week 7- Bone Pathology, Fracture And Healing

Question 1

Name the types of bones?

Answer 1

Long bone (humerus)
Flat bone (sternum)
Irregular bone (vertebra)
Short bone (talus)
Sesamoid (patella)

Question 2

Structure of long bone- description of the diaphysis?

Answer 2

Shaft of a long bone

Question 3

Structure of a long bone- description of the periosteum?

Answer 3

Thin vascular dense connective tissue on outside surface of bone (ex hyaline cartilage). Provides attachment for muscles, tendons and ligaments
Contains osteoblasts and osteoclasts and blood vessels

Question 4

Structure of long bone- description of perforating fibres (sharpey )

Answer 4

Connective tissue consisting of bundles of strong mainly type 1 collagen fibres connecting periosteum to bone

Question 5

Structure of bone- description of the epiphysis?

Answer 5

Found at the end of a long bone, mainly compound of cancellous bone

Question 6

Structure of long bone- description of epiphyseal line?

Answer 6

Bone formed inside the epiphyseal plate when bone is fully grown

Question 7

Structure of long bone- endosteum description?

Answer 7

The inner membrane within the medullary cavity. Contains cells essential for bone formation and repair

Question 8

Structure of long bone- description of yellow marrow?

Answer 8

Storage of fats in cells called adipocytes (energy source as needed). Contains mesenchymal stem cells- differentiate into bone, fat, cartilage cells

Question 9

Structure of long bone- description of red marrow?

Answer 9

In medullary cavity, functions to create red blood cells, white blood cells and platelets

Question 10

Describe the microscopic anatomy of bone?

Answer 10

Composed of pieces of bone= trabeculae
Open spaces filled by marrow,blood vessels and nerves

Compact bone- mature bone cells (osteocytes) found in tiny cavities (lacunae)

Lacunae arranged in concentric circles around central canals called lamellae

Osteon complex consists of central canal and matrix rings

Question 11

Osteoclasts function?

Answer 11

Cells that absorb old bone, bone remodelling

Question 12

Osteoblasts function?

Answer 12

Cells that make new bone, pump cells, move calcium in/out bone, growth portions of bone (periosteum)

Question 13

Osteocytes function?

Answer 13

Mature osteoblasts, homeostatic function, stabilise matrix, located in lacunae and connected to each other by thin processes called canaliculi

Question 14

Bone growth- endochondral ossification, stage one?

Answer 14

Formation of bone collar around hyaline cartilage model

Question 15

Stage two of bone growth?

Answer 15

Cavitation of the hyaline cartilage within the cartilage model

Question 16

Stage three of bone growth?

Answer 16

Invasion of internal cavities by the periosteal bud and spongy bone formation

Question 17

Stage 4 of bone growth?

Answer 17

Formation of the medullary cavity as ossification continues, appearance of secondary ossification centres in the epiphyses

Question 18

Stage 5 of bone growth?

Answer 18

Ossification of the epiphyses when completed hyaline cartilage remains only in the epiphyseal plates and articular cartilages

Question 19

What is appositional growth?

Answer 19

Process by which bones grow in diameter

Question 20

Bones remodelled in response to changes in:

Answer 20

1. Calcium ion level in the blood-
   Low calcium ion level causes PTH release into blood
   PTH activates osteoclasts to break down bone matrix and release Ca ions into blood
   Ca ions levels too high= Ca deposited in bone matrix as hard calcium salts
2. The pull of gravity and muscles on skeleton -
   Stresses on the bone cause osteoblasts to lay down new matrix
   Become trapped turn into osteocytes (mature bone cells)

Question 21

What is Wolfe’s law?

Answer 21

Calcium is laid down in response to stress
Increased physical stress causes bone to respond by increasing the density of the bone matrix
Areas subject to most mechanical stress become stronger
Bone will adapt to the stress placed upon it

Question 22

What are the common clinical features of fracture?

Answer 22

Pain 
Heat/ redness 
Swelling 
Loss of function 
Muscle spasm 
Abnormal movement 
Deformity
Neurovascular changes

Question 23

What other soft tissue damage are sustained along with a fracture?

Answer 23

Periosteum 
Muscle 
Tendon 
Nerves
Major blood vessels 
Capillaries 
Viscera

Question 24

Bone healing stage 1?

Answer 24

Formation of fracture haematoma within 6-8 hours

Phagocytes and osteoclasts remove dead and damaged tissue over several weeks

Closed fracture- haematoma usually constrained by periosteum. When periosteum is torn haematoma is extravasted into soft tissues

Question 25

Stage 2 of bone healing?

Answer 25

Soft granulation tissue known as soft callus forms at fracture site within days.
Capillaries invade the site.
Fibroclasts from the periosteum produce collagen fibres to span the break, some of which differentiate into chondroblasts to secrete intercellular matrix, which become impregnated with calcium salts

At this stage repair is known as fibrocartilaginous callus- 3 weeks following fracture. Osteoblasts form spongy bone throughout the fibro-cartilaginous mass between bone ends. This serves to immobilise the bone ends

Question 26

Stage 3 of bone healing- bony callus formation?

Answer 26

In well vascularised bone tissue osteogenic cells develop into osteoblasts to produce spongy bone trabeculae
The fibrocartilage is converted to spongy bone along lines of stress
Bong (hard) callus occurs and forms union after 2-4 months

Question 27

Stage 4 of bone healing- bone remodelling?

Answer 27

Bone remodelling occurs within the diaphysis and medullary cavity to give the appearance of original bone
Excess callus in medullary cavity and on outside of callus is reabsorbed to regain the normal line of the bone
Compact bone is laid down to form the outer walls of the bone, thus bone is restored to original structure

Question 28

Types of fracture?

Answer 28

Greenstick/hyaline- children due to soft bone, results from direct trauma 
Disruption on 1 side of bone and deformity on other 
Spiral - result of twisting moment 
Transverse- break at a right angle 
Oblique 
Stress 
Epiphyseal 
Comminuted 
Avulsion

Question 29

Factors that affect the speed of union?

Answer 29

Vascularity of bone tissue

Lack of mobility of bone ends

Interposition of soft tissue within the fracture remodelling site

Malnutrition and metabolic factors

Question 30

What is malunion and non-union?

Answer 30

Malunion- failure of the bones to unite aligned

Non-union- failure of the ends of the bone to unite