The course of the following neurovascular structures should be kept in mind:
Anterior circumflex humeral artery
Ascending branch of the anterior circumflex humeral artery
Posterior circumflex humeral artery
Tendon of the long head of the biceps
Another important structure is the tendinous origin of the long head of the biceps, which runs anteriorly and is usually palpable. Make sure not to fix this structure to the bone with pins or K-wires.
2. Safe zones
The anterior motor branch of the axillary nerve crosses the humerus horizontally about 6 cm distal to the lateral border of the acromion. This distance does not significantly vary and is reliable. To protect the axillary nerve mark the skin 5 cm and 7 cm distally to the acromion. This marks the corridor in which the axillary nerve is at risk.
The lateral aspect of the proximal humerus, proximal and distal to this corridor can be regarded as a safe zone.
3. Pin insertion
Safe zones for pins
Pins are inserted from lateral (alternatively from anterolateral or posterolateral) through the deltoid muscle.
The tips of the pins in the humeral shaft should just perforate the far cortex. If inserted too deeply, they can injure the neurovascular bundle.