Shoulder

Acromioclavicular dislocation

Mechanism

A fall directly on the point of the shoulder with the arm at the side. First the acromioclavicular ligament tears, with more force the coracoclavicular ligament too, after which the clavicle rides up.

Recognition

A visible bump over the AC joint, tenderness exactly on the joint line and pain on horizontal adduction. The piano key sign confirms vertical instability.

Course

The bump is the clavicle staying up while the arm sinks with the scapula. In grades I and II conservative management is the rule; from grade III the choice is made per patient.

Structures

• Acromioclavicular ligament
• Coracoclavicular ligament (Conoid & Trapezoid ligaments)

Joints involved

• Acromioclavicular joint

Clinical tests

• Piano key sign
• Cross-body adduction test

Sources

• Magee DJ, Manske RC. Orthopedic Physical Assessment, 7e editie. Elsevier. 2021