Topic Overview

Axilla

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Introduction

• Pyramidal space between the upper limb and thoracic wall.

• Provides passage for nerves, vessels, and lymphatics from neck to upper limb.

• Clinically important for brachial plexus blocks, lymph node dissections, and abscess drainage.

Boundaries

• Apex (cervicoaxillary canal) → bounded by clavicle (anterior), scapula (posterior), and 1st rib (medial).

• Base (floor) → skin, subcutaneous tissue, axillary fascia.

• Anterior wall → pectoralis major, pectoralis minor, clavipectoral fascia.

• Posterior wall → subscapularis, teres major, latissimus dorsi.

• Medial wall → upper 4 ribs with intercostal muscles, covered by serratus anterior.

• Lateral wall → intertubercular sulcus of humerus.

Contents

• Axillary artery and branches.

• Axillary vein and tributaries.

• Brachial plexus cords and branches.

• Axillary lymph nodes.

• Axillary fat and areolar tissue.

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Dissection of Axilla

Step 1: Skin Incisions

• Extend previous pectoral dissection into axilla.

• Remove skin and superficial fascia → expose axillary fat and lymph nodes.

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Step 2: Boundaries

• Identify anterior wall (pectoralis muscles), posterior wall (subscapularis, teres major, latissimus dorsi), medial wall (serratus anterior), and lateral wall (humerus).

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Step 3: Expose Axillary Vein

• Lies anteromedial to axillary artery.

• Formed by union of brachial veins and basilic vein.

• Tributaries: cephalic vein, thoracoacromial vein, lateral thoracic vein.

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Step 4: Expose Axillary Artery

• Continuation of subclavian artery, begins at lateral border of 1st rib, ends at lower border of teres major.

• Divided into 3 parts by pectoralis minor:

  • 1st part → superior thoracic artery.

  • 2nd part → thoracoacromial and lateral thoracic arteries.

  • 3rd part → subscapular, anterior circumflex humeral, posterior circumflex humeral arteries.

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Step 5: Expose Brachial Plexus

• Identify cords of brachial plexus around artery:

  • Lateral cord → musculocutaneous nerve, part of median nerve.

  • Medial cord → ulnar nerve, part of median nerve.

  • Posterior cord → axillary and radial nerves.

• Smaller branches: medial pectoral nerve, lateral pectoral nerve, long thoracic nerve, thoracodorsal nerve.

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Step 6: Axillary Lymph Nodes

• Identify five groups:

  • Pectoral (anterior).

  • Subscapular (posterior).

  • Humeral (lateral).

  • Central.

  • Apical.

• Important in breast carcinoma spread.

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Step 7: Clinical Demonstrations

• Axillary abscess → may spread widely due to loose fat.

• Axillary artery compression → useful in controlling hemorrhage.

• Brachial plexus block → done at axilla for anesthesia of upper limb.

• Axillary node dissection → performed in carcinoma breast; must preserve long thoracic and thoracodorsal nerves.

 

 

Clinical Anatomy of Axilla

1. Axillary Abscess

• Infections (boils, hidradenitis, tuberculosis) can spread into axilla due to loose areolar tissue.

• Abscesses may spread widely along fascial planes.

• Surgical drainage must avoid injury to axillary vessels and nerves.

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2. Axillary Lymph Nodes

• Commonly enlarged in:

  • Breast carcinoma (major pathway of spread).

  • Tuberculosis.

  • Infections of upper limb and chest wall.

• Axillary lymph node dissection is done in breast cancer surgery → long thoracic nerve and thoracodorsal nerve must be preserved.

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3. Brachial Plexus Involvement

• Compression or injury in axilla (e.g., from tumors, aneurysm, trauma) causes motor and sensory deficits of upper limb.

• Axillary block → local anesthetic injected around cords of plexus to anesthetize upper limb for surgery.

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4. Axillary Artery

• Compression: artery can be compressed against 1st rib in axilla to control hemorrhage of limb.

• Aneurysm: pulsatile swelling in axilla → may compress brachial plexus → pain and paresthesia.

• Trauma: injured in penetrating wounds, shoulder dislocation, or fracture of proximal humerus.

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5. Axillary Vein

• Central venous access → axillary vein sometimes used for catheterization.

• Injury during trauma or surgery can cause severe hemorrhage and air embolism (due to negative intrathoracic pressure).

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6. Nerve Injuries in Axilla

• Long thoracic nerve → winged scapula.

• Thoracodorsal nerve → paralysis of latissimus dorsi (weak adduction/extension).

• Axillary nerve → deltoid paralysis, loss of abduction above 15°, regimental badge anesthesia.

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7. Axillary Swellings

• Causes: enlarged lymph nodes, abscess, lipoma, aneurysm of axillary artery, cysts.

• Clinical examination involves palpation of anterior, posterior, lateral, central, and apical groups of nodes.