Avulsion fractures of the anterior superior iliac spine most commonly occur in which age group?

• A. 16-18 years
• B. 13-15 years
• C. 10-12 years
• D. 40-50 years

Answer: (B)

Avulsion fractures at the ASIS happen when a sudden, powerful contraction of the sartorius pulls on the still-developing apophysis at that site. In skeletally immature athletes, the apophyseal growth plate is the weaker link compared to the tendon, so a forceful hip flexion with knee extension can pull off a fragment rather than tear the muscle.

This injury pattern is most common during early to mid-adolescence, when the growth plates are open but the bones aren’t yet fully fused. That’s why the typical age range is around 13 to 15 years. As the skeleton matures and the apophysis fuses (toward late adolescence), avulsion injuries become less common, and in younger children the pattern is less typical, while in adults the apophysis is no longer a vulnerable site.