Review Question - QID 218866

This patient has an iliac crest avulsion fracture, which is caused by a rapid contraction of the abdominal muscles which are innervated by the lower intercostal nerves.

Avulsions of the apophysis of the iliac crest are rare injuries. Typically, they are caused by rapid lateral trunk flexion or twisting resulting in a strong contraction of the lateral abdominal musculature (external and internal oblique muscles and the transverse muscle). Conservative treatment consisting of rest, analgesics, and physical therapy is often successful. Surgical treatment is reserved for fractures displaced >3cm or those that failed nonoperative treatment.

Schiller et al provide a broad review of lower extremity avulsion fractures including the presentation, evaluation, and management of injuries including ischial tuberosity, anterior superior iliac spine, anterior inferior iliac spine, tibial tubercle, calcaneus, and greater and lesser trochanters. Most often avulsion fractures heal with nonoperative management. However, surgery should be considered for patients with displaced tibial tubercle avulsions, failed nonoperative management, nerve impingement symptoms, or displacement >2 cm.

Rossi et al performed a retrospective review of 203 avulsion fractures of the pelvic apophyses. The most common avulsion fractures were ischial tuberosity, AIIS, ASIS, superior corner of pubic symphysis, and iliac crest (IC). Soccer and gymnast were the most common sports implicated in these injuries.

Schuett et al reviewed 228 apophyseal avulsion fractures with mean age of 14.4 and males represented 76% of the cohort. AIIS was the most common, followed by ASIS, ischial tuberosity, and iliac crest. Five patients had nonunions, of which four were ischial tuberosity avulsions. Initial fracture displacement >2 cm increased the risk of nonunion by 26 times. Surgical treatment was indicated in 3% of cases.

Figure A is an AP of the pelvis demonstrating an avulsion fracture of the left iliac crest apophysis with minimal displacement.

Incorrect Answers
Answer 1: The hamstring muscles are innervated by the sciatic nerve.
Answer 2: The rectus femoris is innervated by the femoral nerve.
Answer 3: The adductor longus is innervated by the obturator nerve.
Answer 5: The tensor fascia lata is innervated superior gluteal nerve.