What should a Combat Medic do to prevent external rotation in a casualty with a displaced pelvic fracture?

To prevent external rotation in a casualty with a displaced pelvic fracture, securing the knees and/or feet together is an effective strategy. This method stabilizes the lower extremities and helps to maintain alignment of the pelvis, reducing the risk of further displacement or exacerbation of the injury. By keeping the legs together, external forces that may cause rotational movement are minimized, promoting better stability for the injured area.

Using a pelvic binder is also a commonly accepted intervention for managing pelvic fractures, as it compresses the bony pelvis and can reduce internal bleeding. However, while it addresses the overall stability of the pelvis, it doesn't specifically prevent external rotation in the same direct manner that securing the knees and/or feet together does.

Applying traction and elevating the legs are interventions typically utilized for other types of fractures or injuries and are not specific to managing external rotation in pelvic fractures. Therefore, securing the knees and/or feet together is the most appropriate measure in this scenario.