29. Fractures Flashcards Preview

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Flashcards in 29. Fractures Deck (29):

What happens at the site of a bone fracture at the tissue/cell level?

1. Bone breaks --> there is blood/hematoma

2. usually surrounded by muscle or other soft tissue which can be a source of mesenchymal stem cells (MSCs)

3. the MSCs do a few things: 

-release trophic mediators (Bone Morphogenic Proteins)

-differentiate into osteoblasts, endothelial cells, chondrocytes. all these can become new bone.


what kind of fracture?

stress fracture.


what kind of fracture?

fracture through the "waist" of the scaphoid bone (on the left side of the image)


Fracture on the left is called?

Fracture on the right is called?

Left: simple/hairline

Right: comminuted


open v closed fracture: what do these words mean?

open = has broken the skin (either the bone has punched out, or the skin has been broken by trauma at the site of the break. skins is open either way)

closed = nothing has broken skin


Open fractures: what are the absolutes in terms of treatment?

-sterile dressing using saline (not betadine: it is caustic to tissue)

-Splint (immobilize to prevent further soft tissue damage)

-tetanus prophylaxis

-IV antibiotics

-this is a surgical emergency so irrigate a lot and debride wound


Classification of fractures by anatomic location: terms we use are

-intra v extra articular

-metaphyseal v diaphyseal

-prox, middle, or distal third

-remember that diaphyseal means the shaft/skinny part of the bone (diaphyseal has been on a diet).

-metaphyseal and epiphysis: see pic

-note he never used the word epiphysis, only metaphysis.


what kind of fracture/what kind of force?

transverse fracture. implies a failure under tension.

direct blow, high energy


what kind of fracture/what kind of force?

f him, he only said that it was due to a low skiboot.

either oblique or spiral.


what kind of fracture/what kind of force?

Butterfly fracture

bending prior to breaking.


which bone fragment do we use do describe if the displacement is medial/lateral or anterior/posterior?

typically use the distal fragment to describe.

ie, below would be described as anterior displacement.


Describe this fracture

Skeletally immature, communited fracture. Open fracture (absence of soft tissue medially), valgus position, middle portion of bone.


Special term to describe a fracture: what does greenstick mean? what population does this happen in?

in younger bones, with a bending mechanism, one cortex can fail by fracture, while the other cortex only bends (deforms plastically) and does not fracture, much like what happens when trying to break a “green” stick out in the woods.


what is a buckle fracture?

once again, usually in young bones, with a compression type mechanism, one cortex fails by a forming a “wrinkle”, and the other cortex appears intact.  VERY stable fractures, heal quite quickly


name 2 types of pathologic fractures?

why are they called this?

osteoporosis compression fracture, metastatic fracture

term used to describe a fracture that occurs in bone that is “weakened” by another process, such that the bone “fails” with much less of an insult.


Impacted fracture: what is this?

when either a piece of a joint is driven down into the softer metaphyseal bone, or in a “long” bone when the end of the bone is impaled by the shaft (example - proximal humerus)

occurs around the metaphyseal region of joint, helps indicate long term prognosis for the joint. (usually the joint will progress to OA).


what are the three phases of bone healing?





Inflammatory phase of fracture healing: how long does it last?

why is the hematoma important to maintain?

what happens to dead bone?

lasts 0-2 weeks

Hematoma is impt because it is the site of the non-differentiated cells that can promote healing

Dead bone: the edges look normal initially, but then you will see on imaging that the break site widens slightly as dead bone is removed. 


How long does the reparative phase last?

what occurs during this phase?

-Reparative Phase: 2-12 weeks (wide range because it depends on how much soft tissue surrounds the bone in question)

-the hematoma organizes with mesenchymal precursor cells.

-Callus forms: (=new bone at site of injury). fracture becomes "sticky". will hold together by itself somewhat. 

-increase in a few mediators, and Types I and II collagen.


what is the difference between delayed union and non-union?

If a bone is taking longer the “average” amount of time to heal, the term “delayed union” is used. 

Occasionally the body will abort its attempt to heal, and the bones never “unite”; this is known as a “nonunion”.

(taken from his "notes" since he couldn't get it together to explain this in "lecture")


Remodeling phase of fracture healing: how long can it take?

what determines how long this take, and how well the bone re-forms?

-Can take 6 wks to many years.

-Depends on how young you are (younger -> faster healing)

-Wolff's law: the bone responds to stress. putting a little weight on the bone will actually help it heal.

-Based on stress to the bone and osteoclast/blast activity, the bone may be in a process of remodeling for years.



What are a few biologics/growth factors that enhance the bone healing process?

•Transforming growth factors**

•Bone morphogenetic proteins (BMPs)**

•Fibroblast growth factors**

•Platelet-derived growth factors (PDGF)**

•Insulin-like growth factors**

-Vascular endothelial Growth Factor (VEGF)


(** means he talks more about this)


Transforming Growth Factors: what do they do?

Huge family of proteins.

–Induces synthesis of cartilage-specific proteoglycans and type II collagen

Cartilage then turns to bone


Bone Morphogenic Proteins (type of Transforming Growth Factor). what do they do?

important sub-types?

Promote cartilage growth

Crucial in the three steps of the healing cascade (chemotaxis and mitosis, differentiation into cartilage, replacement by bone)

-BMP 2 and BMP 7 induce endochondral bone formation in segmental defects.


Fibroblast Growth Factors: what do they do?

Enhance Callus formation.


Insulin-like Growth Factor: what does it do?

-Stimulates bone collagen and matrix synthesis

-stimulates replication of osteoblasts

-inhibits bone collagen degradation


Cytokines: what is their role in bone healing?

Stimulate bone resorption.

IL-1 is the most potent for this.

Both IL1 and IL6 synthesis is decreased by estrogen: so in the absence of estrogen, IL1 and IL6 are more plentiful, and resorb more bone.


bones that have more articular surfaces that others are likely to heal less well - why?

more articular surfaces -> less contact with soft tissue (and vasculature, blood supply, mesenchymal cells, etc).

example: scaphoid bone of the wrist - very little soft tissue contact. does not heal well.