Upper limb

Second Dorsal Interosseous

Musculus interosseus dorsalis II manus

Origin

Adjacent sides of the 2nd and 3rd metacarpal bones (bipennate)

Insertion

Radial side of the base of the proximal phalanx of the middle finger, with extension into the extensor hood

Function

Abduction of the middle finger toward the radial side (toward the thumb)

Innervation

Ulnar nerve, deep (motor) branch

Movement & chain

Together with the third dorsal interosseous forms the spreading mechanism of the middle finger to both sides, needed when spreading the fingers (e.g. playing piano).

Palpation

Palpable in the 2nd intermetacarpal space on the dorsal hand during radial deviation of the middle finger.

Clinical

Abducts the middle finger radially (DAB: Dorsal ABduct); innervated by the deep branch of the ulnar nerve (T1).

Segmental innervation

Ulnar nerve, C8-T1.

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