Antebrachium Extensors

Extensor retinaculum

• thick fibrous fascia band at wrist -holds forearm tendons in place

• from lateral radius to medial ulna (styloid process), triquetrum & pisiform bones

Extensor Canals

• six osteofibrous canals: post side of bones

• extensor tendons pass through to dorsal hand

Extensor Canals• a. abductor pollicis longus, \

extensor pollicis brevis / in #1: most lateral • b. extensor carpi radialis longus \

extensor carpi radialis brevis / in #2• c. extensor pollicis longus - in #3 • d. extensor digitorum \

extensor indicis / in #4• e. extensor digiti minimi - in #5 • f. extensor carpi ulnaris - in #6

Anatomical snuff box

• depression on dorsolateral wrist bounded by tendons of:

• abductor pollicis longus, extensor pollicis brevis & extensor pollicis longus (where the scaphoid bone lies in the floor here, most likely be fractured, local tenderness, death & absorption of the bone later)

Muscles

• Muscles 3 Functional groups + brachioradialis & supinator– i) extend hand at wrist = the 3 extensor carpi's

- radialis longus & brevis; & ulnaris– ii) extend medial 4 digits (fingers) = extensors

digitorum; indicis; digiti minimi– iii) extend thumb (1st digit) = abductor pollicis

longus; extensor pollicis longus & brevis

Muscles

• Extensor are arranged in three anatomical layers

• Superficial layer– brachioradialis – extensor carpi radialis longus – extensor carpi radialis brevis– extensor digitorum – extensor digiti minimi – extensor carpi ulnaris

BRACHIORADIALIS

• ORIGINproximal two thirds of lateral supracondylar ridge of humerus, and lateral intermuscular septum

• INSERTIONlateral side of base of styloid process of radius

• ACTIONflex the elbow joint, and assists in pronating and supinating the forearm when these movements are resisted

• NERVEradial nerve C5, C6

EXTENSOR CARPI RADIALIS LONGUS

• ORIGINDistal one third of lateral supracondylar ridge of humerus, and lateral intermuscular septum

• INSERTIONdorsal surface of base of second metacarpal bone, radial side

• ACTIONextends and abducts the wrist, and assists in flexion of the elbow

• NERVEradial nerve C5, C6, 7, 8

EXTENSOR CARPI RADIALIS BREVIS

• ORIGINcommon extensor tendon from lateral epicondyle of humerus, radial collateral ligament of elbow joint, and deep antebrachial fascia

• INSERTIONdorsal surface of base of third metacarpal bone

• ACTIONextends and assists in abduction of the wrist

• NERVEradial C6, 7, 8

EXTENSOR DIGITORUM • ORIGIN

Common extensor tendon fromlateral epicondyle of humerus, and deep antebrachial fascia

• INSERTIONBy four tendons, each penetrating a membranous expansion on the dorsum of the second to fifth digits and dividing over the proximal phalanx into medial and two lateral bands. The medial band inserts into the base of the middle phalanx while the lateral bands reunite over the middle phalanx and insert into the base of the distal phalanx.

• ACTIONExtends the metacarpophalangeal and, in conjunction with the lumbricals and interossei, extends the interphalangeal joints of the second through fifth digits. Assists in abduction of the index, ring, and little fingers; and assists in extension and abducting of the wrist.

• NERVERadial nerve, C6, 7, 8

EXTENSOR DIGITI MINIMI • ORIGIN

Common extensor tendon from lateral epicondyle of humerus, and deep antebrachial fascia

• INSERTIONInto extensor expansion of little finger with extensor digitorum tendon

• ACTIONExtends the metacarpophalangeal joint and, in conjunction with lumbricals interosseus, extends the interphalangeal joints of the little finger. Assists in abduction of the little finger

• NERVEradial nerve C6, 7, C8

EXTENSOR CARPI ULNARIS • ORIGIN

Common extensor tendon fromlateral epicondyle of humerus, by aponeurosis from posterior border of ulna, and deep antebrachial fascia

• INSERTIONbase of fifth metacarpal bone, ulnar side

• ACTIONextends and adducts the wrist

• NERVEradial nerve C6, 7, C8  

Deep layer

• Supinator

• abductor pollicis longus

• extensor pollicis brevis

• extensor pollicis longus

• extensor indicis

SUPINATOR

• ORIGINLateral epicondyle of humerus, radial collateral ligament of elbow joint, annular ligament of radius, and superior crest of ulna

• INSERTIONLateral surface of upper one third of body of radius covering part of anterior and posterior surfaces

• ACTIONsupinates the forearm

• NERVEradial nerve C5, C6, C(7)

ABDUCTOR POLLICIS LONGUS

• ORIGINposterior surface of body of ulna distal to origin of supinator, interosseus membrane, and posterior surface of middle one third of body of radius

• INSERTIONbase of first metacarpal bone, radial side

• ACTIONAbducts and extends the carpometacarpal joints of the thumb; abducts (radial deviation) and assists in flexion the wrist

• NERVERadial nerve C6, 7, C8

EXTENSOR POLLICIS BREVIS

• ORIGINPosterior surface of body of radius distal to origin of abductor pollicis longus, and interosseus membrane

• INSERTIONBase of proximal phalanx of thumb, dorsal surface

• ACTIONExtends the metacarpophalangeal joint of the thumb, extends and abducts the carpometacarpal joint, and assists in abduction (radial deviation) of the wrist

• NERVERadial nerve C6, 7, C8 

EXTENSOR POLLICIS LONGUS

• ORIGINMiddle one third of posterior surface of ulna distal to origin of abductor pollicis longus, and interosseus membrane

• INSERTIONBase of distal phalanx of thumb, dorsal surface

• ACTIONExtends the interphalangeal joint and assists in extension of the metacarpophalangeal and carpometacarpal joints of the thumb. Assists in abduction and extension of the wrist.

• NERVERadial nerve, C6,  C7, C8 

EXTENSOR INDICIS • ORIGIN

posterior surface of body of ulna distal to origin of extensor pollcis longus, and interosseus membrane.

• INSERTIONInto extensor expansion of index finger with extensor digitorium longus tendon

• ACTIONExtends the metacarpophalangeal joint and, in conjunction with the  lumbricals and interossei, extends the interphalangeal joints of the index finger. May assist in adduction of the finger

• NERVERadial nerve C6, 7, C8