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ANATOMY VIVA SCRIPT - UPPER LIMB OSTEOLOGY

1st Year MBBS | Bullet-Point Format

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HOW TO APPROACH A BONE IN VIVA

1. Name it - state what bone it is
2. Side - say which side (right/left) and how you determined it
3. Type - classify it (long, flat, irregular, sesamoid, short)
4. Parts - describe the parts from proximal to distal
5. Features - name markings, facets, grooves, tubercles
6. Articulations - what it articulates with
7. Muscle attachments - origins and insertions
8. Nerve supply - related nerves in grooves/notches
9. Clinical - common fractures, anomalies, clinical relevance

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PART 1: OSTEOLOGY - BONE BY BONE

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1. CLAVICLE

• Long bone (exception: it ossifies in membrane, not cartilage)
• The ONLY bony connection between the upper limb and the trunk
• Palpable along its entire length

• Sternal (medial) end is bulky and rounded - faces medially
• Acromial (lateral) end is flat and faces laterally
• Inferior surface is rough laterally, with subclavian groove on the shaft
• Convexity faces anteriorly on the medial side; concavity anteriorly on the lateral side (S-shape)

• Gentle S-shape: medial two-thirds convex anteriorly, lateral one-third concave anteriorly

• Two ends: sternal end (medial), acromial end (lateral)
• One shaft

• Sternal end: Large facet for manubrium + first costal cartilage (sternoclavicular joint)
• Acromial end: Small oval facet for acromion of scapula (acromioclavicular joint)
• Inferior surface, lateral third: Conoid tubercle + trapezoid line = coracoclavicular ligament attachment
• Subclavian groove: On inferior aspect of medial shaft, for subclavius muscle
• Superior surface is smoother than inferior surface

• Sternoclavicular joint (with manubrium + 1st costal cartilage)
• Acromioclavicular joint (with acromion of scapula)

• Shaft: 5th-6th week of intrauterine life (first bone to ossify in the body)
• Sternal epiphysis: 18-20 years (last to fuse, at 25 years)

• Most commonly fractured bone by indirect violence (fall on outstretched hand)
• Fracture site: junction of medial 2/3 and lateral 1/3 (weakest point)
• The subclavian vein lies posterior-inferior - at risk in fractures
• No nutrient foramen (no medullary cavity in traditional sense)

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2. SCAPULA

• Flat, triangular bone
• Lies on posterior chest wall, ribs 2-7
• Inferior angle at T7 spinous process level; scapular spine at T3

• Costal (anterior) surface is concave - subscapular fossa faces anteriorly
• Posterior surface has spine and spinous processes
• Glenoid cavity faces laterally and slightly anteriorly
• Coracoid process projects anteriorly and laterally
• Notch is on the superior border

• 3 angles: lateral (most important), superior, inferior
• 3 borders: superior (with suprascapular notch), medial (vertebral), lateral (axillary)
• 2 surfaces: costal (anterior/subscapular), posterior
• 3 processes: spine, acromion, coracoid process

• Glenoid cavity: Comma-shaped, at lateral angle; articulates with head of humerus
• Supraglenoid tubercle: Above glenoid; attachment for long head of biceps brachii
• Infraglenoid tubercle: Below glenoid; attachment for long head of triceps brachii
• Suprascapular notch: On superior border; suprascapular nerve passes through; suprascapular artery passes over the ligament (mnemonic: "Army over the bridge, Navy under the bridge")
• Coracoid process: Bent-finger shaped; multiple attachments
• Spine of scapula: Leads to acromion; palpable ridge
• Subscapular fossa: Anterior surface; subscapularis origin
• Supraspinous fossa: Above spine; supraspinatus origin
• Infraspinous fossa: Below spine; infraspinatus origin

• Glenohumeral joint (with head of humerus)
• Acromioclavicular joint (acromion with clavicle)

