Rockwood classification of acromioclavicular joint injury

The Rockwood classification (1998) is the most common (c.2020) classification system in use for acromioclavicular joint injuries ^3,8. 

Usage

This well known 6-type system is a modification of the earlier 3-class classification system described by Allman (1967) ² and Tossy (1963). The Rockwood classification system is limited to describing soft tissue injuries and does not assess osseous injuries ⁸. 

Classification system

The Rockwood classification takes into account not only the acromioclavicular joint itself but also the coracoclavicular ligament, the deltoid, and trapezius muscles, whilst considering the direction of dislocation of the clavicle with respect to the acromion. Essentially types IV, V, and VI are variants of type III ⁶. 

• type I: normal radiographic appearance with clavicle not elevated with respect to the acromion.

  • AC ligament: mild sprain

  • CC ligament: intact

  • joint capsule: intact

  • deltoid muscle: intact

  • trapezius muscle: intact

• type II: widened acromioclavicular joint (>7mm) with <25% clavicular elevation.

  • AC ligament: ruptured

  • CC ligament: sprain

  • joint capsule: ruptured

  • deltoid muscle: minimally detached

  • trapezius muscle: minimally detached

• type III: clavicle elevated above the superior border of the acromion but the coracoclavicular distance is less than twice normal (i.e. <25 mm) or 5mm greater than this distance on the contralateral side.

  • AC ligament: ruptured

  • CC ligament: ruptured

  • joint capsule: ruptured

  • deltoid muscle: detached

  • trapezius muscle: detached

• type IV: clavicle displaced posterior into the trapezius, which is rare.

  • AC ligament: ruptured

  • CC ligament: ruptured

  • joint capsule: ruptured

  • deltoid muscle: detached

  • trapezius muscle: detached

• type V: clavicle is markedly elevated and coracoclavicular distance is more than double normal (i.e. >25 mm) - bilateral weight-bearing projections are able to distinguish type V injuries.

  • AC ligament: ruptured

  • CC ligament: ruptured

  • joint capsule: ruptured

  • deltoid muscle: detached

  • trapezius muscle: detached

• type VI: clavicle inferiorly displaced behind coracobrachialis and biceps tendons, which is rare.

  • AC ligament: ruptured

  • CC ligament: ruptured

  • joint capsule: ruptured

  • deltoid muscle: detached

  • trapezius muscle: detached

See also

• acromioclavicular injury

• acromial types

• acromioclavicular joint configuration