Likely sites of pelvic avulsions in adolescents with incomplete skeletal maturation include ischial tuberosity (hamstring insertion), anterior superior iliac spine (sartorius), anterior inferior iliac spine (rectus femoris), pubic symphysis (adductors), and greater and lesser trochanter (gluteus muscles and iliopsoas) and rarely iliac crest apophysis (abdominal wall insertion) . Chronic avul-sive injuries can also be confused for malignant lesions or chronic infections and often result from chronic overuse injuries in patients participating in organized sports . A review of over 200 cases of apophyseal avulsions showed the most common areas of involvement were the ischial tuberosity, anterior inferior iliac spine (ASIS), and anterior superior iliac spine (AIIS) with the highest association among those participating in soccer, gymnastics, and track and field/athletics  (Fig. 20).
Diagnosis of many avulsive injuries is generally made by history and mechanism of injury along with radiographs. Curvilinear or amorphous bone material is generally seen adjacent to the insertion site of concern although discrete bone fragments may not be seen with pubic symphyseal avulsion . MR usually detects injury as a result of surrounding inflammation but subtle cortical bone fragments often manifest as dark signal voids and can be difficult to detect (Fig. 21). MR in the acute setting reassures that the myotendinous unit or tendon insertions are intact. In the younger child without apophyseal calcifications, MR is useful for diagnosis as radiographs may be negative . Most avulsive injuries are treated conservatively but it is important to comment on a displaced avulsion greater than 2 cm, as the may need to undergo surgical repair [88-90]. Also hamstring avulsion injuries are more prone to complication because of proximity to the sciatic nerve and can be evaluated with MRI .
Fig. 19. Focal edema in quadratus femoris consistent with mild strain (arrows).
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