Antebrachialis Muscles, Cubital Fossa and Its content

depression on the anterior aspect of the elbow

Cubital Fossa

Margins of cubital fossa

Superior: Imaginary horizontal line connecting the humeral epicondyles

Lateral: brachioradialis

Medial: Pronator teres

Floor:

• Lateral: Supinator

• Medial: brachialis

Roof:

• Bicipital aponeurosis

• Fascia

• Skin

Contents of the cubital fossa from lateral to medial

Radial nerve (passes between the brachioradialis and brachialis)

Biceps brachii tendon

Brachial artery

Median nerve

Contents of the cubital fossa (superficial layer to deep)

Skin

Subcutaneous

• Median cubital vein

• Medial and lateral cutaneous nerves of the forearm

Deep fascia

• Bicipital aponeurosis

Deep cubital fossa

• Biceps tendon

• brachial artery

• median nerve

• radial nerve

Floor

• Brachialis

• Supinator

Blood supplies of the cubital fossa

• Brachial artery

  • Ulnar artery

  • Radial artery

• Median Cubital vein

• Cephalic vein

• Basilic vein

common site for sampling and transfusion of blood, and IV injections

Median cubital vein

lies directly on deep fascia

Runs diagonally from cephalic vein to basilic vein

Median cubital vein

Ulnar neuropathy (Cubital tunnel syndrome)

happens when the ulnar nerve (the "funny bone" nerve) gets squeezed or stretched as it passes through the inside of your elbow, particularly at the cubital tunnel retinaculum/arcuate ligament of Osbourne

•Distal humeral fracture

•Common in children

•70% is due to fall on outstretched hand

•Up to 10% are associated with damage to neurovascular structures

Supracondylar fracture

•During fracture and reduction

•MC with posterolateral displacement

•Superior to brachial muscle

Brachial artery injury

•MC: anterior interosseous nerve injury

•Runs with brachial artery 

Median Nerve injury

branch of median nerve most commonly injured 

Anterior interosseous nerve (AIN nerve)

injured with the same frequency as median nerve

Radial nerve

much less common, may be injured with flexion type fractures

Ulnar nerve

the result of an untreated ischemic injury that causes muscle and nerve damage in the involved compartment of the extremity.

Volkmann’s Ischemic Contracture

Bicipital myotatic reflex confirms the integrity of what nerve?

Musculocutaneous nerve

dense connective tissue sheet between the radius and ulna

Interosseous Membrane of the Forearm

puts forearm in its most stable mid-prone position/ position of function

Taut fibers

deep fascia enclosing the arm like a sleeve

-deep to the skin and subcutaneous tissue

-continuous with the antebrachial fascia

Brachial fascia

deep fascia of the forearm

Antebrachial fascia

extend from the deep surface of the brachial fascia to the central shaft and medial and lateral supra-epicondylar ridges of the humerus

Medial and lateral intermuscular septa

Fascial compartments of the forearm

ANTERIOR/ FLEXOR/ PRONATOR

POSTERIOR/EXTENSOR/ SUPINATOR

The fascial compartments of the limbs generally end at the joints; therefore, fluids and infections in compartments are usually contained and cannot readily spread to other compartments. The ______ compartment is exceptional in this regard because it communicates with the central compartment of the palm through the ______.

anterior compartment; carpal tunnel

long flexor tendons that form its roof pass directly beneath the flexor retinaculum to enter the palm

carpal tunnel

TRUE OR FALSE:

•ANTERIOR/FLEXOR/PRONATOR      - MEDIAN N

•POSTERIOR/EXTENSOR/SUPINATOR - RADIAL N

True

Common flexor attachment of the first layer muscles of the forearm

Medial epicondyle of the humerus

All muscles of the anterior forearm cross the elbow joint except ___

•the 3 deep muscles.

All of the muscles in the anterior forearm are supplied by the median nerve except for the ff:

•FCU- ulnar nerve

•Medial part of FDP- ulnar nerve

•The tendons of most of the flexor muscles are locate on the anterior surface of the wrist and are held by:

• palmar carpal ligament

• flexor retinaculum

ALL anterior superficial muscles of the forearm cross the wrist joint except:

Pronator teres

•Fusiform

•Most lateral of the superficial forearm flexors

•Forms medial boundary of the cubital fossa

Pronator teres

•Long fusiform

•Medial to pronator teres

•Belly replaced by long flattened tendon in the middle of forearm

•Passes thru canal in lateral part of flexor retinaculum thru a vertical groove in the trapezium

•Has own synovial tendinous sheath of FCR – guide to radial artery

Flexor carpi radialis

•Fusiform

•Absent in one or both sides, usually left, in 14% of people

•Guide to the median nerve at the wrist : tendon lies deep and slightly medial to the nerve

