Metabolic Bone Disease: Radiology

Question 1

principle issue in osteoporosis

Answer 1

decreased bone mass or density

Question 2

principle issue in osteomalacia and rickets

Answer 2

defective mineralisation

Question 3

what form of hyperparathyroidism accompanies chronic renal def?

Answer 3

secondary hyperparathyroidism

Question 4

what is the radiological sign seen in both osteoporosis and osteomalacia?

Answer 4

Osteopenia – “poverty of bone” – reduced mineral content of bone (not as bad as osteoporosis).

Question 5

what is osteosclerosis?

Answer 5

Osteosclerosis – abnormal hardening of bone and increased bone density.

bone formation that occurs after bone resorption

Question 6

what radiological tools are used for bone density assessment?

Answer 6

X-ray
CT
bone densitometry

Question 7

what radiological tool is used for assessment of biochemical composition of bone?

Answer 7

MRI

Question 8

what radiological tool is used for bone turnover assessment?

Answer 8

radionuclide bone scan

Question 9

what are the properties of osteoporotic bones?

Answer 9

o Decreased bone mass, microstructure normal.
o Normal biochemistry and microstructure
o Fragility fractures, deformity and pain common.

Question 10

what does white in X-ray mean?

Answer 10

the whiter the bone, the denser

Question 11

what is the biochemistry in osteomalacia?

Answer 11

o Biochemistry – low VitD, low/normal Ca2+, high PTH.

o Inadequate/Delayed mineralisation of bone.

Question 12

what is the result of low mineralisation?

Answer 12

osteopenia

soft bones bend and deform

Question 13

what is the result of too much osteoid?

Answer 13

looser’s zones and fractures (pseudo fractures )

these appear with narrow lucency and are perpendicular to bone cortex

Question 14

where do Looser’s Zone fractures happen most of the time?

Answer 14

pubic rami
proximal femur
scapula
lower ribs.

Question 15

what are the ranges in T score and the resulting pathology?

Answer 15

-1.5 to -2.5 –> osteopenia

< or = -2.5 –> osteoporosis

Question 16

example of radiological finding in osteomalacia vertebrae

Answer 16

codfish vertebrae

• biconcave loss of height
• osteopenia
• pencilled in margin

Question 17

what are the bone features of osteoporosis?

Answer 17

• reduced cortical bone
• thinning of cortex
• reduced trabecular
• insufficiency fractures under normal stresses on abnormal bone
• osteopenia
• anterior wedging

Honda sign shows greater uptake in the pelvis
Bone oedema on MRI

Question 18

what are the bone features of osteomalacia?

Answer 18

• decreased mineralisation
• Looser’s zones at areas of higher tensile stress
• sclerotic margins (attempted bone healing thickens bone around fracture line)
• bending and bowing before breakage
• rickets centred in growth plates
• codfish vertebrae (uniform spine deformity)

Question 19

how does osteomalacia differ to rickets?

Answer 19

osteomalacia: in mature bone
sees the normal features e.g. codfish vert, LZ, osteopenia

rickets: changes before growth plate closures i.e. in children is dominates the growth plates. Osteomalacia changes can co-exist

Question 20

what does radiological imaging of osteomalacia/rickets depend on?

Answer 20

age and closure of growth plates

Question 21

which part of the bone shows the most obvious changes in rickets and why?

Answer 21

metaphysis as this area has the most rapid growth

Question 22

what are the bone features of rickets?

Answer 22

o Frayed metaphyseal margin – so metaphysis is indistinct.
o Widened growth plate (no calcification).
o Splaying/cupping metaphyses due to weight bearing.
o “Rickety Rosary” – enlargement of anterior ends of ribs.
o Bowing of weight-bearing legs.
o Osteopenia.

Question 23

what are the types of hyperparathryoidism?

Answer 23

o Primary – PTH adenoma.
 High PTH, high Ca, low phosphate.

o Secondary – Vitamin D deficiency (renal failure, low light, impaired liver, etc.).
 High PTH, low/normal Ca, low/normal phosphate.

o Tertiary – autonomous production of PTH.
High PTH, high Ca, low phosphate (no negative feedback)

Question 24

what occurs in bone in primary hyperPTism?

Answer 24

bone resorption therefore hypercalcaemia

Question 25

what occurs to bone in secondary hyperPTism?

Answer 25

renal osteodystrophy e.g. sub-periosteal erosion as a result of chronic renal def

leads to resorption/ increased density

Question 26

what are the forms of bone resorption?

Answer 26

o Sub-periosteal – affects radial aspect of middle and ring finger phalanges.
o Sub-chondral.
o Intra-cortical.
o Brown tumours.

Question 27

what forms of bone loss are there?

Answer 27

o Slow – involutional osteoporosis. Bone has time to remodel (bone loss occurs due to mechanical needs).

o Fast – HPT, disuse osteoporosis. Bone loss is too rapid and loss does not cater to mechanical needs.

Question 28

what are the radiological signs of renal osteodystrophy?

Answer 28

o Osteomalacia and osteoporosis.

o Secondary hyperparathyroidism features.

Question 29

what are the main secondary hyperparathyroidism features?

Answer 29

Sub-periosteal erosions, brown tumours.

Sclerosis – axial skeleton, vertebral end-plates and “Rugger Jersey” spine.

Soft-tissue calcification (extra-skeletal calcifications such as in arteries).

Question 30

what are the mediators of bone metabolism?

Answer 30

Ca, phosphate, Vit D, PTH, calcitonin.

Question 31

what are the hormones and factors that mediate bone metabolism?

Answer 31

hormones – T4, GH, glucocorticoids, oestrogens, androgens, insulin.

factors – Vit C, cytokines, prostaglandins, growth factors.

Question 32

what are the bone features of Paget’s?

Answer 32

• Cortical thickening
• Bone expansion
• Coarsening of trabeculae
• Osteolytic, osteoclerotic and mixed lesions
• Osteoporosis circumscripta
• Bone pain, deformity, spontaneous fractures
• May get nerve entrapment, spinal stenosis
• deafness
• Osteogenic sarcoma
• Raised serum alk phos, urinary hydroxyproline, pyridinoline cross-links