The Relationship of Multiplanar Distal and Uniplanar Proximal Interlocking Screws to Neurovascular Structures with the Depuy Synthes Humeral Nail-EX: An Anatomic Study.

OBJECTIVE

To determine the proximity of neurovascular structures to multiplanar distal interlocking screws and proximal interlocking devices for an antegrade inserted humeral nail.

METHODS

Humeral nails (Depuy Synthes Humeral Nail-EX, Paoli, PA) were inserted into 10 matched cadavers with 3 distal interlocking trajectories: anterior to posterior (A-P), anterolateral to posteromedial, and anteromedial to posterolateral (AM-PL). The distance of the screw path and screw head to the radial, lateral antebrachial cutaneous nerve (LACN), and median nerves and the brachial artery was measured. Proximally, the distance of spiral blades and/or interlocking screws to the axillary nerve was measured.

RESULTS

The median distance of the screw path/screw head inserted (A-P) to the LACN was 0 mm/0 mm in the left arm and 3.5 mm/1.6 mm in the right arm. The median distance of the screw path/screw head inserted AM-PL to the median nerve was 7.08 mm/0 mm in the left arm and 0 mm/0.12 mm in the right arm. The median distance of the screw path/screw head inserted AM-PL to the brachial artery was 4.05 mm/3.83 mm in the left arm and 2.19 mm/2.84 mm in the right arm. The humeral head was radiographically divided into 3 zones. The average distances of the axillary nerve to interlocking devices placed into zone 2 and zone 3 of the humeral head are 14.65 mm and 1.07 mm, respectively.

CONCLUSIONS

When using the DePuy Synthes Humeral Nail-EX, AM-PL screws may risk the median nerve and brachial artery; thus, this trajectory is not recommended. The LACN may be at risk with A-P and to a lesser degree, anterolateral to posteromedial screws. Proximally, interlocking devices in zone 3 of the humeral head may risk the axillary nerve.