Bone Flashcards
How bone works as a shock absorber
End plates bow
Vertical columns bow
Type of falls/loads that can result in end plate or compression fractures
Fall on buttock
Land on heels
Lift heavy load
The role of spinal percussion in fracture detection
We can use this to indicate a fracture due to the fact that the periosteum is innervated by the nerve!
We can also use this to check for space occupying lesion
Fatigue or stress fractures
Fracture seen in cancellous bone
Fractures tend to be unstable
Shear stress always occurs with compressive or twisting loads
The role of exercise in treating osteoporosis
exercise has the greatest impact when bones are still growing
Working out can help bone to be more osteogenic
The effects of aging and corticosteroids on bone loss
over several decades the skeletal mass may be reduced by 50% of original trabecular and 25% cortical mass
-women lose 2% bone mass per year from 4th decade on men 1%
Corticosteroids effect: in asthma patients who use this for less then one year there is an increase in prevalence of vertebral fractures 1/4 will have a fracture
Wolf’s law
Bed rest = 1% loss of bone mass per week
The relationship between frequency of loading, magnitude of loading and stress
fractures.
When bone is subjected to repetitive stress the way it fractures is not predictable compared to a normal bone break
Bone/fracture response to torsion loads and 3 point bending loads (explain the
mechanisms involved).
Torsion creates a combination of shear, tensile, and compressive stress
How muscular contraction can help to protect bones
Certain muscle groups produce compression stress
this compression can reduce or neutralize the tensile stress of bending
The anisotropic characteristics of bone under tensile loads
Response of cortical bone is dependant on the direction of a torsion stress
Longitudinal tensile stress produces maximum strength, ultimate stress, stiffness, energy storage capacity
Transverse tensile stress produces minimum strength, ultimate strain, minimum storage capacity
What are the most common sites for a compression fracture?
TL junction
Common sites of stress fractures with old age
lumbar vertebra
femoral head
proximal tibia
When do fatigue fractures occur?
When fatigue outspaces remodelling
Fatigue under repetitive stress:
Tensile side vs compression side style of fractures
Tensile side= transverse fracture
Compression side= oblique fracture
