Week 6 - The Forearm and Wrist + Hands

Supination

Turning the palm upward; radius and ulna are parallel.

Pronation

Turning the palm downward; radius crosses over ulna.

Radius

Forearm bone on the thumb side.

Ulna

Forearm bone on the pinky side.

Styloid processes

Projections on radius & ulna that stabilize wrist medially & laterally; prone to fracture.

Distal radius fracture

Causes “dinner fork deformity” due to large radial base taking force.

Annular ligament

C-shaped ligament holding radial head against ulna at proximal radioulnar joint.

Proximal radioulnar joint

Joint where radial head spins within annular ligament.

Distal radioulnar joint

Joint where radius moves around ulnar head at wrist.

Radioulnar ligaments

Anterior & posterior ligaments stabilizing distal radioulnar joint.

Radial notch of ulna

Socket that receives radial head proximally.

Interosseous membrane

Fibrous sheet connecting radius & ulna; transfers force and stabilizes forearm.

Force transmission

Force travels from wrist → radius → interosseous membrane → ulna → humerus.

Carpal bones

Eight irregular wrist bones in two rows of four.

Intercarpal joints

Joints between carpal bones.

Radiocarpal joint

Joint between distal radius and carpal bones; transmits force from hand.

Ulnocarpal disc

Cushion between ulna and carpals that stabilizes wrist.

Carpal tunnel

Narrow passage formed by carpal bones & flexor retinaculum.

Flexor retinaculum

Thick band forming roof of carpal tunnel.

Carpal tunnel contents

Median nerve & flexor tendons with synovial sheaths.

Carpal tunnel syndrome

Tendon inflammation compresses median nerve; ulnar nerve unaffected.

Ulnar canal

Passage superficial to flexor retinaculum transmitting ulnar nerve & artery.

Metacarpals

Five bones forming the palm; numbered from thumb.

Phalanges

Finger bones: proximal, middle, distal; thumb lacks middle phalanx.

Carpometacarpal (CMC) joints

Between carpals and metacarpals.

MCP joints

Between metacarpals and proximal phalanges.

PIP joints

Between proximal & middle phalanges.

DIP joints

Between middle & distal phalanges.

Thumb IP joint

Only interphalangeal joint in thumb.

Osteoarthritis

Common in DIP joints.

Rheumatoid arthritis

Common in MCP and PIP joints.

Digital collateral ligaments

Prevent sideways movement of fingers.

Midline of hand

Middle finger; used for abduction/adduction reference.

Anterior compartment

Flexor/pronator muscles; median & ulnar nerve innervation.

Posterior compartment

Extensor/supinator muscles; radial nerve innervation.

Intermuscular septum

Divides anterior & posterior compartments.

Compartment syndrome

Increased pressure compresses nerves & vessels causing pain and numbness.

Common flexor origin

Medial epicondyle attachment for wrist flexors.

Pronator teres

Pronates forearm; median nerve; forms cubital fossa border.

Flexor carpi radialis

Flexes wrist; radial side; median nerve.

Flexor carpi ulnaris

Flexes wrist; ulnar side; ulnar nerve.

Palmaris longus

Flexes wrist & tenses palmar aponeurosis; absent in 15%.

Flexor digitorum superficialis

Flexes PIP joints & wrist; inserts on middle phalanges.

Flexor digitorum profundus

Flexes DIP joints; medial half ulnar nerve, lateral half median nerve.

Flexor pollicis longus

Flexes thumb IP joint; median nerve.

Pronator quadratus

Primary pronator near wrist; anterior interosseous nerve.

Common extensor origin

Lateral epicondyle attachment for extensors.

Brachioradialis

Flexes elbow best in neutral position (“beer drinking muscle”).

Extensor carpi radialis longus

Extends & abducts wrist.

Extensor carpi radialis brevis

Wrist extension.

Extensor carpi ulnaris

Wrist extension & adduction.

Extensor digitorum

Extends digits 2–5 via extensor expansion.

Extensor digiti minimi

Extends pinky finger.

Supinator

Supinates forearm; radial nerve.

Extensor pollicis longus

Extends distal thumb.

Extensor pollicis brevis

Extends proximal thumb.

Abductor pollicis longus

Abducts thumb.

Extensor indicis

Extends index finger.

Dorsal tubercle of radius

Pulley redirecting thumb extensor tendons.

rachial artery

Splits into radial & ulnar arteries at cubital fossa.

Radial artery

Lateral forearm; contributes to deep palmar arch.

Ulnar artery

Medial forearm; contributes to superficial palmar arch.

Posterior interosseous artery

Supplies posterior compartment.

Deep palmar arch

Mainly radial artery.

Superficial palmar arch

Mainly ulnar artery.

Radial pulse

Lateral wrist near flexor carpi radialis tendon.

Ulnar pulse

Medial wrist near flexor carpi ulnaris; harder to palpate.

Median nerve

Innervates most anterior forearm muscles; passes through carpal tunnel.

Anterior interosseous nerve

Branch of median; innervates deep flexors & pronator quadratus.

Ulnar nerve

Innervates FCU & medial FDP; supplies intrinsic hand muscles.

Radial nerve

Innervates posterior extensors.

Superficial radial nerve

Sensory to dorsum of hand.

Posterior interosseous nerve

Motor branch to deep extensors.

Radial nerve test

Wrist & finger extension.

Median nerve test

Thumb opposition & flexion.

Ulnar nerve test

Finger abduction.

OK sign test

Tests anterior interosseous branch.

Musculocutaneous nerve

Supplies anterior/lateral forearm skin.

Medial cutaneous nerves

Supply medial forearm skin.

Radial nerve

Supplies posterior forearm skin.

Thenar muscles

Thumb movement (median nerve).

Opponens pollicis

Thumb opposition.

Hypothenar muscles

Pinky movement (ulnar nerve).

Lumbricals

Flex MCP & extend IP joints.

Palmar interossei (PAD)

Adduct fingers toward midline.

Dorsal interossei (DAB)

Abduct fingers away from midline.

Adductor pollicis

Adducts thumb; ulnar nerve.

Palmar aponeurosis

Anchors skin for grip.

Opposition

Thumb moves across palm.

Reposition

Thumb returns from opposition.

Saddle joint

Thumb CMC joint allowing wide motion.

Abduction (hand)

Movement away from middle finger.

Adduction (hand)

Movement toward middle finger.

Ape hand

Median nerve damage → loss of opposition.

Claw hand

Ulnar nerve damage affecting intrinsic muscles.

Wrist drop

Radial nerve or posterior interosseous nerve injury.

Scaphoid fracture

Risk of bone necrosis due to retrograde blood supply.