APL and EPB tendons !

The abductor pollicis longus and extensor pollicis brevis tendons run along the thumb side of the wrist; de Quervain tenosynovitis inflames them.

Official name: Abductor pollicis longus and extensor pollicis brevis tendons

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What it is

Two tendons side by side in the first tunnel on the thumb side of the wrist.

What it does

Move the thumb out and back; they form the front edge of the 'snuffbox'.

Key facts

Attaches: 1st dorsal compartment over the radial styloid: APL to the base of the 1st metacarpal (often in several slips), EPB to the base of the thumb's proximal phalanx
Function: Abduct and extend the thumb; front border of the anatomical snuffbox; de Quervain tenosynovitis (Finkelstein test)
Tight in: Thumb flexed into the palm with ulnar deviation of the wrist

Relations

Course: They wind obliquely from the back of the forearm over the ECRL and ECRB tendons, pass through the 1st dorsal compartment over the radial styloid and diverge to the thumb
Superficial: Extensor retinaculum and the branches of the superficial radial nerve; the cephalic vein begins nearby
Deep: Radial styloid and, just beyond it, the radial artery as it enters the anatomical snuffbox
Behind: EPL tendon, the opposite border of the anatomical snuffbox

How to find it

With the thumb extended and pulled back (hitchhiker position), the tendons form the palmar border of the anatomical snuffbox; they are followed back over the radial styloid, where tenderness and swelling point to de Quervain tenosynovitis.

Examination

Finkelstein test: the examiner grasps the thumb and tilts the wrist ulnarly; sharp pain over the radial styloid suggests de Quervain tenosynovitis
Eichhoff test: the fist is closed over the thumb and the wrist tilted ulnarly; pain over the radial styloid is positive, but many normal wrists also hurt
Pain and creaking (crepitus) a few centimetres above the wrist on wrist movement point to intersection syndrome instead

On imaging

Ultrasound shows thick tendons and sheath, fluid and the septum dividing the compartment, and is used to guide injections; it also shows the swelling where they cross the radial wrist extensors in intersection syndrome.

Common problems

De Quervain's tenosynovitis: the tendons and their sheath swell in the first tunnel, causing pain at the thumb side of the wrist.
Common in new parents lifting a baby and with repeated thumb use.

How it is diagnosed

Pain when the thumb is tucked into the fist and the wrist is tilted toward the little finger (Finkelstein-type test).

Treatment

Thumb splint, activity changes and a steroid injection, which helps most people.
Surgical release of the first tunnel's roof, protecting the superficial radial nerve.

Clinical notes

De Quervain release: the superficial radial nerve branches are protected and any separate EPB tunnel is opened
Intersection syndrome affects rowers, paddlers and weightlifters, from friction where the tendons cross
Thumb basal joint arthritis and scaphoid fracture cause pain nearby; the grind test and snuffbox tenderness help tell them apart

Anatomical variants

The APL usually has two or more slips; extra slips of both tendons are common
A septum divides the 1st compartment in many wrists, more often in people with de Quervain tenosynovitis

De Quervain tenosynovitis

Test yourself

Think of the answer, then tap the question to see it.

Where do the APL and EPB tendons insert?

APL on the base of the 1st metacarpal (often in several slips); EPB on the base of the thumb's proximal phalanx.

What classic cause of persistent de Quervain pain involves the EPB tendon?

A septum giving the EPB its own tunnel in the 1st compartment, left unopened at surgery.

Which nerve branches are at risk in de Quervain release of the APL and EPB tendons?

Branches of the superficial radial nerve, which cross over the 1st compartment.

Which border of the anatomical snuffbox do the APL and EPB tendons form?

The front (palmar-radial) border; the EPL forms the back border.

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Educational information, not medical advice. For any symptom, see a health professional.

Its names

Official Latin (TA2): tendines musculorum abductoris longi et extensoris brevis pollicis TA2 2517
Official Spanish (DeCS): Tendones de los músculos abductor largo y extensor corto del pulgar
English (TA2): Abductor pollicis longus and extensor pollicis brevis tendons

Sources: Terminologia Anatomica (TA2); Anatomy, Shoulder and Upper Limb: Hand Anatomical Snuff Box; Anatomy, Shoulder and Upper Limb, Wrist Extensor Muscles.

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Representative model, for educational purposes only.

APL and EPB tendons highlighted on the Durgical 3D model