Stress Radiograph to Detect True Extent of Symphyseal Disruption in Presumed Anteroposterior Compression Type I Pelvic Injuries

BACKGROUND: The differentiation between anteroposterior compression (APC)-I and APC-II pelvic fracture patterns is critical in determining operative versus nonoperative treatment. We instituted a protocol in which a stress examination was performed for patients presenting with an APC-I injury diagnosed with static radiographs to reveal the true extent of the injury. METHODS: During a 4-year study period, we performed 22 stress radiographs in patients with a presumed APC-I injury, which showed symphyseal diastasis ≥ 1.0 cm but <2.5 cm on initial anteroposterior (AP) radiographs of the pelvis or on axial images of the pelvis on computed tomography (CT) scans. In the operating room, a radiopaque marker of known diameter was placed on the skin over the pubic symphysis. A direct AP load was manually applied to both anterior superior iliac spines, and diastasis of the pubic symphysis was measured on stress fluoroscopic images. RESULTS: The mean distance of symphyseal diastasis was 1.8 cm on the AP radiographs, 1.4 cm on the CT scans, and 2.5 cm on fluoroscopic images under a stress examination. Six of 22 patients (27.2%) demonstrated a symphyseal diastasis of >2.5 cm during the stress examination, which changed their treatment from nonoperative to operative. CONCLUSIONS: Measurements of symphyseal diastasis can significantly vary depending on the radiographic modality (CT vs. plain films) and during application of a stress force. The use of stress examination under general anesthesia in the acute setting of pelvic injury can be beneficial in accurately diagnosing the severity of injury and choosing appropriate treatment.