Anatomy of the acromioclavicular and coracoclavicular region. Functional and clinical aspects

BACKGROUND: The acromioclavicular (AC) joint connects the acromion with the lateral end of the clavicle and constitutes an important load-transmitting element between the upper extremity and the skeleton of the trunk. AIM: This review discusses functional aspects that relate the AC and the coracoclavicular (CC) ligaments to AC joint instability and lateral clavicle fracture. RESULTS: In terms of stability the AC and CC ligaments play a pivotal role for this region. Under normal conditions the restraint system is balanced and becomes unbalanced in cases of injury such as AC joint instability or lateral clavicular fractures. Skeletal injuries frequently affect the ligaments with their usually sharp-angled insertion sites, which alters the function of the restraint system. As a consequence these injuries lead to multidirectional dislocating forces acting on the scapula in relationship to the lateral end of the clavicle. Previously, special attention was given to the vertical dislocation of the lateral clavicle, whereas less attention was paid to other factors which could lead to dislocation in other directions. Therefore, in this review emphasis is placed on the anatomical principles of multidirectional dislocation of the AC joint the fractured lateral clavicle. CONCLUSION: Current clinical classification schemes fail to sufficiently include these multidirectional dislocating forces; however, they have to be considered when choosing the appropriate treatment modality. Thus, understanding the anatomical and functional context of the AC/CC region is essential for a sound management of AC joint injuries and fractures of the distal clavicle.