Lec 4 Fracture Healing Flashcards
What does an open fracture mean?
opening between fracture site and skin = open to outside –> more likely to get infected
What is treatment for open fracture?
- antibiotics immediately
- wound debridement +/- surgery
What is a type 1 open fracture? Treat?
< 1 cm
clean wound
minimal soft issue damage
usually can be debrided in ER
What is a type II open fracture? Treat?
1-10 cm
moderate soft tissue damage
high energy injury
some necrotic muscle and periosteal stripping
Need OR to stabilize
What is a type IIIA open fracture?
> 10 cm
high energy injury
extensive muscle devitalization
have enough soft tissue to close
What is a type IIIB open fracture?
high energy
extensive muscle devitalization
periosteal stripping
not enough tissue to close it –> need to get skin from somewhere
What is a type IIIC open fracture?
high energy
increased risk of amputation/infection
have major vascular injury needing repair
What is a simple vs comminuted fracture?
comminuted = 2 or more pieces of bone at the fracture site
What type of fracture line most commonly in pathologic conditions?
transverse
What type of fracture line in compression?
oblique
What type of fracture line in bending injury?
butterfly
What type of fracture line in torsion injury?
spiral
What is an intra-articular fracture?
goes through the joint = more important to get it as anatomic as possible –> put screws in
What are some examples of places where you see woven bone?
- embryonic skeleton
- fracture callus
- pathologic conditions –> osteogenic sarcoma or fibrous dysplasia
What is woven bone?
immature bone; seen in pathology/healing process of breaks
have random orientation, more osteocytes
more flexible; weaker
What is lamellar bone?
mature bone
stress oriented
What is osteocalcin?
protein synthesized by osteoblasts
attracts osteoclasts; regulates bone density
serum/urine osteocalcin = marker of bone formation
What are the 3 blood supplies to long bones?
- nutrient artery [intramedullary and inner 2/3 cortex]
- periosteal vessels [outer 1/3 cortex]
- metaphyseal vessels
What % of CO does bone receive?
5-10%
What direction does nutrient artery flow w/ respect to knee? elbow?
toward knee; away from elbow
What is effect of estrogen on bone growth?
stimulates fracture healing through receptor mediated mech
What is effect of thyroid hormone on bone growth?
thyroxine and triiodothyronine stimulate osteoclastic bone resportion
What is effect of glucocorticoids on bone growth?
inhibit Ca absorption from gut causing increased PTH and thus increase osteoclasic bone resorption
What is effect of parathyroid hormone on bone growth?
intermittent exposure stimulates osteoblasts; increased bone formation
What is effect of growth hormone on bone growth?
mediated via IGF-1
increases callus formation and fracture strength
What is cutting cones?
direct invasion of bone = mech of remodel bone
osteoclast at the front of cutting cone removes bone; trailing osteoblasts lay down new bone
What is intramembranous bone formation?
laying down bone without cartilagenous analog
mech of increasing width of long bone
What is endochondral bone formation?
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
What are the 3 stages of fracture repair?
inflammation
repair
remodeling
What happens in inflammation stage?
- 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
What is the vascular response in fracture repair?
fracture hematoma stimulates release of growth factors that promote angiogenesis and vasodilation
blood flow increased substantially to fracture site
What happens in repair stage?
cells produce extracellular matrix = soft callous
have fibrous tissue, cartilage, woven bone
What type of cartilage in callus?
initially type II from chondrocytes; as cartilage transformed to woven bone increased amount of type 1 collagen = hard callus
What happens in remodeling stage?
replacement of unorganized woven bone with lamellar bone
resorption of unneeded callus
lamellar bone oriented along lines of stress
What is wolff’s law?
bone responds dynamically to stress by altering its internal architecture === bone is laid down where it is needed
What is direct bone healing?
mech of bone healing when there is no motion at the fracture site
does not involve callus formation
What is indirect bone healing?
mech for healing in fractures that are not rigidly fixed
bridging periosteal [soft] and medullary [hard] callus reestablish structural continuity; callous undergoes endochondrial ossification
What is clinical union?
no motion or tenderness at fracture site
What is radiographic union?
plain radiograph shows trabeculae or cortical bone crossing fracture site
When is actual healing complete?
when remodeling complete –> medullary cavity is reconstituted
What are pre-requisities for fracture healing?
- mechanically stable environment
- no infection
- blood supply
- stem/progenitor cells
What is purppose of casting?
hold bone via soft tissue –> decreased risk infection, nerve/tendon damage
may be difficult to maintain alignment of bones
What are downsides of casting?
- joint stiffness
- disuse osteopenia
- muscle atrophy
What is internal fixation?
do it when adequate stability not achievable by closed means
How does DM affect fracture healing?
associated with collagen defects
How does smoking affect fracture healing?
increases time to union; increased rate of nonunion
b/c nicotine causes vasoconstriction + decreased blood flow to bone –> DO NOT USE NICOTINE PATCH
How do NSAIDS affect fracture healing?
longer union time; lower fusion rate
What are some causes of delayed union?
- infection
- lack of stability
- smoking
WHat is non-union?
no further progression in fracture healing = long period of time and no change
need to do bone scan to rule out infection
