10. BONE FRACTURES Flashcards
1
Q
- What are bones in the skeleton designed for?
A
- they are designed for several properties and functions
2
Q
- 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
3
Q
- How much energy do stiff bones need to absorb before they fracture?
A
- relatively little
4
Q
- Which bones are less ideal for muscle action?
A
- more compliant bones
- they resist fractures more
- they are lighter
5
Q
- 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
6
Q
- 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
7
Q
- Why do the bones in the inner ear need to be stiff?
A
- they need to be able to transmit sound efficiently
8
Q
- How come bones in the ear do not need to resist fracture?
A
- they bear no loads
9
Q
- 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)
10
Q
- 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
11
Q
- 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
12
Q
- 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
13
Q
- 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
14
Q
- Which aspects of the body absorb energy upon compression and then propagate stress waves in the body?
A
- skin
- fat
- muscles
- clothing
15
Q
- Name 5 components of the body that brace bones against breaking?
A
- fascia
- tendons
- ligaments
- joint capsules
- contracted muscles
16
Q
- 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
17
Q
- 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
18
Q
- What are bone fractures determined by?
A
- the mode of the applied loads
- the orientations of the bones
19
Q
- When are bone fractures the strongest?
A
- they are the strongest in compression
20
Q
- When are bones fractures the weakest?
A
- in shear
- in torsion
21
Q
- When are bone fractures less strong than in compression and more than in shear?
A
- when the bones experience tension
22
Q
- 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
- 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
- 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
25. Where does the crack/fracture of the bone generate?
- in line with the bone axis
26
26. What is a Butterly fragment?
- it is a crack occurring at two 45° angles
27
27. What happens when the bone twists?
- 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
28. What do direct blows to the human body lead to?
- they lead to direct fractures that break the bone
29
29. What does a low energy direct blow result in?
- 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
30. What does a high energy direct blow result in?
- 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
31. What four types of fractures can indirect blows to the body result in?
- Torsion (Spiral)
- Bending and Torsion (Oblique)
- Transverse with a perpendicular fracture (Traction)
- Transverse with a buttery fragment (Bending)
32
32. What factor induces different fracture patterns?
- the different loading modes
33
33. What induces a buttery fracture?
- bending
34
34. What induces a spiral fracture?
- torsion
35
35. What induces a transverse fragment with a fracture that is perpendicular to the force?
- shear
36
36. How would we lessen the likelihood of the bone breaking when the body is involved in a collision?
- increase the impact area
- increase the collision time
37
37. Bones are viscoelastic.
What does this mean for the function of the
bones?
- 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
38. What three factors does the occurrence of the fractures depend on?
- the ultimate strength of the forces on the bone
- the defects of the bone
- how the loads are applied to the bone
39
39. What is buckling?
- it is a type of macroscopic failure
40
40. How can Euler buckling be demonstrated?
- it can be demonstrated by pushing down on a drinking straw
- this straw must be standing upright on the table
41
41. What happens when long, thin tubes are compressed?
- the middle one bows to one side
- it then collapses
- this is not the failure of the structure itself
42
42. When else can bones fracture with regards to stress being placed on them?
- they can fracture when the stress on them suddenly
exceeds a given failure limit
43
43. What damage causes bones to fracture more gradually?
- prolonged continuous stress
(such as sitting)
- prolonged cyclic stress
(fatigue due to running or walking)
44
44. What is a stress fracture?
- 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
45. What are the the three modes (ways) that stresses can be applied to a bone to cause crack generation?
- Mode 1 (Opening Mode)
- Mode II (Sliding Mode)
- Mode III (Tearing Mode)
46
46. What happens in Mode 1 (Opening Mode)?
- the load is tensile
(is placing tension)
- it is placing tension forces in opposite directions
- it is perpendicular to the crack propagation direction
47
47. What happens in Mode II (Sliding Mode)?
- the load is shear
- it is parallel to the plane of the crack
- it is parallel to the direction of the crack propagation
48
48. What happens in Mode III (Tearing Mode)?
- the sheer load is perpendicular to the crack direction
49
49. Read through this summary.
Does everything make sense?
- yes
50
50. Read through this summary.
Does everything make sense?
- yes
51
51. Read through this summary.
Does everything make sense?
- yes
52
52. Read through this summary.
Does everything make sense?
- yes
53
53. Read through this summary.
Does everything make sense?
- yes
54
53. Read through this summary.
Does everything make sense?
- yes
