Plate Positioning Affects the Pressure on the Axillary Nerve Following a Deltopectoral Approach

Area of Science:

• Orthopedic Surgery
• Biomechanics
• Neuroscience

Background:

• Proximal humerus fractures (PHF) are common, often treated with plate fixation.
• Axillary nerve injury is a potential complication following PHF surgery, leading to shoulder dysfunction.
• Understanding plate positioning's impact on the axillary nerve is crucial for surgical safety.

Purpose of the Study:

• To quantify pressure on the axillary nerve at various plate positions during proximal humerus fracture fixation.
• To identify plate configurations that may increase the risk of axillary nerve compromise.

Main Methods:

• Eight fresh-frozen cadaveric humeri underwent plate fixation.
• Pressure sensors measured axillary nerve pressure with plates in lateral, anteriorly angled, posteriorly angled, and elevated deltoid insertion positions.
• Plate positions were confirmed using fluoroscopy.

Main Results:

• Posteriorly angled plates (Group 3) resulted in significantly higher mean pressure (5.65 ± 1.4 N) on the axillary nerve compared to other groups.
• No significant pressure differences were observed between lateral, anteriorly angled, and elevated deltoid insertion positions.
• Mean pressures for Groups 1, 2, and 4 were 2.65 ± 0.8 N, 2.52 ± 0.8 N, and 2.56 ± 0.9 N, respectively.

Conclusions:

• Posterior angulation of proximal humerus plates significantly elevates pressure on the axillary nerve.
• Anterior plate orientation or elevation of the deltoid insertion may mitigate axillary nerve pressure.
• These findings can help surgeons optimize plate placement to reduce the risk of nerve injury after PHF fixation.