"The acromion index (AI) is a parameter that can be measured on the AP radiograph (or sometimes on coronal CT or MR images) to assess predisposition to rotator cuff pathology."
"GA: distance from the plane of the glenoid cavity to the lateral edge of the acromion and"
"GU: distance from the plane of the glenoid cavity to the lateral edge of the humeral head"
"acromion index (AI) = GA / GU"
"acromion index (AI) = GA / GU"