A 28-year-old female falls on her extended right wrist while rollerblading. She presents with pain and swelling over the dorsal aspect of the distal forearm. On examination, there is loss of pronation and a prominence over the dorsal wrist. X-rays reveal a fracture of the distal third of the radius with dorsal displacement, and the distal radioulnar joint (DRUJ) appears widened on the AP view. What is the most appropriate initial management?