Ulnar nerve injury and perioperative arm positioning.

Primum non nocere. Hippocrates included this admonition in Epidemics, Book I, Second Constitution, to do good or "to do no harm." However, even the most conscientious health care provider will encounter unexpected and serious adverse medical events. This discussion focuses on one relatively common, often perplexing, and usually unexplained perioperative complication: ulnar neuropathy. Perioperative ulnar neuropathy has received increased scientific attention because it accounts for one third of all nerve injury claims in the American Society of Anesthesiologists (ASA) Closed Claims Study database. In addition, these injuries may result in chronic pain or paresthesia, employment disability, catastrophic economic damages, and malpractice litigation. We will explore the current understanding of perioperative ulnar nerve dysfunction by summarizing the relevant scientific literature and information within the ASA closed-claims database, describing the epidemiologic features of perioperative nerve injuries, discussing relevant clinical investigations and recommendations for safe arm positioning during anesthesia, and reviewing the medico-legal issues inevitably intertwined with this topic, particularly the doctrine of res ipsa loquitur.