Pelvic Apophyseal Avulsion Fractures

BACKGROUND: The aim of this study was to assess the patient demographics, epidemiology, mechanism of injury, and natural history of pelvic apophyseal avulsion fractures. METHODS: A retrospective records review of imaging and clinical documentation was performed for patients diagnosed with pelvic apophyseal avulsion fractures at our institution from 2007 to 2013. Patient's Risser score, triradiate status, fracture location, size, and displacement were recorded based on initial injury radiographs. Further clinical and radiographic chart review was utilized to determine mechanism of injury, presence of multiple/bilateral injuries, nonunion, chronic pain, as well as any surgical interventions performed. RESULTS: We identified 225 patients diagnosed with 228 apophyseal avulsion fractures with mean age of 14.4 years. Males represented 76% of the patients. Anterior inferior iliac spine (AIIS) avulsions were the most common, representing 49% of all avulsion fractures, followed by anterior superior iliac spine (30%), ischial tuberosity (11%), and iliac crest (10%). The most common mechanism of injury was sprinting/running (39%) followed by kicking (29%), but the mechanism varied by fracture type with 50% of AIIS avulsions caused by kicking. Multiple pelvic fractures were identified in 6% of patients. Pain >3 months out from initial injury was present in 14% of all patients and AIIS avulsion fractures were 4.47 times more likely to have chronic pain. Five nonunions were identified, 4 of which were ischial tuberosity avulsions. Initial fracture displacement >20 mm increased the risk of nonunion by 26 times. Surgical treatment was indicated in 3% of cases. CONCLUSIONS: In this series, nearly all pelvic avulsion fractures (97%) were managed successfully with a conservative approach. Contrary to prior studies, AIIS avulsions represented half of the avulsion fractures. AIIS and ischial tuberosity fractures are at increased risk of developing future pain and nonunions, respectively. Patients and families need to be counseled about this possibility because future intervention may be necessary. LEVEL OF EVIDENCE: Level IV-therapeutic.