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MSK > Lec 4 Fracture Healing > Flashcards

Lec 4 Fracture Healing Flashcards

1
Q

What does an open fracture mean?

A

opening between fracture site and skin = open to outside –> more likely to get infected

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2
Q

What is treatment for open fracture?

A
  • antibiotics immediately

- wound debridement +/- surgery

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3
Q

What is a type 1 open fracture? Treat?

A

< 1 cm
clean wound
minimal soft issue damage

usually can be debrided in ER

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4
Q

What is a type II open fracture? Treat?

A

1-10 cm
moderate soft tissue damage
high energy injury
some necrotic muscle and periosteal stripping

Need OR to stabilize

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5
Q

What is a type IIIA open fracture?

A

> 10 cm
high energy injury
extensive muscle devitalization

have enough soft tissue to close

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6
Q

What is a type IIIB open fracture?

A

high energy
extensive muscle devitalization
periosteal stripping
not enough tissue to close it –> need to get skin from somewhere

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7
Q

What is a type IIIC open fracture?

A

high energy
increased risk of amputation/infection
have major vascular injury needing repair

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8
Q

What is a simple vs comminuted fracture?

A

comminuted = 2 or more pieces of bone at the fracture site

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9
Q

What type of fracture line most commonly in pathologic conditions?

A

transverse

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10
Q

What type of fracture line in compression?

A

oblique

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11
Q

What type of fracture line in bending injury?

A

butterfly

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12
Q

What type of fracture line in torsion injury?

A

spiral

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13
Q

What is an intra-articular fracture?

A

goes through the joint = more important to get it as anatomic as possible –> put screws in

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14
Q

What are some examples of places where you see woven bone?

A
  • embryonic skeleton
  • fracture callus
  • pathologic conditions –> osteogenic sarcoma or fibrous dysplasia
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15
Q

What is woven bone?

A

immature bone; seen in pathology/healing process of breaks

have random orientation, more osteocytes
more flexible; weaker

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16
Q

What is lamellar bone?

A

mature bone

stress oriented

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17
Q

What is osteocalcin?

A

protein synthesized by osteoblasts
attracts osteoclasts; regulates bone density

serum/urine osteocalcin = marker of bone formation

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18
Q

What are the 3 blood supplies to long bones?

A
  • nutrient artery [intramedullary and inner 2/3 cortex]
  • periosteal vessels [outer 1/3 cortex]
  • metaphyseal vessels
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19
Q

What % of CO does bone receive?

A

5-10%

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20
Q

What direction does nutrient artery flow w/ respect to knee? elbow?

A

toward knee; away from elbow

21
Q

What is effect of estrogen on bone growth?

A

stimulates fracture healing through receptor mediated mech

22
Q

What is effect of thyroid hormone on bone growth?

A

thyroxine and triiodothyronine stimulate osteoclastic bone resportion

23
Q

What is effect of glucocorticoids on bone growth?

A

inhibit Ca absorption from gut causing increased PTH and thus increase osteoclasic bone resorption

24
Q

What is effect of parathyroid hormone on bone growth?

A

intermittent exposure stimulates osteoblasts; increased bone formation

25
Q

What is effect of growth hormone on bone growth?

A

mediated via IGF-1

increases callus formation and fracture strength

26
Q

What is cutting cones?

A

direct invasion of bone = mech of remodel bone

osteoclast at the front of cutting cone removes bone; trailing osteoblasts lay down new bone

27
Q

What is intramembranous bone formation?

A

laying down bone without cartilagenous analog

mech of increasing width of long bone

28
Q

What is endochondral bone formation?

A

ossification in epiphysis –> increases length of bone; convert cartilage to bone at the end

osteoblasts line cartilage precursor; chondrocytes hypertrophy and calcify; vascular invasion of cartilage followed by ossification

29
Q

What are the 3 stages of fracture repair?

A

inflammation
repair
remodeling

30
Q

What happens in inflammation stage?

A
  • bleeding from fracture site + surrounding soft tissue creates hematoma
  • hematoma brings hematopoietic cells that secrete chemotactic and growth factors
  • granulation tissue forms around fracture

osteoclasts resorb dead/necrotic bone; osteoblasts differentiate from precursors

31
Q

What is the vascular response in fracture repair?

A

fracture hematoma stimulates release of growth factors that promote angiogenesis and vasodilation

blood flow increased substantially to fracture site

32
Q

What happens in repair stage?

A

cells produce extracellular matrix = soft callous

have fibrous tissue, cartilage, woven bone

33
Q

What type of cartilage in callus?

A

initially type II from chondrocytes; as cartilage transformed to woven bone increased amount of type 1 collagen = hard callus

34
Q

What happens in remodeling stage?

A

replacement of unorganized woven bone with lamellar bone

resorption of unneeded callus

lamellar bone oriented along lines of stress

35
Q

What is wolff’s law?

A

bone responds dynamically to stress by altering its internal architecture === bone is laid down where it is needed

36
Q

What is direct bone healing?

A

mech of bone healing when there is no motion at the fracture site

does not involve callus formation

37
Q

What is indirect bone healing?

A

mech for healing in fractures that are not rigidly fixed

bridging periosteal [soft] and medullary [hard] callus reestablish structural continuity; callous undergoes endochondrial ossification

38
Q

What is clinical union?

A

no motion or tenderness at fracture site

39
Q

What is radiographic union?

A

plain radiograph shows trabeculae or cortical bone crossing fracture site

40
Q

When is actual healing complete?

A

when remodeling complete –> medullary cavity is reconstituted

41
Q

What are pre-requisities for fracture healing?

A
  • mechanically stable environment
  • no infection
  • blood supply
  • stem/progenitor cells
42
Q

What is purppose of casting?

A

hold bone via soft tissue –> decreased risk infection, nerve/tendon damage

may be difficult to maintain alignment of bones

43
Q

What are downsides of casting?

A
  • joint stiffness
  • disuse osteopenia
  • muscle atrophy
44
Q

What is internal fixation?

A

do it when adequate stability not achievable by closed means

45
Q

How does DM affect fracture healing?

A

associated with collagen defects

46
Q

How does smoking affect fracture healing?

A

increases time to union; increased rate of nonunion

b/c nicotine causes vasoconstriction + decreased blood flow to bone –> DO NOT USE NICOTINE PATCH

47
Q

How do NSAIDS affect fracture healing?

A

longer union time; lower fusion rate

48
Q

What are some causes of delayed union?

A
  • infection
  • lack of stability
  • smoking
49
Q

WHat is non-union?

A

no further progression in fracture healing = long period of time and no change

need to do bone scan to rule out infection

MSK (23 decks)

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