Basics of Skeletal Trauma

• Basics of bone trauma

  • When sufficient force is applied to bone a break will occur:

  -Complete= fracture

  -Incomplete= infarcation

  • Displacement- when 2 broken ends of bone no longer meet
  • Hinge fracture- occur when a break purses through only part of the bone
  • Greenstick fracture- when there is no displacement between broken ends
  • Comminated fractures- fractures resulting in multiple pieces
• Fracture lines

  Originate near the point of impact

  Types:

  • Radiating
  • Concentric

  Dissipation of force

  • Pre-exisitng fractures or open sutures can terminate the path of a fracture
  • Fractures can jump sutures and existing fractures if involving sufficient force

  -Contra-comp fractures
• Non-traumatic fractures

  Pathological fractures

  • Breaks that occure in the bone that are weakened by disease e.g. osteogenesis imperfect or osteoporosis

  Stress fractures

  • Breaks caused by overuse
  • microfracture

  Fatigue fractures

  • occur in bone that are exposed to intermittent stress over long periods of time e.g. vertebral column with age
• Forces causing trauma

  Direction of force- the direction from which the force originates before contacting the bone

  Tension:

  • A force that pulls a bone
  • Usually directed along long axis of bone
  • Common in dislocations- fracture of bony process caused by pull of tendon
  • Usually few fracture lines associated with tension fractures
  • More common in accidents
  • Rarely of forensic relevance
• Forces causing trauma

  Compression

  • Compression forces puch down on bone
  • Cause fracture lines or discontinuities
  • Discontinuity can be complete or incomplete
  • Fracture lines radiate from the point of impact
  • Numerous and far-reaching
  • Compression fractures most common on the skull
  • Shape of displaced bone can follow the configuration of the fracturing instrument
• Forces causing trauma

  Torsion

  • Torsion is a twisting force
  • Most commonly observed in accidents such as pedestrian vs car
  • Occur when one end of the bone is held stationary whilst the other end is twisted
  • Causes the fracture surfaces and their associated fracture lines to spiral down the long axis of the bone at approx. 45 degrees
  • Most common in long bones as a result of accidents
  • Not common in homicide or suicides
• Forces causing trauma

  Bending

  • Most common force
  • Force impacts side of bone at right angles to its long axis
  • Causes break through the cross-section of bone
  • Few fracture lines are associated with this type of break
  • Force can be great enough to produce a comminated fracture
  • In adults bending results in fracture
  • In sub-adults bending results in infarctions

  Parry fractures are also common

  -Typically a defence fracture

  -Inward displacement of bone

  -Usually ossur at distal ends of long bones
• Forces causing trauma

  Shearing

  • Similar to bending
  • Involves fixation of one end of bone
  • Colles' fracture is common shearing fracture (distal radius)
  • Results from a fall onto outstretched hand
  • Ground fixes one end of bone
  • Falling body produces shearing force
  • not common in homicides or suicides
  • Consistent with accidents
  • Cutting a bone is also form of shearing
  • Associated with dismemberment
• Speed of force (longitudinal)

  Can be distinguished as dynamic or static

  Dynamic

  • Sudden stress - force delivered powerfully at high speed
  • Most common form of fracturing force

  Static

  • Stress applied slowly- force starts low and builds to point where bone breaks
  • Usually only results in displacement without any resultant fracture lines
  • e.g, hyoid fracture during strangulation
• Forces of force

  • Size of the area impacted by a force
  • Narrow or wide extremities

  Narrow focus

  • Force applied to single point or narrow line

  Wide focus

  • Force applied over a large area of bone
  • Results in breaks over a wide bone area
  • Can be caused by a variety of instruments that have a wide focus