Radiate ligament of head of rib

At a glance

English

Radiate ligament of head of rib

Latin (TA2)

Ligamentum radiatum capitis costae

System

Ligament

Region

Thorax

Side

Paired, left and right

About the radiate ligament of head of rib

The head of a typical rib fits into a socket formed by two thoracic vertebral bodies and the disc between them. The joint has a capsule, and its front is strengthened by the radiate ligament, so called because its fibres fan out from a single point on the rib like the spokes of a wheel.

From a narrow attachment on the front of the rib head, just outside the articular surface, three flat bundles spread towards the spine. The upper bundle climbs to the side of the next vertebral body up. The lower bundle runs down to the lower vertebral body, which carries the rib's own number. The middle bundle, the shortest and the least obvious, runs horizontally to the intervertebral disc. The arrangement differs where a rib meets only one vertebra. At the first rib the ligament is not split into bundles but still reaches both the seventh cervical and the first thoracic bodies. At ribs ten to twelve, whose heads articulate with one vertebra each, there is no three-part fan, yet some fibres still pass up to the vertebra above.

In front, the ligament lies behind the parietal pleura, with the ganglia of the sympathetic trunk crossing it; on the right side the azygos vein runs over it. Behind it lie the intra-articular ligament and the two small synovial cavities of the joint.

Its job is to hold the rib head snugly in its socket while permitting the slight rotation by which the rib swings up and down in breathing. Its relation to the sympathetic chain is important: in thoracoscopic sympathectomy, done for severe sweating of the hands, the surgeon finds the chain lying on the rib heads and these ligaments just beneath the pleura.

Attachments and function

Attaches from

The front of the rib head, close outside its articular facets.

Attaches to

The sides of the bodies of the vertebra above and the vertebra below, and the intervertebral disc between them.

Function

Strengthens the front of the rib-head joint and holds the head in its socket during the slight rotations of breathing.

Nerve supply

Branches of the thoracic spinal nerves near the joint, with sympathetic fibres from the adjacent trunk.

Blood supply

Small branches of the posterior intercostal arteries.