[Durgical](https://durgical.com/en/) › [DurgiPedia](https://durgical.com/en/durgipedia/) › [Anatomy](https://durgical.com/en/anatomy/) › [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/) › 1st compartment sheath [Muscular system](https://durgical.com/en/anatomy/system/muscular-system/) · [Upper limb](https://durgical.com/en/anatomy/region/upper-limb/) # 1st compartment sheath The first compartment sheath wraps two thumb tendons on the thumb side of the wrist; it lets them glide and swells in de Quervain tenosynovitis. Official name: Tendon sheath of the 1st dorsal compartment [See in 3D →](https://durgical.app/?from=durgipedia&lang=en#region=upper_limb&select=first_compartment_sheath&side=r) Opens in the Durgical app, no sign-up needed. ## What it is The sleeve around the APL and EPB tendons in the first tunnel at the thumb side of the wrist; it swells in De Quervain's tenosynovitis. ## What it does Lets the thumb tendons glide; it swells in De Quervain's tenosynovitis. ## Key points - Holds the [abductor pollicis longus](https://durgical.com/en/anatomy/abductor-pollicis-longus/) (APL) and [extensor pollicis brevis](https://durgical.com/en/anatomy/extensor-pollicis-brevis/) (EPB) tendons over the radial styloid; the APL usually has two or more slips - A septum giving the EPB its own sub-compartment is common; missing it is a cause of failed de Quervain release or injection - Branches of the superficial radial nerve cross over the sheath and are at risk at surgery ## Key facts **Where** Over the radial styloid, under the extensor retinaculum (1st dorsal compartment: APL, EPB) **Function** Lets the thumb tendons glide; thickens in De Quervain tenosynovitis ## Relations **Contents** [APL and EPB tendons](https://durgical.com/en/anatomy/abductor-pollicis-longus-and-extensor-pollicis-brevis-tendons/) in a shared synovial sheath, sometimes split by a septum **Superficial** [Extensor retinaculum](https://durgical.com/en/anatomy/extensor-retinaculum-of-the-wrist/), branches of the [superficial radial nerve](https://durgical.com/en/anatomy/superficial-branch-of-the-radial-nerve/) and the start of the [cephalic vein](https://durgical.com/en/anatomy/cephalic-vein/) **Deep** Shallow groove on the lateral side of the radial styloid **Below** Beyond the retinaculum the tendons form the front border of the anatomical snuffbox, with the [radial artery](https://durgical.com/en/anatomy/radial-artery/) in its floor ## How to find it With the thumb extended and pulled away from the palm, the APL and EPB tendons stand out together along the thumb side of the wrist; followed upward, the sheath lies over the radial styloid, the tender spot in de Quervain tenosynovitis. ## Examination - Finkelstein test: the examiner holds the thumb and tilts the wrist toward the little finger; sharp pain over the radial styloid suggests de Quervain tenosynovitis - Eichhoff test (thumb tucked into the fist, then ulnar deviation): more false positives, since it can hurt in normal wrists ## On imaging Ultrasound shows a thick retinaculum and sheath with fluid and increased Doppler flow, and whether a septum splits the EPB off. X-ray excludes arthritis at the base of the thumb. ## 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 - Surgical release opens the dorsal roof of the sheath; injury to the superficial radial nerve branches over it can leave a painful neuroma - Intersection syndrome: pain and crepitus a few centimetres above the wrist, where the APL and EPB muscle bellies cross over the second-compartment tendons ([ECRL](https://durgical.com/en/anatomy/extensor-carpi-radialis-longus/), [ECRB](https://durgical.com/en/anatomy/extensor-carpi-radialis-brevis/)) - Differential diagnosis: thumb base (carpometacarpal) arthritis, [scaphoid](https://durgical.com/en/anatomy/scaphoid/) problems and Wartenberg syndrome (compression of the superficial radial nerve) ## Anatomical variants - Extra APL slips are the rule rather than the exception, and a separate EPB sub-compartment is frequent; reported frequencies vary widely ## Related conditions - [De Quervain tenosynovitis](https://durgical.com/en/conditions/de-quervain-tenosynovitis/) ## Test yourself Think of the answer, then tap the question to see it. ## Which tendons run in the first extensor compartment sheath, and over which bone? The abductor pollicis longus (APL) and extensor pollicis brevis (EPB), over the radial styloid. ## What is the Finkelstein test, and what does a positive result suggest? The examiner holds the thumb and tilts the wrist toward the little finger; sharp pain over the radial styloid suggests de Quervain tenosynovitis. ## Why can a de Quervain release or injection of the first compartment sheath fail? A common septum gives the EPB its own sub-compartment; if it is missed, the tendon stays tight. ## Which nerve is at risk when the first compartment sheath is released? Branches of the superficial radial nerve, which cross over the sheath; injury can leave a painful neuroma. [Add to my cards (4)](https://durgical.app/estudiar/?add=/en/anatomy/tendon-sheath-of-the-1st-dorsal-compartment/) Educational information, not medical advice. For any symptom, see a health professional. ## Its names **Official Latin (TA2)** vagina tendinum abductoris longi et extensoris brevis pollicis TA2 2577 **Official Spanish (DeCS)** Vaina tendinosa de los músculos abductor largo y extensor corto del pulgar **English (TA2)** Tendon sheath of the 1st dorsal compartment ## Related - [APL and EPB tendons](https://durgical.com/en/anatomy/abductor-pollicis-longus-and-extensor-pollicis-brevis-tendons/) - [Extensor retinaculum](https://durgical.com/en/anatomy/extensor-retinaculum-of-the-wrist/) - [1st metacarpal](https://durgical.com/en/anatomy/1st-metacarpal/) - [Radius](https://durgical.com/en/anatomy/radius/) Sources: Terminologia Anatomica (TA2); [Anatomy, Shoulder and Upper Limb: Hand Anatomical Snuff Box](https://www.ncbi.nlm.nih.gov/books/NBK482228/); [Anatomy, Shoulder and Upper Limb, Wrist Extensor Muscles](https://www.ncbi.nlm.nih.gov/books/NBK534805/). ## **Spotted a mistake?** We are always improving for the community. Tell us what is wrong and our team will review it. Report a mistake Representative model, for educational purposes only. --- Source: https://durgical.com/en/anatomy/tendon-sheath-of-the-1st-dorsal-compartment/ License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/). Cite as: DurgiPedia (durgical.com), https://durgical.com/en/anatomy/tendon-sheath-of-the-1st-dorsal-compartment/