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Upper Limb - Detailed MBBS Notes

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1. OVERVIEW

• Positioning the hand in space (shoulder, arm, and forearm)
• Manipulating objects - both as a mechanical tool (grip/grasp) and a sensory tool (fine touch, proprioception)

Component Parts

• Bones and joints: Pectoral girdle (clavicle + scapula) → humerus → radius + ulna → carpals → metacarpals → phalanges
• Regions: Shoulder, axilla, arm, cubital fossa, forearm, wrist, hand
• Innervation: Via cervical (C5-C8) and upper thoracic (T1) nerves through the brachial plexus

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2. BONES OF THE UPPER LIMB

Pectoral Girdle

Arm

• Humerus: Head articulates with glenoid (glenohumeral joint). Greater + lesser tubercles for rotator cuff insertions. Spiral groove (radial nerve). Medial + lateral epicondyles. Capitulum (for radius), trochlea (for ulna).

Forearm

• Radius: Head at proximal end; styloid process distally. Biceps inserts on radial tuberosity.
• Ulna: Olecranon proximally (triceps insertion). Coronoid process. Styloid process distally.

Wrist & Hand

• Carpals (8): Two rows - proximal (Scaphoid, Lunate, Triquetrum, Pisiform), distal (Trapezium, Trapezoid, Capitate, Hamate). Mnemonic: "Some Lovers Try Positions That They Can't Handle"
• Metacarpals (5) + Phalanges (14: 2 in thumb, 3 in fingers)

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3. JOINTS

Glenohumeral (Shoulder) Joint

• Type: Ball-and-socket (multiaxial synovial)
• Articular surfaces: Head of humerus + glenoid cavity of scapula (deepened by fibrocartilaginous glenoid labrum)
• Stabilizers:
  • Static: Joint capsule, glenohumeral ligaments (superior, middle, inferior), coracohumeral ligament, glenoid labrum
  • Dynamic: Rotator cuff muscles (SITS - Supraspinatus, Infraspinatus, Teres minor, Subscapularis)
• Movements: Flexion/Extension, Abduction/Adduction, Medial/Lateral rotation, Circumduction
• Dislocation: Anteroinferior most common (arm forced into abduction + lateral rotation). Bankart lesion (avulsion of anteroinferior glenoid labrum) + Hill-Sachs lesion (impression fracture of humeral head) in recurrent cases

Elbow Joint

• Type: Hinge + pivot synovial joint (one capsule, 3 articulations)
  • Humeroulnar: hinge (flexion/extension)
  • Humeroradial: hinge + pivot
  • Proximal radioulnar: pivot (pronation/supination)
• Capsule: Reinforced by ulnar (medial) collateral ligament and radial (lateral) collateral ligament; the anular ligament of radius secures the radial head
• Synovial membrane: Lines coronoid fossa, olecranon fossa, radial fossa with fat pads
• Movements: Flexion 0-145°; Supination/Pronation at radioulnar joints

Wrist (Radiocarpal) Joint

• Type: Ellipsoid (condyloid) synovial
• Between: Distal end of radius + articular disc of DRUJ (above) and proximal carpal row - scaphoid, lunate, triquetrum (below)
• Movements: Flexion, extension, abduction (radial deviation), adduction (ulnar deviation), circumduction

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4. THE AXILLA

Openings in the Posterior Wall

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5. BRACHIAL PLEXUS

Formation: Roots → Trunks → Divisions → Cords → Branches

Branches

• Dorsal scapular nerve (C5) - rhomboids + levator scapulae
• Long thoracic nerve (C5, C6, C7) - serratus anterior (winged scapula if injured)
• Contribution to phrenic nerve (C5)

• Suprascapular nerve (C5, C6) - supraspinatus + infraspinatus
• Nerve to subclavius (C5, C6)

• Lateral pectoral nerve (C5-C7) - pectoralis major
• Musculocutaneous nerve (C5-C7)
• Lateral root of median nerve