• Body: 8th week IU life
• Coracoid: 1st year postnatal
• Acromion: 15-18 years (secondary centers)
• Acromion fuses at 25 years

• Scapular foramen: ossification of superior transverse ligament traps suprascapular nerve (scapular notch syndrome - weakness of supraspinatus + infraspinatus)
• Winging of scapula: Long thoracic nerve (nerve to serratus anterior) palsy
• Os acromiale: failure of acromion to fuse (seen in ~8% people, may impinge on rotator cuff)

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3. HUMERUS

• Head faces medially and superiorly
• Greater tubercle is lateral, lesser tubercle is anterior
• Bicipital groove (intertubercular sulcus) is anteriorly placed
• Medial epicondyle is larger; trochlea is medial at distal end
• Capitulum is lateral at distal end
• Olecranon fossa is posterior

• Upper end: head, anatomical neck, greater tubercle, lesser tubercle, surgical neck, bicipital groove
• Shaft
• Lower end: condyle (trochlea + capitulum), medial + lateral epicondyles, olecranon fossa, coronoid fossa, radial fossa

• Head: Half-spherical; faces medially, superiorly, and posteriorly; articulates with glenoid cavity
• Anatomical neck: Constriction at margin of head articular surface
• Surgical neck: Below tubercles; MOST COMMONLY FRACTURED PART of humerus; axillary nerve at risk
• Greater tubercle (laterally placed): Three facets - superior for supraspinatus, middle for infraspinatus, inferior for teres minor
• Lesser tubercle (anteriorly placed): Subscapularis attachment
• Bicipital groove (intertubercular sulcus): Lodges long head of biceps; medial lip: teres major; lateral lip: pectoralis major; floor: latissimus dorsi

• Deltoid tuberosity: Mid-lateral shaft; deltoid insertion
• Radial groove (spiral groove): Posterior surface; radial nerve + profunda brachii artery; runs obliquely
• Medial border: Coracobrachialis attachment

• Trochlea: Medial, pulley-shaped; articulates with trochlear notch of ulna
• Capitulum: Lateral, ball-shaped; articulates with head of radius
• Medial epicondyle: Non-articular; ulnar nerve passes posterior to it
• Lateral epicondyle: Non-articular; common extensor origin
• Olecranon fossa: Posterior, receives olecranon in extension
• Coronoid fossa: Anterior, receives coronoid process in flexion
• Radial fossa: Anterior (above capitulum), receives radial head in flexion
• Carrying angle: 10-15° in males, 15-20° in females

• Shoulder (glenohumeral) joint - with glenoid cavity
• Elbow joint - trochlea with ulna; capitulum with radius

• C - Capitulum: 1 year
• R - Radial head: 3 years
• I - Internal (medial) epicondyle: 5 years
• T - Trochlea: 7 years
• O - Olecranon: 9 years
• E - External (lateral) epicondyle: 11 years All fuse by 16-17 years (except medial epicondyle fuses last at 18-20)

• Surgical neck fracture: Axillary nerve + posterior circumflex humeral artery injured → loss of shoulder abduction (deltoid paralysis) + loss of sensation over the badge area (regimental badge area)
• Shaft fracture: Radial nerve injury in radial groove → wrist drop (loss of extension of wrist and fingers)
• Medial epicondyle fracture: Ulnar nerve injury → claw hand (ring + little finger), loss of medial 1.5 digits sensation
• Supracondylar fracture in children: Anterior interosseous nerve or brachial artery injury
• Fracture carrying angle disturbance: Cubitus valgus or varus

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4. RADIUS

• Radial tuberosity is on medial side
• Styloid process is lateral and longer than ulnar styloid
• Radial head is at proximal end (circular, disc-shaped)
• Pronator tubercle / ulnar notch is medially placed distally

• Upper end: head, neck, radial tuberosity
• Shaft
• Lower end: styloid process, ulnar notch, carpal articular surface, dorsal (Lister's) tubercle

