Upper Limb — Comprehensive Study Notes Summary & Study Notes

🔎 Overview

Short summary of the upper limb: a functional unit for positioning the hand. It includes the shoulder girdle (clavicle, scapula), arm (humerus), forearm (radius and ulna), and hand (carpals, metacarpals, phalanges). Major systems: skeletal, joints, muscles, nerves, blood vessels, and lymphatics.

🦴 Bones

• Clavicle: transmits force from limb to axial skeleton; common fracture site in the middle third.
• Scapula: features include acromion, coracoid process, and glenoid cavity.
• Humerus: anatomical neck, surgical neck (common fracture site), greater/lesser tubercles, deltoid tuberosity, medial/lateral epicondyles.
• Radius and Ulna: radius lateral (thumb side) with radial head and styloid process; ulna medial with olecranon and coronoid process.
• Carpals: (proximal) scaphoid, lunate, triquetrum, pisiform; (distal) trapezium, trapezoid, capitate, hamate.
• Metacarpals and Phalanges: 5 metacarpals; proximal, middle, distal phalanges (thumb lacks middle phalanx).

🔗 Joints and Movements

• Sternoclavicular (SC): only true bony attachment to trunk; allows clavicular elevation/depression, protraction/retraction.
• Acromioclavicular (AC): scapular rotation; susceptible to sprain/dislocation.
• Glenohumeral: highly mobile ball-and-socket; actions: flexion, extension, abduction, adduction, rotation.
• Elbow complex: humeroulnar (hinge) for flexion/extension, humeroradial, and proximal radioulnar for pronation/supination.
• Distal radioulnar: important for forearm rotation.
• Wrist (radiocarpal) & midcarpal: flexion/extension and radial/ulnar deviation.
• Carpometacarpal (CMC) of thumb: saddle joint enabling opposition.

💪 Major Muscle Groups

• Shoulder/Scapular movers: deltoid, pectoralis major/minor, latissimus dorsi, teres major, trapezius, levator scapulae, rhomboids, serratus anterior.
• Rotator cuff (key stabilizers): Supraspinatus, Infraspinatus, Teres minor, Subscapularis (SITS). These stabilize the glenohumeral joint and initiate abduction/rotation.
• Arm: anterior—biceps brachii (flexion + supination), brachialis (primary elbow flexor), coracobrachialis; posterior—triceps brachii (elbow extension).
• Forearm compartments:
  • Anterior (flexor/pronator): superficial (e.g., flexor carpi radialis, flexor carpi ulnaris, palmaris longus, pronator teres) and deep (e.g., flexor digitorum profundus, flexor pollicis longus, pronator quadratus).
  • Posterior (extensor/supinator): superficial (e.g., extensor carpi radialis longus/brevis, extensor digitorum, extensor carpi ulnaris) and deep (e.g., supinator, abductor pollicis longus, extensor pollicis longus/brevis).
• Intrinsic hand muscles: thenar eminence (median nerve) for thumb movements, hypothenar eminence (ulnar nerve) for little finger, lumbricals (flex MCP, extend IP), and interossei (DAB/PAD — dorsal abduct, palmar adduct).

🧠 Nerves & Brachial Plexus

• Brachial plexus organization: roots (C5–T1) → trunks → divisions → cords → branches.
• Major terminal nerves:
  • Musculocutaneous (C5–C7): anterior arm flexors; lateral forearm sensation.
  • Axillary (C5–C6): deltoid and teres minor; lateral shoulder sensation.
  • Radial (C5–T1): posterior compartment extensors; sensory posterior arm/forearm and dorsum of hand; injury → wrist drop.
  • Median (C5–T1, mainly C6–T1): most forearm flexors and thenar muscles; sensory lateral palm and fingertips; entrapment → carpal tunnel syndrome.
  • Ulnar (C8–T1): intrinsic hand muscles, flexor carpi ulnaris; sensory medial hand; injury → claw hand.
• Note cord relationships: lateral cord → musculocutaneous, posterior cord → axillary + radial, medial cord → ulnar, median nerve from lateral+medial.