• Medial pectoral nerve (C8, T1)
• Medial cutaneous nerve of arm (T1)
• Medial cutaneous nerve of forearm (C8, T1)
• Ulnar nerve (C7, C8, T1)
• Medial root of median nerve

• Upper subscapular nerve (C5, C6) - subscapularis
• Thoracodorsal nerve (C6-C8) - latissimus dorsi
• Lower subscapular nerve (C5, C6) - subscapularis + teres major
• Axillary nerve (C5, C6)
• Radial nerve (C5-C8, T1)

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6. MAJOR TERMINAL NERVES

Musculocutaneous Nerve (C5, C6, C7)

• From lateral cord; pierces coracobrachialis
• Supplies: Coracobrachialis, biceps brachii, brachialis (arm flexors)
• Continues as lateral cutaneous nerve of forearm
• Injury: Weak elbow flexion, sensory loss over lateral forearm

Axillary Nerve (C5, C6)

• Exits through quadrangular space with posterior circumflex humeral artery
• Supplies: Deltoid, teres minor; skin over deltoid (upper lateral arm)
• Injury: With surgical neck of humerus fracture or shoulder dislocation → inability to abduct arm 15-90° (supraspinatus initiates 0-15°), loss of roundness of shoulder

Radial Nerve (C5-C8, T1)

• Largest branch; from posterior cord
• Path: Exits triangular interval → spiral groove of humerus → lateral epicondyle → divides into superficial (sensory) and deep (posterior interosseous nerve) branches
• Supplies: All posterior compartment muscles of arm + forearm; skin on posterior arm, forearm, and dorsal hand (lateral 3.5 digits)
• Injury sites:
  • At spiral groove (mid-shaft humerus fracture) → wrist drop (loss of wrist + finger extension), loss of sensation over anatomical snuffbox (first dorsal web space)
  • At lateral epicondyle → weakness of finger extension (posterior interosseous nerve)
  • "Saturday night palsy" (compression in axilla/spiral groove)

Median Nerve (C6-T1)

• From medial + lateral cords (C6, C7 from lateral; C8, T1 from medial)
• Path: Medial to brachial artery in arm → enters forearm between heads of pronator teres → passes through carpal tunnel under flexor retinaculum
• Supplies:
  • Arm: nothing
  • Forearm: most flexors (except FCU and medial 1/2 FDP), pronators
  • Hand (via recurrent branch): LOAF muscles - Lateral 2 lumbricals, Opponens pollicis, Abductor pollicis brevis, Flexor pollicis brevis
  • Sensory: Palmar surface of lateral 3.5 fingers
• Injuries:
  • High injury (above elbow): "Hand of benediction" (pointing index finger on attempted fist) + loss of pronation, wrist flexion, thumb opposition, sensory loss over lateral palm
  • Low injury (at wrist/carpal tunnel): "Ape hand" deformity (thenar wasting, cannot oppose thumb), sensory loss lateral 3.5 digits; no wrist flexion loss

Ulnar Nerve (C7, C8, T1)

• From medial cord
• Path: Posterior to medial epicondyle (groove) → between heads of FCU → Guyon's canal at wrist → superficial + deep branches
• Supplies:
  • Forearm: FCU, medial half of FDP (ring + little fingers)
  • Hand: Hypothenar muscles, medial 2 lumbricals, all dorsal + palmar interossei, adductor pollicis, deep head of FPB
  • Sensory: Medial 1.5 fingers (palm + dorsum)
• Injury:
  • At medial epicondyle: "Claw hand" (ring + little fingers flexed at IPJ, extended at MCPJ); loss of grip, interossei weakness (cannot separate/adduct fingers), wasting of hypothenar + interossei; Froment's sign (flexes IPJ of thumb when gripping paper due to adductor pollicis weakness)
  • Note: Paradox - high lesion produces less claw (FDP also paralysed), low lesion more pronounced claw

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7. MUSCLES (Key Tables)

Rotator Cuff - SITS

Arm Muscles

Forearm - Anterior Compartment (Flexors)

