Ulnar nerve injury after a comminuted fracture of the humeral shaft from a high-velocity accident: a case report

INTRODUCTION: Injury to the ulnar nerve following humerus shaft fracture is a very rare entity because the ulnar nerve is well protected from the bone by muscle and soft tissue, and thus remains unaffected in these fractures. We report what is, to the best of our knowledge, the first case of ulnar nerve injury due to a comminuted humeral shaft fracture. The injury manifested and was diagnosed the day after a high-velocity accident. The paucity of related literature and the necessity for early diagnosis and subsequent treatment of such injuries in high-velocity accidents urged us to document this case. CASE PRESENTATION: A 30-year-old Indian man presented to our Emergency Department after a road traffic accident. Our patient complained of right arm pain and the inability to move his extremity. The following morning he developed clawing. Nerve conduction studies on the peripheral nerves of his arm in addition to an X-ray confirmed the diagnosis of a possible injury to the ulnar nerve. Our patient was taken to our Operating Room for surgery, during which a fragment of bone was found abutting the ulnar nerve after penetrating his triceps. This fragment of bone was replaced and the fracture was reduced by open reduction and internal fixation using a dynamic compression plate and screws. Postoperatively, our patient received physical therapy and was discharged two weeks after surgery with no neurological deficit. CONCLUSIONS: This case emphasizes the urgency and importance of careful neurological examination of all the peripheral nerves supplying the arm in patients with a fracture of the shaft of the humerus. In the setting of injury to the arm in high-velocity accidents, a differential diagnosis of ulnar nerve injury should always be considered.