A 55-year-old man from Mumbai falls directly on the dorsum of his flexed right wrist while trying to break his fall. He presents with wrist pain, swelling, and a 'reverse dinner fork' deformity on clinical examination. X-ray shows a transverse fracture of the distal radius with volar displacement and volar angulation of the distal fragment. The patient is concerned about loss of wrist extension. Which nerve is at highest risk of acute compression injury in this fracture pattern?