A 70-year-old woman with a 20-year history of diabetes mellitus undergoes open reduction and plate and screw fixation (medial and posterolateral plates) of a bicolumnar fracture of the distal humerus, using an olecranon osteotomy for exposure. The ulnar nerve is protected by mobilizing it completely from at least 10 cm proximal through the flexor pronator aponeurosis, and then is left transposed anteriorly in the subcutaneous tissues at the end of the surgery. Approximately 2 months after surgery, the patient notices numbness in the small and ring fingers. Electrodiagnostic testing demonstrates nonrecordable latencies in the left ulnar nerve, suggestive of a severe, active left ulnar neuropathy at or distal to the elbow. The patient incidentally also has bilateral moderately severe median neuropathies.