Epidemiology of Isolated Acromioclavicular Joint Dislocation

Table 1

The Rockwood classification takes into account not only the acromioclavicular joint, but also the coracoclavicular ligament, the deltoid and trapeziusmuscles, and the direction of dislocation of the clavicle with respect to the acromion. According to this classification, AC dislocations can be divided into 6 types.

Type	AC ligament	AC joint capsule	CC ligament	AC joint displacement	Delta-trapezial fascia
Type I	Sprained	Intact	Intact	None	Intact
Type II	Torn	Disrupted	Intact	50% AC subluxation	Intact
Type III	Torn	Disrupted	Torn	100% AC superior dislocation	Intact
Type IV	Torn	Disrupted	Torn	100% AC posterior dislocation.; Posterior displacement of the distal clavicle into or through the trapezius muscle	Disrupted
Type V	Torn	Disrupted	Torn	100–300% AC superior dislocation.; Complete detachment of deltoid and trapezius muscle from their clavicular insertion	Disrupted
Type VI	Torn	Disrupted	Torn	100% AC inferior dislocation.; Inferior displacement of the distal clavicle into a subacromial or subcoracoid position	Intact