Forearm - Posterior Compartment (Extensors - all via radial nerve)

Intrinsic Muscles of the Hand

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8. BLOOD SUPPLY

Axillary Artery (3 parts relative to pectoralis minor)

Brachial Artery

• Continuation of axillary below lower border of teres major
• Lies medial in arm, courses with median nerve (medial in upper arm → anterior at elbow)
• Divides at neck of radius into radial + ulnar arteries
• Branch: Profunda brachii (with radial nerve through triangular interval → spiral groove)

Palmar Arches

• Superficial palmar arch: Mainly ulnar artery; gives common palmar digital arteries
• Deep palmar arch: Mainly radial artery (from dorsum through 1st interosseous space); gives palmar metacarpal arteries and perforating branches
• Allen's test confirms radial-ulnar anastomosis before radial artery cannulation

Veins

• Cephalic vein: Lateral dorsal hand → lateral forearm → deltopectoral groove → pierces clavipectoral fascia → axillary vein
• Basilic vein: Medial dorsal hand → medial forearm → perforates deep fascia in mid-arm → axillary vein
• Median cubital vein: Connects cephalic to basilic in cubital fossa (used for venepuncture)

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9. IMPORTANT CLINICAL SPACES

Cubital Fossa

• Boundaries: Base = line between medial + lateral epicondyles; Lateral = brachioradialis; Medial = pronator teres; Roof = bicipital aponeurosis + deep fascia
• Contents (lateral to medial): Radial nerve (superficial branch), Biceps tendon, Brachial artery, Median nerve - Mnemonic: "Really Need Beer To Be At My Best" (R.N.B.T.B.A.M.N. → Radial N., Biceps Tendon, Brachial Artery, Median N.)

Carpal Tunnel

• Boundaries: Flexor retinaculum (roof), carpal bones (floor + walls)
• Contents: Median nerve + 9 flexor tendons (FDS ×4, FDP ×4, FPL ×1)
• Note: Ulnar nerve and radial artery are NOT in the carpal tunnel (they pass through Guyon's canal and superficially, respectively)
• Carpal Tunnel Syndrome: Median nerve compression → pain/paraesthesia in lateral 3.5 digits (worse at night), thenar wasting, positive Tinel's and Phalen's signs

Anatomical Snuffbox

• Borders: Lateral - APL + EPB tendons; Medial - EPL tendon; Floor - scaphoid + trapezium
• Contents: Radial artery, superficial branch of radial nerve, cephalic vein origin
• Clinical: Scaphoid fracture (tender snuffbox after fall on outstretched hand; avascular necrosis risk); radial pulse can be felt here

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10. KEY NERVE INJURY SUMMARY

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11. CLINICAL CORRELATIONS (MBBS High-Yield)

Fractures

De Quervain's Tenosynovitis

• Inflammation of APL + EPB in first extensor compartment (lateral wrist)
• Positive Finkelstein's test (ulnar deviation with thumb in fist causes pain)

Rotator Cuff Tears

• Supraspinatus most commonly torn (degenerative or acute trauma)
• Presents with pain on abduction, especially 60-120° (painful arc)
• Supraspinatus wasting on examination

Shoulder Dislocation

• Anterior (95%+): arm in abduction + external rotation, neurovascular injury risk (axillary nerve, anterior circumflex humeral artery)
• Bankart lesion (torn anteroinferior labrum) + Hill-Sachs lesion in recurrent cases

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12. SURFACE ANATOMY LANDMARKS

• Cephalic vein in deltopectoral groove - useful for IV access
• Biceps tendon palpable in cubital fossa - Biceps reflex (C5, C6)
• Brachial artery - medial bicipital groove; blood pressure measurement; divides at neck of radius
• Radial pulse - lateral to flexor carpi radialis tendon at wrist, or in anatomical snuffbox
• Ulnar pulse - lateral to flexor carpi ulnaris at wrist
• Medial epicondyle - subcutaneous, ulnar nerve palpable behind it; "funny bone"
• Olecranon - tip of elbow (triceps insertion)

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