What are the extensor tendons of the thumb and where do they insert?

The thumb has three extensor tendons: Abductor pollicis longus (APL) inserts on the base of the 1st metacarpal, Extensor pollicis brevis (EPB) inserts on the base of the proximal phalanx, and Extensor pollicis longus (EPL) inserts on the base of the distal phalanx.

How are the extensor digitorum tendons structured on the dorsum of the hand?

Four tendons for digits 2–5 diverge across the dorsum, connected by three oblique intertendinous bands. They form a common aponeurotic sheath with deep fascia, anchored to the 2nd and 5th metacarpals.

What is a dorsal digital expansion and what is its function?

A dorsal digital expansion is a hood-like structure formed by each extensor digitorum tendon over the metacarpophalangeal (MP) joint. It coordinates actions of long flexors, extensors, lumbricals, and interossei for finger movement.

Where do the slips of the dorsal digital expansion insert?

The dorsal digital expansion has two main insertions: the central slip inserts into the base of the middle phalanx, and the lateral slips insert into the base of the distal phalanx.

What muscles contribute to the dorsal digital expansion?

The dorsal digital expansion receives contributions from intrinsic hand muscles: lumbricals and interossei insert into it, and it is reinforced by extensor indicis for the index finger and extensor digiti minimi for the little finger.

What causes a mallet finger deformity?

Mallet finger is caused by avulsion or rupture of the extensor tendon at the base of the distal phalanx due to forceful flexion. This results in a drooping distal phalanx in flexion, known as a swan neck deformity, with no active extension.

What is a boutonnière deformity and how does it occur?

Boutonnière deformity occurs from rupture of the central slip of the extensor expansion due to trauma. It presents with flexion at the proximal interphalangeal (PIP) joint and hyperextension of the distal interphalangeal (DIP) joint.

Extensor Tendons – Dorsal Digital Expansions Explained

❓ Frequently Asked Questions