This 17-year-old presents with acromioclavicular (AC) separation. How do we classify shoulder injuries in young adults at ProScan?
Image 1 (green line) indicates a measured distance 11mm between the acromion and clavicle (normal in males is 7mm; females is 6mm). Note edema surrounds the clavicle. No microtrabecular fracture.
Injury is classified according to the system of Tossy, which simplifies the six shoulder descriptors by Rockwood and Green, and is helpful in MRI characterization. Tossy 1 represents contusion or strain, without offset of the inferior margin of the acromion at the clavicle. Tossy 2 has less than 50% offset or overlap with subtype 2A involving sprain of the trapezoid segment and 2B involved both conoid and trapezoid segments of the CC ligament. Tossy 3 has greater than 50% overlap. In this case, we see that the more lateral ligament (trapezoid) from the clavicle to the coronoid process demonstrates a high-grade tear (image 2, orange arrow). Further, there is a more swollen and perhaps minimally torn more medial conoid ligament (image 3, red arrow, and image 4, yellow arrows).
The cuff and labrum are normal, and no fracture is seen. Mixed hemorrhage and edema along the superior joint space margin with low-grade strain of a few deltoid fibers originate at the metaphysis and epiphysis of the distal clavicle separate from the AC joint (image 5, pink arrows).
Image 6 (purple arrow) highlights nominal strain, and contusion of the posterior most fibers of the lateral trapezius.
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