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AIIS avulsion

Case Detail

Anatomy: Musculoskeletal
Heather Borders, MD
Diagnostic Category: Trauma
Created: over 10 years ago
Updated: over 10 years ago
Tags: PEDS
Modality/Study Types: CR MRI
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Two different patients:
Radiograph history is right hip pain after a soccer injury.
MRI history is right hip pain after several episodes of a “pulled muscle.”

Case Images


AIIS avulsion


CR-Crescentic nondisplaced avulsed fragment of bone at the AIIS
MRI-Crescentic fragment of mildly displaced bone at the level of the AIIS with adjacent inflammation, periosteal reaction and edema.


Avulsion injury at the AIIS occurs due to traction by the rectus femoris muscle. The injury can be acute or chronic.
Chronic injury results in reparative new bone formation and can be mistaken for a more aggressive process.

These injuries occur at typical locations and are common in adolescents and attempt should be made not to mistake this for a more aggressive process.

Findings include:
Acute-radiographically, an avulsed fragment of bone with variable degrees of displacement. If injury is non-osseous a fragment may not be visible radiographically. MRI shows similar findings to radiographs with a variable amount of associated edema. MRI demonstrates associated musculotendinous and cartilaginous injury.

Correlation with radiographs should always be performed when interpreting the MRI to help avoid mistaking an avulsion for a more aggressive process.

Chronic-healing with variable degrees of callus and new bone depending on the degree of displacement. If initial injury was cartilaginous, periosteal new bone/reparative change may be the only finding.


Caffey, pediatric imaging. pp. 2796-2797.
Greenspan, orthopedic imaging pp. 222-224.

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