Ulnar nerve problems can occur when the elbow is immobilized in flexion beyond a right angle (ie, less than 90 degrees). This can compress the ulnar nerve as it travels through the cubital tunnel, a problem especially likely if the ulnar nerve is relatively mobile and moves up against the epicondyle, as it did in this patient who had sustained a radial fracture. Ulnar neuropathy developed after a longarm cast was applied with the elbow hyperflexed. I have occasionally seen this complication in patients who are anesthetized with the elbow flexed beyond a right angle. It is often a complaint of patients who fall asleep with the elbow hyperflexed. The consequence is usually a temporary ischemic neuropathy of the sensitive ulnar nerve that causes weakness of the intrinsic muscles of the hand supplied by the nerve.