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Fractures - Coggle Diagram
Fractures
Fracture biomechanics
Weight bearing causes loading of bones
Structure affects properties
Biphasic
Inorganic phase
Hydroxyapatite crystals
Strong but brittle
Organic phase
Collagen
Flexible but weak
Combined
Stronger per unit weight than either substance alone
Under physiologic loads
microscopic changes in shape
no permanent deformation
Under excessive loading, bones fracture
Load-deformation curve Four Forces
Tension
Bone lengthens and narrows
Maximum stress is perpendicular to load
Fails by debonding of osteonal cement lines
Compression
Bone shortens and widens
Maximum stress is perpendicular to load
Fails from shear stresses with oblique cracking of osteons
Bending
Compressive and tensile stresses
Bone fails 1st in tension
Then obliquely on the compression side
Stress increases with increasing distance from the neutral axis
Torsion
Bone twists around the neutral axis
Shear stress is produced
Spiral/long oblique fxs
Fracture Etiology
Direct overloading
HBC
Gunshot wound
Indirect overloading
Avulsion from tension
Pathologic
Bone tumor
Fatigue
repetitive stress
microfractures
too little time for repair
fracture classification
Communication with environment
Closed
No gas in ST
No break in skin
Open
Gustilo grading of open fractures
Grade I
Wound < 1 cm;
minimal contamination
minimal comminution
minimal soft tissue damage
infection rate 0-2%
Grade II
Wound > 1 cm; moderate soft tissue damage,
minimal periosteal stripping
Infection rate 2-5%
Grade IIIA
Severe soft tissue damage
substantial contamination
coverage adequate for closure
infection rate 5-10 %
Grade IIIB
Severe soft tissue damage
substantial contamination
coverage inadequate for closure
infection rate 10-50%
Grade IIIC
Arterial injury
requiring immediate repair
infection rate 25-50%
Skin opened
Severity/Extent of damage
Simple (2-piece)
Comminuted
Greenstick (incomplete)
Fissure
Direction/type of fracture
Transverse
Oblique
Spiral
Compression
Avulsion
Location of fracture
Right or left?
Specific section
Diaphyseal
Metaphyseal
Physeal
Salter-Harris classification
Used when physeal growth plates are open
Based on data on experimental animals
Lower grade meant to predict prognosis
Poorly correlated with outcome
Real life injuries more severe
Growth plates are not all flat
Grades 1- V, sometimes VI
young animals only
Condylar (intra-articular)
Trochanteric
Which bone?
Energy absorbed
Kinetic energy = 1/2 mass x velocity2
More energy absorbed - more comminution
Viscoelasticity & Anisotropy
How the bone reacts (changes in response) to load depends on rate the load is applied
Behavior depends on axis/direction of applied load
Fracture displacement
Displacement
Distal fragment relative to proximal fragment
Need two orthogonal radiographs