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Module 7 > Bone Pathology > Flashcards

Bone Pathology Flashcards

(53 cards)

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1
Q

how do osteocytes and osteoblasts interact

A

connected by long cytoplasmic processes

changes in bone tissue fluid (BTF) when changes in stress/strain on bone or microcracks

osteocytes detect changes in BTW flow –> signal to osteoblasts –> bone formation or resorption

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2
Q

what can osteoclasts not bind to

A

unminderalized bone

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3
Q

what role does parathyroid hormone play (4)

A
  1. osteoblasts retract and secrete collagenases –> osteoclasts have access to bone
  2. osteblasts secrete RANKL –> activates resorption process
  3. osteoblasts also produce osteoprotegrin –> inhibition of formation of osteoclasts
  4. osteoblasts can both upregulate and downregulate osteoclastic bone resorption
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4
Q

what is the organic matrix made up of

A

type I collagen arranged in parallel

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5
Q

what is the ground susbtance of bone matrix made up of

A

non-collagenous proteins, proteoglycans, lipids

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6
Q

what is the mineral of bone matrix

A

hydroxyapatite

contains minderals (Ca and P) –> hardness

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7
Q

how do flat bones develop

A

intramembranous ossification

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8
Q

how do long bones develop

A

endochondral ossification

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9
Q

how do bones grow in length

A

metaphyseal growth plates via endochonral ossification

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10
Q

how do bones grow in width

A

osteogenic layer of periosteum

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11
Q

what is the cortex and subchondral bone made of

A

osteons –> concentric layers of lamellae

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12
Q

what is the bone in the medullary cavity made of

A

trabecular bone –> lamellae arranged in parallel to sruface of trabecules

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13
Q

what is bone remodelling

A

change of shape or contour of bone in response to normal growth, changed mechanical use or disease

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14
Q

what is the reaction to a bone injury

A
  1. change of size and shape
  2. change of density
  3. disruption of endochondral ossification –> change to metaphyseal trabeculae
  4. rapidly deposited bone is woven (not lamellar)
  5. injured periosteum often also forms bone
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15
Q

what is a traumatic bone fracture

A

force exceeding design

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16
Q

what is a pathological bone injury

A

force below design

abnormal bone (osteomyelitis, neoplasm, metabolic bone disease) is broken by minimal trauma or normal weight bearing

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17
Q

what is a stable fracture

A

fracture ends have been immobilized (clinical stability) –> callus formation

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18
Q

what is a unstable fracture

A

callus formation

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19
Q

what is a rigid fracture

A

usually surgical intervention

bone ends in close contact or close proximitity

ideally contact feeding

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20
Q

what is an external callus

A

formed by the periosteum

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21
Q

what is an internal callus

A

between ends of fragments and in medullary cavity

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22
Q

what is the function of a callus

Study These Flashcards
A

bridge the gap

encircle the fracture site

stabilize the area

23
Q

what does a callus contain

Study These Flashcards
A

hyaline cartilage if the blood supply is less than optimal –> not as strong but eventually undergoes endochondral ossification

