Anatomy, Shoulder and Upper Limb, Cubital Fossa

Introduction

• The cubital fossa is a small triangular area located on the anterior surface of the elbow.
• It contains important structures that transition from the arm to forearm.
• It is analogous to the popliteal fossa of the lower limb.

Structure and Function

• Borders of the Cubital Fossa:
  • Superior (base): Imaginary line between the medial and lateral epicondyles of the humerus.
  • Medial: Lateral boundary of the pronator teres.
  • Lateral: Medial border of the brachioradialis.
• Apex: Directed distally, formed by the joining of borders.
• Floor: Formed by brachialis muscle (proximal) and supinator muscle (distal).
• Roof: Composed of skin, fascia, and bicipital aponeurosis.
• Contents (lateral to medial):
  • Radial nerve
  • Biceps tendon
  • Brachial artery
  • Median nerve
• Median Cubital Vein: Located in the roof, connects cephalic and basilic veins.

Blood Supply and Lymphatics

• Brachial artery: Passes through, bifurcates into radial and ulnar arteries at the fossa's apex.
• Veins: Median cubital vein connects cephalic and basilic veins. Basilic vein joins brachial vein to form axillary vein.

Nerves

• Median Nerve (C6-T1): Innervates anterior forearm muscles, thenar eminence, medial two lumbricals.
  • Role in wrist flexion, pronation, and finger movement.
  • Sensory innervation to lateral palm and volar surface of lateral 3.5 digits.
• Radial Nerve (C5-T1): Innervates posterior compartment muscles of the forearm.
  • Role in wrist extension and finger movement.
  • Sensory innervation to lateral dorsum of the hand and dorsum surface of lateral 3.5 digits.

Muscles

• Pronator Teres:
  • Forms medial border.
  • Nerve supply: Median nerve.
  • Action: Pronation of forearm.
• Brachioradialis:
  • Forms lateral border.
  • Nerve supply: Radial nerve.
  • Action: Flexes forearm.
• Brachialis:
  • Forms proximal floor.
  • Nerve supply: Musculocutaneous nerve.
  • Action: Weak forearm flexor.
• Supinator:
  • Forms distal floor.
  • Nerve supply: Posterior interosseus branch of radial nerve.
  • Action: Supination of forearm.

Physiologic Variants

• Variability in anatomy includes:
  • Radial nerve bifurcation site.
  • Bifurcated biceps tendon.
  • Brachial artery bifurcation site.
  • Median nerve variations at the carpal tunnel.
  • Median cubital vein configurations.

Surgical Considerations

• Supracondylar fractures can impact structures in the cubital fossa.
• Gartland classification for fracture types:
  • Type I: Undisplaced
  • Type II: Displaced, posterior cortex intact
  • Type III: Completely displaced
  • Type IV: Completely displaced, instability during movement
• Potential for nerve and artery damage.

Clinical Significance

• Venepuncture: Median cubital vein is a common site due to superficial location.
• Blood Pressure: Brachial artery auscultation in the fossa for Korotkoff sounds.
• Cubital Tunnel Syndrome:
  • Ulnar nerve compression in cubital tunnel.
  • Symptoms: Sensory paraesthesia, motor symptoms in the hand.
  • Treatment: Conservative or surgical.

Figures

• Surface anatomy of the upper extremity, cubital tunnel syndrome, and cubital fossa images included for reference.