The shape of the glenoid can vary between pear and oval, depending on the presence of a glenoid notch. We measured the glenoid notch angle (the angle between the superior and inferior part of the anterior glenoid rim) in 53 embalmed cadavers and investigated its relationship with the labral attachment to the glenoid at that point.
The attachment of the anterosuperior labrum at the site of the glenoid notch was classified as tight or loose or, in some cases, there was a sublabral foramen. The anterior labrum was then removed and digital images perpendicular to the glenoid notch were taken. Using a digital image analysis program, the angle of the glenoid notch was measured.
In 37 shoulders (70%) the attachment of the labrum at the site of the glenoid notch was assessed as tight and in eight (15%) as loose. In eight shoulders (15%) a sublabral foramen was found. The mean glenoid notch angle was 153° in the loosely attached group, 159° in the sublabral foramen group and 168° in the group with a tight attachment. The presence of a glenoid notch was noted only when the glenoid notch angle was less than 170°.
The glenoid notch angle is related to the attachment of the labrum. In the presence of a glenoid notch, there is more likely to be a loosely attached labrum or sublabral foramen. The loose attachment of the anterosuperior labrum may be a predisposing factor in traumatic anterior instability.
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