Flashcards in Fracture biomechanics and classification Deck (44)
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1
What are the forces that must be neutralized for a fracture to heal?
1. bending
2. torsion
3. compression
4. tensino
2
What determines what forces predominate at a fracture site?
1. geometry of fracture
2. location of muscle groups
3
Compression is good for what type of fracture and bad for what other type of fracture?
1. good for transverse fracture to reduce motion
2. bad for oblique fracture because fragments shear past
4
How are fractures classified?
1. extent of soft tissue
2. degree of cortical disruption
3. geometry
4. location in bone
5. degree and direction of displacement
5
What does bending cause?
agnulation
6
What happens to the bone with bending?
1. one side is being compressed (concave) and one side is has tension (convex)
7
Where is the neutral axis of a bone?
usually in the centre of the medullary canal and is where there is neither tension nor compression
8
What happens if you fix a bone with something that runs down the neutral axis?
the apparatus will be subjected to less bending force than something running down the outside of the bone
9
What does torsion cause?
rotation
10
What is torsion
the tendency for a bone or its pieces to twist around long axis
11
Where does compressino act?
along the long axis of bone and moves ends of bone twoard eachother
12
What happens if compression is applied to an oblique fracture?
there is overriding-->shear
13
What does tension cause?
distraction/avulsion fractures of apophyses (olecranon and calcaneus)
14
What control do casts and splints provide?
1. bending
2. ok torsion
15
What control do wires provide
1. good tension
(no others)
16
What control do intramedullary pins provide?
1. good bending
(no others)
17
What control do interlocking nails provide
1. bending
2. tension
3. torsion
4. compression
18
What control do external skeletal fixation provide?
1. bending
2. tension--but rare use for this
3. torsion
4. compression
19
What control do bone plates provide?
good control of all but
weakest in combined compression and bending
20
What control do bone plates provide?
good control of all but
weakest in combined compression and bending
21
When does a bone fracture?
when the magnitude of the force placed upon it at a specific site exceeds its ability to resist the force without deforming permanently
22
What is a closed fracture?
no wound connecting bone to outside world
23
What is an open fracture
there is a connection with open world
24
What is a greenstick gracture
bending or folding fracture. the cortex doesn't actually break all the way through but bones deforms
25
What is a fissure?
it is a crack and only involves one cortex and is usually longitudinally oriented
26
What is a saucer?
a divot that gets taken out of one cortex (e.g. horse 3rd metacarpal)
27
what is a complete fracture?
both cortices are disrupted
28
What is a depression
e.g. in skull
29
What is a transverse fracture?
A fracture perpendicular to long axis of bone
Torsion is a big problem, compression good
30
