A novel radiographic index for the diagnosis of posterior acromioclavicular joint dislocations.

Background: Posterior acromioclavicular (AC) joint dislocations are frequently misclassified because posterior translation of the clavicle is difficult to evaluate in Zanca radiograph views. A novel radiographic index was used in this study to accurately diagnose posterior dislocations of the AC joint.

Hypothesis: This novel index has a high degree of accuracy for the diagnosis of posterior AC joint dislocations.