Unit 9 Forearm

The region of the upper limb between the elbow joint and the wrist joint.

Posterior and Anterior compartments

• A lateral intermuscular septum
• An interosseus membrane
• The attachment of deep fascia along the posterior border of the ulna

Contains muscles that predominately flex the wrist and digits and pronate the forearm

• Contains muscles that predominately extend the wrist and digits and supinate the forearm
• Major nerve and vessels supply or pass through each compartment

• Narrow proximally
• In cross-section it appears triangular with three borders and three surfaces

• Anterior
• Posterior
• Interosseous

• Two facets for articulation with 2 carpal bones
• -Facet for articulation with scaphoid
• -Facet for articulation with lunate

• The shaft of the ulna is broad superiorly where it is continuous with the large proximal end and narrow distally to form a small distal head.
• Like the radius, the shaft of the ulna is triangular in corss-section and has three borders and three surfaces

• Anterior
• Posterior
• Interosseous

The distal end of the ulna is small and characterized by a rounded head and the ulnar styloid process

Covered by articular cartilage

Originates from the dorsomedial aspect of the ulna and projects distally

• Head of the ulna
• Ulnar notch on the radius
• Fibrous articular disc

Modified ovoid joint

Allows the distal end of the radius to move anteriomedially over the ulna producing pronation and supination

Radius rotates at the elbow and distal end of the radius moves over the ulna

• Superior articular surface of the radius head spins on the capitulum
• The articular surface on the side of the head slides against the radial notch of the ulna

The ulnar notch slides anteriorly over the convex surface of the head of the ulna

• Annular ligament of radius (PRUJ)
• Interosseous membrane
• the articular disc (DRUJ)

• Pronator teres
• Flexor carpi radialis
• Palmaris longus
• Flexor carpi ulnaris

Flexor digitorum superficialis

• Flexor digitorum profundus
• Flexor pollicis longus
• Pronator quadratus

• Anconeus
• Brachioradialis
• Extensor carpi radialis longus
• Extensor carpi radialis brevis
• Extensor digitorum
• Extensor digiti minimi
• Extensor carpi ulnaris

• Supinator
• Abductor pollicis longus
• Extensor pollicis longus
• Extensor pollicis brevis
• Extensor indicis

From the brachial artery in the cubital fossa

• Passes along the lateral aspect of the forearm traveling:
• -Proximal 1/3 just deep to the brachioradialis muscle
• -Middle 1/3 with the superficial branch of the radial nerve
• -Distal 1/3 superficially covered only by deep fascia, superficial fascia, and skin

Supplies the lateral forearm and forms the deep arch of the hand

Can be palpated in the distal forearm by moving lateral to the tendon of the FCR muscles

Radial recurrent artery

Superificial palmar branch

Enters the hand by passing through or superficial to the thenar muscles at the base of the thumb

superificial palmar arch form by the ulnar artery

Supplies the medial forearm

• Leaves the cubital fossa by passing deep to the pronator teres muscle and then passes through the forearm in the fascial plane between FCU and FDP.
• In the distal forearm it remains tucked under the FCU tendion and is not easily palpable

• Anterior ulnar recurrent artery
• Posterior ulnar recurrent artery
• Common interosseous artery

• Supplies muscles of the deep layer of the anterior forearm and the radius and ulna
• Contributes to the vascular network around the carpal bones

Passes dorsally over the proximal margin of the interosseous membrane into the posterior compartment of the forearm

• Median Nerve - all muscles but 1 1/2
• Ulnar nerve - only 1 1/2 muscles

Radial nerve

Supplies all of the muscles in the anterior compartment of the arm except for FCU/ulnar 1/2 FDP

• Passes between the two head of the pronator teres muscle
• Travels in the forearm on the deep surface of the FDS
• Leaves the forearm and enters the palm by passing through the carpal tunnel deep to the flexor retinaculum

• Anterior interosseous nerve
• Palmar cutaneous nerve

• Originates between the 2 heads of the pronator teres
• Passes distally down the forearm with the anterior interosseous artery
• Innervates the muscles in the deep layer
• Terminates as articular branches to joints of the distal forearm and wrist

• Oringinates in the distal forearm immediately proximal to the flexor retinaculum
• Innervates the skin over the base and central palm

• Enters the anterior compartment by passing posteriorly around the medial epicondyle of the humerus and between the humeral and ulnar heads of the FCU.
• Travels in the medial side of the forearm in the plane between the FCU and FDP muscles.
• The ulnar artery is lateral to the ulnar nerve in the distal 2/3 of the forearm

Superficial to the flexor retinaculum and lateral to the pisiform bone through Guyon's canal

• muscular branch to FCU and FDP
• Palmar cutaneous branch
• Dorsal cutaneous branch

• Originates in the middle forearm
• Supplies the skin on the medial side of the palm

• Originates in the distal forearm and passes posteriorly deep to the tendon of the FCU
• Innervates the skin on the dorsomedial side of the hand and most skin on the dorsal surface of the medial 1 1/2 digits

• Passes between the two heads of the supinator
• Predominately motor - innervates muscles of the superficial layer

• Predominately cutaneous
• It passes down the anterolateral aspect of the dorearm deep to the brachioradialis muscle
• About 2/3 of the way down the fore the nerve becomes lateral and dorsal to the brachioradialis

• Deep Radial n. becomes the posterior interosseous n. after emerging from between the two heads of the supinator muscle
• Supplies the muscles in the deep layer
• Terminates as articular branches which pass deep to the extensor pollicis longus muscle to reach the wrist

• Lateral antebrachial cutaneous n. - musculocutaneous n.
• Medial antebrachial cutaneous n. - medial cord of the brachial plexus
• Posterior antebrachial cutaneous n. - radial n.