❤️ Blood Supply

• Subclavian → Axillary → Brachial → Radial + Ulnar.
• Important branches: thyrocervical, subscapular, circumflex humeral arteries, profunda brachii (deep artery of the arm) supplying posterior arm.
• Radial and ulnar arteries form the superficial and deep palmar arches, which supply the hand and digital arteries.

🩸 Veins & Lymphatics

• Superficial veins: cephalic (lateral) and basilic (medial), connected by median cubital at the cubital fossa (common venipuncture site).
• Deep veins accompany arteries (venae comitantes) and drain toward the axillary.
• Lymph drains to cubital (epitrochlear) nodes and axillary nodes.

📌 Surface Anatomy & Landmarks

• Clavicle palpable; acromion marks lateral shoulder; deltoid tuberosity palpable on lateral humerus.
• Cubital fossa borders: pronator teres (medial), brachioradialis (lateral), line between epicondyles superiorly; contains biceps tendon, brachial artery, median nerve (lat→med).
• Palpate radial pulse at wrist lateral to flexor carpi radialis.

🩺 Clinical Correlations

• Clavicle fracture: common in middle third; shoulder droop, tenting skin.
• Anterior shoulder dislocation: humeral head moves anteroinferiorly; risk to axillary nerve (deltoid weakness, sensory loss over regimental badge area).
• Rotator cuff tear/impingement: supraspinatus commonly affected; pain with abduction 15–120° (painful arc).
• Proximal humerus fracture: surgical neck injury → axillary nerve.
• Midshaft humeral fracture: risk to radial nerve → wrist drop and sensory loss dorsal hand.
• Supracondylar fracture (children): risk to brachial artery and median nerve; may cause Volkman ischemic contracture.
• Scaphoid fracture: anatomical snuffbox tenderness; risk of avascular necrosis of proximal pole due to retrograde blood supply.
• Colles fracture: distal radius fracture with dinner-fork deformity.
• Carpal tunnel syndrome: compression of median nerve → thenar wasting, paresthesia in lateral 3½ digits.
• Ulnar nerve entrapment at elbow (cubital tunnel) → numbness of medial 1½ digits, intrinsic weakness.
• Lateral/medial epicondylitis: tendon overuse injuries of forearm extensors/flexors.

🔍 Examination & Key Tests

• Muscle strength: test deltoid (abduction), biceps (flexion/supination), triceps (extension), wrist extensors/flexors, thumb opposition (median), finger abduction (ulnar).
• Reflexes: biceps (C5–C6) tests musculocutaneous and C5–6 roots; brachioradialis (C5–C6); triceps (C7–C8).
• Sensory mapping: dermatomes C5–T1 across lateral→medial forearm/hand; map peripheral nerve distributions (radial dorsum, median palmar lateral, ulnar palmar medial).

🧭 Functional Movements & Biomechanics

• Shoulder abduction: supraspinatus initiates 0–15°, deltoid continues 15–90°, scapulothoracic rotation contributes above.
• Scapulohumeral rhythm: ~2:1 ratio of glenohumeral to scapulothoracic motion during full abduction.
• Pronation/Supination: occurs largely at proximal and distal radioulnar joints; biceps is a powerful supinator when elbow flexed.

📝 Key Exam Pearls

• Loss of shoulder abduction beyond 15° with preserved supraspinatus suggests axillary nerve lesion.
• Wrist drop = radial nerve injury; test finger extension and triceps too.
• Thenar wasting and positive Tinel/Phalen tests suggest carpal tunnel.
• Anatomical snuffbox tenderness = scaphoid fracture until proven otherwise.

These notes provide a structured framework to recall anatomy, function, neurovascular relationships, and common clinical problems of the upper limb. Use them as a checklist when studying imaging, physical exams, and surgical anatomy.