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Year 2 - LCRS - Musculoskeletal > Metabolic Bone Disease - Radiology (13.01.2020) > Flashcards

Metabolic Bone Disease - Radiology (13.01.2020) Flashcards

1
Q

Main imaging methods

A

 X-rays
 CT
 Bone densitometry

=> density

 MRI
 Radionuclide bone scans
=> biochemical composition (MRI), bone turnover (RBS)

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2
Q

Radiological sign vs. pathology

A

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

-> not the same thing

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3
Q

Osteoporosis

A

 Decreased quantity of bone mass
 Microstructure normal

  • gives rise to:
     Fragility fractures
     Deformity
     Pain
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4
Q

Radiological diagnosis of osteoporosis

A
  • 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
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5
Q

FRAX

A

fracture risk assessment tool

=> likelihood of major fracture in 10 years time
-> as a practitioner it will also give you guidelines re management

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6
Q

What do you see radiologically in osteoporosis?

A
  • Loss of cortical bone/thinning of cortex
  • Loss of trabeculae
  • Insufficiency fractures (due to normal stress on abnormal bones)
    => not easy to differentiate between osteoporosis and osteomalacia
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7
Q

Insufficiency fractures

A
  • due to normal stress on abnormal bones
  • e.g. in sacrum, underside of femur neck, pubic rami, vertebral bodies
  • XR/CT: density
  • MRI: chemical composition
  • Bone scan: bone turnover. Areas of increased uptake, Honda sign
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8
Q

Osteomalacia

A
  • Decreased bone mineral
    • Osteopenic bone
    • Soft bones
    • Too much un-mineralised osteoid:
      Looser’s zone
  • Compensatory: secondary hyperparathyroidism may be superimposed if calcium stays low
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9
Q

Osteomalacia vs. Rickets (radiology)

A
  • 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
  • Indistinct/frayed metaphyseal margin
  • Widened growth plate without calcification
  • Cupping/splaying metaphyses due to weight bearing (not clean margin, normally it is a very nice clean cut margin; also widened metaphysis)
  • Enlargement of anterior ribs
  • Osteopenia (bending of the bones, soft bones)
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10
Q

Looser’s zones

A

Pseudo/insufficicnecy fractures at high tensile stress areas

  • Medial proximal femur
  • Lateral scapula
  • Pubic rami
  • Posterior proximal ulna
  • Ribs

=> typically short Lucent lines, whiter around the fracture (sclerosis, attempt to lay down new bone)

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11
Q

Codfish vertebrae

A
  • Biconcave deformity of vertebrae (should be a bit concave normally, but these are exaggerated)
  • also, they are larger radiologically
  • Seen in
  • Osteoporosis
  • Osteomalacia
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12
Q

Rickets - radiological features

A
  • Indistinct/frayed metaphyseal margin
  • Widened growth plate without calcification
  • Cupping/splaying metaphyses due to weight bearing (not clean margin, normally it is a very nice clean cut margin; also widened metaphysis)
  • Enlargement of anterior ribs
  • Osteopenia (bending of the bones, soft bones)
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13
Q

Hyperparathyroidism

A
  • Primary (due to parathyroid adenoma)
    • PTH up, calc down, phosphate down
    • Bone resorption
  • Secondary(duetoothersystemicbiochemical 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

Common theme:

  • bone resorption
  • increased density
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14
Q

Bone resorption in HPT

A
  • Subperiosteal
  • Subchondral (e.g. dark gleonoid fossa)
  • Intracrotical (salt and pepper skull)
  • Brown tumours (not a real malignancy, caused by collection of large cells
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15
Q

Renal osteodystrophy

A

-> collection of bone changes in renal disease

Osteomalacia and osteoporosis

Secondary hyperparathyroidism

  • Subperiosteal erosions, brown tumours
  • Sclerosis – vertebral endplates giving a rugger jersey spine (sclerosis of end plate, resorption of middle part of vertebrae)
  • Soft tissue calcification (vessels, cartilages) -> gap between knee and tibia should be dark but: meniscus calcified)
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16
Q

Paget’s disease

A
  • Disease of bone remodelling
    1. Lytic phase
    2. Mixed lytic/sclerotic phase
    3. Sclerotic phase
  • Bone pain, deformity, spontaneous fractures
  • usually one bone, unlikely to jump over joints
  • May get nerve entrapment (because bones expand in the sclerotic phase), spinal stenosis and
    deafness
  • Osteogenic sarcoma
  • Raised serum alk phos, urinary hydroxyproline,
    pyridinoline cross-links
17
Q

Radiological aspects of Paget’s disease

A
  • Cortical thickening
  • Bone expansion
  • Coarsening of trabeculae
  • Osteolytic, osteoclerotic and mixed lesions
  • Osteoporosis circumscripta (in scalp)

=> most patients found in the mixed or in the sclerotic phase.

18
Q

What can radiology show in terms of bones?

A
  • Imaging can reveal structural failures such as fractures and ligamentous injuries
  • Also serves as proxy to metabolic dysfunction
19
Q

What does DEXA stand for?

A

dual energy x-ray absorptiometry

20
Q

Insufficiency fractures - how do they appear on scans?

A

XR/CT: looks at density

  • initially normal
  • later you may get some callus, periosteal reaction
  • more commonly increased sclerosis around fracture lines (you see loosened line and white (sclerosis as an attempt to heal) surrounding it.

MRI: looks at chemical composition
- acute: bone oedema i.e. low signal on T1, high signal in T2 and STIR

Bone scan: looks at bone turnover.

  • increased bone turnover as the bone attempts to heal
  • Areas of increased uptake, Honda sign in stress fractures
21
Q

What does the imaging in osteomalacia depend on?

A
  • on the age and if the growth plates have closed.
22
Q

In which conditions are codfish vertebrae seen?

A
  • osteomalacia

- osteoporosis

23
Q

Conclusion

A
  • Use the right tools for the right pathology
  • Remember bone has a structural as well as a
    metabolic role.
  • Some radiological signs are characteristics
    but many will be common to different pathologies. Thus always start from first principles.
24
Q

When is a salt and pepper skull seen?

A
  • in hyperparathyroidism, brown tumours in the skull
25
Q

rugger jersey spine

A
  • sclerosis of end plate, resorption of middle part of vertebrae
  • center of vertebrae dark, edges are white on XR or CT
  • seen in renal osteodystrophy (here secondary hyperparathyroidism)
26
Q

Mickey Mouse sign

A
  • seen in Paget’s disease on bone scan
  • increased uptake by a single vertebrae
  • when 1 vertebrae is affected
  • thick cortex, coarse trabeculae, bigger

Year 2 - LCRS - Musculoskeletal (10 decks)

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