Axillary nerve palsy after retrograde humeral nailing: clinical confirmation of an anatomical fear

Introduction  Locked antegrade or retrograde nailing of humeral shaft and proximal humerus fractures is a well etablished treatment option. Anatomic-morphological studies revealed a potential high risk of axillary nerve injury within proximal interlocking screw insertion. However, clinical experiences do not seem to confirm this, as there is a lack of interlocking screw insertion associated axillary lesions in literature. Case report  We report about a 69-year-old man with a humeral shaft fracture (AO-type 12-A3) stabilized by a retrograde implanted interlocking nail. Proximal interlocking screw insertion was performed in a posterior-to-anterior direction. The fracture healed uneventfully. In a follow-up examination 2 years later, an atrophy and paralysis of the deltoid muscle were visible. Electrophysiological evaluation confirmed an isolated axillary nerve injury. Nevertheless, the patient showed good functional recovery with almost free range of motion. Conclusion  Even for clinical practise proximal interlocking screw insertion is associated with a substantial risk of axillary nerve injury. Particularly for posterior-to-anterior screw insertion anatomic conditions should be considered. In spite of axillary nerve lesion, recovery of almost full shoulder function is possible by compensating the loss of deltoid function by rotator cuff muscles.