MSK pt 1 Flashcards

1
Q

Label this image

A

A: epiphysis
B: Physis
C: metaphysics
D: Diaphysis
E: cortex/cortical bone/compact bone
F: medullary cavity
G: cancellous bone/spongy bone

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2
Q

During endochondral ossification, where are the primary and secondary centres of ossification?

A

primary: diaphysis (prenatal)
secondary: physis (post-natal)

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3
Q

Why are eunuchs tall with long fingers?

A

normal development:
maturity = increase in sex hormones –> growth plate thins and is replaced by bone

early castration:
maturity ≠ increase in sex hormones –> delayed growth plate closure –> tall, long fingers, etc.

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4
Q

What is the implication of castrating animals too young? (eunuchs)

A

they are taller with longer limbs/bones, so femoral head fxs in young happen lots, and overweight castrated male cats is a thing

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5
Q

What is Wolff’s law?

A

bone is remodelled in response to forces placed on them

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6
Q

what are the 2 responses to injury that bone has?

A
  1. resorption/lysis
  2. production of new bone (woven bone)
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7
Q

What is an exostosis?

A

projecting proliferation of bone from the periosteum, benign
AKA bony spurs

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8
Q

What is the arrow pointing to?

A

Exostosis
(bony spur)

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9
Q

Where is the weakest place in growing bones? why?

A

growth plate
cartilage is weaker than bone

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10
Q

How do we classify growth plate fractures?

A

Salter-Harris classification

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11
Q

What is the most common Salter Harris fracture? What is the consequence?

A

SH 2 (break along physics and into metaphysis)
growth still possible

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12
Q

What are the more serious Salter-Harris fractures? What is the consequence?

A

SH 3 & SH 4 (break across growth plate, going up or down, but either way going to the articular surface)

healing bone “closes” it –> no growth at site

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13
Q

What is the blue arrow pointing to? What type of fracture is the red arrow pointing to?

A

physis/growth plate (blue arrow)
Salter Harris fx (don’t have to know specific classification)

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14
Q

angular limb deformities are common in ____-____ animals. What are the 2 types?

A

fast-growing
1. valgus
2. varus

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15
Q

Describe the difference between valgus and varus.

A

Valgus: splay-legged. knees go together, feet go out laterally

varus: bow-legged. knees go out, feet go together medially

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16
Q

What angular limb deformity is this animal displaying?

A

valgus

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17
Q

What angular limb deformity is this animal displaying?

A

Varus

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18
Q

List 6 causes of angular limb deformities (you have to know the first one for sure!)

A
  1. asymmetric damage to growth plate –> one side closes while the other grows
  2. malposition in utero
  3. joint laxity due to weak supporting structures
  4. hypothyroidism
  5. malnutrition
  6. abnormalities in endochondral ossification
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19
Q

What is the definition of a fracture? when does this occur?

A

a break/rupture resulting in a physical discontinuity in a bone

occurs when there is a mechanical force that exceeds the bone’s strength

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20
Q

What are the 2 types of fractures? what do they mean?

A
  1. traumatic - excessive forces exerted on normal bone
  2. pathological - normal/minimal forces exerted on abnormal bone
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21
Q

What bone abnormalities can cause pathological fractures?

A

infection (osteomyelitis), neoplasia, metabolic bone disease

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22
Q

Tell me the main fracture descriptors (there are 5)

A
  1. closed/simple vs open/compound
  2. displaced vs non-displaced
  3. comminuted vs transverse/linear/oblique/spiral
  4. location (proximal/distal/midshaft)
  5. name the bone
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23
Q

What is an avulsion fracture?

A

ligament pulls bone at site of insertion

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24
Q

What is a greenstick fracture?

A

1 cortex is broken, the other bent
not displaced
usually young animals

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25
Q

List the steps of fracture healing and the timing. also note if it’s stable/unstable. (very general) (5 steps)

A
  1. hematoma - immediate - unstable
  2. fibrous tissue - 24-48 h - unstable
  3. woven bone & cartilage - 36 hr - unstable
  4. primary callus - 4-6 wks - stable
  5. secondary callus - months to years - stable

Hi Fred, We Prefer Salt

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26
Q

What is a non-union?

A

fracture doesn’t heal

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27
Q

List the reasons for non-unions to occur (6 things)

A
  1. inadequate blood supply
  2. instability
  3. infection
  4. fx result of bone pathology vs trauma
  5. malnutrition
  6. necrotic tissue (sequestrum) in fx site
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28
Q

What is osteodystrophy? can more than 1 type affect the same individual?

