What is the diagnosis?

This patient has an acute avulsion fracture of the iliac crest apophysis.

Image 2:  Left Iliac crest avulsion fracture (arrow). AP x-ray of the pelvis. Image from Ortho EM Pearls Image Bank

What age group is most at risk for this injury?

Pelvic avulsion fractures are rare injuries. Most avulsion fractures in the pelvis occur in children and adolescent athletes between the ages of 8-14 at the apophyses. This is because the apophyses of the pelvis fuse between the ages of 15 and 17 years [1,2].

• Pearl: Avulsion fractures of the iliac crest are the rarest. They account for 2% of all pelvic avulsion fractures in children and adolescents [3].

• Pearl: Apophyses are an outgrowth of bone where muscles and tendons attach. It develops from a separate ossification center and fuses to its parent bone during skeletal maturity [1]. 

What is the mechanism of injury?

The most common mechanism is via indirect trauma due to sudden contractions of the muscle groups: transverse abdominal, internal oblique, and external oblique muscles inserted on the iliac crest.  The sudden contractions of the 3 lateral abdominal muscle groups cause an increased strain across the iliac crest apophysis leading to a fracture. 

• Pearl: Extreme passive stretching and chronic repetitive microtrauma can also cause an apophyseal avulsion fracture [3].

What is the management in the ED? Does the patient need to see orthopedics?

The patient can be discharged on crutches with analgesia and made non-weight bearing for 2 weeks. Most iliac crest avulsion fractures can be managed by conservative management. They do not need to see orthopedics in the Emergency Department but should have follow-up to ensure proper healing.  

• Pearl: Avulsion fractures greater than 3 cm displacement require open reduction and internal fixation to avoid future deformities. Surgical intervention is also necessary if there is nerve or vascular entrapment [1, 2].