Ulnar nerve compression by heterotopic ossification in a head-injured patient.

Although heterotopic ossification (HO) at the elbow is a frequent occurrence following head injury, nerve compression by heterotopic bone is quite rare. We report the case of a 22-year-old woman with head injury and well-documented HO at the left elbow who developed signs and symptoms of an ulnar neuropathy four months after her original injury. Electrodiagnostic studies confirmed the presence of a severe ulnar nerve lesion at the level of the elbow. Anterior transposition of the left ulnar nerve showed the nerve to have been compressed by heterotopic bone.