• Head: Circular, disc-shaped; superior concave surface articulates with capitulum; medial rim articulates with radial notch of ulna
• Neck: Short cylinder between head and tuberosity
• Radial tuberosity: Medial blunt projection; biceps brachii insertion

• Anterior (interosseous) border: Sharp; gives attachment to interosseous membrane
• Oblique line: From radial tuberosity to interosseous border
• Pronator teres attachment: Mid-lateral surface

• Styloid process: Lateral projection; brachioradialis inserts
• Ulnar notch: Medial concavity; articulates with head of ulna
• Carpal surface: Inferior articular surface; articulates with scaphoid (lateral) and lunate (medial)
• Dorsal tubercle (Lister's tubercle): On dorsal surface; extensor pollicis longus tendon hooks around it

• Proximal radioulnar joint (head with radial notch of ulna)
• Elbow joint (head with capitulum)
• Distal radioulnar joint (ulnar notch with head of ulna)
• Radiocarpal (wrist) joint (with scaphoid + lunate)

• Shaft: 8th week IU life
• Lower end: 1 year (fuses at 20 years)
• Upper end (head): 5 years (fuses at 17 years)

• Colles' fracture: Most common fracture of distal radius, 2.5 cm above wrist; dinner fork deformity (dorsal displacement + radial shift); associated with fall on outstretched hand; common in postmenopausal women
• Smith's fracture: Reverse Colles; garden spade deformity (volar displacement)
• Monteggia fracture: Upper 1/3 ulna fracture + dislocation of radial head
• Galeazzi fracture: Radial shaft fracture + dislocation of distal radioulnar joint
• Colles' fracture complication: Median nerve compression in carpal tunnel

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5. ULNA

• Olecranon is large, posteriorly projecting - palpated as the "tip of the elbow"
• Trochlear notch (olecranon + coronoid) faces anteriorly
• Radial notch is on the lateral side
• Styloid process is medial and shorter than radial styloid
• Subcutaneous (posterior) surface is palpable throughout

• Upper end: olecranon, coronoid process, trochlear notch, radial notch, tuberosity of ulna
• Shaft
• Lower end: head, styloid process

• Olecranon: Posterior projection; tip is attachment for triceps brachii; anterolateral surface is articular (part of trochlear notch)
• Coronoid process: Anterior projection; superolateral = articular (part of trochlear notch); lateral = radial notch
• Trochlear notch: Formed by olecranon + coronoid process; articulates with trochlea of humerus
• Radial notch: On lateral side of coronoid; articulates with head of radius
• Tuberosity of ulna: Brachialis muscle insertion
• Supinator crest: Posterior margin of fossa below radial notch; supinator origin

• Three borders, three surfaces
• Posterior border: Subcutaneous, palpable throughout
• Interosseous border: Sharp, faces radius; interosseous membrane attachment
• Pronator quadratus attaches to distal fourth of anterior surface

• Head of ulna: Convex; separated from carpus by articular disc (does NOT articulate with carpals directly)
• Styloid process: Projects distally from head

• Proximal radioulnar joint (radial notch with head of radius)
• Elbow joint (trochlear notch with trochlea of humerus)
• Distal radioulnar joint (head with ulnar notch of radius)

• Shaft: 8th week IU life
• Olecranon: 9-11 years (fuses at 16 years)
• Distal (head): 5-6 years (fuses at 17 years)

• Olecranon fracture: Triceps avulsion; treated with tension band wiring
• Nightstick fracture: Isolated ulnar shaft fracture (defense injury - raising arm to block a blow)
• Pulled elbow (nursemaid's elbow): Radial head subluxation from annular ligament; seen in children < 5 years when arm is yanked

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6. CARPAL BONES (8 bones in 2 rows)

