Posterior Forearm

How is the posterior forearm organized?

It has *superficial and deep layers of extensors, all innervated by the Radial nerve* (or its deep branch). ⚡ Mnemonic: "Posterior = power = Radial."

Where do the superficial extensors originate?

From the *lateral epicondyle* of the humerus via a common extensor tendon. 📍

Name the superficial extensor muscles.

From lateral to medial: *Brachioradialis, Extensor carpi radialis longus, Extensor carpi radialis brevis, Extensor digitorum, Extensor digiti minimi, Extensor carpi ulnaris.* Mnemonic: "Beer Drinkers Extend Digits Using." 🍺

What is the function of Brachioradialis?

Flexes the elbow (even though it's posterior!). Most visible on the lateral forearm. Supplied by *Radial nerve*. 💪 Mnemonic: "The rebel extensor."

Where is the Extensor carpi radialis longus (ECRL)?

Just medial to Brachioradialis — long tendon to *base of 2nd metacarpal*. Extends and abducts wrist.

Where is the Extensor carpi radialis brevis (ECRB)?

Beneath ECRL — shorter tendon to *base of 3rd metacarpal*. Also extends and abducts wrist. ⚡ Mnemonic: "Long = index, Brevis = middle."

Where is the Extensor digitorum (ED)?

Central large muscle — splits into 4 tendons to digits 2-5. Extends fingers and wrist. ✋ Mnemonic: "ED = extends digits."

What is the Extensor digiti minimi (EDM)?

Small muscle medial to ED that specifically extends the *little finger*. Mnemonic: "EDM = pinky party."

Where is the Extensor carpi ulnaris (ECU)?

Most medial superficial extensor — runs to *base of 5th metacarpal*. Extends and adducts wrist. ⚡

Where are the deep extensors?

Beneath the superficial group, attached to the *radius, ulna, and interosseous membrane.* 🎯

Name the deep extensor muscles.

*Supinator, Abductor pollicis longus (APL), Extensor pollicis brevis (EPB), Extensor pollicis longus (EPL), Extensor indicis (EI)*. Mnemonic: "S-A-B-E-E."

Where is the Supinator?

Proximal and deep — wraps around the radius. It *supinates the forearm. Supplied by Deep branch of radial nerve*. 🌀

Where is the Abductor pollicis longus (APL)?

Most lateral deep tendon — abducts the thumb. Runs to the *base of 1st metacarpal*. 👍 Mnemonic: "A for away thumb."

Where is the Extensor pollicis brevis (EPB)?

Next to APL runs to *base of proximal phalanx of thumb*. Extends thumb at MCP. 📏

Where is the Extensor pollicis longus (EPL)?

Long thin tendon crossing diagonally over wrist to *distal phalanx of thumb. Creates the anatomical snuffbox*. Mnemonic: "Long = long way to tip."

What forms the borders of the anatomical snuffbox?

Lateral: APL + EPB, Medial: EPL, Floor: *Scaphoid bone*. Mnemonic: "Sits by the Snuffbox."

Which artery runs through the snuffbox?

The *Radial artery* — visible on Anatomage as a red vessel crossing the wrist.

What happens if you fracture the Scaphoid?

Pain in the snuffbox + risk of avascular necrosis due to poor blood supply. ⚠️ Mnemonic: "Snuffbox soreness = Scaphoid snap."

Where is the Extensor indicis (EI)?

Medial to EPL, tendon joins the extensor digitorum tendon for the index finger — gives extra control. ☝️

What nerve supplies all the deep extensors?

The *Posterior interosseous nerve (PIN)* — branch of the Radial nerve after it passes the Supinator. ⚡ Mnemonic: "PIN powers extension."

What is the Posterior interosseous nerve (PIN)?

Deep branch of Radial nerve → motor to extensors runs on interosseous membrane. ⚡

Where is the Superficial branch of the Radial nerve?

Runs under *Brachioradialis* along radial artery, sensory to the dorsum of the hand. ✋

How to identify the Radial nerve on Anatomage?

In the *posterior arm*, it spirals in the radial groove → at the elbow, divides into superficial & deep branches. Yellow with two clear divisions. 🎯

What does the Posterior interosseous artery supply?

From the *Common interosseous (ulnar branch)* → runs with PIN in the deep extensor compartment.

What is "Tennis elbow" (lateral epicondylitis)?

Overuse of *common extensor tendon* at lateral epicondyle → pain on wrist extension. 🎾 Mnemonic: "Lateral pain = tennis strain."

What is "Golfer's elbow" (medial epicondylitis)?

Overuse of *flexor origin* on medial epicondyle → pain during wrist flexion. ⛳ Mnemonic: "Medial = golf deal."

How to tell superficial vs deep extensors on Anatomage?

Superficial = long, parallel, visible tendons Deep = short, diagonal, attached closer to radius/ulna.

What color/shape helps you find Radial structures on Anatomage?

Radial artery (red), Radial nerve (yellow), running together along lateral (thumb) side. Mnemonic: "Red & yellow = radial fellows." 🌈