Ortho

• Brachial plexus is formed by nerve roots C5 to T1
• C5 + C6 form the Superior Trunk:

  • Dorsal Scapular nerve (C5) innervates Levator scapulae, rhomboid major & rhomboid minor muscles
  • Nerve to subclavius (C5 & 6) innervates subclavius muscle
  • Suprascapular nerve (C5 & 6) innervates supraspinatus and infraspinatus muscle
• C7 is the Middle Trunk:

  • Long thoracic nerve (C5, 6 & 7) innervates serratus anterior muscle
• C8 + T1 form the Inferior Trunk
• Lateral Cord is formed by the anterior divisions of the superior and middle trunks:

  • Lateral Pectoral Nerve innervates Pectoralis major muscle
• Posterior Cord is formed by the posterior divisions of the superior, middle, and inferior trunks
• Medial Cord is formed by the anterior division of the inferior trunk
• Lateral Cord gives rise to musculocutaneous nerve, which innervates the Anterior compartment of the arm
• Medial Cord gives rise to ulnar nerve (Passes medial to medial epicondyle)
• Lateral Cord + medial cord form the median nerve (travels with brachial artery)
• Posterior Cord gives rise to Axillary nerve (innervates Deltoid Muscle) and Radial nerve (Passes posterior to lateral epicondyle)
• <|>Radial Nerve injury affects the posterior compartment of the arm & forearm:

  • Causes loss of extension at the wrist joint and the Metacarpophalangeal joint
  • Results in loss of sensation in the dorsum of the hand from the thumb to the index finger
• <|>Median Nerve injury affects various muscles:

  • Flexor carpi radialis: Flexes & abducts the wrist joint
  • Flexor digitorum profundus (II & III): Flexes the proximal interphalangeal joint of II & III digits
  • Flexor pollicis longus: Flexes the thumb
  • Adductor pollicis brevis: Adducts the first metacarpal
  • Opponens pollicis: Responsible for opposition
  • Lumbricals: Flex each finger at Metacarpophalangeal joint & Extend each finger at interphalangeal joints
• <|>Ulnar Nerve injury affects various muscles:

  • Flexor Carpi ulnaris: Flexes & adducts the hand at the wrist joint
  • Flexor digitorum profundus (IV & V): Flexes the proximal interphalangeal joint of IV & V digits
  • Lumbricals: Flex each finger at Metacarpophalangeal joint & extend each finger at interphalangeal joints
  • Adductor pollicis: Adducts thumb at carpometacarpal & metacarpophalangeal joint
  • Opponens digiti Mini: Responsible for opposition
  • Interossei muscles: Adduct & flex each finger (except middle) or Abduct fingers (II - IV) at metacarpophalangeal joints
• <|>Brachial Plexus Injury:

  • Erb palsy (C5 & C6) results in "waiter's tip" position and affects Dorsal Scapular nerve, Nerve to subclavius, Suprascapular nerve, Axillary nerve, Musculocutaneous nerve, Infraspinatus, Supraspinatus, Deltoid, and Biceps brachii muscles
  • Klumpke palsy (C8 & T1) results in claw hand and affects Median nerve, Ulnar nerve, Thenar muscles, Hypothenar, interossei, and lumbricals muscles
  • Thoracic outlet syndrome causes compression of lower trunk and subclavian vessels, leading to atrophy of intrinsic hand muscles, ischemia, pain, and edema