The physical exam is key in making this diagnosis in a timely manner. There will be soft tissue injury communicating with underlying fracture. When fractured bone is clearly exposed on exam, the diagnosis is straightforward. However, this diagnosis is difficult when the skin disruption is minimal and there is no appreciated fracture on initial inspection.
Utilize radiographs after the physical exam to evaluate for underlying fracture. If the bone is fractured, focus on the soft tissue injury. The x-rays may reveal that the fracture is indeed likely through the soft tissue.
Go back and re-examine any wounds after the x rays to make sure you did not underestimate any benign appearing wounds that may be open fractures. If the base of the soft tissue injury is appreciated and there is no exposed bone, there is no open fracture. If after minor wound probing, the base cannot be appreciated, the fracture must be treated as open until evaluated by an orthopedic surgeon. If the wound base is in communication with the bone, the fracture is open.