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# Extensor tendon sheaths

The extensor tendon sheaths are fluid-lined tubes on the back of the wrist; they let the [extensor tendons](https://durgical.com/en/anatomy/extensor-digitorum-tendons/) glide under the extensor retinaculum.

Official name: Wrist extensor tendon sheaths

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## What it is

Sleeves around the extensor tendons in the tunnels on the back of the wrist.

## What it does

Let the extensor tendons glide under the retinaculum.

## Key points

- The 3rd compartment (EPL) turns around Lister's tubercle; the EPL can rupture there weeks after a distal radius fracture, often an undisplaced one
- The 6th compartment (ECU) has its own subsheath in a groove of the ulna; it can sublux with supination and ulnar deviation
- In rheumatoid arthritis tendons rupture from the ulnar side first over an eroded ulnar head (Vaughan-Jackson lesion)

## Key facts

**Where**
Six dorsal compartments under the extensor retinaculum: 1 APL/EPB; 2 [ECRL](https://durgical.com/en/anatomy/extensor-carpi-radialis-longus/) / [ECRB](https://durgical.com/en/anatomy/extensor-carpi-radialis-brevis/); 3 EPL; 4 ED/EIP; 5 EDM; 6 ECU

**Function**
Let the extensor tendons glide under the retinaculum

## Relations

**Contents**
Six synovial sheaths, one per compartment; the [extensor digitorum](https://durgical.com/en/anatomy/extensor-digitorum/) and [extensor indicis](https://durgical.com/en/anatomy/extensor-indicis/) share the 4th

**Superficial**
[Extensor retinaculum](https://durgical.com/en/anatomy/extensor-retinaculum-of-the-wrist/); over it the [superficial radial nerve](https://durgical.com/en/anatomy/superficial-branch-of-the-radial-nerve/), the dorsal branch of the [ulnar nerve](https://durgical.com/en/anatomy/ulnar-nerve/) and the origins of the cephalic and basilic veins

**Deep**
Grooves of the distal [radius](https://durgical.com/en/anatomy/radius/) and [ulna](https://durgical.com/en/anatomy/ulna/) and the dorsal [wrist capsule](https://durgical.com/en/anatomy/wrist-joint-capsule/); the [posterior interosseous nerve](https://durgical.com/en/anatomy/posterior-interosseous-nerve/) lies in the floor of the 4th compartment

**Below**
The sheaths end over the carpus and bases of the metacarpals; the tendons then run under the [dorsal hand fascia](https://durgical.com/en/anatomy/dorsal-fascia-of-the-hand/)

## How to find it

Lister's tubercle is felt on the back of the distal radius, roughly in line with the third metacarpal; the EPL runs on its ulnar side, the ECRL and ECRB on its radial side. The ECU is felt in its groove beside the ulnar head.

## Examination

- Thumb lift test: with the palm flat, inability to lift the thumb off the table suggests EPL rupture
- ECU synergy test: resisted thumb abduction with the forearm supinated reproduces ulnar-sided wrist pain in ECU tendinitis

## On imaging

Ultrasound shows fluid in a sheath, ECU subluxation on dynamic scanning and the gap of a ruptured tendon; MRI shows tenosynovitis in inflammatory arthritis.

## Clinical notes

- EPL rupture is usually treated by transferring the extensor indicis tendon
- Dorsal wrist arthroscopy portals are named after the compartments: 3-4, 4-5, 6R and 6U
- Rheumatoid dorsal tenosynovitis may need tenosynovectomy to prevent tendon rupture

## Anatomical variants

- A septum often splits the 1st compartment, giving the EPB its own tunnel
- The [extensor digiti minimi](https://durgical.com/en/anatomy/extensor-digiti-minimi/) in the 5th compartment is commonly doubled, and extra slips of the extensor indicis and extensor digitorum are frequent

## Memory aid

Tendons per compartment, from the radial side: 2-2-1-2-1-1 (APL/EPB, ECRL/ECRB, EPL, ED/EIP, EDM, ECU).

## Related conditions

- [Chikungunya](https://durgical.com/en/conditions/chikungunya/)
- [Ganglion cyst](https://durgical.com/en/conditions/ganglion-cyst/)
- [Rheumatoid arthritis of the hand and wrist](https://durgical.com/en/conditions/rheumatoid-arthritis-of-the-hand-and-wrist/)

## Test yourself

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

## Which tendon runs in the 3rd extensor compartment, and why can it rupture after a distal radius fracture?

The extensor pollicis longus (EPL); it turns around Lister's tubercle and can rupture there weeks later, often after an undisplaced fracture.

## What is the Vaughan-Jackson lesion?

In rheumatoid arthritis, extensor tendons rupture from the ulnar side first over an eroded ulnar head.

## Which test suggests extensor pollicis longus rupture?

The thumb lift test: with the palm flat, the thumb cannot be lifted off the table.

## Which tendon has its own subsheath in the 6th extensor compartment, and how does it fail?

The extensor carpi ulnaris (ECU), in a groove of the ulna; it can sublux with supination and ulnar deviation.

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

## Its names

**Official Latin (TA2)**
vagina tendinis extensoris ulnaris carpi TA2 2582

**Official Spanish (DeCS)**
Vainas tendinosas carpianas dorsales

**English (TA2)**
Wrist extensor tendon sheaths

## Related

- [EPL tendon](https://durgical.com/en/anatomy/extensor-pollicis-longus-tendon/)
- [Extensor retinaculum](https://durgical.com/en/anatomy/extensor-retinaculum-of-the-wrist/)
- [Capitate](https://durgical.com/en/anatomy/capitate/)
- [Hamate](https://durgical.com/en/anatomy/hamate/)
- [5th metacarpal](https://durgical.com/en/anatomy/5th-metacarpal/)
- [Radius](https://durgical.com/en/anatomy/radius/)
- [Triquetrum](https://durgical.com/en/anatomy/triquetrum/)
- [Ulna](https://durgical.com/en/anatomy/ulna/)

Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb, Wrist Extensor Muscles](https://www.ncbi.nlm.nih.gov/books/NBK534805/).

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Representative model, for educational purposes only.

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Source: https://durgical.com/en/anatomy/wrist-extensor-tendon-sheaths/
License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/wrist-extensor-tendon-sheaths/