Lecture 1 2102 - Intro To Bones

Question 1

What are the 3 purposes of bones?

Answer 1

• rigid weight bearing structure (ie. bedridden lowers weight bearing ability)
• attachment sites for muscles, tendons and ligaments
• protect vulnerable soft tissues and vascular and nervous

Question 2

Can bones remodel in response to the environment?

Answer 2

Yes, if inactive they weaken, and if active they strengthen

Question 3

What forces can bones withstand?

Answer 3

• compression forces, more than tension or torsion

Question 4

Define a bone

Answer 4

• metabolic active tissue

- subject to continuous turnover with a balance between bone formation (osteoblastic) and bone resorption (osteoclastic)

Question 5

What if there is excessive stress on bone?

Answer 5

• bone failure, as there is more osteoclastic action

Question 6

What is bone remodelling?

Answer 6

• the development of the bone using osteoblasts and osteoclasts

Question 7

What are osteoblasts?

Answer 7

• bone coming cells

- found on surface of the bone

Question 8

What are osteoclasts?

Answer 8

• bone reporting cells

- for growth, maintenance and bone repair

Question 9

What are the layers of the bone?

Answer 9

• spongy (cancellous) bone

- compact bone

Question 10

Explain spongy bone

Answer 10

• gives bones stage the and contains red and brown bone marrow

Red bone marrow is for metastasis

Osteoporosis usually affects spongy bone

It’s the internal layer with lattice work of bone tissue, made of trabeculae

Question 11

Explain compact bone

Answer 11

It’s the external layer “lamellar bones”

Protective with a periosteal covering

Contributes to bone strength also and protection

They are majority of long bones

Question 12

What are the differences between the underlying Conditions that cause a stress or pathological fracture?

Answer 12

Fatigue: form of stress fracture, normal bone but abnormally continuous stress ie. jogging on hard surfaces creates shin splits, thus, micro fractures

Secondary to pre-existing abnormality: form of pathological fracture, abnormal bone as a result of usually a bone tumour. Abnormal to begin with

Insufficiency fractures: both stress and pathological fractures. Cause there’s abnormal bone with a normal stress ie. elderly falling over and fracturing bones like vertebrae

Question 13

How can we say that there is a fracture on the image?

Answer 13

Must visualise a fracture line

Or a loss of bone alignment

Patient needs to move to displace bone fragments

Re Ray in 10 days to make sure

Question 14

What is a MARCHA fracture?

Answer 14

Form of fatigue fracture of diaphysis of 2nd metatarsal

Question 15

What causes a MARCH fracture?

Answer 15

Related force applied to longitudinal arch of foot creates a tensile force to the heads of 2-4 metatarsals. If force is applied for long periods of time

It’s a form of fatigue fracture ….thus, stress

Question 16

Explain a pathological fracture?

Answer 16

Due to a weakened/destroyed trabeculae

Benign bone lesions (eg. lipoma) have clear geographic borders,
malignant tumours have ill defined borders
Metastatic leads to secondary tutors and lyric lesions

Loss of compact bone suggests bone tumour

Can be from breast or lung cancer, etc

Question 17

What are insufficient fractures?

Answer 17

Thinned trabeculae being unable to withstand the compression forces and tensile forces

Ie. tensile forces on lateral aspect of femur will cause compact bone to have micro fractures present and cause bone repair generating a buttressing effect (bone thickening)

Question 18

What is the buttressing effect?

Answer 18

Occurs when there are micro fractures or intrameduallary diseases that exert pressure

Hence, thickening of bone on affected side for stability

Question 19

What are incomplete fractures?

Answer 19

Mostly occur in children

3 forms…:
Bowing - bending of bone as children’s bones bend while developmental stand
Torus - buckling of one cortex, thus, experiencing compression
Greenstick - fracture of one cortex

Question 20

What are complete fractures?

Answer 20

2 types

Simple - complete fracture through bone

Communitive - a fragment of bone residing in the fracture

Question 21

Name the directions fractures can go?

Answer 21

Transverse
Oblique (may not be visible on both projections)
Spiral
Longitudinal (axially applied pressure, usually only occurs in lower body)

Question 22

What’s an impaction fracture?

Answer 22

Occur in long tubular bones ie. femur, lower radius, proximal humerus. Dense line created by the jamming of distal and proximal fragments.

Broken ends of bone are jammed together by force of injury
Ie. fracture of neck of femur can go unnoticed for this reason, therefore blood supply is stunted therefore bone will began to degrade thus medical attention is required

Usually because of a fall

Question 23

What’s a depression fracture?

Answer 23

Ie. blunt force trauma of the skull. Bone forms a depression from force

A force going medially can lead to this ie. car hitting the lateral or medial side of knee

Question 24

What’s a compression fracture?

