fracures through the ages lecture - (osteoporosis etc.)

Question 1

effect of age on trabeculae

Answer 1

thick, high density trabeculae when young, but as get older they get thinner and become more fragile

Question 2

composition of bone

Answer 2

matrix (organic: type 1 collagen, mucopolysaccharides, non-collagenous proteins; inorganic (hydroxyapatite: calcium, phosphorus) and cells (osteoprogenitor, osteocyte, osteoblast, osteoclast)

Question 3

function of inorganic bone

Answer 3

Ca2+ reservoir

Question 4

what can bone cells (10% of bone) respond to

Answer 4

hormones and other EC signals

Question 5

normal bone turnover

Answer 5

amount reabsorbed by osteoclasts = amount laid down by osteoblasts

Question 6

reason for bone turnover

Answer 6

replenished as otherwise more susceptible to fracture

Question 7

what happens to bone turnover in osteoporosis

Answer 7

osteoclasts predominate, so more bone reabsorbed than is laid down (increase risk of fracture)

Question 8

what measures bone density to give likelihood of fracture, and consequence

Answer 8

DEXA scan (score compares to same ethnicity but peak bone mass age), but doesn’t give information on health of bone (e.g. strength of trabeculae)

Question 9

what measures bone density to give likelihood of fracture, and consequence

Answer 9

DEXA scan, but doesn’t give information on health of bone (e.g. strength of trabeculae)

Question 10

how do bisphosphonates work, and consequence

Answer 10

kill osteoclasts (half life of 7 years) to prevent bone reabsorption, but no turnover of bone so bone may get microcracks, causing atypical fractures e.g. of shaft cortex which can’t heal due to long bisphosophonate half-life

Question 11

who are more susceptible to osteoporosis

Answer 11

post-menopausal women (less protective effect of oestrogen), amputees (Wolff’s law - socket means it don’t load bone properly, and lost muscle insertion and pulling)

Question 12

treatment for osteoporosis in amputees

Answer 12

not bisphosphonates as local, so exercise etc. to increase bone loading locally

Question 13

alternative to bisphosphonates which is more specific

Answer 13

demosumab, which binds to RANKL to prevent upregulation of osteoclasts

Question 14

fracture location with high mortality

Answer 14

neck of femur (generally associated with other medical problems in elderly)

Question 15

why is exercise good for osteoporosis

Answer 15

Wolff’s law, as it stimulates bone lay-down (e.g. loaded deep flexion)

Question 16

when is Ca2+ at maximum capacity, and consequence of Ca2+ on osteoporosis

Answer 16

when children (hence drinking milk etc.), and this affects osteoporosis later on (e.g. bone cleaved when need Ca2+, so higher risk of osteoporosis if less Ca2+ reservoir when child)

Question 17

3 major signalling molecules of calcium homeostasis

Answer 17

vitamin D (increase Ca2+), PTH (increase Ca2+) and calcitonin (decrease Ca2+)

Question 18

2 ways fractures heal

Answer 18

surgical, callous

Question 19

describe surgical fracture healing

Answer 19

if two broken bones held directly together using plate or rod, bone can directly join across

Question 20

describe 4 stages of callous fracture healing

Answer 20

week 1: blod pouring in to fracture to form haematoma, contained by soft tissue either side -> week 2-3: soft callus as cartilage laid down to improve stability -> week 4-16: cartilage becomes calcified to turn into woven (disorganised) bone so less strong -> week 17+: Wolff’s law as disorganised bone gets loaded, so forms cortical and trabeculae bone (excess bone reabsorbed by osteoclasts)

Question 21

age at which bone fracture is fastest

Answer 21

when baby/young child

Question 22

injuries causing different fracture patterns: spiral

Answer 22

twisting torsional injury

Question 23

injuries causing different fracture patterns: oblique diagonal

Answer 23

compression injury

Question 24

injuries causing different fracture patterns: butterfly fragment

Answer 24

direct hit injury

Question 25

injuries causing different fracture patterns: completely transverse

Answer 25

pulling tension injury

Question 26

what is a fracture

Answer 26

soft tissue injury with underlying discontinuity of bone

Question 27

what is a greenstick fracture in children, and why it is easier to treat

Answer 27

breaks on one side, bends on the other (thick periosteum), so easier to treat as in continuity