The risk of injury to neurovascular structures from distal locking screws of the Unreamed Humeral Nail (UHN): a cadaveric study

When performing distal interlocking of an intramedullary humeral nail, there is risk of iatrogenic injuring to the neurovascular structures. Our cadaveric study with frozen sections through the distal humerus presents the anatomic relationship of the different neurovascular bundles and the trajectories used for the implantation of the three distal interlocking screws of the AO-UHN. The middle lateromedial pin was in direct contact with the radial nerve in 3 out of 10 cases, with the ulnar nerve in 3 out of 10 cases and with the brachial artery in 1 out of 10 cases. We recommend using only the two anteroposterior screws for distal interlocking, avoiding the lateromedial locking option. If this lateromedial locking screw is needed to gain adequate stability, it should be introduced under visual control