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CVSOH BVSc4 > Lame - bone pathology > Flashcards

Lame - bone pathology Flashcards

1
Q

What are the two causes of fracture?

A

Traumatic - normal bone with excessive force
Pathological - abnormal bone with minimal trauma

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2
Q

What are the 3 locations of bone fractures?

A

Growth plate
Trabecular bone
Cortical bone

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3
Q

What do fractures that cross/crush the growth plate cause?

A

Angular limb deformities

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4
Q

What type of fractures of the growth plate are more likely to heal easily?

A

Fractures that involve only the growth plate and primary bone trabeculae

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5
Q

What type of fractures of the growth plate are more likely to cause irreversible damage?

A

Fractures crossing growth plate through metaphysis/epyphisis
Crush of growth plate

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6
Q

What is the first step of fracture repair?

A

Formation of a haematoma around fracture site

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7
Q

What does damage to blood vessels from a fracture cause?

A

Reduced blood flow
Necrosis of bone fragments
Release of growth factors by macrophages from dying bone

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8
Q

What is formed from the haematoma in fracture repair?

A

Soft tissue callus/procallus

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9
Q

How is the procallus formed in fracture repair?

A

Blood vessels proliferate and undifferentiated mesenchymal cells penetrate, forming loose collagenous tissue

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10
Q

What is formed from the procallus in fracture repair? How?

A

A primary callus - metaplasia of the collagenous tissue into cartilage and woven bone

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11
Q

What is the secondary callus made of? What is it?

A

Replaces the primary callus over time with lamellar bone

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12
Q

What does the makeup of the primary callus depend on?

A

Blood an oxygen supply
The poorer the blood and o2 supply, the greater amount of cartilage in a callus - takes bone longer to heal

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13
Q

How does the bone return to its original shape over time?

A

The portions of callus that dont undergo physical stress are reabsorbed over time

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14
Q

What can complicate bone repair?

A

Insufficient bone supply
Instability
Infection poor nutrition

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15
Q

What happens when there is instability during bone repair?

A

Non union - procallus cant mature into bone so forms fibrous tissue instead
Fibrous tissue not strong enough

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16
Q

What can be formed by a non-union of bone due to instability?

A

Cysts
False joints
Pseudoarthritis

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17
Q

What is common in open fractures?

A

Septic bone inflammation/infection

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18
Q

Why is it easier for bacteria to invade under the articular epiphyseal cartilage complex?

A

Capillaries bend sharply to joining veins so there is turbulent blood flow and a discontinuous endothelial lining - easier for bacteria to invade

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19
Q

What pathogens cause osteomyelitis?

A

Almost always bacterial eg. strep, staph, truperella, E. coli

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20
Q

What causes inflammation during osteomyelitis?

A

Bacteria invade
Neutrophils recruited to the site causing inflammation

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21
Q

What does inflammation stimulate during osteomyelitis? What does this cause?

A

Inflammation stimulates osteoclasts to reabsorb bone and enzymes released - bone loss

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22
Q

What does the density of bone cause during osteomyelitis?

A

Density of bones means exudate cant get out of bone - the increased pressure is very painful, compresses blood vessels
Leads to thrombosis and infarction of intramedullary fat, marrow and bone

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23
Q

What is deposited at the side of osteomyelitis?

A

Fibrous tissue

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24
Q

What are sequelae?

A

Complications of osteomyelitis

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25
Q

What are some sequelae?

A

Inflammation extending to the surrounding soft tissues causing abcesses
Skin fistula
Septic arthritis
Sepsis
Pathologic fractures
Bone sequestra

26
Q

Where can osteomyelitis spread to?

A

Surrounding soft tissues
Adjacent bones
Across joints
Into the bloodstream

27
Q

What are bone squestra?

A

fragments of pale, chalky necrotic bone that are cut off from their blood supply and surrounded by exudate
Have no blood supply so cant resorb

28
Q

Why are bone sequestra bad?

A

They can interrupt/undermine bone healing

29
Q

What can cause bone sequestra?

A

Bone fractures
Osteomyelitis

30
Q

What mechanism causes bone growth in width?

A

Intramembranous bone formation - osteoblasts for new concentric layers of cortical bone

31
Q

What mechanism causes bone growth in length?

