as fractures and ligamentous injuries - Also serves as proxy to metabolic dysfunction

Question 3

types of imaging available:

Answer 3

X-rays 
CT  
Bone densitometry 
MRI  
Radionuclide bone scan

Question 4

what is X ray, CT and bone densitometry used for?

Answer 4

density

Question 5

what is MRI used for

Answer 5

biochemical composition

Question 6

what is radionucleotide bone scans used for?

Answer 6

bone turnover

Question 7

difference between pathology and radiological sign

Answer 7

Pathology 
-A disease process that gives rise to symptoms, signs, biochemical disturbances and changes in imaging appearance. 

Radiological sign 
-A change in imaging appearance, whether structural or functional, that may point towards a pathology

Question 8

what is osteoporosis?

Answer 8

Decreased quantity of bone mass  Microstructure normal Fragility fractures  Deformity 
Pain

Question 9

how do you diagnose osteoporosis?

Answer 9

 Diagnosis is with bone densitometry (aka dual-energy absortiometry, DEXA)  A measure of bone mineral density (BMD)  Compares BMD to normal reference databases and gives ▪ T-score (ref database white adult premenopausal females) ▪ Z-score (ref database age and sex matched)  T-score -1.5 to -2.5 = osteopenia; less than -2.5 = osteoporosis

Question 10

what do you see in a radiology of a patient with osteoporosis?

Answer 10

Loss of cortical bone/thinning of cortex 

Loss of trabeculae  Insufficiency fractures

Question 11

what is osteomalacia?

Answer 11

Decreased bone mineral 
-Osteopenic bone
- Soft bones 
Too much un-mineralised osteoid:  - Looser’s zone

Question 12

what might be compensatory to osteomalacia?

Answer 12

Compensatory: secondary hyperparathyroidism may be superimposed if calcium stays low

Question 13

biochemistry of osteomalacia?

Answer 13

 Vitamin D deficiency  Biochemistry: vit d low, calc: N/low, PTH up  Inadequate or delayed mineralisation

Question 14

radiological signs of osteomalacia:

Answer 14

Radiology depends on age and closure of growth plate 

Osteomalacia 

• Mature skeleton 
• Osteopenia 
• Looser’s zones 
• Codfish vertebrae
• Bending deformities 

Rickets 

• Before growth plate closure 
• Radiological signs centred mainly to growth plates 
• Changes of osteomalacia

Question 15

what are loser’s zones?

Answer 15

 Pseudo/insufficiency fractures at high tensile stress areas  Medial proximal femur  Lateral scapula  Pubic rami  Posterior proximal ulna  Ribs

Question 16

define insufficiency fractures

Answer 16

Insufficiency fractures are a type of stress fracture, which are the result of normal stresses on abnormal bone.

Question 17

what is codfish vertebrae?

Answer 17

 Biconcave deformity of vertebrae  Seen in  Osteoporosis  Osteomalacia

Question 18

radiological evidence of rickets

Answer 18

 Indistinct/frayed metaphyseal margin  Widened growth plate without calcification  Cupping/splaying metaphyses due to weight bearing  Enlargement of anterior ribs  Osteopenia

Question 19

What are the three types of hyperparathyroidism

Answer 19

 Primary (due to parathyroid adenoma)  PTH up, calc down, phosphate down  Bone resorption 

Secondary (due to other systemic biochemical imbalance, chronic kidney disease, rickets/osteomalacia)  PTH up, calc down, phophate normal or down  Bone resorption AND increased density 

Tertiary (autonomous)  PTH up, calc up, phosphate down

Question 20

signs of bone resorption

Answer 20

Subperiosteal  Subchondral  Intracrotical 

Brown tumours

Question 21

renal osteodystrophy causes

Answer 21

 Osteomalacia and osteoporosis  Secondary hyperparathyroidism  Subperiosteal erosions, brown tumours  Sclerosis – vertebral endplates giving a rugger jersey spine  Soft tissue calcification (vessels, cartilages)

Question 22

what is renal osteodystrophy

Answer 22

Renal osteodystrophy is a bone disease that occurs when your kidneys fail to maintain proper levels of calcium and phosphorus in the blood.

Question 23

what is paget’s disease?

Answer 23

 Disease of bone remodelling  Lytic phase  Mixed lytic/sclerotic phase  Sclerotic phase  Bone pain, deformity, spontaneous fractures  May get nerve entrapment, spinal stenosis and deafness  Osteogenic sarcoma  Raised serum alk phos, urinary hydroxyproline, pyridinoline cross-links

Question 24

radiological signs in paget’s disease

Answer 24

 Cortical thickening  Bone expansion  Coarsening of trabeculae  Osteolytic, osteoclerotic and mixed lesions  Osteoporosis circumscripta