For the association between acromion morphology and rotator cuff tears, two independent meta-analyses confirmed moderate evidence that a far lateral extension of the acromion is a risk factor for rotator cuff tears (Andrade R et al., Docter S et al.). The risk for a re-tear after primary rotator cuff repair also appears to increase with far lateral extension of the acromion (Docter S et al., Sheean AJ et al.). However, a reliable cut-off value cannot be given. This limits the clinical utility of the “critical shoulder angle” and the “acromion index”.
For the lateral downslope of the acromion and type III acromion there is even more controversy. Recently Andrade et al. reported moderate evidence for a correlation with rotator cuff tears, Sasiponganan et al. did not (Andrade R et al., Sasiponganan C et al.).