In the anterolateral (front and to the side) approach to the shoulder, should the deltoid split be made distal (further away) or proximal (closer) to the axillary nerve?

From the Guidelines

In the anterolateral approach to the shoulder, the deltoid split should be made distal to the axillary nerve to minimize the risk of nerve injury. The axillary nerve typically courses approximately 5-7 cm below the lateral edge of the acromion, so the deltoid split should be performed at least 7-8 cm distal to the acromion to ensure safety. When performing this approach, it's essential to identify and protect the axillary nerve, which innervates the deltoid muscle and provides sensory innervation to the lateral shoulder. Injury to this nerve can result in deltoid muscle weakness or paralysis and sensory deficits. The anterolateral approach is commonly used for procedures such as rotator cuff repairs, subacromial decompressions, and certain fracture fixations. Surgeons should always maintain awareness of the neurovascular structures in this region and use careful dissection techniques to avoid iatrogenic injury. Palpation of the deltoid muscle and knowledge of surface anatomy landmarks can help guide proper placement of the deltoid split, as noted in general surgical principles 1. Key considerations in this approach include:

• Identifying the axillary nerve and protecting it from injury
• Performing the deltoid split at a safe distance from the axillary nerve
• Using careful dissection techniques to avoid iatrogenic injury
• Maintaining awareness of neurovascular structures in the region. While the provided evidence does not directly address the anterolateral approach to the shoulder, general surgical principles and anatomy guide the recommendation to make the deltoid split distal to the axillary nerve 1.

From the Research

Anterolateral Approach to the Shoulder

The anterolateral approach to the shoulder is a surgical technique used to access the proximal humerus. When performing this approach, the deltoid muscle is split to allow for exposure of the underlying structures.

Deltoid Split Location

The location of the deltoid split is crucial to avoid injury to the axillary nerve. According to the studies, the deltoid split should be made:

• Proximal to the axillary nerve to avoid injury, as the axillary nerve enters the deltoid muscle at a distance of 5.0 cm from the humeral head and 6.8 cm from the acromion 2
• The "safe zone" during transdeltoid approaches is the anterior region of the deltoid muscle for a maximum of 6.7 cm from the acromion 2
• The axillary nerve traverses rows C, D, and E of the proximal humeral plate using the PHILOS aiming system, and the closest distance to the axillary nerve achieved was 4.5 mm, corresponding to the distal screw in row B 3

Key Considerations

When performing the anterolateral approach to the shoulder, the following key considerations should be taken into account:

• The axillary nerve is at risk of injury during the procedure, and careful planning and execution are necessary to avoid this complication 4, 5, 2, 3, 6
• The deltoid split should be made proximal to the axillary nerve to minimize the risk of injury
• The use of a modified anterolateral deltoid splitting approach with axillary nerve bundle mobilization can yield excellent outcomes in the treatment of proximal humeral fractures 4
• The inverted-L anterolateral deltoid flip approach provides the most posterior access to the proximal humerus, but requires more soft tissue dissection and awareness of tension on the axillary nerve 6