24
Q

what are the steps in callus formation

Study These Flashcards
A
  1. hematoma –> immediate
  2. invasion of mesenchymal cells and neovascularization –> 24-48h
  3. earliest woven bone: 36h –> primary callus 4-6 wks
  4. months to years for secondary cells (trabecular bone) and restoration of normal bone
25
what is the histological difference between woven and lamellar bone
collagen not in parallel irregularly arranged
26
what are the advantages of healing by callus
1. natural process 2. minimal intervention - minimal risk 3. minimal intervention - lowest cost option
27
what are the disadvantages of healing by callus
1. callus may not be able to stabilize fracture 2. callus takes time to stabilize fracture 3. large callus may interfere with function of joints or tendons
28
what is healing with fixation or by 1st intention
direct osteonal bridging of fracture site, no callus formation
29
what occurs if the gap is less than 1mm in healing by fixation
osteoblasts form lamellar bone at right angle to fracture line --\> become osteons parallel to long axis
30
what occurs if the gap is greater than 1mm in healing by fixation
first formation of woven bone --\> remodelled into osteons
31
what are the complications of fracture healing (8)
1. inadequate blood supply/O2 --\> cartilage formation; if anoxia --\> necrosis 2. instability (movement and high tension) --\> development of fibrous tissue --\> no bone formation --\> non-union, false joint/pseudarthrosis 3. infection --\> osteomyelititis, sequestra 4. malnutrition, age 5. tissue between fracutre ends --\> delayed or non-union 6. too large metallic implants --\> lack of mechanical force to bone --\> atrophy 7. intramedullary implants may damage blood supply 8. premature closure of growth plates --\> deformed limbs
32
what are the disorders of bones
1. vascular 2. inflammatory (infectious/immune-mediated) 3. traumatic 4. anomaly (congenital) 5. metabolic/toxic 6. idiopathic/iatrogen 7. neoplastic 8. degenerative (VITAMIND)
33
what are the terms used to describe bone inflammation
1. osteitis: inflammation of bone 2. periostitis: inflammation of periosteum 3. osteomyelitis: involves the medullary cavity 4. sequestrum: fragment of dead bone isolated from blood supply and surrounded by a pool of exudate
34
what are the portals of entry for bone infection
1. direct 2. hematogenous
35
what are the causes of direct trauma that cause infectious inflammation
trauma (may or may not break bone) extension from direct inflammation (eg. periodontitis/otitis)
36
how does indirect entry of infectious inflammation of bone occur
mostly young animals usually bacterial (embolic) --\> suppurative inflammation most commonly on metaphyseal side of growth plate at articular-epiphyseal complex capillaries with sharp bends to join medullary viens (slow flow, turbulence, lower phagocytic capacity, discontinuous endothelial lining, no anastomosis)
37
what are the consequences of infectious inflammation of bone
1. thrombosis, infarction, inflammation --\> bone resorption 2. possible sequela --\> extension into joint and periosteum, formation of sequestra, formation of sinus tracts, spread to other bones and soft tissues, pathological fractures
38
what are the types of fractures of cortical bone
1. closed: skin unbroken 2. open/compound: skin broken 3. simple: clean break into two parts 4. comminuted: bone shattered into fragments 5. greenstick: cortex on one side broken, on other side only bent (no displacement of fracture site) 6. transverse/spiral: depending on fracture line
39
what occurs when there is a fractrure of growht plates or trabecular bone
metaphyseal cortex is very thin (weakest part) --\> growth plate fractures in young animals
40
what are the types of growth plate fractures
type I and II: few or no complications type III-V: may have growth abnormalities as growth plate involved
41
what is an infraction
fracture of trabeculae without involvment of cortex
42
what are the congential/anomaly abnormalities in growth and development
1. osteopetrosis 2. osteogenesis imperfecta 3. chondrodysplasia
43
what is osteopetrosis
too much bone defect in bone resorption by osteoclasts (also infectious)
44
what is osteogenesis imperfecta
too little bone mutations in genes for collagen I
45
what is chondrodysplasia
disproportionate dwarfism mutations in genes which control formation of cartilage, storage dx (MPS)
46
what is metabolic bone disease
osteoporosis rickets/osteomalacia fibrous osteodystrophy
47
what is osteoporosis
less bone (reduction in the amount of normally mineralized bone) malnutrition, immobilization, low dietary Ca, oestrogen/androgen deficiency
48
what is rickets/osteomalacia
soft bones (defect in mineralization of bone) Vit D/phosphorus deficiency rubberjaw
49
what is fibrous osteodystrophy
replacement of bone by fibro-osseus tissue hyperparathyroidism
50
what are the types of primary neoplasms of bone (7)
1. fibroma: ex. ossifying fibroma --\> maxilla and mandible of horse and cattle 2. fibrosarcoma: ex. oral masses in dogs 3. chondroma: often arise from flat bones, very rare 4. chondrosarcoma: most often flat bones, large breed dogs and sheep, grow slower than osteosarcomas, develop metastases later 5. osteoma: usually bone of head 6. osteosarcoma 7. liposarcoma, hemangiosarcoma
51
what is an osteosarcoma
malignant neoplastic cells form osteoid, bone or both most common tumour of bone in dogs and cats
52
where do osteosarcomas most commonly occur
giant breed dogs; metaphyses (distal radius, distal tibia, proximal humerus) early hematogenous spread to lungs and soft tissues and other bones
53
what is a secondary neoplasm
carcinoma is most common dogs: rib shafts, vertebral bodies, humoral and femoral metaphyses; most common primary site: mammary gland, lung, liver, prostate gland cats: rare; mets to appendicular skeleton; lung carcinoma to digits

Module 7 (50 decks)

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