The radiograph demonstrates a transverse fracture of the distal half of the humeral shaft. The radial nerve runs in a groove on the posterior aspect of the humerus as it courses into the forearm compartment and is therefore at high risk of injury. If the nerve injury is apparent before any manipulation has been done, the fracture should be reduced; the nerve injury should be observed since the nerve function will likely improve with time. If the nerve injury is only present after reduction, immediate surgical exploration is warranted because the nerve might be trapped in the fracture site. At this level of the arm, the ulnar and median nerves are well protected by muscle. The posterior interosseous nerve is a distal branch of the radial nerve and may be injured in fractures near the radial head, but it is in no danger from injuries at the level seen in this radiograph. There is no "ascending circumflex brachial nerve."