# Risk of Axillary Nerve Injury With Medial Support Screws in Intramedullary Nails: An Anatomical Study

## TL;DR

This anatomical study finds that medial support screws in proximal humeral nails can risk injuring the axillary nerve.

## Contribution

The study is the first to investigate the anatomical relationship between medial support screws and the axillary nerve in proximal humeral nails.

## Key findings

- In 6.9% of cases, axillary nerves contacted medial support screws.
- In 93.1% of cases, nerves were located proximal to the screws.

## Abstract

Background: In recent years, intramedullary nails with medial support screws for proximal humeral fractures have become available. Although these devices have a potential risk of iatrogenic axillary nerve injury, no studies have investigated the anatomical relationship between the medial support screws in the modern intramedullary nail and the axillary nerve. This study aimed to clarify the anatomical relationship between the medial support screws in the intramedullary nail and the axillary nerve.

Materials and methods: In total, 29 cadaveric shoulders (mean age: 82.6 years old (range: 61-105); 15 males and 14 females) were included in this study. Shoulders within whole-body cadavers were used in all cases. A single proximal humeral nail with medial support screws (ARISTO Proximal Humeral Nail; MDM, Tokyo, Japan) was used. The distance of each medial support screw from the axillary nerve and its branches was measured.

Results: In two (6.90%) of 29 shoulders, the axillary nerves came into contact with the medial support screws. In the remaining 27 of 29 shoulders (93.1%), the nerves were located proximal to the medial support screws.

Conclusion: Medial support screws in proximal humeral fracture nails had the potential to injure the axillary nerve and its branches.