Fractures through the ages

Question 1

How does bone change before and after birth

Answer 1

before birth: increase in bone

after birth: decrease in bone (trabecular tissue lost….. trabeculae which are not aligned in the load axes are lost)

Question 2

Why is there increase in bone before birth

Answer 2

Bone used in muscle and growth (needed in utero)

When bone tissue is then lost after birth, these nutrients released from bone can then be used for muscle growth etc

=CONSTRUCTIVE REGRESSION

Question 3

…..

Answer 3

…….

Question 4

Makeup of bone

Answer 4

90% matrix = inorganic (most, calcium and hopshorus), organic (collagen, type 1 in bone)

10% cellular (osteoprogenitors, osteoclasts, osteoblasts, osteocyte)

Question 5

What is the ruffled border of the osteoclast

Answer 5

The surface of the osteoclast which secretes enzymes to break down the damaged bone

Question 6

What do mature osteoblasts lay down in bone repair

Answer 6

Inorganic material (matrix) which is subsequently mineralised

Question 7

What is oestrogen responsible for

Answer 7

Osteoclast apoptosis (in menopause osteoclasts won’t apoptose)

Question 8

What happens in old age with remodelling

Answer 8

Less apoptosis of osteocytes so harder for osteoblasts to keep up with oteoclasts and there is an imbalance, reduced bone density

Question 9

Why does bone remodelling need to happens

Answer 9

Because of microfilament fatigue damage (tiny cracks appearing during loading on bone…. osteoclasts come and remove the damaged bone and osteoblasts lay down knew bone matrix)

Question 10

How do bisphosphonates work

Answer 10

They are taken up into the bone in mineralisation

Then te osteoclast will come and try to resorb the bone, but the bisphosphnate is taken up into the ostoclasts and damages the cytoskeleton so that hte ruflfled border of the osteoclast cannot break down the bone

But side effects are fractures too due to microcracks

Question 11

How do osteoclasts form

Answer 11

FROM MACROPHAGES

The osteoblast will then release factors whihc activate RANKL

Question 12

How does denosumab work

Answer 12

It is bound to RANKL on osteoclast (blocking RANK action)

Question 13

3 main types of hip fracture

Answer 13

Hip, vertebral (causing stooping) and distal radial

Question 14

Why is it important to build up bone in youth

Answer 14

To build up bone mass (can afford to lose more when the menopause sets in)

Question 15

Outline stage 1 of fracture healing

Answer 15

Haematoma and inflammation

• Macrophage, leukocytes, IL-6, BMPs
• Granulation tissue forms
• Progenitor cells invade

Question 16

Outline stage 2 of fracture healing

Answer 16

SOFT CALLUS

-Chondroblasts and fibroblasts differentiate and form (collagen II and fibrous tissue)

Question 17

Stage 3 of fracture foration

Answer 17

HARD CALLUS

Soft callus invaded by blood vessels

Chondrocytes break down to calficied callus

Replaced by osteoid (type 1 collagen) from osteoblasts

Osteoid calcifies leading to woven bone

Question 18

Stage 4 of fracture

Answer 18

several years

Remodelling

Lamellarbone

Shape relative to stresses (wolffs law)

medullary canal reforms