bone growth and fracture healing

Question 1

Describe bone growth

Answer 1

We start of with long bones as a hyaline cartilage model

Then it gets a primary ossification centre which allows it to grow and then further secondary ossification centres at each end

A medullary cavity is formed as the bones continues to grow

Epiphyseal plate forms at the end of the long bone which allows it to grow until it is closed at the end of puberty

The long bone at the very right of the image has articular cartilage which is hyaline

Spongy bone is present in the metaphysis which is shock absorbing

In the diaphysis there is the medullary cavity, compact bone and then periosteum on the outside

Question 2

What is the diaphysis

Answer 2

the shaft of long bone

Question 3

What is mataphysis

Answer 3

flare at the end of the shaft on either end

Question 4

What are the properties of cortical bone

Answer 4

Mainly seen in diaphysis

Resists bending and torsion

It is laid down circumferentially and is less biologically active so it is slow growing

Question 5

What are the properties of cancellous bone

Answer 5

It lies in the metaphysis and resists/ absorbs compression (shock absorber)
It is very biologically active due to getting micro-injured a lot
It is the site of longitudinal growth

Question 6

What is a fracture

Answer 6

break in the structural continuity of bone - can be a crack, break, split, crumpling or buckle

Question 7

what is the shorthand sign for a fracture

Answer 7

#

Question 8

What causes a bone to fracture

Answer 8

High energy transfer - requires a lot of energy

Repetitive stress in the bone - stress fracture

Bone disorders which require less energy to cause damage:
Osteoporosis
Osteomalacia, metastatic tumour

Question 9

What is different about regenerative process of fracture

Answer 9

There is no scar
Bone is replaced by original structure that was there before the break occurred

Question 10

Describe stage 1of regenerative process of fracture

Answer 10

Inflammation - Haematoma and fibrin clot is released into the area which causes platelets, neutrophils, monocytes and macrophages to be releases - local areas of cell death release lysosomal enzymes which brings in new cells to initiate repair and then angiogenesis to provide a blood supply

Question 11

What cells repair the fracture in stage one

Answer 11

Fibroblasts, mesenchymal and osteoprogenitor cells

Question 12

What drug shouldn’t be given with fractures

Answer 12

NSAIDS - reduces the inflammation which reduces the ability to repair the fracture

Question 13

What can reduce the effectiveness of stage 1 - inflammation

Answer 13

NSAIDS - antiinflammatory

Loss of haematoma - open fracture and surgery where the blood is lost

Extensive tissue damage where there is poor blood supply

Question 14

What can be done to aid the fracture repair stage one (inflammation)

Answer 14

Platelet concentrates are used - platelet derived growth factor, transforming growth factor-beta, Insulin like growth factor and vascular endothelial growth factor which all bring in cells and blood vessels to the site of fracture

Question 15

When does stage 2 of fracture occur

Answer 15

When the pain and swelling subside

Question 16

What is the name of stage 2 of fracture repair

Answer 16

soft callus

Question 17

When happens in stage 2 (soft callus) fracture repair

Answer 17

It lasts until the bony fragments are united by cartilage or fibrous tissue
It provides some stability
Angulation can still occur due to soft tissue holding the bone together \The vascularity remains increased throughout

Question 18

How can we help stage 2 (soft callus) of fracture repair

Answer 18

Replace the cartilage - demineralised bone matrix which is essentially chopped up soft callus

Or a bone graft or bone substitute can be put in place of the callus in between the bone fragments

Question 19

What is the gold standard bone graft

Answer 19

Autogenous cancellous (spongy) bone graft - cancellous bone scooped out of patient - normally from the iliac crest

It is osteoconductive - allows cells to grow through it to create bone

It is osteoinductive - has many factors in it which can be used for bone production

Question 20

What is allograft bone and what are its properties

Answer 20

Bone which is grafted from someone else and can be used - it is osteoconductive but not osteoinductive - bone slowly replaces it but there is a risk in the transmission of disease

Question 21

What happens in stage 3 (hard callus)

Answer 21

Conversion of cartilage into woven bone

There is an obvious callus seen on X-ray

It increases rigidity

Question 22

What happens in stage 4 of fracture healing (bone remodelling)

Answer 22

Conversion of woven bone into lamellar bone
The medullary canal is reconstituted
The bone responds to loading characteristics through Wolff’s Law - Where it needs to be thick, it thickens and where it needs to be thin, it thins out

Question 23

What is the difference between adults and children for remodelling

Answer 23

Children bone remodelling is back to normal while adult remodelling has some swelling or change to the bone

Question 24

What is delayed union

Answer 24

A fracture fails to heal in the expected time

Question 25

What causes delayed union

Answer 25

High energy injury
Distraction - far distance between the ends of the fracture
Instability
infections
steroids and immune suppressants
warfarin NSAIDS and ciprofloxacin

Question 26

What is non union

Answer 26

Failure of fracture to heal