A 32-year-old male construction worker is brought to the emergency department after a fall from a height of 3 meters onto his left arm. He complains of severe pain and deformity in the left forearm and elbow region. On examination, there is obvious swelling over the proximal forearm with a palpable prominence over the anterior aspect of the elbow. X-rays of the forearm show a fracture of the proximal third of the ulna with anterior displacement of the radial head. The patient is neurologically intact. What is the most appropriate next step in management?