Radial head of flexor digitorum superficialis

At a glance

English

Radial head of flexor digitorum superficialis

Latin (TA2)

Caput radiale flexoris superficialis digitorum

System

Muscle

Region

Upper limb

Side

Paired, left and right

About the radial head of flexor digitorum superficialis

Flexor digitorum superficialis, the main flexor of the middle finger joints, arises by two heads. The larger humero-ulnar head comes from the inner elbow and the ulna, while the radial head is a thin, flat sheet of muscle that comes from the radius. A fibrous arch joins the two at their upper edges.

The radial head takes origin from the anterior oblique line of the radius, the ridge that runs down and outward across the front of the upper shaft, below the radial tuberosity. Its fibres pass downward and inward to blend with the humero-ulnar head into one muscle mass. From this mass come four tendons that cross the carpal tunnel and enter the fingers, where each splits around the deep flexor tendon before attaching to the sides of the middle phalanx.

Together the two heads flex the proximal interphalangeal joints of the fingers, and then the knuckles and the wrist. The radial head adds width to the muscle but has no separate action of its own. The median nerve supplies the whole muscle, and the radial artery sends branches to this head, with the ulnar artery supplying most of the rest.

The median nerve and the ulnar artery pass from the cubital fossa into the forearm by running behind the arch between the two heads. The nerve then clings to the deep surface of the muscle down to the wrist. A thick arch can squeeze the nerve, one of the sites of median nerve entrapment in the upper forearm. In the forearm the radial head lies on top of flexor pollicis longus.

Attachments, action and supply

Origin

Anterior oblique line of the radius, on the upper part of the shaft below the radial tuberosity.

Insertion

With the humero-ulnar head, by four split tendons into the sides of the middle phalanges of the fingers.

Action

Flexes the proximal interphalangeal joints, then the metacarpophalangeal joints and the wrist.

Nerve supply

Median nerve (C8, T1).

Blood supply

Branches of the radial artery, with the ulnar artery supplying the rest of the muscle.