Degloving injury. (Photo contributor: Lawrence B. Stack, MD.)
Injury to the acromioclavicular (AC) joint usually results from an impact on the superior aspect of the acromion. The classification system includes six types: type I: stretching of the AC ligament; type II: tearing of the AC ligaments and stretching of the coracoclavicular ligaments; and types III to VI: complete disruption of the AC and coracoclavicular ligaments.
Shoulder Ligaments. The ligaments that stabilize the glenohumeral and acromioclavicular joints. (Reproduced with permission from The Shoulder. In: Parks E, ed. Practical Office Orthopedics. New York, NY: McGraw Hill; Copyright 2018.)
Patients complain of pain at the AC joint and will actively splint the injured shoulder. Ecchymosis may be present; however, an obvious deformity is not always seen. There is significant tenderness upon AC joint palpation.
Standard radiographs should include anteroposterior (AP) and axillary lateral views of the shoulder. Type I injuries will appear normal. Type II injuries may show 0% to 50% displacement at the AC joint but no increase in the coracoclavicular interval. Types III to VI will demonstrate displacement at the AC joint and the clavicle will appear to be displaced superiorly (the acromion actually is rotated inferiorly) 50% to greater than 100% its width when compared with the normal side.
AC Joint Separation Types. The anatomic basis (left), clinical appearance (middle, with arrow pointing to the AC joint deformity), and x-ray findings seen with a type I, II, III, and V AC joint separation (A-C). (Reproduced with permission from The Shoulder. In: Parks E, ed. Practical Office Orthopedics. New York, NY: McGraw Hill; Copyright 2018.)
AC Joint Separation. Large deformity at the right distal clavicle suggesting complete ligament disruption. (Photo contributor: R. Jason Thurman, MD.)
Management and Disposition
Types I and II injuries are treated with rest, ice, analgesics, and a simple sling until acute pain with movement is relieved. Type III injuries may ...