This is Barry Belosis, one of the musculoskeletal radiology fellows at Stanford University. 15-year-old male presented during varsity high school football game with pain in the left hip. Concerned for anterior superior iliac spine avulsion fracture. The patient in this case presented with this left hip radiograph demonstrating avulsion fracture of the apophysis at the anterior superior iliac spine. This is the attachment of the sartorius and tensor fascia lata. On a different patient, here we can see on the anterior inferior iliac spine is a bony fragment of the apophysis consistent with avulsion fracture. This is the rectus femoris attachment. Avulsion fracture is usually the result of a sudden forceful concentric or eccentric contraction of the muscle attached to the apophysis. Avulsion fractures of the pelvis are most common in young athletes due to the discordance between an increased muscle strength and unfused physis at the muscle tendon bone unit. Avulsion fracture typically demonstrates abnormal widening at the apophysis such as here. Asymmetry to the contralateral side as we can see on the right anterior inferior iliac spine. Any irregular bone fragments. However, knowledge of tendon attachments in the pelvis is important in determining the location of avulsion fracture. For instance, the most common location is the ischial tuberosity. So right here and right here where the hamstring tendons attach. It is followed by the anterior inferior iliac spine and then the anterior superior iliac spine. The other potential location is the lesser trochanter which is the iliopsoas attachment and the greater trochanter which is the gluteus medius and minimus attachment. The pubic symphysis which is the adductor muscles attachment and the iliac crest which is the abdominal muscle attachment are the least common location for avulsion fracture.

2nd Edition, CASE 22

2nd Edition

Hip

avulsion fracture

anterior superior iliac spine

young athletes

tendon attachment

diagnosis