Most acromial and scapular spine fractures after reverse shoulder arthroplasties are related to increased tension in the deltoid muscle or stress fractures. In fact, after reverse prosthesis, the arm becomes approximately 2.5 cm longer and this increases the tension over the deltoid and together with the increase in the lever arm that causes medialization of the center of rotation, made to increase the loads on the acromion.

Classification of acromial fractures from Levy et al:

• type I: small fractures of the anterior acromion
• type II: fractures through the anterior acromion just posterior to AC joint
• type III: fractures of the posterior acromion or scapular spine

Radiographer: TSRM Fabio Imola.