Radial Nerve

Roots: - C5 – T1.

• Motor Functions
  • Triceps brachii
  • Muscles in the posterior compartment of the forearm (which are primarily, but not exclusively, extensors of the wrist and fingers)
• Sensory Functions
  • Innervates the posterior aspect of the arm and forearm, and the posterolateral aspect of the hand.

Radial Nerve in the Axilla

• Fibers from C5, C6, C7, C8, T1
• Continuation of the Posterior Cord of the Brachial Plexus
• Crosses lower border of posterior axillary wall lying on the tendon of Latissimus dorsi
• Passes out of sight through Triangular Interval below lower border of Latissimus dorsi tendon as it lies in front of Teres major, between Long Head of Triceps and Humerus
  • Borders of Triangular Interval:
    • Superior: Inferior border of Teres Major
    • Lateral: Shaft of Humerus and Lateral Head of Triceps Brachii
    • Medial: Lateral border of Long Head of Triceps Brachii
  • Supplies: Long Head of Triceps AND the Medial Head of Triceps (a nerve which accompanies the Ulnar Nerve along the medial side of the arm)
• Before disappearing, gives off the Posterior Cutaneous Nerve of the Arm
  • Supplies: Posterior surface of the arm

Radial Nerve in the Arm

• Passes obliquely across back of Humerus from medial to lateral in shallow groove between Long and Medial Heads of Triceps with the Profunda Brachii Artery
  • Supplies: Lateral and Medial Heads of Triceps again
    • Branch to Medial Head also supplies Anconeus
• Gives off Lower Lateral Cutaneous Nerve of Arm and Posterior Cutaneous Nerve of the Forearm which perforate the Lateral Head of Triceps
• Pierces the Lateral Intermuscular Septum to enter anterior compartment
• Runs towards elbow between Brachialis medially and first Brachioradialis and then Extensor Carpi Radialis Longus laterally
• Supplies: Brachioradialis, Extensor Carpi Radialis Longus, and Lateral part of Brachialis
• Divides into its terminal Superficial Branch and Posterior Interosseous Nerve at the level of the Lateral Epicondyle
  • Supplies: Elbow joint
• Posterior Interosseous Nerve passes into the extensor compartment of the forearm between the two layers of Supinator

Radial Nerve Branches in the Forearm

• Superficial Terminal Branch of Radial Nerve
  • Cutaneous continuation of the main Radial Nerve
  • Runs from the Cubital Fossa on the surface of Supinator, Pronator Teres tendon, and Flexor Digitorum Superficialis
  • Runs on the lateral side of the forearm under cover of Brachioradialis
  • Lies lateral to the Radial Artery in the middle third of the forearm
  • Leaves flexor compartment by passing backwards deep to tendon of Brachioradialis
  • Crosses Abductor Pollicis Longus, Extensor Pollicis Brevis and Extensor Pollicis Longus (as one of the contents of the Anatomical Snuffbox)
  • Breaks up into 2-3 branches (which can be rolled on the surface of the taut Extensor Pollicis Longus)
  • Reaches back of the hand
  • Supplies: Radial 2/3 of Dorsum of the Hand and proximal parts of Dorsal surfaces of Thumb and lateral two and a half or three and a half fingers
• Posterior Interosseous Nerve
  • Passes downwards over the Abductor Pollicus Longus origin
  • Dips deeply to reach the Interosseous Membrane
  • Passes between the muscles as far as the wrist joint
  • Ends in a small nodule
    • Supplies: Wrist Joint
  • Supplies: Muscles arising from the common extensor origin and deep muscles of the extensor compartment, i.e.
    • Supinator
    • Extensor Carpi Radialis Brevis
    • Extensor Digitorum
    • Extensor Digiti Minimi
    • Extensor Carpi Ulnaris
    • Abductor Pollicis Longus
    • Extensor Pollicis Longus
    • Extensor Pollicis Brevis
    • Extensor Indicis

Summary

• Origin
  • C5 – T1
  • On of continuing branches of the posterior cord
• Motor Functions
  • Triceps brachii
  • Muscles in the posterior compartment of the forearm (which are primarily, but not exclusively, extensors of the wrist and fingers)
• Sensory Functions
  • Innervates the posterior aspect of the arm and forearm, and the posterolateral aspect of the hand.
• Course
  • Axilla
    • Crosses lower border of posterior axillary wall lying on the tendon of Latissimus dorsi
    • Passes out of sight through Triangular Interval below
    • Supplies:
      • Triceps
      • Posterior Cutaneous Nerve of the Arm
  • Arm
    • Passes obliquely across back of Humerus from medial to lateral in shallow groove
    • Branch
      • Lateral Cutaneous Nerve of Arm
      • Posterior Cutaneous Nerve of the Forearm
    • Pierces the Lateral Intermuscular Septum to enter anterior compartment
    • Runs towards elbow between Brachialis medially, thenBrachioradialis and then Extensor Carpi Radialis Longus laterally
    • Supplies
      • Brachioradialis, Extensor Carpi Radialis Longus, and Lateral part of Brachialis
    • Divides (level of lateral epicondyle
      • Superficial Branch
      • Posterior Interosseous Nerve
  • Forearm
    • Posterior Interosseous Nerve
      • Passes into the extensor compartment of the forearm between the two layers of Supinator
      • Reach the Interosseous Membrane
      • Supplies all extensor muscles
    • Superficial Terminal Branch of Radial Nerve
      • Cutaneous continuation of the main Radial Nerve
      • Runs on the lateral side of the forearm under cover of Brachioradialis
      • Leaves flexor compartment by passing backwards deep to tendon of Brachioradialis
      • Reaches back of the hand
      • Supplies: Radial 2/3 of Dorsum of the Hand and proximal parts of Dorsal surfaces of Thumb and lateral two and a half or three and a half fingers