Anatomy Msk · Year 1 · from Anatomy Msk
Case 3: Acromioclavicular Joint Separation
Clinical Image
Source: Wikimedia Commons - AC Joint Separation - CC BY-SA 3.0
Case Presentation
A 32-year-old hockey player presents to the emergency department after being checked into the boards and landing directly on his right shoulder with his arm at his side. He reports immediate pain at the top of his shoulder. Physical examination reveals localized swelling and tenderness directly over the right acromioclavicular (AC) joint. There is a visible step-off deformity with the distal clavicle sitting higher than the acromion ("piano key" sign). Cross-body adduction elicits pain at the AC joint. Shoulder range of motion is limited by pain but neurovascular examination is intact. Weighted radiographs (holding 10 lb weights) demonstrate complete AC joint dislocation with the clavicle displaced superiorly by 100-300% of normal AC joint width, but the coracoclavicular (CC) distance is less than 100% increased compared to the opposite side. This is classified as a Rockwood Type III injury. The patient is given the option of nonoperative treatment with sling and physical therapy versus surgical reconstruction. He elects for initial conservative management. At 8-week follow-up, he has returned to full hockey participation with mild residual cosmetic deformity but full function.
Key Learning Points
- The AC joint is stabilized by the AC ligaments (horizontal stability) and coracoclavicular ligaments (vertical stability)
- The coracoclavicular ligaments (conoid and trapezoid) prevent superior migration of the distal clavicle
- Rockwood classification: Type I (sprain), II (AC ligament tear), III (AC + CC ligament tear), IV-VI (severe displacement)
- Direct trauma to the point of the shoulder is the typical mechanism
- Type III injuries remain controversial; many athletes return to sport with conservative treatment