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Fracture Types and Mechanisms of Injury
Knowledge of fracture types and mechanisms can be useful for a variety of reasons.Mechanisms of Injury
- You will tend to look for certain types of fractures if you know the patient's mechanism of injury.
- You are more likely to look for associated fractures/co-morbidity
- You can describe the fracture to another health professional with greater accuracy and economy
Fracture Type Description Mechanism Avulsion fracture fragments tend to be small bone fragments. They are often at the ends of long bones and tend to be adjacent to joints. Anywhere that there is a tendon or ligament attachment is a potential site for an avulsion fracture.
Common avulsion fractures are the ulna styloid fracture (associated with a Colles fracture) and fractures of the base of the 5th metatarsal associated with ankle inversion injuries.
An avulsion fracture occurs when an injury causes a ligament or tendon to tear off (avulse) a small piece of a bone to which it's attached. The mechanism is usually a tension force which pulls the avulsed fragment off the bone.
Fracture Type Description Mechanism Buckle Fracture
A buckle fracture is an incomplete fracture in which an isolated radius of the cortex of the bone is buckled.
Buckle FractureA buckle fracture will usually be the result of a compression force that is not evenly loaded. The compression will be slightly off the centre axis of the bone. This can causes the cortex to buckle on one side of the bone only.
Fracture Type Description Mechanism Butterfly FractureA fracture in which the centre fragment is triangular shaped. Butterfly FractureNo particular mechanism is associated with butterfly fractures
Chondral, osteochondral and subchondral Fractures
Fracture Type Description Mechanism Comminuted FractureA comminuted fracture is one in which there are multiple bone fragments.
This is a comminuted fracture of the calcaneum caused by a fall from a height (so-called lover's fracture or Don Juan fracture)
Memory aid- just think of lots of minute pieces.
Comminuted FractureComminuted fractures do not result from a specific mechanism but do tend to be a result of moderately large forces.
Crush Fracture in Longbone
Fracture Type Description Mechanism Crush FractureA crush fracture is a fracture type associated with a crushing injury. Long bone crush fractures are usually comminuted. The term crush fracture is commonly used to refer to crushing injuries of the digits and spine, but could refer to a crushing injury of any bone. Crush FractureCrush fractures in long bones result from a compression force that is applied transversely with respect to the long axis of a bone. For non-longbones, the axis of compression could be from any direction. The spine is a special case.
Crush Fracture in Spine
Fracture Type Description Mechanism Crush FractureA crush fracture is a fracture type associated with a crushing injury. The term crush fracture is commonly used to refer to fractures of the vertebral bodies. These fractures are associated with trauma and osteoporosis. Crush FractureCrush fractures of the spine can result in compression and/or wedging of the vertebral bodies. The mechanism is axial compression but may include other forces (e.g. bending, rotational)
Fracture Type Description Mechanism Depressed FractureA depressed fracture is one in which a fragment or group of fragments is 'pushed in'. These fractures are most frequently associated with the skull. Depressed FractureDepressed fractures suggest a direct blow or shearing force. The forces tend to be localised. For example, a blow from a hammer to the skull can cause a depressed skull fracture.
"Fracture" Type Description Mechanism A diastasis is an abnormal separation of two anatomical structures that are normally located together. This pelvis image demonstrates a iastasis of the symphysis pubis and the right sacroiliac joint Mechanism of injury for diastasis would include shear and tension.
Fracture Type Description Mechanism Fracture-DislocationThis is a term which is used to refer to an injury that includes a fracture and a dislocation.
The image shown (left) is a Galeazzi fracture characterised as a fracture of the distal third of the radius and a dislocation of the distal radio-ulnar joint (DRUJ)
Fracture-DislocationThere is no specific mechanism for fracture-dislocations
Fracture Type Description Mechanism This 3 year old boy fell of the monkeybars onto an outstretched hand. He has a greenstick fracture of the distal 1/3 of the radius and ulna. Greenstick FractureA greenstick fracture is more commonly seen in children's longbones. When a bending force is applied to a bone, the cortex on the concave side experiences a compression force (white arrow) and the cortex on the convex side experiences a tension force(black arrow). Children's bones are sufficiently pliable to fracture the bony cortex on the tension side, but not on the compression side. The result is the very aptly named greenstick fracture. The effect can be similar to bending a green sapling compared to bending a dry twig or branch.