• Largest bone in proximal row
• Boat-shaped
• Waist is palpable in anatomical snuffbox
• Articulates with: radius (proximal), trapezium + trapezoid (distal), lunate (medial), capitate (medial)
• Blood supply enters distally - proximal pole is avascular
• Clinical: Most commonly fractured carpal bone (fall on outstretched hand); tenderness in anatomical snuffbox; avascular necrosis of proximal fragment is common complication
• X-ray may be normal initially - treat as fracture until proven otherwise

• Crescent-shaped; moon-like
• Most commonly dislocated carpal bone
• Clinical: Lunate dislocation compresses median nerve in carpal tunnel
• Kienbock's disease: avascular necrosis of lunate

• Pyramidal/triangular bone
• Articulates with pisiform anteriorly

• Sesamoid bone in tendon of flexor carpi ulnaris
• Articulates only with triquetrum
• Forms lateral boundary of Guyon's canal (ulnar nerve and artery pass through)

• Saddle-shaped articular surface for thumb (1st metacarpal)
• Groove on palmar surface for flexor carpi radialis
• Tubercle of trapezium forms part of flexor retinaculum attachment

• Smallest bone in distal row
• Least commonly dislocated/fractured

• Largest carpal bone
• Has a rounded head
• Center of wrist

• Has a hook (hamulus) on palmar surface
• Hook of hamate forms medial boundary of carpal tunnel (with pisiform)
• Ulnar nerve and artery pass lateral to the hook
• Clinical: Hook of hamate fracture seen in golfers/baseball players; may compress ulnar nerve

• 4 tendons of flexor digitorum superficialis
• 4 tendons of flexor digitorum profundus
• 1 tendon of flexor pollicis longus
• Median nerve (most superficial, compressed first)

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7. METACARPALS (5 bones)

• Base (proximal end) - articulates with carpal bones + adjacent metacarpals
• Shaft
• Head (distal end) - articulates with proximal phalanges (knuckles)

• Shortest and most mobile
• Has saddle-shaped base articulating with trapezium (carpometacarpal joint - most mobile)
• Bennett's fracture: base of 1st metacarpal + dislocation of CMC joint
• Rolando's fracture: comminuted Bennett's fracture

• Has a styloid process at base
• Most stable (articulates with trapezium, trapezoid, capitate)

• Dorsal interossei originate from adjacent metacarpal shafts (PAD - Palmar Adduct, DAB - Dorsal ABduct)
• Palmar interossei origin from single metacarpal

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8. PHALANGES

• 14 phalanges: 2 in thumb, 3 in each finger (proximal, middle, distal)
• Each has: base (proximal), shaft, head (distal)
• Distal phalanx: expanded tuberosity at tip; no head
• Flexor digitorum superficialis inserts into sides of middle phalanx
• Flexor digitorum profundus inserts into base of distal phalanx
• Extensor expansion (dorsal hood) inserts into middle and distal phalanges

• Mallet finger: Avulsion of extensor tendon from distal phalanx; finger tip drops
• Jersey finger: Avulsion of FDP from distal phalanx; cannot flex DIP
• Boutonniere deformity: Central slip rupture; PIP flexed, DIP extended
• Swan neck deformity: PIP extended, DIP flexed

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PART 2: GROSS SPOTTER DISCUSSION

Spotter: Clavicle

• "This is the right/left clavicle - a long bone connecting the trunk to the upper limb"
• State the S-shape and how you determine the side
• Point to: sternal end, acromial end, conoid tubercle, trapezoid line, subclavian groove
• Mention: only bone in body to ossify in membrane (intramembranous) AND be classified as a long bone

Spotter: Scapula

• "This is the right/left scapula - a flat irregular bone"
• Point to: glenoid cavity, coracoid process, spine, acromion, suprascapular notch
• Say the surfaces and fossae
• Mention: lies over 2nd-7th rib; inferior angle at T7

Spotter: Humerus

• "This is the right/left humerus - a long bone of the arm"
• Point to: head, greater and lesser tubercle, bicipital groove, deltoid tuberosity, radial groove, medial epicondyle, trochlea, capitulum
• Give CRITOE ossification ages if asked