A

abnormal bone metabolism (metabolic bone disease)

yes

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29
Q

What are the causes of osteodystrophy?

A

nutritional/hormonal deficiencies/imbalances/toxicities

can be multifactorial

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30
Q

what is the possible result of osteodystrophy?

A

pathological fractures, pain (lameness)

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31
Q

Osteodystrophy is more common & severe in ____ animals. Why?

A

growing

rapid skeletal development vs slower remodelling of adults

32
Q

What are the osteodystrophies/metabolic bone diseases that we have to know?

A
  1. malnutrition and starvation
  2. osteoporosis
  3. rickets
  4. osteomalacia
  5. fibrous osteodystrophy

MOROF

33
Q

What are growth arrest lines?

A

slow longitudinal bone growth –> trabeculae in metaphysis are abnormally aligned

34
Q

what are the 2 causes of growth arrest lines?

A

debilitating disease, malnutrition

35
Q

Describe the pathogenesis of growth arrest lines?

A
  1. inciting cause (debilitating disease, malnutrition)
  2. long bone growth stops
  3. abnormal osteoclast activity
  4. lines are carried into metaphysis as growth resumes
36
Q

What is the blue arrow pointing to?

A

growth arrest line

37
Q

what is serous atrophy of fat?

A

normally dense fat becomes watery and gelatinous, in response to malnutrition/starvation

38
Q

What is going on?!

A

serous atrophy of fat

39
Q

What is osteoporosis?

A

reduced bone mass and density with associated pathological fractures

40
Q

what is osteopenia?

A

reduced bone mass/density without pathological fractures

41
Q

what is the difference between osteopenia and osteoporosis?

A

both are reduced bone mass and density, but osteopenia is without pathologic fx, and osteoporosis is with pathologic fx

42
Q

What are the 3 causes of osteoporosis?

A
  1. Ca2+ deficiency
  2. starvation
  3. physical disuse (atrophy)

basically anything that tips the balance so more bone is absorbed than replaced during remodelling

43
Q

what is the pathogenesis of how calcium deficiency leads to osteoporosis?

A

low serum Ca2+ –> increase in parathyroid hormone –> stimulates osteoclasts to increase bone resorption

44
Q

You treated a patient with a broken limb and put a cast on the limb. What metabolic bone disease is something that you should be wary of?

A

osteoporosis

45
Q

What is this picture showing?

A

bone with osteoporosis

46
Q

bones with osteoporosis are _____ mineralized. (extremely, normally, limitedly)

A

normally

47
Q

How can bones be normally mineralized in osteoporosis if pathogenesis involves low calcium?

A
  1. bones were formed in a healthy individual = normal mineralization
  2. subsequent Ca2+ deficiency
  3. stimulates osteoclasts to resorb bone
  4. reduced bone density because removed bone isn’t replaced
  5. weak & brittle (but normal mineralization of trabeculae that remain)
48
Q

The top bone is normal. What is wrong with the bottom one? (ignore the red lines)

A

osteoporosis (thin cortex, hardly any trabecular bone left)

49
Q

Bone with osteoporosis is more _____ in radiographs (radiolucent/radiopaque)

A

radiolucent

50
Q

What is rickets?

A

failure of bone mineralization in young, growing animals

thickened growth plates from lack of cartilage mineralization and abnormal endochondral ossification

51
Q

what is the cause of rickets?

A

vitamin D & phosphorus deficiency

52
Q

This is from the metatarsal of a young sheep. What is the lesion?

A

rickets
*note the thick cartilage still present

53
Q

What are the white arrows pointing to?

A

retained cartilage deep in metaphysis of an animal with rickets

54
Q

what are the gross lesions of rickets? where can you see these lesions best on necropsy?

A
  • segmental growth plate thickening
  • multifocal physis lesions (on multiple bones)
  • tongues of un-resorbed cartilage extending into the metaphysis

most prominent at sites of rapid growth

55
Q

What is rachitic rosary?

A

segmental growth plate thickening in the costochondral junctions, causing growths that looks like rosary beads

56
Q

Even though this is a human, it has the same pathology as something we’ve talked about in class. What is the pathology? (hint: look at the white arrows)

A

rachitic rosary - rickets

57
Q

What is osteomalacia?

