When the wing is folded the long glenoid surface of the head of the humerus is bordered above by the tuberculum externum or superius, in the middle and below by the tuberculum medium or inferius for the insertion of the coraco-brachialis posterior muscle.
The glenoid surface for the articulation of the mandible is greatly extended transversely, concave from side to side, convex from before backwards in front, and hollow behind, and is bounded posteriorly at its inner part by a prominent post-glenoid process.
At less than 90 degrees of abduction the deltoid muscle force creates a shear vector in the glenoid fossa.
Glenoid rim Up to half the patients with glenohumeral instability have an osseous avulsion of the glenoid rim Up to half the patients with glenohumeral instability have an osseous avulsion of the glenoid rim, a bony Bankart lesion.
Arthroscopic surgery for removal of loose bodies and of a torn glenoid labrum would be the current recommended procedure rather than open surgery.