Upper limb

Extensor Hood of the Index Finger

Aponeurosis dorsalis digiti II manus

Origin

Dorsal aspect of the base of the proximal phalanx of the index finger, where the tendons of extensor digitorum and extensor indicis join the lumbrical and the interossei

Insertion

Base of the middle and distal phalanx of the index finger

Function

Distributes the pulling force of the extensors and intrinsic hand muscles across the proximal and distal interphalangeal joints, allowing coordinated finger extension

Innervation

Mixed: radial nerve (extensor digitorum/indicis) and median/ulnar nerve (lumbrical and interossei)

Movement & chain

Allows the metacarpophalangeal joint to flex while the interphalangeal joints remain extended, such as when typing or holding a pen.

Palpation

Directly palpable beneath the dorsal skin of digit II over the MCP joint and proximal phalanx.

Clinical

Triangular expansion where EDC, interossei, and 1st lumbrical blend; central slip rupture causes a boutonniere deformity; sagittal band rupture causes tendon subluxation.

Segmental innervation

C7–C8 (radial nerve) & C8–T1 (median nerve)

In clinical practice

Focus on hand function and edema prevention; ensure IV cannulas and splints maintain functional hand position to prevent joint contractures.

Region in the model

Upper limb