Component alignment is important for stability and proper function and mobility of the prosthesis. Optimal component positioning on radiographs is:
Facing angle: the angle between the longitudinal axis of the glenoid and the medial border of the scapula. Mild downward tilting of the glenoid is thought to lessen the upward subluxation of the humerus.
Glenoid version should mimic normal human anatomy with approximately 5 degrees of retroversion with respect to the scapular blade.
Humeral head component:
For optimal function of rotator cuff musculature, the superior margin of the prosthetic humeral head should be just superior to the greater tuberosity.
Greater tuberosity too proximal
Greater tuberosity too distal