Rockwood classification of acromioclavicular injuries. Type I: neither acromioclavicular nor coracoclavicular ligaments are disrupted. Type II: acromioclavicular ligament is disrupted, and coracoclavicular ligament is intact. Type III: both ligaments are disrupted. Type IV: ligaments are disrupted, and distal end of clavicle is displaced posteriorly into or through trapezius muscle. Type V: ligaments and muscle attachments are disrupted, and clavicle and acromion are widely separated. Type VI: ligaments are disrupted, and distal clavicle is dislocated inferior to coracoid process and posterior to biceps and coracobrachialis tendons.