Conoid ligament

At a glance

English

Conoid ligament

Latin (TA2)

Ligamentum conoideum

System

Ligament

Region

Upper limb

Side

Paired, left and right

About the conoid ligament

The clavicle is held down onto the scapula not only at the acromioclavicular joint but also, a short distance medially, by the coracoclavicular ligament. That ligament has two parts that lie close together and are often joined along one border: the trapezoid ligament in front and laterally, and the conoid ligament behind and medially.

The conoid ligament is a dense, triangular or cone-shaped band standing almost vertically, with its point below and its broad base above. Its apex is fixed to a roughened area on the knee-like bend of the coracoid root, just medial to the trapezoid ligament. From there it fans upwards to the conoid tubercle, a small bump on the underside of the clavicle near its posterior border at the junction of its outer and middle thirds, and to a short ridge running medially from it for about a centimetre. Where its front edge meets the back of the trapezoid ligament the two form an angle open forwards, and a bursa sometimes lies in the gap. In front of the pair lie subclavius and the deltoid; behind them is trapezius.

The conoid part resists upward movement of the clavicle relative to the scapula; put the other way, it stops the scapula and arm dropping away from the collarbone. It also limits forward rotation of the scapula and, when the arm is raised, its tension makes the clavicle rotate on its long axis, which allows full elevation of the limb.

In a high-grade shoulder separation both parts of the coracoclavicular ligament tear and the outer end of the clavicle rides up well above the acromion. Surgical repairs aim to rebuild the conoid and trapezoid bands, often with grafts or synthetic loops passed around the coracoid. The conoid tubercle is a useful landmark for placing tunnels in these operations.

Attachments and function

Attaches from

The posteromedial part of the root (knee) of the coracoid process of the scapula.

Attaches to

The conoid tubercle on the inferior surface of the clavicle and a short line medial to it.

Function

Resists upward displacement of the clavicle on the scapula, carries part of the weight of the limb and helps rotate the clavicle when the arm is raised.

Nerve supply

Twigs of the suprascapular and lateral pectoral nerves.

Blood supply

Branches of the suprascapular and thoraco-acromial arteries.