Greenstick fractures are incomplete fractures. They tend to be more stable than complete fractures.
Greenstick FractureGreenstick fractures tend to occur when a compressive or bending force is applied to a child's longbone. In the case of a fall onto an outstretched hand that results in a greenstick fracture of the radius and ulna, the force is axial or compressive.
Fracture Type Description Mechanism Incomplete Fracture
Fracture Type Description Mechanism This 3 year old boy fell of the monkeybars onto an outstretched hand. He has a greenstick fracture of the distal 1/3 of the radius and ulna. Incomplete FractureAn incomplete fracture occurs when the fracture does not traverse the bone completely i.e. some of the bone remains intact. Greenstick fractures provide a common example of incomplete fractures. Adults can also experience incomplete fractures. Incomplete FractureA variety of forces could result in an incomplete fracture including mixed forces. The bending force would be one of the most common mechanisms.
Fracture Type Description Mechanism Intra-articular FractureThis calcaneal fracture extends into the proximal joint and would therefore be classified as an intra-articular fracture. Intra-articular FractureThere is no specific mechanism of injury for intra-articular fractures or extra-articular fractures.
Fracture Type Description Mechanism Spiral FractureA spiral fracture is an obliquely orientated fracture in the shape of a spiral. These fractures sometimes have a very distinctive spiral shape.
This is a spiral fracture of the mid/distal 1/3 of the femur.
Spiral FractureSpiral fractures are caused by a rotational or torsion force. A typical mechanism would be if your foot is caught and you rotate your leg, you are at risk of spiral fracture of the tibia.
Fracture Type Description Mechanism Pathological FractureA pathological fracture is a fracture that occurs at a site where the bone is weakened by a pathological process.
The white arrows identify the fracture line through the tibial metaphysis weakened by the bone cyst
Pathological FractureNo particular mechanism is associated with pathological fracture. Pathological fractures are often caused by trivial force.
Fracture Type Description Mechanism This patient suffered a fractured patella after falling directly onto her knee. Stellate fractures are most commonly associated with the patella. The term stellate refers to the fracture being star-shaped with the fracture lines radiating outwards from a central point. Stellate fractures could occur when any plate-like bony structure receives a sufficiently large (localised) blow. Other anatomical regions that can demonstrate stellate fractures are the skull and acetabulum. The mechanism of injury is commonly a direct impact to the patella associated with a patient falling directly onto his/her kneeor striking the knee on a dashboard in a frontal collision. This is a shearing force.
Fracture Type Description Mechanism
Fracture Type Description Mechanism This patient suffered a subluxation of the right SI joint and symphysis pubis. This is not a fracture but is worthy of inclusion in a list of fracture types given that is a term used to describe bone trauma. SubluxationA subluxation is a partial or incomplete dislocation. The definition is a little vague. Certain joints, when traumatically separated, tend to be described as subluxed (or showing diastasis) rather than dislocated. Synovial joints can be described as dislocated and incomplete dislocations can be described as subluxations (see pseudosubluxations of the shoulder joint). Non-synovial joints (i.e. cartilaginous and fibrous joints) such as the symphysis pubis and SI joints, for example, tend to be more likely to be described as subluxed when traumatically or otherwise abnormally separated. SubluxationA subluxation suggests a shearing or a distracting/tension force.
Fracture Type Description Mechanism Torus FractureA torus fracture is a circumferential impacted buckle fracture. The term torus refers to a 3 dimensional circular shape as shown below. Torus FractureA torus fracture will usually be the result of a compression force.
Fracture Type Description MechanismWedge fractures are caused in trauma patients by an axial compression force.
This patient fell from a roof and landed on his feet. There is an wedge fracture of L2.
Wedge fractures are commonly seen in the vertebral bodies.
Still to come
- Longitudinal fracture
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