Unit 6a: Fractures Flashcards
(35 cards)
Why might fractures, in general, be getting treated earlier when they could heal by themselves?
More cost effective (reduced hospital stay)
What are the 2 most important mechanical properties of bone?
Strength
Stiffness
What does ‘anisotropic’ mean?
A material has different properties depending on the direction it is loaded
What types of load are long bones most resistant to/
Strongest in compression
Then tension
Weakest in shear
What is the the location and mode of fracture determined by?
The geometry and structure of the bone
The loading mode
The laoding rate
In tension and compression what is the stiffness of a bone proportional to?
The cross sectional area of the bone
larger the area, stiffer the bone
What affects a bone’s mechanical behaviour in bending?
Cross-sectional area
Distribution of bone tissue around a neutral axis
What is the second moment of area?
A measure of the fficiency of a shape to resist bending
What is second moment of area also called?
Moment of inertia
What does a larger second moment of area indicate about a bone?
It is stronger and stifeer ``
Why do long bones have a high second moment of area for the amount of bone material and why is this beneficial?
Because much of the bone tissue is distributed at a distance from the neutral axis - means they are more resistant to bending
What factors affect bone strength and stiffness in torsional loading?
The cross-sectional area
Distribution of bone tissue around a neutral axis
What is the polar moment of inertia?
Th efficiency of a shape to resist torsional loads
Why does the proximal tibia have a higher polar moment of inertia than the distal tibia despite its smaller cross-sec area?
Much of the bone tissue is distributed away from the neutral axis
Where does torsional fracture of the tibia most commonly occur?
Distally
Would an accompanying fibula fracture under torsional load take place lower or higher than the tibia?
Higher (within proximal third) - weakest point
What type of bone is found mid-diaphysis?
Cortical bone
What type of bone makes up the metaphyses?
Cancellous bone
Which type of bone is significantly weaker under axial compressive loading?
Cancellous bone
Give 2 fractures of tibial fracture caused by the weakness of cancellous bone under axial compressive loading?
Supracondylar fracture
Tibial plateau fracture
In adults, in pure bending which side of the bone will fail first and why?
Convex side (as bone is weaker in tension)
In children, in pure bending which side of the bone will fail first?
Concave side
What fracture pattern usually results from pure bending?
Transverse fracture pattern
What fracture pattern results from pure compression?
Oblique
