Presentation
Fall from a motorbike at the left shoulder. Pain and limitation of movement
Patient Data
There is dislocation of the left acromioclavicular joint (ACJ) with loss of normal alignment of the inferior surfaces of clavicle and acromion.
The inferior border of the clavicle is elevated beyond the superior border of the acromion in the dedicated AC joint view.
There is increased coracoclavicular distance on the affected side. It is 30.5 mm on the symptomatic left compared to 11.5mm on right. (Normal coracoclavicular distance is 11 - 13mm). So it is more than double the normal and indirect evidence of coracoclavicular ligament injury. Hence suggestive of Rockwood type V injury.
Comparison is done with the contralateral acromioclavicular joint, which is in normal alignment.
The glenohumeral joint is in normal alignment
Head, neck and proximal shaft of the left humerus are normal.
Weight-bearing or stress views of ACJ further confirmed the widening of ACJ with loss of normal alignment of the acromion and clavicle suggestive of dislocation.
CT confirms the findings of acromioclavicular dislocation.
Case Discussion
Normally, the inferior border of the acromion should be in level with the inferior margin of the clavicle. In this case, there is a loss of alignment and upward displacement of the distal clavicle with acromion on the affected side.
ACJ is usually imaged with a standard AP projection radiograph. Additional views include AP with weight-bearing, comparison AP view of the opposite side and Zanca view with 10-15º cephalad angulation. This will avoid superimposition of ACJ from the rest of the shoulder.
The normal coracoclavicular distance is 10-13mm. On the symptomatic side, it was 30.5 mm compared to 11.5mm on the normal side. An asymmetry of more than 5mm is significant. When the clavicle is markedly elevated and coracoclavicular distance is more than double normal (i.e. >25 mm), it is classified as a Rockwood type V injury.