Bone Disease Flashcards
arthritis
inflammation of joints
arthrosis
non inflammatory joint disease
arthralgia
joint pain
3 main features of bone
- load bearing
- dynamic - constantly changing so adaptive
- self repairing
describe bone turnover cycle
bone removed by osteoclasts and deposited by osteoblasts
osteoclasts eat away at bone matrix and are replaced by osteoblasts which deposit osteoid matrix that is mineralised to leave resting bone
cycle takes place over 3-6mths
bone cycling requires what nutrients
calcium
phosphate
Vit D
bone + calcium
bone provides store for Ca, some of which is exchangeable and some which isn’t
Ca moves from bone to ECF and is absorbed from here into the gut
Ca can be lost from gut and urine
involved in nerve & muscle function so must maintain Ca levels at all times
bone & ECF work together with parathyroid hormone to maintain calcium homeostasis
what happens if low dietary Ca detected
reduction in plasma Ca -> increased PTH secretion causes:
- increased active Vit D so intestinal Ca absorption increased
- decreased urinary Ca so conservation of dietary Ca
- increased bone loss so increased bone Ca release
leads to restoration of normal plasma Ca
parathyroid hormone and Ca
maintains serum Ca level; raised if Ca levels fall
increases Ca release from bone
reduces renal Ca excretion
hypoparathyroidism
low serum Ca
hyperparathyroidism
primary - gland dysfunction; potential tumour, high serum Ca results due to inappropriate activation of osteoclasts
secondary - low serum Ca causes activation of osteoclasts
both result in increased bone reabsorption
what causes reduced Vit D synthesis
low sunlight exposure
poor GI absorption i.e. poor nutrition, small intestinal disease - malabsorption
drug interactions - some antiepileptic drugs e.g. carbamazepine, phenytoin
osteoporosis
bone adequately mineralised but not enough bone mass
an age related change that is inevitable
osteomalacia
poorly mineralised osteoid matrix & poorly mineralised cartilage growth plate
during bone formation = rickets
after bone formation = osteomalacia
serum calcium preserved at expense of bone
bone effects of osteomalacia
bones bend under pressure - bow legs in kids / vertebral compression in adults
bones ache to touch
hypocalcaemia effects of osteomalacia
muscle weakness
trousseau & chvostek signs positive - carpal muscle spasm & facial twitching from VII tapping
osteomalacia management
correct cause i.e. malnutrition & control GI disease
sunlight exposure
dietary Vit D
risk factors of osteoporosis
age
female
endocrine - oestrogen & testosterone deficiency, Cushing’s (increased corticosteroid levels in blood)
genetic - family history, race (caucasian/asian), early menopause
patient factors - inactivity, smoking, excess alcohol use, poor dietary calcium
drugs - steroids, antiepileptics
osteoporosis & gender
males have higher peak bone mass
oestrogen lost during menopause so protection it offers is lost
effects of osteoporosis
increased bone fracture risk
height loss
kyphosis - stooping forwards
scoliosis
nerve root compression - back pain
lifetime risk of hip fracture >50yrs
prevention of osteoporosis
- build max peak bone mass - exercise / high dietary Ca intake
- reduce rate of bone mass loss - exercise & Ca intake, reduce hormone related effects i.e. HRT in early menopause
- reduce drug related effects i.e. osteoporosis prevention via bisphosphonates
hormone replacement therapy
oestrogen only - reduces osteoporosis risk but increased breast cancer risk, increased endometrial cancer risk - ptx who have not had a hysterectomy so combine with progestogen to reduce risk, increases DVT risk, may reduce ovarian cancer risk
benefit lost after HRT stops
3 main bisphosphonates prescribed
alendronate
zoledronate
ibandronate
effect of bisphosphonates
act by prevention of osteoclast action by poisoning them & reducing their numbers
reduce vertebral fracture risk by 50%
benefit lost if drug discontinued
can be combined with HRT
risks of bisphosphonates in dentistry
as they interfere with bone resorption by osteoclasts they can inhibit tooth movement, impair bone healing and induce osteonecrosis of the jaw