Spotter: Radius

• "This is the right/left radius - a long bone of the lateral forearm"
• Point to: head, neck, radial tuberosity, Lister's tubercle, styloid process, ulnar notch
• State: radius is the main bone taking weight at the wrist

Spotter: Ulna

• "This is the right/left ulna - a long bone forming the medial forearm"
• Point to: olecranon, trochlear notch, coronoid process, radial notch, subcutaneous posterior border
• Mention: ulna is the main bone of the elbow

Spotter: Carpal bones

• Name the bone, identify proximal vs distal row
• State immediate articulations
• Mention the clinical relevance (scaphoid fracture, lunate dislocation, hook of hamate)

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PART 3: EMBRYOLOGY OF UPPER LIMB BONES

Timeline

• Day 24-26: Upper limb buds appear (as mesenchymal proliferations from lateral plate mesoderm + somites)
• Week 4: Limb bud elongation begins
• Week 5: Hand plate develops; radiating digital rays appear
• Week 6: Finger rays delineated; interdigital apoptosis begins
• Week 7-8: Fingers separated by programmed cell death (apoptosis) of interdigital tissue
• Week 8: Upper limb rotates 90° laterally (thumb points laterally)
• Week 12: Primary ossification centers appear in most long bones

Cellular Origin

• Bone (cartilage models): Lateral plate mesoderm (limb skeleton)
• Muscles: Myoblasts migrate from somites (dermomyotome)
• Blood vessels: Lateral plate mesoderm (angiogenesis)
• Nerves: Neural crest cells + ventral horn neurons grow into the limb bud

Endochondral Ossification (all long bones of upper limb)

• Mesenchyme → Condensation → Cartilage model → Primary ossification center (shaft/diaphysis) → Secondary ossification centers (epiphyses)
• Clavicle: Exception - ossifies by INTRAMEMBRANOUS ossification (no cartilage stage); yet classified as long bone

Regulating Factors

• AER (Apical Ectodermal Ridge): Controls proximo-distal growth; produces FGFs
• ZPA (Zone of Polarizing Activity): Posterior mesoderm; controls anterior-posterior (thumb vs little finger) patterning; produces SHH (sonic hedgehog)
• HOX genes (HOXA, HOXD): Pattern the limb segments; HOXD13 mutations cause synpolydactyly
• Ectoderm + Wnt signaling: Dorso-ventral (back vs palm) patterning

Anomalies

Ossification Sequence (practical exam point)

• First bone to start ossifying: Clavicle (5th-6th week IU)
• First long bone to ossify: Clavicle (intramembranous, not endochondral)
• Last epiphysis to fuse in body: Medial epicondyle of humerus and sternal end of clavicle (~25 years)
• Ossification of bones proceeds from shaft → epiphyses
• In upper limb: elbow epiphyses use CRITOE rule

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QUICK REFERENCE: NERVE INJURIES AT EACH BONE

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VIVA TIP: ONE-LINER ANSWERS

• Q: Which bone is most commonly fractured in fall on outstretched hand? A: Scaphoid (young adults); Distal radius/Colles' (elderly/postmenopausal)
• Q: Which carpal bone is most commonly dislocated? A: Lunate
• Q: What is the carrying angle? A: Angle between long axis of humerus and ulna with elbow extended; 10-15° males, 15-20° females; formed because trochlea projects lower medially
• Q: Which is the only long bone to ossify by intramembranous ossification? A: Clavicle
• Q: Nerve felt behind medial epicondyle? A: Ulnar nerve ("funny bone" sensation)
• Q: What passes through bicipital groove? A: Tendon of long head of biceps brachii (with its synovial sheath)
• Q: What are the contents of the anatomical snuffbox? A: Radial artery, cephalic vein (origin), superficial branch of radial nerve; floor = scaphoid + trapezium; tendons = extensor pollicis longus (medial), extensor pollicis brevis + abductor pollicis longus (lateral)

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