This paper reviews the Rockwood classification of acromioclavicular joint separations — a six-type system introduced in 1984. It describes the pathoanatomy underlying each type and examines validation studies assessing reliability across imaging modalities and clinical specialties. The central question: how well does this classification perform in practice, and what are its limitations for guiding surgical decisions?
Every shoulder trauma patient gets a Rockwood type assigned — but this paper quantifies how unreliable that assignment actually is. When you see a high-energy shoulder injury, get an axial view: Type IV (posterior displacement) is specifically missed on AP alone, and it requires surgery while the AP film may look deceptively like a Type II or III.
For Type III injuries, the classification alone cannot drive your decision. Incorporate clinical findings. If the distal clavicle cannot be manually reduced, suspect buttonholing through the deltotrapezial fascia, which pushes toward operative management regardless of what the radiograph shows.
Types I and II are nonoperative; Types IV, V, and VI go to the OR. Type III is where judgment lives: individualize based on activity level, occupational demands, sport, and patient preference. The moderate reliability of this classification is why Type III outcomes research has been so hard to interpret. Studies disagree partly because surgeons are not classifying the same injuries the same way.
This paper reviews the Rockwood classification of acromioclavicular joint separations — a six-type system introduced in 1984. It describes the pathoanatomy underlying each type and examines validation studies assessing reliability across imaging modalities and clinical specialties. The central question: how well does this classification perform in practice, and what are its limitations for guiding surgical decisions?
Every shoulder trauma patient gets a Rockwood type assigned — but this paper quantifies how unreliable that assignment actually is. When you see a high-energy shoulder injury, get an axial view: Type IV (posterior displacement) is specifically missed on AP alone, and it requires surgery while the AP film may look deceptively like a Type II or III.
For Type III injuries, the classification alone cannot drive your decision. Incorporate clinical findings. If the distal clavicle cannot be manually reduced, suspect buttonholing through the deltotrapezial fascia, which pushes toward operative management regardless of what the radiograph shows.
Types I and II are nonoperative; Types IV, V, and VI go to the OR. Type III is where judgment lives: individualize based on activity level, occupational demands, sport, and patient preference. The moderate reliability of this classification is why Type III outcomes research has been so hard to interpret. Studies disagree partly because surgeons are not classifying the same injuries the same way.