chapter 21 - metabolic bone disease Flashcards

1
Q

name the 3 main groups of metabilic bone disease

A

osteoporosis
osteomalacia
osteitis fibrosa

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2
Q

define osteoperosis

A

abnormal decrease in bone mass per unit volume

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3
Q

mechanism of osteoperosis

A

low bone mass –> subsequent resorption –> increased bone fragility + increased tendency to fracture

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4
Q

what is the cause of primary osteoporosis

A

post menopausal osteoporosis

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5
Q

rate of bone loss post menopause relative to before?

A

pre: 0.3% per year
post: 3% per year

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6
Q

how does menopause affect the bones?

A

decreased estrogen - therefore increased osteoclastic activity

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7
Q

risk factors for primary osteoporosis - 6

A
caucasian
hereditary
premature menopause
early hysterectomy
smoking
alcohol abuse
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8
Q

clinical features of primary osteoporosis -3

A

back pain
thoracic kyphosis
fracture of distal radius - often initial event

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9
Q

3 investigations for the diagnosis of osteoporosis

A

xray
dexa scan
bone turn over and biochemical tests - usually normal

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10
Q

xray features of osteoporosis

A

wedging of vertebral bodies
end plate collapse
loss of normal trabecular pattern of bone

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11
Q

treatment of osteoporosis

A
  1. prevention: normal diet + atleast 1500mg ca per day from 20 yrs of age
  2. avoid RF
  3. HRT
  4. calcitonin or bisphosphonates if HRT CI
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12
Q

most effective therapy for osteoporosis

A

HRT

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13
Q

why must you monitor patients on HRTs ?

A

slightly increased risk of breast and uterine cancer

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14
Q

what is senile osteoporosis?

A

15 yrs after menopause and at the same age in men there is still a 0.5% decline in bone mass per year –> may lead to increased fractures from minor trauma

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15
Q

RF for senile osteoporosis

A
prolonged menopausal bone loss
chronic illness
urinary insufficiency
muscular atrophy
dietary deficiency
lack of exposure to sunlight
increased tendency to fall
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16
Q

typical fracture found in patients with senile osteoporosis

A

fracture of femoral neck of minor trauma

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17
Q

treatment of senile osteoporosis

A
  1. manage fracture
  2. optimise medical condition
  3. sodium fluoride + vitamin D may increase bone mass
  4. bisphosphonates may minimise further loss
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18
Q

causes of secondary osteoporosis - 6 broad groups

A
nutritional 
endocrine
drug
malignant disease
non malignant disease
other
19
Q

nutritional causes of secondary osteoporosis 3

A

scurrvy
malnutrition
malabsorption

20
Q

4 endocrine causes of secondary osteoporosis

A

hyperparathyroidism
gonadal insufficiency
cushings disease
thyrotoxicosis

21
Q

4 drug induced causes of 2 osteoporosis

A

corticosteroids
alcohol
nicotine
heparin

22
Q

3 malignant diseases causing secondary osteoporosis

A

carcinomatosis
leukemia
multiple myeloma

23
Q

4 non malignant diseases causing secondary osteoporrosis

A

rheumatoid arthritis
ankylosing spondylitis
tuberculosis
chronic renal disease

24
Q

other causes of secondary osteoporosis 2

A

weightlessness - space workers

immobilisation

25
Q

what is the mechanism of rickets and osteomalacia?

A

inadequate mineralisation of bone

26
Q

which population presents with rickets ?

A

children

27
Q

which population presents with osteomalacia?

A

adults

28
Q

which areas are affected in rickets

A

areas of endochondral growth

29
Q

which areas are affected in osteomalacia?

A

areas of new bone in the skeleton is incompletely calcified and structurally weak

30
Q

3 reasons for inadequate bone mineralisation

A
  1. calcium deficiency
  2. hypophosphataemia
  3. aberrant metabolic pathway for vitamin D
31
Q

5 causes of aberrant metabolic pathway for vitamin D

A
  1. nutritional
  2. lack of sunlight
  3. intestinal malabsorption
  4. decreased 25 hydroxylation - liver disease/ anticonvulsants
  5. reduced 1 alpha hydroxylation - renal disease
32
Q

8 clinical features of rickets

A

1 failure to thrive
2 tetany, convulsions
3 muscular flaccidity
4 deformity of skull - craniotabes
5 thickening of ankles knees and wrists from epiphyseal overgrowth
6 enlargement of costachondral junctions - rickety rosary
7 lateral indentation of chest - harrisons sulcus
8 bow legs, coxa vara, spinal deformtiy, fractures of long bones

33
Q

what is craniotabes?

A

skull deformity in rickets

34
Q

what is rickety rosary

A

enlargement of costachondral junctions

35
Q

what is harrisons sulcus

A

lateral indentation of chest

36
Q

4 clinical features of osteomalacia

A

more insidious than rickets
bone pain
weight loss
stress or insufficiency fracture

37
Q

radiological features of rickets 2

A

thickening and widening of the growth plate

bowing of the diaphysis

38
Q

radiological features of osteomalacia 3

A

looser zone
biconcave vertebrae
trefoil pelvis

39
Q

what is the loosers zone?

A

a transverse band of rarefaction in an otherwise normal bone - osteomalacia

40
Q

what is trefoil pelvis?

A

lateral indentations into the pelvis by the acetabulae - osteomalacia

41
Q

biochemistry of rickets and osteomalacia

A
  • decreased serum calcium and phosphate
  • increased alkaline phosphatase
  • diminished urinary excretion of calcium
  • in vitamin D deficiency 25 HCC levels are low
  • diminished calcium phosphate product ( < 2.4mmol/l)
42
Q

which value of calcium phosphate product is diagnostic for rickets and osteomalacia

A

< 2.4mmol/l

43
Q

in some cases of rickets and osteomalacia another investigation is needed - what is this ?

A

bone biopsy