Which AC joint sprain type is characterized by posterior displacement of the distal clavicle into or through the trapezius?

Which AC joint sprain type is characterized by posterior displacement of the distal clavicle into or through the trapezius?

• A. Type 4
• B. Type 5
• C. Type 6
• D. Type 1

Answer: (A)

The main idea is recognizing the direction of distal clavicle displacement in AC joint injuries. A posterior displacement of the distal clavicle into or through the trapezius is the posterior-type pattern in the Rockwood classification. This pattern is distinct from injuries with no displacement, those with a large upward (superior) displacement and a big increase in the coracoclavicular distance, or rare downward displacement behind the coracoid. The posterior direction matters because the distal clavicle can get wedged into or through the trapezius, which carries implications for stability and potential neurovascular risk. Axillary views on imaging are helpful to reveal this posterior displacement, and such posterior-type injuries are often managed surgically due to instability and the risk to surrounding structures. Therefore, the scenario described matches the posterior displacement pattern into the trapezius.

The main idea is recognizing the direction of distal clavicle displacement in AC joint injuries. A posterior displacement of the distal clavicle into or through the trapezius is the posterior-type pattern in the Rockwood classification. This pattern is distinct from injuries with no displacement, those with a large upward (superior) displacement and a big increase in the coracoclavicular distance, or rare downward displacement behind the coracoid. The posterior direction matters because the distal clavicle can get wedged into or through the trapezius, which carries implications for stability and potential neurovascular risk. Axillary views on imaging are helpful to reveal this posterior displacement, and such posterior-type injuries are often managed surgically due to instability and the risk to surrounding structures. Therefore, the scenario described matches the posterior displacement pattern into the trapezius.