forearm

Anterior compartment

plan

Muscles

· mobile wad of 3 on lateral side

· BR, ECRL, ECRB (radial n)

· flexor-pronator group on medial side

· superficial PT, FCR, PL, FCU (median n)

· middle FDS (median n)

· deep FDP, FPL, PQ (ant int n)

· biceps tendon in middle

· special points

· FCR, PL from flexor origin only

· PT, FCU also from ulna

· FDS also from radius and ulna

· FDP from ulna, FPL from radius, PQ both

Neurovascular

· arm framed by nerves

· LCN laterally and MCN medially

· median cephalic and basilic on inside

· superficial radial n on radial side

· radial a on inside of it distally

· ulnar n on ulnar side

· ulnar a on inside of it distally

· down middle

· median n (medial)

· brachial a (lateral)

· ant int n and ant int a deep in middle

· radial and ulnar aa

· branches of brachial a

· special points

· median n crosses ulnar a beneath FDS

· median n between and ulnar a under PT heads

· ulnar n between FCU heads

superficial muscles

· 5 muscles

· originate from common flexor origin

· medial epicondyle of humerus

· supplied by median nerve

· cross elbow

· represented by hand

· thumb is PT

· index is FCR

· middle is FDS

· ring is PL

· little is FCU

Pronator teres

Origin

· large superficial head

· common flexor origin

· medial supracondylar ridge

· small deep head

· medial coronoid process of ulna

Path

· forms medial border of cubital fossa

· runs obliquely across forearm

· forms flat tendon

Relations

· median nerve passes between 2 heads

Insertion

· into lateral convexity of radius

· behind anterior profile of radius

Flexor carpi radialis

Origin

· common flexor origin

Path

· lies distal to PT

· tendon forms in middle of forearm

· tendon perforates flexor retinaculum at wrist

· lies in groove of trapezium

· passes deep to tendon of FPL

Relations

· radial artery lies lateral to tendon

· median nerve lies medial to tendon

Insertion

· bases of MC II and III

· may give slip to scaphoid

Flexor digitorum superficialis

Origin

· humeroulnar head

· common flexor origin

· medial ligament of elbow joint

· sublime tubercle on medial coronoid process of ulna

· radial head

· whole length of anterior oblique line

· heads joined by fibrous arch

Path

· belly hidden by other superficial flexors

· referred to as middle layer

· tendons appear above wrist

· superficial muscle gives rise to tendons III and III

· deep muscle gives rise to tendons II and V

· tendons pass deep to flexor retinaculum

Relations

· median nerve plastered to deep surface of FDS in forearm

Insertion

· into P2 of fingers

Palmaris longus

· absent in 15% of arms

· phylogenetically degenerating

Origin

· common flexor origin

Insertion

· palmar aponeurosis

Flexor carpi ulnaris

Origin

· humeral head

· common flexor origin

· ulnar head

· wide aponeurosis

· medial border of olecranon

· upper 3/4 of subcutaneous border of ulna

· lies edge to edge with aponeurosis of ECU

Path

· passes down ulnar border of forearm

Relations

· ulnar nerve passes between 2 heads

· ulnar nerve and artery are medial to tendon at wrist

Insertion

· into pisiform

· thus into hamate and base of MC V

deep muscles

· 3 muscles

· FDP

· FPL

· PQ

· do not cross elbow joint

· supplied by anterior interosseous nerve

· and ulnar nerve for FDP

Flexor digitorum profundus

Origin

· medial surface of olecranon

· upper 3/4 of anteromedial ulna

· interosseous membrane

Path

· tendon for index separates in forearm

· other tendons partly attached in carpal tunnel

· tendons separate in palm

· lumbricals take origin here

Insertion

· into P3 of fingers

Flexor pollicis longus

Origin

· anterior surface of radius below anterior oblique line

· interosseous membrane

Path

· tendon forms on ulnar side of muscle

· fleshy fibres until just above wrist

· tendon passes in carpal tunnel deep to FCR

· spirals around ulnar side of FCR to become superficial

Insertion

· P2 of thumb

Pronator quadratus

Origin

· lower 1/4 of ulna

Insertion

· distal radius

· from anterolateral border superficially

· to triangular interosseous area deeply

space of parona

· bounded by

· long finger flexors superficially

· pronator quadratus deeply

· limited

· proximally by oblique origin of FDS

· contains

· proximal parts of flexor sheaths

Cubital fossa

· triangular area between

· pronator teres

· brachioradialis

· line joining humeral epicondyles

· roof formed by

· deep fascia of forearm

· bicipital aponeurosis medially

· floor formed by

· brachialis

· on roof lies (medial to lateral)

