The risk of injury to the axillary nerve, artery, and vein from proximal locking screws of humeral intramedullary nails.

An elderly female cadaver fore-quarter amputation was dissected, and a custom straight intramedullary nail with a 55 degrees oblique downward lateral to medial proximal screw was inserted with a trocar protruding beyond the medial cortex of the humeral surgical neck. The main trunk of the axillary nerve was found to be at risk with any penetration from anterior to posterior and any screw penetration beyond the medial cortex with internal rotation. The axillary artery and vein were at risk with penetration of over 3 cm by a drill point or screw tip whether a transverse or oblique downward screw was used. Transverse screws inserted through the humeral neck from lateral to medial have the potential for damaging a small branch of the axillary nerve laterally, and care must be taken of the lateral humerus while inserting these screws. Screws inserted in a downward direction near the greater tuberosity, if originating above the equator of the humeral head, may cause impingement.