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Glenohumeral Ligaments and Joint Capsule

The GH joint capsule consists mainly of Type I collagen, with smaller amounts of Types II and III. Localized thickenings of the capsule make up the GH ligaments, which are named according to their attachments on the glenoid rim. The GH ligaments function as static restraints to shoulder motion.

These discrete, capsular thickenings function as checkreins at the limits of rotation, preventing excess GH translation and becoming taut at varying positions of abduction and humeral rotation. Because of the orientation of these ligaments, portions of the capsule reciprocally tighten and loosen as the GH joint rotates, thus limiting translation and rotation by load sharing. Their function is dependent on the arm position and on the direction of the applied force on the joint.

Variation exists in the presence and size of these ligaments. The anatomical configuration of the inferior glenohumeral ligament (IGHL) is fairly consistent, but the configuration of the superior glenohumeral ligament (SGHL) and the middle glenohumeral ligament (MGHL) is variable.

In a study of 84 cadaveric shoulders, the MGHL was separate from the origin of the SGHL in 56%, and the remaining 34%, the MGHL originated at the same location as the SGHL. Overall 94% of the specimens had a SGHL. Only 63% had a discrete MGHL, however, and of these, 17.9% had cordlike MGHL.

Normal variants, such as a sublabral foramen, a cordlike MGHL, and a Buford complex, have been reported. A sublabral foramen or sulcus in which the labrum is not attached to the anterosuperior glenoid can be confused with a labral detachment. The prevalence of a sublabral foramen has been reported to be between 12% and 19%. In addition, the medial and lateral edges of the MGHL can appear to be rolled in a cordlike fashion.

The Buford complex is a cordlike MGHL originating directly from the superior labrum and crossing the subscapularis tendon to insert on the humerus. With a Buford complex, no anterosuperior labrum is present, and this can be confused with a Bankart lesion. The reported prevalence of a Buford complex has ranged from 1.5% to 6% . It is important to recognize these anatomical variants and not to confuse them with a pathologic lesion.

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