The superior transverse ligament (transverse or suprascapular ligament) converts the scapular notch into a foramen or opening.

It is a thin and flat fasciculus, narrower at the middle than at the extremities, attached by one end to the base of the coracoid process, and by the other to the medial end of the scapular notch.

The suprascapular nerve

Suprascapular nerve

The suprascapular nerve arises from the upper trunk . It innervates the supraspinatus muscles and infraspinatus muscles....

 runs through the foramen; the transverse scapular vessels cross over the ligament.

The ligament is sometimes ossified.