Introduction to Trauma X-ray
Dislocation injury

Key points

  • Joint dislocations are described in terms of the position of the distal bone in relation to the proximal bone
  • Diastasis is the separation of 2 normally adjacent bone parts

Dislocation is an injury resulting in loss of anatomical congruence of bones at a joint. Joint dislocations are described in terms of the position of the distal bone in relation to the proximal bone. This means that distal bones can dislocate from proximal bones, but not vice versa.

Subluxation is a term which may be used to describe incomplete dislocation.

Dislocation example - Finger

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Dislocation example - Finger

  • Middle phalanx of the little finger dislocated dorsally and laterally from the proximal phalanx

Fracture-dislocation

A fracture combined with a dislocation is called a fracture-dislocation.

Fracture-dislocation example - Ankle

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Fracture-dislocation example - Ankle

  • Highly comminuted fracture of the distal fibula
  • Talus dislocated from the tibia - these bones are no longer aligned at the ankle joint (white lines not parallel - compare with normal)
  • The combined injuries are termed 'fracture-dislocation'

Diastasis

Diastasis is a term used to describe the separation of 2 normally adjacent bone parts, either at a ligamentous joint, or at a growth plate.

Diastasis example - Pelvis

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Diastasis example - Pelvis

  • There is separation of the pubic bones at the pubic symphysis - a ligamentous joint
  • Careful observation also shows widening of the right sacroiliac joint
  • The entire right pelvic bone is disconnected