By the direction of the fracture line

By whether the fracture is linear or comminuted
Greenstick fractures Open fractures, closed fracture Pathologic and stress fractures
Traction or tension fractures Angulation fractures Rotational fractures Compression fractures Fractures due to angulation, rotation, and axial compression
Extrinsic Factors
Force = Mass x Acceleration Stress = Load / Area on which the load acts (kg/cm2) Strain is defined as the change in linear dimensions of a body resulting from the application of a force or a load. Tensile strain. Compression strain. Shear strain.
Classification of Fractures by Mechanism of Injury
Direct
trauma
Indirect
trauma
Tapping fractures Crush fractures Penetrating (gunshot) fractures
Fatigue
strength
Fatigue failure (subjected to repeated or cyclical stresses)
Biomechanical Properties of Bone(1)

Bone is a two-phase material consisting of matrix, which is mostly collagen, and bone mineral.

Mangled extremity severity score(MESS) MESS score > 7 amputation

Stabilization of the bone
Description of Fractures
Greenstick
fractures (common in children) and stress fractures
Description of Fractures

Fractures
By anatomical location

Proximal, middle, or distal third of the shaft; supracondylar; subtrochanteric Transverse, oblique, spiral
Orthopedic Trauma
Principles of Fractures and Dislocations





Description of fractures Biomechanics of fractures Classification of fractures by the mechanism of injury Clinical features of fractures Clinical features of dislocations Emergency management of fractures Definitive treatment of fractures Fracture care Rehabilitation following fractures
Biomechanical Properties of Bone(2)

Fatigue (stress) fractures
Fatigue fractures are most commonly seen in military installations Frankel and Burstein: a key factor: muscle fatigue The pattern of fracture:
Extrinsic
factors factors properties of bone
The magnitude, duration, and direction of the forces acting on the bone, as well as the rate at which the bone is loaded Intrinsic Energy-absorbing capacity, modulus of elasticity (young's modulus), fatigue strength, and density Biomechanical Fatigue (stress) fractures Holes in bone Effect of metallic implants

A transverse fracture formed on the tension side An oblique fracture formed on the compression side.

Holes in bone
When the diameter of the hole is greater than 30% of the diameter of bone, the weakening effect becomes exponential..
Biomechanical Properties of Bone(3)

Effect of metallic implants
Orthopaedic implants weaken bone by stress shielding Predispose to fracture by increasing the stiffness of a segment of bone so that there is an abrupt transition between the degree of elasticity of the supported and unsupported segments of bone
Incompletely fractured, with part of the cortex and periosteum remaining intact on the compression side
Pathologic
Greenstick Fx
Path.Fx
Stress Fx

Biomechanics of Fractures

Open Fracture

Definition:
Break in the skin and underlying soft tissues leads directly into or communicates with the fracture and its hematoma.
Classification: Gustilo-Anderson Irrigation and debridement Immediate or early amputation versus limb salvage
Intrinsic Factors(2)
Young's
modulus and stress-strain curves
Elastic strain, plastic strain, break point The steeper the curve, the stiffer the material; The gradient is known as the modulus of elasticity (E) or young's modulus.

Tension
and compression strains are always associated with shear strains
Intrinsic Factors(1)
Energy-Absorbing
Capacity
Work = Force x Distance (ft lbs) (kg cm) (Nm) Strain energy is the energy a body is capable of absorbing by changing its shape under the application of an external load. The more rapidly a bone is loaded, the greater will be the energy absorption before failure. Fractures associated with slow loading are generally linear, whereas rapid loading infuses enormous strain energy so that an explosion of the bone takes place at failure, giving rise to the severe comminution of high-energy fractures.
Direct Trauma
Low V