17 y/o male brought to PED2 by EMS after hurting his hip playing basketball. He was running down the court when his friend collided with hip, hitting friend's elbow on patient's bony pelvis. Patient said he couldn't walk afterwards, his dad seems to think he's being overly dramatic. No PMH. VSS. Exam shows tenderness on right side of bony pelvis without brusing or deformity. No other abnormalities on exam.

AP pelvis XRAY

What's the diagnosis? Treatment?

OK, now that you've thought about it a while, I'm sure you've diagnoses an avulsion fracture of the anterior superior iliac spine or ASIS. These tend to occur in athletic adolescents who have a forceful contraction of the muscles that attach there (sartorious and tensor fascia lata). They fracture because the apophyses are forming in puberty. Other areas prone to avulsion fractures are ischial tuberosity, and AIIS (anterior inferior iliac spine). 

Xrays are often not obtained as the mechanism (sprinting, jumping) sounds like it wouldn't cause bony injury, and the injuries are misdiagnosed as a muscle strain. The good news is that the treatment is generally similar- rest with partial weight bearing on cructhes, pain control, followed by PT. If the bony fragments are more than 3 cm appart or healing is delayed, the patient is a candidate for surgical repair.