Upper limb

Extensor retinaculum and dorsal extensor tendon sheaths of wrist (Compartments I–VI)

Retinaculum extensorum et vaginae tendinum musculorum extensorum carpi et digitorum

Origin

Extensor retinaculum along dorsal radius, ulna, and carpus

Insertion

Organizes extensor tendons into 6 osteofibrous compartments: I (APL/EPB), II (ECRL/ECRB), III (EPL around Lister tubercle), IV (ED/EI), V (EDM), VI (ECU)

Function

Retinaculum prevents extensor tendon bowstringing; synovial sheaths provide low-friction glide channels for all wrist, thumb, and digital extensor tendons

Innervation

Posterior interosseous nerve (radial nerve C6–C8)

Movement & chain

Facilitates gliding during wrist extension, thumb abduction, and digital extension

Palpation

Compartment I (radial styloid) and Compartment III (Lister's tubercle) are easily palpable

Clinical

De Quervain's tenosynovitis (Compartment I stenosing tenosynovitis; positive Finkelstein test); EPL tendon rupture after distal radius fracture; intersection syndrome; ECU subluxation.

Segmental innervation

C6–C8

In clinical practice

Finkelstein test, thumb spica splinting, eccentric loading, and first compartment release surgery

Region in the model

Upper limb