Injection-related ulnar neuropathy.

Two previously healthy people sustained mild ulnar mononeuropathies at the level of the upper arm after injections by the same nurse. In both, the nurse was attempting to inject into the middle deltoid; the ulnar nerve was presumably reached by standing at the patient's side and injecting "sidearm" into the upper arm. These cases point out the careful attention to local anatomy required for those administering injections, and the importance of proper positioning.