Avulsion injury

Avulsion injuries or fractures occur where the joint capsule, ligament, tendon or muscle attachment site is pulled off from the bone, usually taking a fragment of cortical bone. Avulsion fractures are commonly distracted due to the high tensile forces involved. There are numerous sites at which these occur. Being familiar with them is important as subacute/chronic injuries can appear aggressive.

Avulsion injuries are common among those who participate in sports, in particular adolescents. 

Avulsion fractures can be classified as acute, subacute or chronic. In acute avulsion fractures, there is usually a clear preceding traumatic incident. Subacute and chronic avulsion injuries can be due to delayed presentation of an acute injury or secondary to repetitive use / overuse injuries 4

The mechanism is from either 4:

  • high muscle activity
  • forced extreme range of motion
  • greater tuberosity: insertion of rotator cuff
  • lesser tuberosity: insertion of subscapularis (rare)
  • coracoclavicular avulsion

Many avulsion fractures are apparent of plain radiographs. The avulsed bone fragment is typically displaced in the direction of the tendon, ligament or joint capsule which is attached to it 5. CT and/or MRI may be required for detection and further characterization. Appearances will vary depending on classification 4:

  • acute: avulsed bone fragment with donor site and typically associated soft tissue swelling / joint effusion
  • subacute: fracture healing results in a mixed lytic/sclerotic appearance
  • chronic: sclerosis and osseous hypertrophy

On MR small avulsion fractures can easily be missed, as the avulsed cortical fragment is often poorly visualized, and the bone marrow edema is absent at the site of injury 5

Most avulsion injuries/fractures are treated non-operatively 4

Fractures

Article information

rID: 953
Synonyms or Alternate Spellings:
  • Avulsion injuries
  • Avulsion fracture
  • Avulsion injury - General
  • Avusion type injuries
  • Avusion type injury

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Cases and figures

  • Case 1: superior peroneal retinaculum avulsion fracture
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  • Case 2: ischial tuberosity avulsion
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  • Case 4: avulsion at medial malleolus
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  • Case 5: bilateral hamstring avulsion
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  • Case 6: avulsion fracture - right anterior superior iliac spine
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  • Case 7: iliac crest avulsion
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  • Case 8: hamstring avulsion
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  • Case 9: lesser trochanter avulsion
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  • Case 10: volar plate avulsion - middle phalanx
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  • Case 11: greater tuberosity avulsion
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  • Case 12: lesser tuberosity avulsion
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  • Case 13: volar plate avulsion - middle phalanx
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  • Case 14: calcaneal avulsion fracture
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  • Case 15: Dorsal avulsion fracture of the navicular bone
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  • Case 16: medial knee ? adductor magnus
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  • Case 17: avulsion of dorsolateral process of the calcaneum
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