A

Endochondral ossification in the metaphyseal growth plates

32
Q

When are growth plates thickest?

A

When growth is most rapid, closes at skeletal maturity

33
Q

What are the 4 different cartilage zones in the growth plate?

A

The reserve/resting zone
Proliferative zone
Hypertrophic zone
Calcifying zone

34
Q

What is the reserve/resting zone for?

A

A source of cells for the proliferating zone

35
Q

What happens in the proliferative zone?

A

Cells multiply
Produce matrix
Become arranged in longitudinal columns

36
Q

What happens in the hypertrophic zone?

A

Chondrocyte volume expands
Chondrocytes modify the matrix to allow capillary invasion
Initiation of matrix mineralisation

37
Q

What happens in the calcifying zone?

A

Blood vessels from metaphysis invade into advancing growth plate
Cartilage mineralisation

38
Q

What do the invading blood vessels from the metaphysis allow?

A

They provide entry for the osteoblasts - critical step

39
Q

What is the primary spongiosa?

A

The junction between cartilage and bone in the metaphysis
A fragile lattice of bone covered spicules of calcified cartilage

40
Q

What is the secondary spongiosia? What is it made up of?

A

More mature trabeculae when growth plate advances - fewer, thicker and made up of mostly bone

41
Q

What is chondrodysplasia?

A

Hereditary disorders of bone growth - primary lesions in growth cartilage of the physeal/epiphyseal cartilage of long bones

42
Q

What are some disorders of bone growth in chondrodysplasia?

A

Growth plates reduced
Disorganised chondrocytes
Cartilage matrix less dense
Trabeculae/spongiosa thickened
Cartilage retained in the secondary spongiosa

43
Q

What type of dwarfism is caused by chondrodysplasia?

A

Disproportionate dwarfism - normal sized head with short legs

44
Q

Why does disproportionate dwarfism not affect the head?

A

Bones of the head are not formed by endochondral ossification

45
Q

What is not caused by chondrodysplasia?

A

Proportionate dwarfism - due to endocrine disease, malnutrition, or artificial breeding selection instead
Just small dogs

46
Q

What causes angular limb deformities?

A

Partial or complete premature closure of growth plates

47
Q

What is the most common site of angular limb deformities?

A

Distal ulnar physis - most stress on this growth plate

48
Q

What causes angular limb deformities in horses?

A

Physeal osteochondrosis

49
Q

What area is the most commonly affected thing in physeal osteochondrosis?

A

Hypertrophic cartilage layer

50
Q

What is the result of physeal osteochondrosis?

A

A well demarcated wedge of retained cartilage in the physis - columns of chondrocytes that dont mineralise
Can cause growth plate fractures?

51
Q

What is the weakest part of the bone?

A

Metaphyseal cortex adjacent to the growth plate

52
Q

What breed of dogs most commonly get elbow dysplasia?

A

Large to giant breed dogs

53
Q

What are some elbow abnormalities that cause elbow dysplasia?

A

Medial coronoid disease
Humeral osteochondrosis
Ununited anconeal process
Elbow instability

54
Q

What disease does a short radius cause?

A

Medial coronoid disease

55
Q

What disease does a short ulna cause?

A

Ununited anconeal process

56
Q

What can cause aseptic/ischaemic necrosis?

A

Trauma causing vascular damage
Neoplasm infiltration
Thromboembolism

57
Q

What does ischaemic necrosis of the metaphysis of the bone and bone marrow cause?

A

Retained growth cartilage - conversion of epiphyseal cartilage to bone is impaired

58
Q

What does ischaemic necrosis of the epiphysis of the bone cause?

A

Premature growth plate closure - death of the proliferating chondrocytes

59
Q

What can aseptic/ischaemic necrosis lead to?

A

Avascular necrosis of the femoral head (legg-calve-perthes)

60
Q

What breeds are predisposed to avascular necrosis of the femoral head (legg-calve-perthes)?

A

Minature poodle
Yorkie

61
Q

Why does ischaemic necrosis cause avascular necrosis of the femoral head?

A

Ischaemia causes dead femoral head bone to be replaced by fibrous tissue - this is not supportive enough so femoral head collapses

62
Q

What does not happen in avascular necrosis of the femoral head because it is a sterile disease?

A

Bone sequestra

CVSOH BVSc4 (86 decks)

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