Unraveling Anatomical Variations of the Acromioclavicular Joint: A Comprehensive Inquiry Into Their Impact on Instability.

The acromioclavicular (AC) joint, an essential element in the complex biomechanics of the shoulder, displays a diverse range of anatomical variations among individuals. This review aimed to study and present these variations. A detailed search was conducted on the PubMed medical database by using the terms "acromioclavicular joint variations". Initially, 108 articles were retrieved and, after applying the inclusion and exclusion criteria, only 11 articles were found eligible. Eight more papers were selected from the citations in those 108 papers. As a result, a total of 19 papers and studies were used for the final analysis. This comprehensive review highlights the existence of a wide range of anatomical variations, concerning joint alignment, dimensions of articular surfaces, ligament arrangements, as well as acromion types and joint angles. Gender-related differences in joint dimensions and angles, as well as comparisons between intact groups and patients with rotator cuff tears, are also examined. Delving into the intricacies of anatomical variations is essential in comprehending how these differences may contribute to joint instability. Through a synthesis of anatomical studies, clinical observations, and biomechanical analyses, this narrative review provides an up-to-date assessment of the existing information regarding the AC joint.