Lateralization and inclination angle in reverse arthroplasty-what do we know?

Since the original Grammont design of a reverse shoulder arthroplasty there has been a trend to decrease inclination angle from 155° to 145 or 135°. Furthermore, lateralization on the glenoid side has been advocated. These changes decrease the risk for impingement between humerus and the inferior part of the glenoid (notching). These changes were also made to improve restoration of rotation. However, there is very little evidence that rotation has improved due to these changes. A negative effect of lateralization is that it increases the risk for glenoid loosening. Furthermore, the stress on acromion increases which may lead to more acromion or scapula spine fractures. More randomized studies are needed to define optimal design of a reverse shoulder arthroplasty.