Anterior inferior iliac spine avulsion injury
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Anterior inferior iliac spine (AIIS) avulsion 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
myositis ossificans of straight head of rectus femoris muscle
-<p><strong>Anterior inferior iliac spine (AIIS) avulsion injuries</strong> are one of the six main types of <a href="/articles/apophyseal-avulsion-fractures-of-the-pelvis-and-hip">pelvic apophyseal avulsion fractures</a>. Subacute or chronic avulsion injuries can be mistaken for a pseudotumour. </p><h4>Epidemiology</h4><p>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.</p><h4>Pathology</h4><p>The straight head of the <a href="/articles/rectus-femoris-muscle">rectus femoris muscle</a> originates from the AIIS and forceful extension at the <a href="/articles/hip-joint-1">hip joint</a> can lead to an <a href="/articles/avulsion-injury-1">avulsion injury</a> at this point. The mechanism is one of forced hip extension with the knee in flexion <sup>4</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>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.</p><h4>Treatment and prognosis</h4><p>Almost all cases are managed conservatively.</p><h4>Differential diagnosis</h4><ul>- +<p><strong>Anterior inferior iliac spine (AIIS) avulsion injuries</strong> are one of the six main types of <a href="/articles/apophyseal-avulsion-fractures-of-the-pelvis-and-hip">pelvic apophyseal avulsion fractures</a>. Subacute or chronic avulsion injuries can be mistaken for a pseudotumour. </p><h4>Epidemiology</h4><p>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.</p><h4>Pathology</h4><p>The straight head of the <a href="/articles/rectus-femoris-muscle">rectus femoris muscle</a> originates from the AIIS and forceful extension at the <a href="/articles/hip-joint-1">hip joint</a> can lead to an <a href="/articles/avulsion-injury-1">avulsion injury</a> at this point. The mechanism is one of forced hip extension with the knee in flexion <sup>4</sup>.</p><h4>Radiographic features</h4><h5>Plain radiograph</h5><p>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.</p><h4>Treatment and prognosis</h4><p>Almost all cases are managed conservatively.</p><h4>Differential diagnosis</h4><ul>