Flexor Digitorum Superficialis Radial Head

caput radiale m. flexoris digitorum superficialis

The radial head of FDS arises from the anterior radius and supplies the index and middle finger FDS slips. Its separate AIN innervation makes it the component tested in anterior interosseous nerve palsy assessment.

Nerve: Median nerve — AIN branch to the radial… Blood Supply: Ulnar artery Region: Forearm

Anatomical Data

Origin, Insertion & Supply

Origin	Anterior oblique line of the radius (proximal third)
Insertion	Middle phalanges of index and middle fingers predominantly
Nerve Supply	Median nerve — AIN branch to the radial head (C7, C8, T1)
Blood Supply	Ulnar artery

Biomechanics

Function & Actions

Actions	Flexes the PIP joints of index and middle fingers; Assists wrist flexion

Clinical Relevance

Clinical Notes

AIN palsy denervates the radial head, producing weakness of middle and index PIP flexion. The AIN branch arises proximal to the humero-ulnar head, making radial head innervation the key localising finding in AIN syndrome.

Palpation

Tested by isolated PIP flexion of index or middle finger with other fingers held in full extension.

Pathology

Common Injuries & Conditions

Radial Head FDS Denervation in AIN Palsy

AIN compression producing weakness of FDS radial head with impaired index and middle PIP flexion, managed conservatively or by decompression.