A reverse shoulder replacement can provide solution in cases that the active elevation of the arm is below 90 degrees. Further reading at the JBJS study: http://dx.doi.org/10.2106/JBJS.K.01206
It must be highlighted though that if the active elevation of the shoulder is at 90 degrees or more then a reverse shoulder replacement may not provide significant benefits.
Below is an example of an elderly person with loss of motion (<90 degrees) and a high riding humeral head treated with a reverse shoulder replacement. The coronal CT shows the high riding humeral head and the sagittal oblique CT shows the significant atrophy of the supraspinatus and the contact of the humerus with the acromion making the repair of the rotator cuff impossible (Goutallier stage 3)