Risk of injury to the axillary nerve during antegrade proximal humeral blade nail fixation - an anatomical study.

Introduction: The antegrade intramedullary Locking Blade Nail (Marquardt, Germany) is a device aimed at improving purchase in the humeral head and reducing varus displacement by providing medial buttress support and triangular stability within the humeral head. The aim of this study is to measure the relationship of the proximal fixation screws to the axillary nerve.

Methods: 13 whole cadavers underwent insertion of an antegrade proximal humeral blade nail via a deltoid split approach to both shoulders. The anatomic proximity of the anterior branch of the axillary nerve to the screws was measured following soft tissue dissection and inspection of the nerve.

Results: The mean distance of the nerve from the anterolateral acromion was 62 mm (range 45-81 mm). The nerve lay closest to the distal blade fixation screw 4.9 mm (range 0-19 mm). In three cases the nerve lay directly underneath the washer and in all three cases there was macroscopic evidence of damage to the nerve. In 5 cases the nerve travelled obliquely in a cranial direction to lie 1.8 mm (range 0-3 mm) from the distal blade fixation screw, in 2 of these cases the nerve lay beneath the washer.

Conclusion: The anterior branch of the axillary nerve is placed at risk during insertion of the locking screws despite use of protection sleeves and trocars. We advocate that when using antegrade intramedullary nails that incorporate an inferomedial calcar screw an extended anterolateral acromial approach is undertaken.