A

softening of bones. similar cause and pathogenesis to rickets but occurring in adults

involves defective mineralization during bone remodelling

58
Q

describe the difference between osteomalacia and rickets

A

Rickets is failure of bone mineralization in young growing animals and involves thickened growth plates.

osteomalacia involves defective mineralization during bone remodelling resulting in soft bones. It has the same/similar cause/pathogenesis as rickets but occurs in adults and does not have growth plate involvement

59
Q

what is the consequence of osteomalacia?

A

bones have reduced resistance to pressure and tension - fractures occur

60
Q

what are the gross lesions of osteomalacia?

A

expansion of the marrow cavity (bones often enlarged)
thin, spongy, soft cortex
pathologic fractures

61
Q

what is fibrous osteodystrophy?

A

excessive bone resorption and replacement by fibrous connective tissue

62
Q

what is the pathogenesis of fibrous osteodystrophy?

A
  1. hyperparathyroidism
  2. elevated parathyroid hormone (PTH)
  3. increase osteoclastic resorption and replacement by fibrous tissue
  4. soft, malleable bones
63
Q

What are the two types of hyperparathyroidism and what is the difference between them?

A
  1. primary hyperparathyroidism: excessive PTH secreted from parathyroid glands. rare, often associated with parathyroid gland neoplasia. (usually excessive PTH secreted from functional parathyroid gland tumor)
  2. secondary hyperparathyroidism: stimulus to decrease serum Ca2+ leads to increase in PTH. Common, 2 subtypes
64
Q

What are the 2 types of secondary hyperparathyroidism?

A
  1. nutritional
  2. renal
65
Q

what is the overall cause of fibrous osteodystrophy? (very general)

A

hyperparathyroidism

66
Q

Nutritional secondary hyperparathyroidism:
1. cause?
2. affects who?
2a. who is the exception?
3. who is resistant to this?

A
  1. diets low in calcium & high in phosphorus
  2. young growing animals
    2a. horses - can occur in young and adult animals
  3. cattle & sheep
67
Q

Nutritional secondary hyperparathyroidism:
1. what are horses & sheep with this disease called?
2. what are the associated diets in horses & sheep?
3. gross lesions in horse?
4. what happens in severe cases?

A
  1. big heads
  2. cereal hay (oat straw), bran, grain
  3. bilateral enlargement of fascial bones = fascial swelling; can also lead to loose teeth
  4. develop lesions in other bones = lameness ± pathologic fxs
68
Q

Tell me 1 lesion that you can see on the face of a horse with nutritional secondary hyperparathyroidism and 2 lesions you can see in the maxillary bone/nose area

A
  1. bilaterally symmetrical distorted facial contours
  2. maxillary bone is replaced with fibrous tissue including areas around teeth, fibrous tissues compress the nasal cavity towards the septum
69
Q

what is the associated diet to nutritional secondary hyperparathyroidism in dogs/cats & pigs?

A

dogs/cats: all meat/offal
pigs: grain

70
Q

what are the gross lesions of nutritional secondary hyperparathyroidism in dogs/cats/pigs?

A

facial swelling not always present, but skull affected: long bones predominantly affected (pathologic fxs common presenting signs)

71
Q

Renal secondary hyperparathyroidism:
1. AKA?
2. lesions?

A
  1. renal osteodystrophy
  2. soft malleable bones (can cut bones with a knife); soft pliable mandible (rubber jaw); deformed mandible/maxilla & tooth loss
72
Q

renal osteodystrohpy is a combination of _____ ____ and ______.

A

fibrous osteodystrophy & osteomalacia

73
Q

renal osteodystrohpy is associated with severe, ___ (acute/chronic), _____ disease. Common in ____ (older/younger) ____ & ___.

A

severe, chronic renal disease
older dogs & cats

74
Q

describe the pathogenesis of renal osteodystrophy

A
  1. renal disease
  2. reduced renal phosphate excretion
  3. hyperphosphatemia; phosphate reacts with Ca2+
  4. increase PTH
  5. increased bone resorption

AND

  1. renal disease
  2. reduced renal vitamin D metabolism
  3. reduced Ca2+ absorption from intestines
75
Q

This is a maxilla from a dog. What caused this? (ignore the arrows/lines)

A

renal secondary hyperparathyroidism

76
Q

What caused this poor horse to look like this?

A

nutritional secondary hyperparathyroidism