Clinical application

Arterial Anastomoses Around the Scapula

• Multiple anastomoses occur around the scapula, forming networks on the anterior and posterior surfaces.
• The dorsal scapular, suprascapular, and subscapular arteries join to form these networks.

Importance of Collateral Circulation

• Anastomoses enable collateral circulation, which becomes crucial when ligation of a lacerated subclavian or axillary artery is necessary.
• Ligation can occur between the 1st rib and subscapular artery.

Blood Flow and Anastomoses

• The subscapular artery receives blood through anastomoses with the suprascapular artery, dorsal scapular artery, and intercostal arteries.
• Reversed blood flow in the subscapular artery enables blood to reach the third part of the axillary artery.

Occlusion of Axillary Artery

• Slow occlusion enables sufficient collateral circulation to develop, preventing ischemia.
• Sudden occlusion does not allow time for adequate collateral circulation, leading to inadequate blood supply to the arm, forearm, and hand.

Surgical Ligation and Compression

• Surgical ligation of the axillary artery between the subscapular artery and profunda brachii artery cuts off blood supply to the arm.
• Compression of the third part of the axillary artery against the humerus may be necessary to control bleeding.

Anatomy and Clinical Significance

• The axillary artery can be palpated in the inferior part of the lateral wall of the axilla.
• The axillary artery can enlarge (aneurysm) and compress the trunks of the brachial plexus, causing pain and anesthesia.

Axillary Vein

• Wounds in the axilla often involve the axillary vein due to its large size and exposed position.
• Surgical or traumatic wounds in the proximal part of the axillary vein are particularly dangerous due to profuse bleeding and the risk of air emboli.

Lymphangitis

• Characterized by warm, red, tender streaks in the skin of the limb
• Can also produce enlargement of axillary nodes in infections in the pectoral region and breast, including the superior part of the abdomen

Axillary Lymph Nodes

• Enlargement of apical nodes may obstruct the cephalic vein superior to the pectoralis minor
• May adhere to the axillary vein in metastatic cancer of the apical group, requiring excision of part of this vessel

Role in Cancer Diagnosis and Treatment

• Excision and pathologic analysis of axillary lymph nodes are necessary for staging and determining the appropriate treatment of cancer, such as breast cancer

Complications of Axillary Node Removal or Radiation

• Lymphatic drainage of the upper limb may be impeded, resulting in lymphedema
• Lymphedema is characterized by swelling due to accumulated lymph, especially in the subcutaneous tissue

Brachial Plexus Types

• A prefixed brachial plexus occurs when the superior root is C4 and the inferior root is C8.
• A postfixed brachial plexus occurs when the superior root is C6 and the inferior root is T2.

Brachial Plexus Injuries

• Injuries to the brachial plexus affect movements and cutaneous sensations in the upper limb.
• Causes of brachial plexus injuries include disease, stretching, and wounds in the lateral cervical region (posterior triangle) of the neck or in the axilla.

Superior Brachial Plexus Injuries

• Injuries to the superior parts of the brachial plexus (C5 and C6) usually result from an excessive increase in the angle between the neck and shoulder.
• Characteristic signs of superior trunk injury include the "waiter's tip position" and paralysis of the muscles of the shoulder and arm supplied by the C5 and C6 spinal nerves.
• Clinical appearance of superior brachial plexus injuries include an adducted shoulder, medially rotated arm, and extended elbow.
• Chronic microtrauma to the superior trunk of the brachial plexus can produce motor and sensory deficits in the distribution of the musculocutaneous and radial nerves.
• Superior brachial plexus injuries may produce muscle spasms and severe disability in hikers (backpacker's palsy).

Acute Brachial Plexus Neuritis

• Acute brachial plexus neuritis is a neurologic disorder of unknown cause, characterized by the sudden onset of severe pain, usually around the shoulder.
• Pain begins at night and is followed by muscle weakness and sometimes muscular atrophy (neurologic amyotrophy).
• Inflammation of the brachial plexus is often preceded by some event (e.g., upper respiratory infection, vaccination, or nonspecific trauma).

Hyperabduction Syndrome

• Compression of cords of the brachial plexus may result from prolonged hyperabduction of the arm during performance of manual tasks over the head.
• Common neurologic symptoms include pain radiating down the arm, numbness, paresthesia (tingling), erythema (redness of the skin caused by capillary dilation), and weakness of the hands.
• Compression of the axillary artery and vein causes ischemia of the upper limb and distension of the superficial veins.

Inferior Brachial Plexus Injuries

• Injuries to inferior parts of the brachial plexus (Klumpke paralysis) are much less common.
• Inferior brachial plexus injuries may occur when the upper limb is suddenly pulled superiorly—for example, when a person grasps something to break a fall or a baby's upper limb is pulled excessively during delivery.
• These events injure the inferior trunk of the brachial plexus (C8 and T1) and may avulse the roots of the spinal nerves from the spinal cord.
• The short muscles of the hand are affected, and a claw hand results.

Tendon Injuries

• Inflammation of the tendon (biceps tendinitis) results from microtears, causing degeneration of the tendon, vascular disruption, and an inflammatory repair response.
• Tendinosis is a degeneration of the tendon's collagen, causing disorganization of collagen in response to poor vascularization, chronic overuse, or aging, with no inflammatory response.

Biceps Tendon Dislocation and Rupture

• The tendon of the long head of the biceps can be partially or completely dislocated from the intertubercular sulcus in the humerus.
• Rupture of the tendon usually results from wear and tear of an inflamed tendon, causing a tear from its attachment to the supraglenoid tubercle of the scapula.
• The detached muscle belly forms a ball near the center of the distal part of the anterior aspect of the arm (Popeye deformity).

Blood Pressure Measurement

• The first instance of sound marks the systolic blood pressure.
• The sound of turbulent flow from the brachial artery remains audible until the artery is no longer compressed, marking the diastolic blood pressure.

Ischemic Compartment Syndrome

• Muscles and nerves can tolerate up to 6 hours of ischemia.
• After this, fibrous scar tissue replaces necrotic tissue, causing the involved muscles to shorten permanently, producing a flexion deformity.

Nerve Injuries

• A midhumeral fracture may injure the radial nerve in the radial groove in the humeral shaft.
• Injury to the musculocutaneous nerve in the axilla results in paralysis of the coracobrachialis, biceps, and brachialis.
• Injury to the radial nerve superior to the origin of its branches to the triceps brachii results in paralysis of the triceps, brachioradialis, supinator, and extensor muscles of the wrist and fingers.

Veins in the Cubital Fossa

• The pattern of veins in the cubital fossa varies greatly.
• The median cubital vein is a common site for sampling and transfusion of blood and intravenous injections.
• The median cubital vein lies directly on the deep fascia, running diagonally from the cephalic vein of the forearm to the basilic vein of the arm.