Acromioclavicular joint injury - Rockwood type III
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Motorcycle accident with head and left shoulder trauma. Piano key sign upon physical examination.
Radiographs revealed a 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: 16.11 mm
- AC distance: 12.75 mm
An acromioclavicular joint injury with a CC distance of <25 mm is classified as a Rockwood type III.
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 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.
- Charles M. Court-Brown, James D. Heckman, Margaret M. McQueen et al. Rockwood and Green's Fractures in Adults. (2015) ISBN: 9781451175318 - Google Books