How to Diagnose Avulsion of the AIIS

An avulsion fracture occurs when a joint capsule, ligament or muscle insertion is pulled away from the bone, possibly pulling fragments of bone away with it. The anterior inferior iliac spine (AIIS) is the origin for the direct head of the rectus femoris, a powerful leg muscle. The following steps will show how to diagnose avulsion fractures of the anterior inferior iliac spine.

Instructions

Difficulty: Challenging

1. Obtain the patient history. This injury most commonly occurs in young athletes who are sprinters or hurdlers. An avulsion of the anterior inferior iliac spine is caused by the hip being forcefully flexed by the rectus femoris. Adolescents are predisposed to avulsion fractures of the hip due to the relative weakness of the apophysis.
2. Observe the common presenting symptoms of an avulsion in the hip to be the sudden onset of a severe shooting pain in the hip. The patient also may experience swelling, local tenderness or even loss of muscular function.
3. Examine the patient. The clinical findings may be similar to soft tissue injuries to ligaments, muscles and tendons.
4. Take plain radiographs as the imaging technique of choice for avulsion fractures. An avulsed bony fragment immediately adjacent to the anterior inferior iliac spine should confirm the diagnosis. A fracture healing with bony callus formation is a typical finding.
5. Use magnetic resonance imaging (MRI) if needed to differentiate avulsion of the anterior inferior iliac spine from a tear in the tendon of the rectus femoris. This injury also may be confused with a bone tumor.