Lec 4 Fracture Healing

Question 1

What does an open fracture mean?

Answer 1

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

Question 2

What is treatment for open fracture?

Answer 2

• antibiotics immediately

- wound debridement +/- surgery

Question 3

What is a type 1 open fracture? Treat?

Answer 3

< 1 cm
clean wound
minimal soft issue damage

usually can be debrided in ER

Question 4

What is a type II open fracture? Treat?

Answer 4

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

Need OR to stabilize

Question 5

What is a type IIIA open fracture?

Answer 5

> 10 cm
high energy injury
extensive muscle devitalization

have enough soft tissue to close

Question 6

What is a type IIIB open fracture?

Answer 6

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

Question 7

What is a type IIIC open fracture?

Answer 7

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

Question 8

What is a simple vs comminuted fracture?

Answer 8

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

Question 9

What type of fracture line most commonly in pathologic conditions?

Answer 9

transverse

Question 10

What type of fracture line in compression?

Answer 10

oblique

Question 11

What type of fracture line in bending injury?

Answer 11

butterfly

Question 12

What type of fracture line in torsion injury?

Answer 12

spiral

Question 13

What is an intra-articular fracture?

Answer 13

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

Question 14

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

Answer 14

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

Question 15

What is woven bone?

Answer 15

immature bone; seen in pathology/healing process of breaks

have random orientation, more osteocytes
more flexible; weaker

Question 16

What is lamellar bone?

Answer 16

mature bone

stress oriented

Question 17

What is osteocalcin?

Answer 17

protein synthesized by osteoblasts
attracts osteoclasts; regulates bone density

serum/urine osteocalcin = marker of bone formation

Question 18

What are the 3 blood supplies to long bones?

Answer 18

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

Question 19

What % of CO does bone receive?

Answer 19

5-10%

Question 20

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

Answer 20

toward knee; away from elbow

Question 21

What is effect of estrogen on bone growth?

Answer 21

stimulates fracture healing through receptor mediated mech

Question 22

What is effect of thyroid hormone on bone growth?

Answer 22

thyroxine and triiodothyronine stimulate osteoclastic bone resportion

Question 23

What is effect of glucocorticoids on bone growth?

Answer 23

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

Question 24

What is effect of parathyroid hormone on bone growth?

Answer 24

intermittent exposure stimulates osteoblasts; increased bone formation

Question 25

What is effect of growth hormone on bone growth?

Answer 25

mediated via IGF-1 | increases callus formation and fracture strength

Question 26

What is cutting cones?

Answer 26

direct invasion of bone = mech of remodel bone osteoclast at the front of cutting cone removes bone; trailing osteoblasts lay down new bone

Question 27

What is intramembranous bone formation?

Answer 27

laying down bone without cartilagenous analog mech of increasing width of long bone

Question 28

What is endochondral bone formation?

Answer 28

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

Question 29

What are the 3 stages of fracture repair?

Answer 29

inflammation repair remodeling

Question 30

What happens in inflammation stage?

Answer 30

- 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

Question 31

What is the vascular response in fracture repair?

Answer 31

fracture hematoma stimulates release of growth factors that promote angiogenesis and vasodilation blood flow increased substantially to fracture site

Question 32

What happens in repair stage?

Answer 32

cells produce extracellular matrix = soft callous have fibrous tissue, cartilage, woven bone

Question 33

What type of cartilage in callus?

Answer 33

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

Question 34

What happens in remodeling stage?

Answer 34

replacement of unorganized woven bone with lamellar bone resorption of unneeded callus lamellar bone oriented along lines of stress

Question 35

What is wolff's law?

Answer 35

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

Question 36

What is direct bone healing?

Answer 36

mech of bone healing when there is no motion at the fracture site does not involve callus formation

Question 37

What is indirect bone healing?

Answer 37

mech for healing in fractures that are not rigidly fixed bridging periosteal [soft] and medullary [hard] callus reestablish structural continuity; callous undergoes endochondrial ossification

Question 38

What is clinical union?

Answer 38

no motion or tenderness at fracture site

Question 39

What is radiographic union?

Answer 39

plain radiograph shows trabeculae or cortical bone crossing fracture site

Question 40

When is actual healing complete?

Answer 40

when remodeling complete --> medullary cavity is reconstituted

Question 41

What are pre-requisities for fracture healing?

Answer 41

- mechanically stable environment - no infection - blood supply - stem/progenitor cells

Question 42

What is purppose of casting?

Answer 42

hold bone via soft tissue --> decreased risk infection, nerve/tendon damage may be difficult to maintain alignment of bones

Question 43

What are downsides of casting?

Answer 43

- joint stiffness - disuse osteopenia - muscle atrophy

Question 44

What is internal fixation?

Answer 44

do it when adequate stability not achievable by closed means

Question 45

How does DM affect fracture healing?

Answer 45

associated with collagen defects

Question 46

How does smoking affect fracture healing?

Answer 46

increases time to union; increased rate of nonunion b/c nicotine causes vasoconstriction + decreased blood flow to bone --> DO NOT USE NICOTINE PATCH

Question 47

How do NSAIDS affect fracture healing?

Answer 47

longer union time; lower fusion rate

Question 48

What are some causes of delayed union?

Answer 48

- infection - lack of stability - smoking

Question 49

WHat is non-union?

Answer 49

no further progression in fracture healing = long period of time and no change need to do bone scan to rule out infection