Which parameters are more reliable in proximal humerus surgery in terms of the axillary nerve?

This study aims to examine the reliability of the old and new parameters in determining the axillary nerve safe area for surgical interventions in the proximal humerus by measuring the distances between the top of the humeral head, the top of the greater tuberosity, the base of the greater tuberosity, and the acromion and axillary nerve.

Between 2020 and 2022, a total of 52 shoulders of 26 fresh frozen male human cadavers (mean age: 46±25.5 years; range, 28 to 64 years), 26 right and 26 left were included. The deltopectoral approach was used. The intersection distances of the anterolateral end of the acromion, the top of the humeral head, the top of the tuberculum majus, and the base of the tuberculum majus with the N. axillaries were determined. All measurements were performed using the Microscribe® G2X.

The mean distance from the top of the tuberculum majus to the axillary nerve (shown as "A") was measured as 4.36±0.17 cm and 4±0.21 cm on the right and left, respectively. The mean distance from the center of the base of the tuberculum majus to the axillary nerve (shown as "B") was measured as 1.27±0.18 cm and 1.24±0.11 cm on the right and left, respectively. The mean distance from the apex of the humeral head to the axillary nerve (shown as "C") was measured as 6.15±0.39 cm and 5.89±0.34 cm on the right and left, respectively. The mean distance between the anterolateral end of the acromion (shown as "D") was measured as 6.15±0.39 cm and 5.89±0.34 cm on the right and left, respectively. There was a moderate positive correlation between distances A and B measured on the right and left side, respectively (r=0.484; p=0.012) (r=0.454; p=0.020).

A strong positive correlation was found between the distances A and B. The A, B, and C parameters had a weak correlation with parameter D. The anatomical parameters A and B was found to be less variable and more reliable than parameter D.