Acromioclavicular joint injury - Rockwood type III

Case contributed by Leonardo Lustosa
Diagnosis certain


Motor vehicle accident. Right shoulder deformity upon physical examination.

Patient Data

Age: 35 years
Gender: Male

Raised clavicle. The coracoclavicular and acromioclavicular distances are widened (see annotated images below). These findings indicate an acromioclavicular joint injury.

There are no associated fractures.

Annotated images of the coracoclavicular (CC) distance and acromioclavicular (AC) distance. Both distances are widened.

  • CC distance: 16.7 mm

  • AC distance: 20.4 mm

An acromioclavicular joint injury with a CC distance of <25 mm is classified as a Rockwood type III.

Case Discussion

Acromioclavicular joint injuries are usually the result of a direct hit to the shoulder which can rupture ligaments such as the coracoclavicular and acromioclavicular ligaments.

In the present case, the presence of positive piano key sign raised suspicion of an acromioclavicular dislocation upon physical examination.

The coracoclavicular and acromioclavicular distances are important measurements in the evaluation of their respective ligaments which may be injured when an acromioclavicular joint injury is suspected.

The normal range of the CC distance is 11-13 mm.

The normal range of the AC distance is 1-3 mm.

Widened distances indicate an acromioclavicular joint injury.

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