Answer 24

T

Question 25

What makes an examination inadequate?

Answer 25

Only providing one projection

Question 26

What are the bone regions? Look at power point

Answer 26

``` Order on femur: Articulations hyaline cartilage Epiphysis Epiphyseal plate Metaphysis Diaphysis Peritoseum Medullary cavity Endosteum ```

Question 27

What is the peritoseum?

Answer 27

It is a bone region, external lining of compact bone of diaphysis and metaphysis Dense layer of vascular connective tissue enveloping bones except at surfaces of joints

Question 28

What is the endosteum?

Answer 28

Bone region, a thin layer lining the medullary cavity Thin vascular membrane of connective tissue

Question 29

Explain the salter Harris classification for the extremity fractures

Answer 29

1. Fracture through growth plate 2. Fracture through growth plate and metaphysis 3. Fracture through growth plate and epiphysis 4. Fracture through growth plate, metaphysis and epiphysis 5. Compression fracture through growth plate

Question 30

Explain the endochondral bone formation?

Answer 30

Osteoblasts deposit bone matrix forming spongy bone trabeculae, which develop into compact bone near the external surfaces Middle of bone, osteoclasts breakdown spongy bone trabeculae forming medullary cavity Medullary cavity will have red and yellow bone marrow

Question 31

Explain the age distribution of red and yellow bone marrow?

Answer 31

Age determines the distribution of red and yellow bone marrow As you age the red bone marrow retracts back to the head of humerus (example bone) and yellow takes over

Question 32

Explain the age distribution of bone tumours? Look at supporting graph on slides

Answer 32

Distribution of bone pathologies within long tubular bones that require blood supply or are blood borne vary in terms of age Adults: secondary bone tumours, metastatic deposits in long bones found on proximal humerus or femurs Ie. myeloma, chordoma, osteosarcoma, extraosscous sarcoma, malignant fibrous histiocytoma, metastases. Teenagers: malignant bone tumours located in distal and proximal femur and tibia with the same distribution for humerus Ie Ewing sarcoma, osteosarcoma

Question 33

What happens when a fracture occurs?

Answer 33

Blood clot will form around break (fracture haematoma) causing periosteal elevation Procallus forms (organisation of fracture haematoma into granulation tissue) Collagen and fibrocartilage turns procallus into fibrocartageous (soft) callus Broken bone ends bridged by callus Osteoblasts sand spongy bone formed Callus responses by osteoclasts, compact bone replaced spongy bone, thus bone has been remodelled to original.

Question 34

What is a periosteal elevation/reaction?

Answer 34

Formation of new bone in response to injury or other stimulus of the periosteum Cussed by new bone formation from osteoclasts stimulated by the lift of periosteum Can be due to tumour, pus, haemorrhage, increased vascularity or serum “Occurs when some part wants more blood supply”

Question 35

Why is it important to distinguish periosteal elevation on a radiograph?

Answer 35

Cause it indicates bone injury and bone physiology disruption due to either increased pressure on endosteum (in medullary cavity), periosteum or Parosteal (shrouding the periosteum) Injury to periosteum can lead to acute osteomyelitis or lead to chronic osteomyelitis

Question 36

How does a periosteal reaction look on a central bone tumour? Go ,look at slides

Answer 36

Linear solid structure

Question 37

How does a periosteal reaction look on the parosteal bone tumour?

Answer 37

Not clearly visible There is pressure put on the bone by the tumour therefore bone thinks it’s under threat thus lays down more bone

Question 38

Name and define the type of periosteal reactions due to bone tumour within meduallry cavity? Look at slides

Answer 38

Single layered solid periosteal reaction occurs when bone tumour invades endosteum. Penetrating wound injuring the peritoseum and creates an Acute osteomyelitis (benign lesion) will have a single layer that will become a solid periosteal reaction Lamellated (onion skin) periosteal reaction as a result of multiple reactions occurring within a region Speculated periosteal reaction caused by involvement of sharpey’s fibres

Question 39

How does acute osteomyelitis (benign lesion) look on a radiograph?

Answer 39

Acute osteomyelitis will lead to periosteal reaction, in which it will have a single layer with a mottled bone appearance similar to a malignant tumour

Question 40

What is enchondroma? Look at slides

Answer 40

A benign bone tumour In phalanges, it has a well defined border, expansive lyric lesion with sclerotic (osteoblastic) margin and fine calcification In ulna, an expansive lytic lesion with geographic border and no calcification

Question 41

What are bone islands?

Answer 41

Benign lesions, relativity common and are identified as incidental findings Oriented in direction of trabeculae, ill defined contour and be sclerotic Stress fracture or osteoblastic bone metastasis from breast or prostate cancer similar to bone island