Anatomic study of the axillary nerve in a Chinese cadaveric population: correlation of the course of the nerve with proximal humeral fixation with intramedullary nail or external skeletal fixation.

Introduction: The axillary nerve can be injured during external skeletal fixation with Schanz screws or proximal locking screws of intramedullary nails. Being aware of the axillary nerve's anatomic relationship to the proximal humerus is vital for avoiding complications.

Methods: We investigated the relationship of the axillary nerve to surrounding bony landmarks by studying 88 axillary nerves in 44 embalmed cadaveric adult Chinese males. These measurements were then compared with the results from a similar study among Caucasians using the same reference points.

Results: We identified three significantly different parameters between our Chinese and the previously studied Caucasian subjects (P ≤ 0.05): the distances from the superior aspect of the humeral head to the axillary nerve (D1) (5.2 ± 0.7 vs. 6.09 ± 0.65 cm, respectively); surgical neck to axillary nerve (D2) (2.0 ± 0.7 vs. 1.72 ± 0.84 cm); and humeral length (D3) (29.0 ± 2.2 vs. 35.25 ± 5.7 cm). The D1 distance ranged from 4.0 to 6.7 cm; the D2 distance ranged from 1.0 to 4.1 cm; and the entire humeral length (D3) ranged from 23.3 to 33.3 cm. Iatrogenic injury to the axillary nerve could be reduced by placing pins and screws in proper directions using portable C-arm fluoroscopic guidance, drill-guided protective systems, and a mini-open-incision with muscle spreading and drill protective systems directly placed on the bone.

Conclusion: Because of physical variability among individual patients and populations, surgeons should consider the possible courses of the axillary nerve when treating proximal humeral fractures.