Forensic Anthropology - Bone Fractures and Trauma

Broken Bones

Direction of Force & Bone Fractures

• The type of break depends on the direction from which force was applied to the bone.
• Forensic Anthropologists have identified 5 types of forces that cause bone fractures:
  • Compression
  • Shearing
  • Bending
  • Torsion
  • Tension

Compression

• A force that pushes down on a bone.
• Fracture lines tend to radiate outward from the point of impact (like broken glass in a windshield).
• Often happens on the skull and matches the weapon used to create the wound; a wide surface area is affected.

Shearing

• Similar to bending.
• A linear shearing type of fracture occurs, usually caused by a person trying to stop themselves from falling.
• Most of these fractures occur because of accidents.
• Can also occur if the victim is dismembered by a saw.

Bending

• A force that impacts a bone at a right angle.
• This is the most common type of fracture.
• It causes a triangular break.
• Often a bending fracture called a parry fracture occurs in the ulnar bone of the arm.
• This happens when someone holds up their arm to defend themselves, implying a violent struggle.

Torsion

• A twisting force.
• One end of a bone stays stationary while the other end twists.
• This fracture causes a spiral.
• This happens most often in skiing and biking accidents, and unfortunately often in cases involving child abuse.

Tension

• A force that pulls on the long axis of a bone.
• Usually, tension forces dislocate bones, but if strong enough, a part of the bone can break away.
• These most often occur in accidents.

Bone Trauma

• Bones usually exhibit clues concerning violent deaths.
• Forensic Anthropologists can interpret bone trauma to the best of their ability but can only highly suggest the cause of death.
• The expression “is consistent with” is often used when reporting their results.
• Perhaps something happened before the death.

5 Main Causes of Death

• Accident
• Homicide
• Natural
• Suicide
• Unknown

Blunt Force

• An injury caused by a wide instrument with a flat or round surface.
• Forces: compression, bending, shearing
• Bone Injury: wide surface area

Projectile Force

• Forces: compression, bending
• Bone Injury: displacement of bone with radiating fracture lines from the impact point

Sharp Force

• Forces: compression, shearing
• Bone Injury: puncture wounds, grazing cut marks

Strangulation

• Forces: compression
• Bone injury: A fractured hyoid bone implies strangulation.
• Note: The hyoid bones in young children are still separate; as we age, they fuse.