Palmaris longus

•Most medial of the superficial flexors

•Simultaneously flexes and adducts the hand at the wrist if acting alone

•With FCR: flexes wrist

•With ECU: adducts wrist

•The only superficial muscle innervated by ulnar nerve

Flexor carpi ulnaris

•Forms intermediate layer between the superficial and deep muscles

•2 heads: humero-ulnar and radial heads

•Median N and ulnar A enter the forearm by passing between the 2 heads

Flexor digitorum superficialis

•Muscle belly splits into 4 distinct tendons near the wrist

•Pass deep to the flexor retinaculum thru carpal tunnel to the fingers

•At level of proximal phalanx, splits to create small openings called Chiasma of Camper, allowing FDP tendons to pass

Flexor digitorum superficialis

•Tendons are enclosed in a synovial common flexor sheath

•Action: flexes the middle phalanges of the medial 4 fingers at the PIP joints

•Capable of flexing each finger it serves independently

Flexor digitorum superficialis

•the only muscle that can flex the Distal interphalangeal joints

•“clothes” the anterior aspect of the ulna

•Crucial element for grip strength and pincer grip

Flexor digitorum profundus

•Long flat flexor of the thumb

•Lies lateral to the FDP

•Clothes the anterior aspect of the radius distal to the attachment of the supinator

Flexor pollicis longus

•Quadrangular muscle

•Prime mover for pronation

•Deepest muscle in the anterior aspect of the forearm

•The only muscle that attaches only to the ulna at one end and only to the radius at the other end

Pronator quadratus

Initiates pronation and is assisted by the Pronator Teres when more speed and power are needed

Pronator quadratus

Supination muscles

•Biceps brachii

•Supinator

Pronator muscles

•Pronator teres

•Pronator quadratus

puts the forearm in mid-prone position

Brachioradialis

True or false:

•Muscle of the posterior forearm are Extensor-supinator muscles

True

True or false:

Muscles of the posterior forearm are All are innervated by radial N

True

True or false:

Muscles of the posterior forearm are held in place at the wrist by the extensor retinaculum to prevent bowstringing of tendons

True

Posterior Forearm Muscles that extend and abduct/ adduct the hand at the wrist joint:

ECRL
ECRB
ECU

Posterior Forearm Muscles that extend the medial 4 fingers

Extensor digitorum

Extensor digiti minimi

Extensor indices

Posterior forearm muscles that extends the thumb

Abductor Pollicis Longus

Extensor Pollicis Longus

Extensor Pollicis Brevis

The only muscles that do not cross and are incapable of acting at the wrist

Brachioradialis

Supinator

•Fusiform muscle

•Lies superficially on the anterolateral surface of the forearm

•Forms lateral border of the cubital fossa

•Rotated to the anterior aspect of the humerus and thus flexes forearm at the elbow

Brachioradialis

•Powerful elbow fixator

•Radial N bifurcates before diving deep to this muscle

•Insertion: proximal to radial styloid process

Brachioradialis

•Relatively short muscle belly and longer tendon

•Indispensable when clenching the fist

•Wrist extension and abduction

ECRL

•Larger muscle belly, shorter tendon

•Last superficial muscle of the posterior forearm supplied by the radial N before it passes thru the supinator

Extensor Carpi radialis brevis

•Principal extensor of the medial 4 digits

•Occupies much of the posterior surface of the forearm

Extensor digitorum

•Accessory extensor of the little finger

•Functions to extend the 5^th digit

Extensor digiti minimi

•Extensor and adductor of the wrist

•Short muscle belly with a long flat tendon that converges distally into a round tendon

•Inserts at the medial base of metacarpal V

Extensor carpi ulnaris

•Triangular in shape

•Small muscle that provides accessory support to other posterior forearm muscles

Anconeus

•Has superficial and deep heads that help supinate the forearm

•Passing between the 2 heads is the deep branch of the radial N

•Prime mover for slow, unopposed supination

Supinator

•Thumb abduction bet metacarpal I and the trapezium

•Assists in wrist abduction

•Inferior margin of the anatomical snuffbox

Abductor pollicis longus

•Inferior margin of the anatomical snuffbox

Extensor pollicis longus

•Larger, tendon longer than EPB

•Adducts the extended thumb and rotates it laterally

Extensor pollicis longus

•Triangular depression on the lateral aspect of dorsum of hand

Anatomical snuffbox

The tendons of the APL and EPB bound the anatomical

snuff box _____, and the tendon of the EPL bounds it

______

Anteriorly; posteriorly

lies in the floor of the snuffbox

Radial artery

•palpated proximally in snuffbox

Radial styloid process

Palpated distally in snuff box

Base of the first metacarpal

Floor of the snuffbox

Scaphoid

Trapezium

most frequently fractured carpal bone

Scaphoid

•Initial X-rays may not reveal fracture

•Repeat X-rays taken 10-14 days reveal bone resorption

•Union of fractured parts may take up to 3 months because of poor blood supply

•Avascular necrosis of the proximal fragment of scaphoid

SKL