skull fractures
 

head injury

blunt force trauma

sharp force trauma


 

online fracture references



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Copyright Forensic Medicine Resources 2007. All rights reserved

The normal thickness of the skull is approximately 4-15 mm (depending upon the site at which it is measured), and the presence of a skull fracture is an indication that severe force has been applied to the skull. Fractures occur when the elastic limit of the bone has been exceeded, and the formation of a skull fracture depends upon the force applied, the point of impact (thickness of the skull), presence of scalp hair and the direction of impact.

The presence or absence of a skull fracture does not, however, determine survival, as it is the presence or absence of underlying damage to the brain or its coverings that is important.

Saukko and Knight (2004) reviewed the force required to cause fractures of the skull, and noted that the average adult head weighs 4.5Kg. A simple fracture can occur by walking into a fixed object (force required = 73N), whilst a simple fall through 1 m causing a frontal impact (510N) can also result in linear or mosaic fractures. Fractures have been absent when an impact force of 1314 N was recorded.

Skull fractures may be classified by their appearance (Saukko and Knight 2004);

  • Linear – straight or curved fracture lines, which may radiate from a depressed region, or occur at a distance from the impact site, and tend to occur at ‘unsupported’ regions of the skull (e.g. across the supra-orbital ridges). Linear fractures in children or young adults may pass through the suture lines (‘diastatic fracture’). ‘Hinge’ fractures occur when the linear fracture passes across the middle cranial fossa, separating the skull base into 2 halves, and may be caused by a heavy blow to the side of the head (e.g. in motorcycle accidents).
  • Ring – these occur in the posterior fossa around the foramen magnum, particularly following a fall from a height (with primary ‘feet first’ impact), where the kinetic energy transfer is transmitted up the cervical spine.
  • Pond – this is a shallow depressed fracture, more common in infants.
  • Mosaic (‘spider’s web’) – a comminuted depressed fracture with radiating fissures.
  • Depressed – a fracture caused by force applied in a ‘focussed’ area e.g. by a hammer. The outer and inner tables of the skull are driven inwards, often causing damage to the brain or its coverings. The shape of the fracture may indicate the type of weapon used.

 

Complications of skull fractures

1.      Immediate

·        Meningeal haemorrhage

·        Brain damage

2.  Late

  • ·Infection – spreading directly from the wound, through the nose (following a fracture of the ethmoid bone) or through the other sinuses (e.g. mastoid). (See Matschke and Tsokos 2001 and Friedman et al 2001 for further details).
  • ·Post-traumatic epilepsy – usually requires a depressed skull fracture and appears within 2 years of the traumatic episode. (Saukko and Knight 2004).
  • ·Post-traumatic dementia – boxers who have died in the ring often have subdural haemorrhages. Repeated episodes of head injury can, however, lead to cortical atrophy and hydrocephalus, with damage to the corpus callosum and septum pellucidum. Patches of gliosis may be seen within the brain substance, and neuronal loss may be evident in the cerebellum. In addition, there may be pigment loss in the substantia nigra, as well as diffuse neurofibrillary tangles (‘Alzheimer-like’) within the cortex. (Saukko and Knight 2004).