Image Interpretation: Marked cortical irregularity with a probable step-off deformity is noted at the anterior superior iliac spine with accompanying tenderness to sonopalpation. No hyperemia is noted. The Sartorius tendon is normal. The Tensor fascia latae is normal. The Gluteus Medius tendon origin is normal. These findings are suggestive of a chronic anterior superior iliac spine avulsion fracture.
Teaching Pearl: Pelvic avulsion fractures are a rare subset of fractures occurring primarily in active adolescents due to forceful contractions of the attaching musculature in movements such as kicking, running, and sprinting. These fractures most commonly occur at the ASIS, AIIS, and ischial tuberosity. Although traditionally X-ray is used for diagnosis, point-of-care ultrasound allows for visualization of bony structures, dynamic assessment of surrounding musculature, and measurement of displacement of the fracture. Treatment of ASIS avulsions fractures is usually conservative with surgery only considered for those with displacement > 15-20mm.
Sources:
Chen L-W, Yeh W-C. Musculoskeletal sonography facilitates the diagnosis of adolescent anterior superior iliac spine avulsion fracture. J. Med. Ultrasound. 2010;18(4):158-160. https://doi.org/10.1016/j.jmu.2010.11.003.
Mori T, Ihara T, Nomura O. Avulsion fracture of the anterior superior iliac spine in a young athlete detected by point-of-care ultrasound. POCUS J. 2022;7(1):140-143. https://doi.org/10.24908/pocus.v7i1.15096.