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MED 101- PHYSICS I > 10. BONE FRACTURES > Flashcards

10. BONE FRACTURES Flashcards

1
Q
  1. What are bones in the skeleton designed for?
A
  • they are designed for several properties and functions
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2
Q
  1. How do muscles create motion?
A
  • they swing bones at joints
  • they are efficient with relatively still bones
  • they do not cause the bones to deform when they swing them
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3
Q
  1. How much energy do stiff bones need to absorb before they fracture?
A
  • relatively little
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4
Q
  1. Which bones are less ideal for muscle action?
A
  • more compliant bones
  • they resist fractures more
  • they are lighter
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5
Q
  1. What can be seen in children with regards to the efficiency of their motion?
A
  • the efficiency of their motion is less important than their resistance to fracture
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6
Q
  1. What is the difference between the femoral bone in children and in adults?
A
  • the femoral bone is about 2/3 as stiff in children as it is in adults
  • it requires 50% more energy to break
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7
Q
  1. Why do the bones in the inner ear need to be stiff?
A
  • they need to be able to transmit sound efficiently
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8
Q
  1. How come bones in the ear do not need to resist fracture?
A
  • they bear no loads
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9
Q
  1. What is the work of the fracture?
    (WF)
A
  • it is the amount needed to break a material
  • it is defined as the energy (J) that is needed for the fracture per area (m2)
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10
Q
  1. How can the work of the fracture be estimated?
A
  • it can be estimated from the elastic energy stored
  • a stress-strain curve can be used
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11
Q
  1. What establishes how tough a material is?
A
  • how high the work of fracture is
  • the higher the work of fracture:
    - the tougher the material
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12
Q
  1. When is there enough energy for a sudden fracture?
A
  • when the available kinetic energy is distributed to several of the long bones in the body
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13
Q
  1. Why do our bones regularly not break?
A
  • most of the energy acting on the body is absorbed by:
    - muscle contractions
    - deformation of soft tissues
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14
Q
  1. Which aspects of the body absorb energy upon compression and then propagate stress waves in the body?
A
  • skin
  • fat
  • muscles
  • clothing
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15
Q
  1. Name 5 components of the body that brace bones against breaking?
A
  • fascia
  • tendons
  • ligaments
  • joint capsules
  • contracted muscles
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16
Q
  1. How is the bracing of bones against breakage achieved?
A
  • every part of the tensile forces is supported

TENSILE= related to a tension

  • energy is absorbed as the components of the body are stretched
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17
Q
  1. Why do bones fracture more easily for the elderly?
A
  • their bones are weaker
  • their tissues are less situated to absorb energy
  • they may fall more awkwardly
  • this would result in more body breaking action
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18
Q
  1. What are bone fractures determined by?
A
  • the mode of the applied loads
  • the orientations of the bones
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19
Q
  1. When are bone fractures the strongest?
A
  • they are the strongest in compression
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20
Q
  1. When are bones fractures the weakest?
A
  • in shear
  • in torsion
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21
Q
  1. When are bone fractures less strong than in compression and more than in shear?
A
  • when the bones experience tension
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22
Q
  1. What force do bones usually break under?
    Which force do they not break under?
A
  • they break under shear stresses
  • they break under tension
  • THEY DO NOT BREAK under Compression
23
Q
  1. When the bone is bending, what forces does it experience on either side?
A
  • it experiences tension on the one side
  • it experiences bending on the other side
24
Q
  1. When a bone is bending, from which end will the fracture begin?
A
  • the fracture will start at the side with the tension
  • this is because the compression fracture on a bone is stronger than the tension fracture
  • therefore, the tension end is the weaker end
25
Q
  1. Where does the crack/fracture of the bone generate?
A
  • in line with the bone axis
26
Q
  1. What is a Butterly fragment?
A
  • it is a crack occurring at two 45° angles
27
Q
  1. What happens when the bone twists?
A
  • the tensile (tension) forces produce a spiral crack
  • this crack winds around the bone
  • the bone breaks when the ends of the crack/fracture are connected
  • this is when they meet in the middle
28
Q
  1. What do direct blows to the human body lead to?
A
  • they lead to direct fractures that break the bone
29
Q
  1. What does a low energy direct blow result in?
A
  • it breaks the bone into two pieces
  • these two pieces are non comminuted
  • this means that they are broken into no more than 2 pieces
  • THIS IS CALLED A TRANSVERSE FRACTURE
  • the force on the bone is perpendicular to the direction of the bone fracture
30
Q
  1. What does a high energy direct blow result in?
A
  • it breaks the bone into many pieces
  • there is soft tissue injury
  • the bone is markedly comminuted
  • this means that it is broken into more than two pieces
31
Q
  1. What four types of fractures can indirect blows to the body result in?
A
  • Torsion (Spiral)
  • Bending and Torsion (Oblique)
  • Transverse with a perpendicular fracture (Traction)
  • Transverse with a buttery fragment (Bending)
32
Q
  1. What factor induces different fracture patterns?
A
  • the different loading modes
33
Q
  1. What induces a buttery fracture?
A
  • bending
34
Q
  1. What induces a spiral fracture?
A
  • torsion
35
Q
  1. What induces a transverse fragment with a fracture that is perpendicular to the force?
A
  • shear
36
Q
  1. How would we lessen the likelihood of the bone breaking when the body is involved in a collision?
A
  • increase the impact area
  • increase the collision time
37
Q
  1. Bones are viscoelastic.
    What does this mean for the function of the
    bones?
A
  • this means that the bones have behaviour that is time dependent
  • they absorb shock more when the collision time is greater
  • this lessens the chance of a fracture
38
Q
  1. What three factors does the occurrence of the fractures depend on?
A
  • the ultimate strength of the forces on the bone
  • the defects of the bone
  • how the loads are applied to the bone
39
Q
  1. What is buckling?
A
  • it is a type of macroscopic failure
40
Q
  1. How can Euler buckling be demonstrated?
A
  • it can be demonstrated by pushing down on a drinking straw
  • this straw must be standing upright on the table
41
Q
  1. What happens when long, thin tubes are compressed?
A
  • the middle one bows to one side
  • it then collapses
  • this is not the failure of the structure itself
42
Q
  1. When else can bones fracture with regards to stress being placed on them?
A
  • they can fracture when the stress on them suddenly
    exceeds a given failure limit
43
Q
  1. What damage causes bones to fracture more gradually?
A
  • prolonged continuous stress
    (such as sitting)
  • prolonged cyclic stress
    (fatigue due to running or walking)
44
Q
  1. What is a stress fracture?
A
  • it is a fracture that happens when the rate of the damage on the bone
    EXCEEDS
    the rate that the body repairs the bone
  • the bone fails
45
Q
  1. What are the the three modes (ways) that stresses can be applied to a bone to cause crack generation?
A
  • Mode 1 (Opening Mode)
  • Mode II (Sliding Mode)
  • Mode III (Tearing Mode)
46
Q
  1. What happens in Mode 1 (Opening Mode)?
A
  • the load is tensile
    (is placing tension)
  • it is placing tension forces in opposite directions
  • it is perpendicular to the crack propagation direction
47
Q
  1. What happens in Mode II (Sliding Mode)?
A
  • the load is shear
  • it is parallel to the plane of the crack
  • it is parallel to the direction of the crack propagation
48
Q
  1. What happens in Mode III (Tearing Mode)?
A
  • the sheer load is perpendicular to the crack direction
49
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes
50
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes
51
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes
52
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes
53
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes
54
Q
  1. Read through this summary.
    Does everything make sense?
A
  • yes

MED 101- PHYSICS I (28 decks)

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