Intercostal Chest Tube Insertion

The Triangle of Safety

The internationally recognized anatomical zone for routine, safe chest drain insertion is the 'triangle of safety'. This area minimizes the risk of inadvertently damaging major muscle groups, the breast tissue, and the intra-abdominal organs (such as the liver or spleen) which sit surprisingly high under the diaphragm across the lower ribs.

• Anterior Border: Formed by the lateral edge of the pectoralis major muscle.
• Posterior Border: Formed by the lateral edge of the latissimus dorsi muscle.
• Superior Border: The base of the axilla.
• Inferior Border: A horizontal line corresponding to the level of the fifth intercostal space, typically situated just superior to the nipple line in males.

The Neurovascular Bundle

Each intercostal space is supplied by an intercostal vein, artery, and nerve (ordered V-A-N from superior to inferior).

• Anatomical Position: This primary neurovascular bundle runs protected within the subcostal groove, which is located on the inferior margin of the upper rib defining the space.
• Collateral Branches: Smaller collateral branches of the nerve and artery run along the superior margin of the lower rib, but these are significantly smaller and less dangerous if injured.
• Insertion Technique: To avoid the major subcostal bundle, the chest tube and any surgical instruments must always cross the chest wall by passing immediately over the superior margin of the lower rib.