· medial cutaneous nerve of forearm

· basilic vein

· cephalic vein

· lateral cutaneous nerve of forearm

· in fossa lies (medial to lateral)

· median nerve

· brachial artery

· biceps tendon

· radial nerve (under brachioradialis)

vessels

Brachial artery

· enters forearm through midline of cubital fossa

· divides into radial and ulnar arteries

· radial is direct continuation

· ulnar branches at right angle

Radial artery

· passes distally

· medial to biceps tendon

· over supinator

· over tendon of PT

· across radial origin of FDS

· across origin of FPL

· over insertion of PQ

· over lower end of radius

· disappears under tendons of APL and EPL

· crosses snuffbox

· in upper forearm

· overlapped by BR

· in middle forearm

· on ulnar side of radial nerve

Ulnar artery

· passes

· deep to deep head of PT

· beneath fibrous arch of FDS

· lies near median nerve

· then leaves median nerve and approaches ulnar nerve

· passes deep to median nerve (crossed by it)

· lies on FDP

· lies on radial side of ulnar nerve

· passes over front of wrist

· on radial side of tendon of FCU

Branches

· gives off common interosseous artery

· divides into anterior and posterior branches

Anterior interosseous artery

· liees deeply on interosseous membrane

· between FDP and FPL

· gives off branches to

· FDP and FPL

· radius and ulna

· extensor muscles

· pierces IOM at upper border of PQ

· gives off median artery to median nerve

Posterior interosseous artery

· passes backwards through interosseous space

Anastomoses

Around elbow joint

· recurrent branches from

· radial artery

· ulnar artery

· interosseous arteries

· run up to anastomose with

· descending articular branches of profunda brachii

· ulnar collateral arteries

Around wrist joint

· ulnar and radial arteries give off anterior and posterior carpal branches

· anastomose to form anterior and posterior carpal arches

Anterior carpal arch

· lies transversely across wrist joint

· supplies carpal bones

· anastomoses with deep palmar arch

Posterior carpal arch

· lies transversely across wrist joint

· sends dorsal metacarpal arteries into each metacarpal space

· anastomose with palmar digital and metacarpal branches of palmar arches

Veins

Deep

· accompany arteries

· drain forearm only

Superficial

· blood from hand drains into venous network on dorsum

Cephalic vein

· starts on radial side of network

· in snuffbox

· runs up preaxial border of limb

· up radial forearm

· lateral to biceps

· in deltopectoral groove

· pierces clavipectoral fascia

· drains into axillary vein

Basilic vein

· starts on ulnar side of network

· runs up postaxial border of limb

· pierces deep fascia halfway up arm

· joins brachial veins to form axillary vein

Median forerm vein

· drains subcutaneous tissue on volar wrist and forearm

· divides at elbow

· median cephalic vein

· median basilic vein

· each drains into respective axial vein

nerves

Sensory

Lateral cutaneous nerve of forearm

· terminal branch of musculocutaneous nerve

· pierces deep fascia at elbow joint

· supplies radial border of forearm

· anterior and posterior branches

· as far as ball of thumb

Medial cutaneous nerve of forearm

· branch of medial cord of plexus

· symmetrical with LCNFA

· supplies ulnar border of forearm

Radial nerve

· superficial branch

· runs distally from cubital fossa

· under BR on

· supinator

· PT tendon

· FDS

· lies on radial side of radial artery

· leaves flexor forearm

· backwards under tendon of BR

· few cm above radial styloid

· breaks up into branches

· supplies

· radial dorsum of hand

· radial 3 1/2 fingers to nailbeds

Median nerve

· passes between 2 heads of PT

· joins ulnar artery under arch of FDS

· crosses over ulnar artery

· passes down middle of forearm

· attached to deep surface of FDS

· on FDP

· emerges between PL and FCR

· passes beneath flexor retinaculum

· supplies

· PT

· FCR

· PL

· FDS

Branches

Anterior interosseous branch

· runs down with artery

· ends at wrist

· supplies

· radial FDP

· FPL

· PQ

· IOM and periosteum

· wrist capsule

Ulnar nerve

· lies behind medial epicondyle

· passes between 2 heads of FCU

· lies under FCU

· lies on FDP

· ulnar artery on radial side

· passes across wrist radial to tendon of FCU

· supplies

· FCU (C7 fibres)

· ulnar FDP

Branches

Dorsal branch

· passes between tendon of FCU and ulna

· supplies

· ulnar dorsum of hand

· ulnar 1 1/2 fingers to nailbeds