IMG_0033

Axilla and Brachial Plexus

The axilla, also known as the armpit, is a concave area located at the junction of the arm and trunk.
Components:
- Base: Formed by hairy skin, subcutaneous fat, and axillary fascia.
- Apex: Bounded by:
  - Posterior border of the clavicle
  - Superior border of the scapula
  - Rib I
- Anterio Wall: Formed by the pectoralis major and minor muscles.
- Posterior Wall: Composed of:
  - Lateral parts of latissimus dorsi
  - Teres major
  - Subscapularis muscles
- Medial Wall: Made up of ribs I to IV and intercostal and serratus anterior muscles.
- Lateral Anterior Wall: The intertubercular groove of the humerus.
Structural Support: Provided by the lateral rib cage, clavicle, and scapula.

Definition: A complex network of nerves originating from the anterior rami of spinal nerves C5 to T1.
Location: Enclosed with the axillary artery and vein within the axillary sheath (extension of cervical fascia).
Components: Comprised of nerve roots, trunks, divisions, cords, and branches.

Roots: Emerging from the intervertebral foramina of lower cervical vertebrae, situated between the anterior and middle scalene muscles.
Trunks:
- Superior trunk: Formed by C5, C6.
- Middle trunk: Formed by C7.
- Inferior trunk: Formed by C8, T1.

From Roots:
- Dorsal scapular nerve (to levator scapulae, rhomboids)
- Long thoracic nerve (to serratus anterior)
From Trunks:
- Suprascapular nerve
- Subclavian nerve

Divisions: Each trunk splits into anterior and posterior divisions.
Cords: The divisions form:
- Lateral cord: Anterior divisions of superior and middle trunks.
- Medial cord: Anterior division of the inferior trunk.
- Posterior cord: Posterior divisions of all three trunks.

Lateral Cord:
- Lateral pectoral nerve (becomes musculocutaneous nerve)
Medial Cord:
- Medial pectoral nerve
- Medial cutaneous nerve of arm
- Medial cutaneous nerve of forearm
Posterior Cord:
- Superior subscapular nerve
- Thoracodorsal nerve
- Inferior subscapular nerve

Main Terminal Branches:
- Musculocutaneous nerve (C5-C7)
- Axillary nerve (C5-C6)
- Radial nerve (C5-T1)
- Median nerve (C6-T1)
- Ulnar nerve (C7-T1)

Axillary Artery: A continuation of the subclavian artery, bifurcates into 3 parts related to the pectoralis minor muscle.
- First Part: Runs between rib I and pectoralis minor, branches into superior thoracic artery.
- Second Part: Posterior to pectoralis minor, branches into thoracoacromial artery and lateral thoracic artery.
- Third Part: Extends to the lower border of teres major with branches:
  - Subscapular artery
  - Anterior and posterior circumflex humeral arteries.

Axillary Vein: Located medially to the axillary artery, becomes the subclavian vein at rib I.
Lymphatic Drainage: Includes five groups of lymph nodes:
- Pectoral nodes (drain chest wall, mammary glands)
- Humeral nodes (drain upper limb)
- Subscapular nodes (drain back muscles)
- Central nodes (drain lateral quadrants of the breast)
- Apical nodes (drain other axillary nodes & structures in the neck).

Types of Injuries: Superior and inferior trunk injuries
Superior Trunk Injury:
- Caused by forceful neck flexion and shoulder depression.
- Causes inability to flex the arm, abduct, and supinate forearm.
Inferior Trunk Injury:
- Due to extreme abduction of the upper limb.
- Leads to paralysis or weakness of fingers.

Diagnosis: Confirmed via electrical stimulation and imaging techniques.
Prognosis: Poor if complete avulsion occurs; some restoration of function is possible with injury management.

Brachial Plexus Structure: Really Thirsty? Drink Cold Beer (Roots, Trunks, Divisions, Cords, Branches)
Terminal Nerves: MARMU (Musculocutaneous, Axillary, Radial, Median, Ulnar)

Definition: Superior posterior surface of the trunk defined by muscles that attach to the scapula.
Muscle Groups:
- Extrinsic Muscles: Connect axial to appendicular skeleton (trapezius, latissimus dorsi, levator scapulae).
- Intrinsic Muscles: Attach scapula to humerus (deltoid, rotator cuff muscles).

Bony Landmarks:
- Borders: Superior, medial, lateral
- Angles: Inferior angle, lateral angle
- Spine: Divides the scapula posterior surface into supraspinous fossa (above) and infraspinous fossa (below).

Superficial Extrinsic Muscles:
- Trapezius and latissimus dorsi connect trunk to upper limb.
Deep Extrinsic Muscles:
- Levator scapulae, rhomboid major, and rhomboid minor elevate/retract scapula.
Intrinsic or True Muscles:
- Deltoid (three parts), supraspinatus, infraspinatus, teres minor, teres major, subscapularis, all contributing to shoulder movements.

Sensory Innervation: From medial branches of posterior rami of cervical nerves C4-C8 and thoracic nerves T1-T6.
Motor Innervation:
- From brachial plexus branches including dorsal scapular nerve, suprascapular nerve, etc.

Blood Supply: Formed by scapular anastomosis via multiple arteries.
Venous Drainage: Corresponds to arterial drainage into axillary or subclavian veins.

Often due to high-velocity injuries; associated with other serious injuries (e.g., pneumothorax).
Symptoms: Extreme upper back pain, difficulty lying comfortably, respiratory symptoms.
Assessment: Immediate evaluation includes airway, breathing, circulation checks.
Treatment: Conservatively with immobilization, pain control, or surgical repair if necessary.

Types of Joints:
- Sternoclavicular joint (saddle-type),
- Acromioclavicular joint (plane-type),
- Glenohumeral joint (ball-and-socket).

Components: Head of humerus articulating with glenoid cavity; supported by rotator cuff muscles.
Nerve Supply: Suprascapular, axillary, and subscapular nerves.

Rotator Cuff Tears: Caused by repetitive overhead movements or trauma. Symptoms include pain and limited range of motion.
Acromioclavicular Joint Injuries: Common due to downward forces; treated with conservative methods or surgical stabilization based on injury severity.