Anterior inferior iliac spine avulsion injury

Changed by Yahya Baba, 8 Jul 2023

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Disclosures - updated 8 Apr 2023: Nothing to disclose

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Anterior inferior iliac spine (AIIS) avulsion injuries are one of the six main types of pelvic apophyseal avulsion fractures. Subacute or chronic avulsion injuries can be mistaken for a pseudotumour.

Epidemiology

As with many pelvic avulsion injuries, they most often occur in adolescents (mostly between the ages of 14-17). There is a slight male predilection and they tend to occur most often in sports involving kicking.

Pathology

The straight head of the rectus femoris muscle originates from the AIIS and forceful extension at the hip joint can lead to an avulsion injury at this point. The mechanism is one of forced hip extension with the knee in flexion ⁴.

Radiographic features

Plain radiograph

The avulsed bony fragment may not be as obvious on the AP projection. An oblique projection can be utilised to demonstrate the fragment in profile.

Treatment and prognosis

Almost all cases are managed conservatively.

Differential diagnosis

pelvic digit
osteochondroma
rectus femoris heterotopic ossification ~~following tendon injury~~ ⁵
myositis ossificans of straight head of rectus femoris muscle

~~-<li><a href="/articles/heterotopic-ossification" title="Heterotopic ossification">heterotopic ossification</a> following tendon injury 5</li>~~
+<li><a href="/articles/rectus-femoris-heterotopic-ossification" title="Rectus femoris heterotopic ossification">rectus femoris heterotopic ossification </a>5</li>

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